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© tutor2u AQA A Level Psychology Revision Guide (Edition 1) Specification 7181, 7182 For Teaching from September 2015

NERVOUS SYSTEM Topic: The divisions of the nervous system: central and peripheral (somatic and autonomic).

WHAT YOU NEED TO KNOW 1. Outline the structure (components) of the nervous system.2. Outline the role of the nervous system, including:

a. Central nervous system (CNS)i. Brain

ii. Spinal cordb. Peripheral nervous system

i. Somatic nervous systemii. Autonomic nervous system

1. Sympathetic nervous system2. Parasympathetic nervous system

3. Identify similarities and differences between the components of the peripheralnervous system and/or central nervous system

1. The nervous systemThe nervous system is divided into the two main components: 1) the central nervous system (CNS) and 2) the peripheral nervous system (PNS). The nervous system has the following structure:

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2a. The CNS – Brain and spinal cord The CNS consists of the brain and the spinal cord. The brain provides conscious awareness and is involved in all psychological processes. The brain consists of many regions, which are responsible for different functions.

For example, the brain consists of four main lobes: frontal lobe, parietal lobe, temporal lobe and occipital lobe. The occipital lobe processes visual information; the temporal lobe processes auditory information; the parietal lobe integrates information from the different senses and therefore plays an important role in spatial navigation; the frontal lobe is associated with higher-order functions, including planning, abstract reasoning and logic.

The brain stem connects the brain and spinal cord and controls involuntary processes, including our heartbeat, breathing and consciousness. The role of the spinal cord is to transfer messages to and from the brain, and the rest of the body. The spinal cord is also responsible for simple reflex actions that do not involve the brain, for example jumping out of your chair if you sit on a drawing pin. 2a. The PNS – somatic and autonomic nervous systems The role of the peripheral nervous system (PNS) is to relay messages (nerve impulses) from the CNS (brain and spinal cord) to the rest of the body. The PNS consists of two main components: 1) the somatic nervous system and 2) the autonomic nervous system. The somatic nervous system facilitates communication between the CNS and the outside world. The somatic nervous system is made up of sensory receptors that carry information to the spinal cord and brain, and motor pathways that allow the brain to control movement. Therefore, the role of the somatic nervous system is to carry sensory information from the outside world to the brain and provide muscle responses via the motor pathways. The autonomic nervous system plays an important role in homeostasis, which maintains internal processes like body temperature, heart rate and blood pressure. The autonomic nervous system only consists of motor pathways and has two components: 1) the sympathetic nervous system and 2) the parasympathetic nervous system.

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The sympathetic nervous system is typically involved in responses that prepare the body for fight or flight. Impulses travel from the sympathetic nervous system to organs in the body to help us prepare for action when we are faced with a dangerous situation. For example, our heart rate, blood pressure and breathing rate increase, while less important functions like digestion, salivation and the desire to urinate are suppressed. The role of the parasympathetic nervous system is to relax the body, and return us to our ‘normal’ resting state. Consequently, the parasympathetic nervous system slows down our heart rate and breathing rate, and reduces our blood pressure. Furthermore, any functions that were previously slowed down during a fight or flight reaction are started again (e.g. digestion).

CENTRAL NERVOUS SYSTEM SIMILARITIES DIFFERENCES

BRAIN The brain stem and spinal cord both control involuntary processes (e.g. the brain stem controls breathing and the spinal cord controls involuntary reflexes).

The brain provides conscious awareness and allows for higher-order thinking, while the spinal cord allows for simple reflex responses. The brain consists of multiple regions responsible for different functions, whereas the spinal cord has one main function.

SPINAL CORD

PERIPHERAL NERVOUS SYSTEM SIMILARITIES DIFFERENCES

SOMATIC AUTONOMIC

The sympathetic nervous system (part of the autonomic nervous system) and the somatic nervous system respond to external stimuli. The sympathetic nervous system responds to external stimuli by preparing the body for fight or flight and the somatic nervous system responds to external stimuli (by carrying information from sensory receptors to the spinal cord and brain).

The autonomic nervous system consists of two sub-components, whereas the somatic nervous system only has one. The somatic nervous system has sensory and motor pathways, whereas the autonomic nervous system only has motor pathways. The autonomic nervous system controls internal organs and glands, while the somatic nervous system controls muscles and movement.

SYMPATHETIC / PARASYMPATHETIC

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Possible Exam Questions 1. Which of the following statements is false?

The autonomic nervous system: a) comprises of two subsystems; b) controls communication between the CNS and the environment; c) plays an important role in homeostasis; d) maintains internal processes like blood pressure. (1 mark)

2. Joline has just been to the cinema with her friend to watch a new horror movie.

While she is walking home alone she believes that she can hear footsteps following her and starts to panic. Without thinking she starts sprinting and gets home as fast as she can. She bursts through the front door, heart pounding, dripping with sweat and shaking.

Outline the role of the autonomic nervous system and central nervous system, referring to Joline’s experience in your answer. (4 marks)

3. Outline the role of the central nervous system/somatic nervous system/autonomic nervous system. (4 marks each)

4. Outline two differences in the organisation/function of the somatic nervous system and autonomic nervous system. (4 marks)

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© tutor2u AQA A Level Psychology Course Companion (Edition 1) Specification 7181, 7182 For Teaching from September 2015

NEURONS & NEUROTRANSMISSION Topic: The structure and function of sensory, relay and motor neurons. The process of synaptic transmission, including reference to neurotransmitters, excitation and inhibition. WHAT YOU NEED TO KNOW 1. Outline the structure and function of:

a. Sensory neurons b. Relay neurons c. Motor neurons

2. Outline the process of synaptic transmission and explain the difference between: a. Excitation b. Inhibition

1. Sensory, relay and motor neurons There are three main types of neurons, including: sensory, relay and motor. Each of these neurons has a different function, depending on its location in the body and its role within the nervous system. Note: All three types of neuron consist of similar parts, however their structure, location and function are different and this is what you need be aware of.

SENSORY RELAY MOTOR

Sensory neurons are found in receptors such as the eyes, ears, tongue and skin, and carry nerve impulses to the spinal cord and brain. When these nerve impulses reach the brain, they are translated into ‘sensations’, such as vision, hearing, taste and touch. However, not all sensory neurons reach the brain, as some neurons stop at the spinal cord, allowing for quick reflex actions.

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Relay neurons are found between sensory input and motor output/response. Relay neurons are found in the brain and spinal cord and allow sensory and motor neurons to communicate. Motor neurons are found in the central nervous system (CNS) and control muscle movements. When motor neurons are stimulated they release neurotransmitters that bind to the receptors on muscles to trigger a response, which lead to movement. As you can see from the diagrams above, all three neurons consist of similar parts. The dendrites receive signals from other neurons or from sensory receptor cells. The dendrites are typically connected to the cell body, which is often referred to as the ‘control centre’ of the neuron, as it’s contains the nucleus. The axon is a long slender fibre that carries nerve impulses, in the form of an electrical signal known as action potential, away from the cell body towards the axon terminals, where the neuron ends. Most axons are surrounded by a myelin sheath (except for relay neurons) which insulates the axon so that the electrical impulses travel faster along the axon. The axon terminal connects the neuron to other neurons (or directly to organs), using a process called synaptic transmission. 2. Synaptic transmission Information is passed down the axon of the neuron as an electrical impulse known as action potential. Once the action potential reaches the end of the axon it needs to be transferred to another neuron or tissue. It must cross over a gap between the pre-synaptic neuron and post-synaptic neuron – which is known as the synaptic gap. At the end of the neuron (in the axon terminal) are the synaptic vesicles which contains chemical messengers, known as neurotransmitters. When the electrical impulse (action potential) reaches these synaptic vesicles, they release their contents of neurotransmitters.

Neurotransmitters then carry the signal across the synaptic gap. They bind to receptor sites on the post-synaptic cell that then become activated. Once the receptors have been activated, they either produce excitatory or inhibitory effects on the post-synaptic cell. Some neurotransmitters are

excitatory and some are inhibitory. Excitatory neurotransmitters (e.g. noradrenaline) make the post-synaptic cell more likely to fire, whereas inhibitory neurotransmitters (e.g. GABA) make them less likely to fire. For example, if an excitatory neurotransmitter like noradrenaline binds to the post-synaptic receptors it will cause an electrical charge in the cell membrane which results in an excitatory post-synaptic

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potential (EPSP), which makes the post-synaptic cell more likely to fire. Whereas, if an inhibitory neurotransmitter like GABA binds to the post-synaptic receptors it will result in an inhibitory post-synaptic potential (IPSP), which makes the post-synaptic cell less likely to fire. Possible Exam Questions 1. Complete the following sentence (1 mark): Motor neurons…

a. are found in receptor cells b. carry nerve impulses to the brain c. are found between the brain and spinal cord d. are found in the central nervous system

2. Briefly outline the process of synaptic transmission. (4 marks) 3. Outline two differences between sensory neurons and motor neurons. (4 marks)

4. Jack is 8-years-old and has recently been prescribed Ritalin to help with his ADHD.

Jack’s mother searches for Ritalin on the internet and learns that Ritalin elevates the level of dopamine, which is an excitatory neurotransmitter. Outline the role of excitatory neurotransmitters, referring to Jack in your answer. (4 marks).

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THE ENDOCRINE SYSTEM Topic: The function of the endocrine system: glands and hormones. WHAT YOU NEED TO KNOW 1. Outline the function of the endocrine system, including:

a. Glands b. Hormones

Exam Hint: For this part of the course it is important to know what hormones are released by the different glands in the body and what effect these hormones have. 1. The Endocrine System - Glands The endocrine system works alongside the nervous system. It is a network of glands across the body that secrete chemical messages called hormones. Instead of using nerves (sensory and motor neurons) to transmit information, this system uses blood vessels. Different hormones produce different effects (behaviours). The glands which make up the endocrine system can be found in the diagram below.

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Each gland produces a different hormone. The word ‘hormone’ comes from the Greek work ‘hormao’ which means ‘excite’, as hormones excite (stimulate) a particular part of the body. 2. The Endocrine System - Hormones The hypothalamus is connected to the pituitary gland and is responsible for stimulating or controlling the release of hormones from the pituitary gland. Therefore, the hypothalamus is the control system which regulates the endocrine system. The pituitary gland is sometimes known as the master gland because the hormones released by the pituitary gland control and stimulate the release of hormones from other glands in the endocrine system. The pituitary gland is also divided into the anterior (front) and posterior (rear) lobes (see right), which release different hormones. A key hormone released from the posterior lobe is oxytocin (often referred to as the ‘love hormone’) which is responsible for uterus contractions during childbirth. A key hormone released from the anterior lobe is adrenocortical trophic hormone (ACTH) which stimulates the adrenal cortex and the release of cortisol, during the stress response. The main hormone released from the pineal gland is melatonin, which is responsible for important biological rhythms, including the sleep-wake cycle. The thyroid gland releases thyroxine which is responsible for regulating metabolism. People who have a fast metabolism typically struggle to put on weight, as metabolism is involved in the chemical process of converting food into energy. The adrenal gland is divided into two parts, the adrenal medulla and the adrenal cortex. The adrenal medulla is responsible for releasing adrenaline and noradrenaline, which play a key role in the fight or flight response. The adrenal cortex releases cortisol, which stimulates the release of glucose to provide the body with energy while suppressing the immune system. Males and females have different sex organs, and in males the testes release androgens, which include the main hormone testosterone. Testosterone is responsible for the development of male sex characteristics during puberty while also promoting muscle growth. In females, the ovaries release oestrogen which controls the regulation of the female reproductive system, including the menstrual cycle and pregnancy.

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GLAND MAIN HORMONE RELEASED EFFECT

Hypothalamus Stimulates and controls the release of hormones from the pituitary gland.

Pituitary Gland (Master Gland)

Anterior - adrenocortical trophic hormone (ACTH)

Stimulates the adrenal cortex and the release of cortisol during the stress response.

Posterior – oxytocin Responsible for uterus contractions during childbirth.

Pineal Gland Melatonin Responsible for important biological rhythms, including the sleep-wake cycle.

Thyroid Gland Thyroxine Responsible for regulating metabolism.

Adrenal Gland

Adrenal medulla – adrenaline & noradrenaline

The key hormones in the fight or flight response.

Adrenal cortex - cortisol

Stimulates the release of glucose to provide the body with energy, while suppressing the immune system.

Ovaries (female) Oestrogen Controls the regulation of the female reproductive system, including the menstrual cycle and pregnancy

Testes (male) Testosterone

Responsible for the development of male sex characteristics during puberty, while also promoting muscle growth.

Possible Exam Questions 1. Which of the following glands is responsible for the release of hormones from all

other glands within the endocrine system? a. Thyroid b. Adrenal c. Hypothalamus d. Pituitary

2. Identify one gland that forms part of the endocrine system and outline its function.

(2 marks)

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3. Outline the relationship between glands and hormones. (4 marks) 4. Describe the functions of the endocrine system. (6 marks)

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FIGHT OR FLIGHT Topic: The fight or flight response, including the role of adrenaline. WHAT YOU NEED TO KNOW 1. Outline and evaluate the fight or flight response, including the role of adrenaline.

The ‘Fight or Flight’ Response When someone enters a potentially stressful situation, the amygdala (part of the limbic system) is activated. The amygdala responds to sensory input (what we see, hear, smell, etc.) and connects sensory input with emotions associated with the fight or flight response (e.g. fear and anger). If the situation is deemed as stressful/dangerous, the amygdala sends a distress signal to the hypothalamus, which communicates with the body through the sympathetic nervous system. If the situation requires a short-term response the sympathomedullary pathway (SAM pathway) is activated, triggering the fight or flight response.

Exam Hint: Adrenaline causes a number of physiological changes (e.g. increased heart rate); however, it is important that you understand why these changes occur in relation to the fight or flight response.

Adrenaline causes a number of physiological changes to prepare the body for fight or flight.

The adrenal medulla secretes the hormones adrenaline and noradrenaline into the bloodstream.

The SNS stimulates the adrenal medulla, part of the adrenal gland.

The hypothalamus activates the sympathomedullary pathway (SAM pathway) – the pathway running to the adrenal medulla and the sympathetic nervous system

(SNS).

The amygdala (part of the limbic system) is activated which send a distress signal to the hypothalamus.

A person enters a stressful/dangerous situation.

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PHYSIOLOGICAL CHANGE REASON

Increased heart rate To increase blood flow to organs and increase the movement of adrenaline around the body.

Increased breathing rate To increase oxygen intake.

Pupil dilation To increase light entry into the eye and enhance vision (especially in the dark).

Sweat production To regulate temperature.

Reduction of non-essential functions (e.g. digestive system, urination, salivation)

To increase energy for other essential functions.

Following the fight or flight response, the parasympathetic nervous system is activated to return the body back to its ‘normal’ resting state. Consequently, the parasympathetic nervous system slows down our heart rate and breathing rate and reduces our blood pressure. Furthermore, any functions that were previously slowed down are started again (e.g. digestion). Evaluation When faced with a dangerous situation our reaction is not limited to the fight or

flight response; some psychologists suggest that humans engage in an initial ‘freeze’ response. Gray (1988) suggests that the first response to danger is to avoid confrontation altogether, which is demonstrated by a freeze response. During the freeze response animals and humans are hyper-vigilant, while they appraise the situation to decide the best course of action for that particular threat.

The fight or flight response is typically a male response to danger and more recent research suggests that females adopt a ‘tend and befriend’ response in stressful/dangerous situations. According to Taylor et al. (2000), women are more likely to protect their offspring (tend) and form alliances with other women (befriend), rather than fight an adversary or flee. Furthermore, the fight or flight response may be counterintuitive for women, as running (flight) might be seen as a sign of weakness and put their offspring at risk of danger.

Exam Hint: It is possible to incorporate knowledge of the issues and debates in psychology into your evaluation. For example, the above point is linked to the ‘Gender Bias’ topic and therefore you could explore the ideas of androcentrism and beta bias within this evaluation point. Early research into the fight or flight response was typically conducted on males

(androcentrism) and consequently, researchers assumed that the findings could be generalised to females. This highlights a beta bias within this area of psychology as psychologists assumed that females responded in the same way as males, until Taylor provided evidence of a tend and befriend response.

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While the fight or flight response may have been a useful survival mechanism for our ancestors, who faced genuinely life-threatening situations (e.g. from predators), modern day life rarely requires such an intense biological response. Furthermore, the stressors of modern day life can repeatedly activate the fight or flight response, which can have a negative consequence on our health. For example, humans who face a lot of stress and continually activate the sympathetic nervous system, continually increase their blood pressure which can cause damage to their blood vessels and heart disease. This suggests that the fight or flight response is a maladaptive response in modern-day life.

Possible Exam Questions 1. Which of the following responses is not caused by the activation of the

sympathetic nervous system? a. Pupil dilation b. Sweat production c. Decreased digestion d. Increased salivation

2. Outline the function of adrenaline in the fight-or-flight response. (4 marks) 3. Lynn’s husband John works night shifts and she hates being at home alone. One

night she is suddenly woken by a crashing sound coming from the kitchen. With her heart racing, she slowly walks into the kitchen, trembling and sweating with fear. She turns on the light to see that her cat has knocked a plate off the kitchen worktop. She picks up the cat and within minutes she is feeling much more relaxed.

Outline the fight or flight response, referring to the changes that occurred in Lynn in the first minute and the changes that occurred after a few minutes. (4 marks)

4. Outline and evaluate the fight or flight response. (12/16 marks)

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LOCALISATION AND LATERALISATION Specification: Localisation of function in the brain and hemispheric lateralisation: motor, somatosensory, visual, auditory and language centres; Broca’s and Wernicke’s areas, split brain research. Plasticity and functional recovery of the brain after trauma. WHAT YOU NEED TO KNOW 1. Outline and evaluate what research has shown about localisation of function in

the brain, with reference to the following regions: a. Motor area b. Somatosensory area c. Visual area d. Auditory area

2. Outline the role of language centres in the brain, including: a. Broca’s area b. Wernicke’s area

3. Outline and evaluate research into lateralisation and/or the split brain. 4. Outline and evaluate evidence for plasticity and/or functional recovery of the

brain after trauma. KEY TERMS DEFINITIONS

Localisation of Function Localisation of function is the idea that certain functions (e.g. language, memory, etc.) have certain locations within the brain.

Hemispheric Lateralisation

Lateralisation is the fact that the two halves of the brain are functionally different and that each hemisphere has functional specialisations, e.g. the left is dominant for language, and the right excels at visual motor tasks.

Motor Area The motor area is responsible for voluntary movements by sending signals to the muscles in the body.

Somatosensory Area The somatosensory area receives incoming sensory information from the skin to produce sensations related to pressure, pain, temperature, etc.

Visual Area

The visual area receives and processes visual information. The visual area contains different parts that process different types of information including colour, shape or movement.

Auditory Area The auditory area is responsible for analysing and processing acoustic information.

Broca’s Area The Broca’s area is found in the left frontal lobe and is thought to be involved in language production.

Wernicke’s Area The Wernicke’s area is found in the left temporal lobe and is thought to be involved in language processing/comprehension.

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Split-Brain Research Split-brain patients are individuals who have undergone a surgical procedure where the corpus callosum, which connects the two hemispheres, is cut.

Plasticity Brain plasticity refers to the brain’s ability to change and adapt because of experience.

Functional Recovery Functional recovery is the transfer of functions from a damaged area of the brain after trauma to other undamaged areas.

Introduction – Localisation of Brain Function Localisation of function is the idea that certain functions (e.g. language, memory, etc.) have certain locations or areas within the brain. This idea has been supported by recent neuroimaging studies, but was also examined much earlier, typically using case studies. One such case study is that of Phineas Gage, who in 1848 while working on a rail line, experienced a drastic accident in which a piece of iron went through his skull. Although Gage survived this ordeal, he did experience a change in personality, such as loss of inhibition and anger. This change provided evidence to support the theory of localisation of brain function, as it was believed that the area the iron stake damaged was responsible for personality. There are four key areas that you need to be aware of: motor, somatosensory, visual and auditory areas. 1a. Motor Area The motor area is located in the frontal lobe and is responsible for voluntary movements by sending signals to the muscles in the body. Hitzig and Fritsch (1870) first discovered that different muscles are coordinated by different areas of the motor cortex by electrically stimulating the motor area of dogs. This resulted in muscular contractions in different areas of the body depending on where the probe was inserted. The regions of the motor area are arranged in a logical order, for example, the region that controls finger movement is located next to the region that controls the hand and arm and so on. 1b. Somatosensory Area The somatosensory area is located in the parietal lobe and receives incoming sensory information from the skin to produce sensations related to pressure, pain, temperature, etc. Different parts of the somatosensory area receive messages from different locations of the body. Robertson (1995) found that this area of the brain is

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highly adaptable, with Braille readers having larger areas in the somatosensory area for their fingertips compared to normal sighted participants. 1c. Visual Area At the back of the brain, in the occipital lobe is the visual area, which receives and processes visual information. Information from the right-hand side visual field is processed in the left hemisphere, and information from the left-hand side visual field is processed in the right hemisphere. The visual area contains different parts that process different types of information including colour, shape or movement. 1d. Auditory Area The auditory area is located in the temporal lobe and is responsible for analysing and processing acoustic information. Information from the left ear goes primarily to the right hemisphere and information from the right ear goes primarily to the left hemisphere. The auditory area contains different parts, and the primary auditory area is involved in processing simple features of sound, including volume, tempo and pitch.

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2a. Language Centres: Broca’s Area The Broca’s area is named after Paul Broca, who discovered this region while treating a patient named Leborgne, who was more commonly referred to as ‘Tan’. Tan could understand spoken language but was unable to produce any coherent words, and could only say ‘Tan’.

After Tan’s death, Broca conducted a post-mortem examination on Tan’s brain and discovered that he had a lesion in the left frontal lobe. This led Broca to conclude that this area was responsible for speech production. People with damage to this area experience Broca’s aphasia, which results in slow and inarticulate speech. Extension: Due to the significance of this finding,

Dronkers et al. (2007) decided to conduct an MRI scan on Tan’s brain, to try to confirm Broca’s original work. Although there was a lesion found in Broca’s area, they also found evidence to suggest that other areas may have also contributed to the failure in speech production. Therefore it is likely that the Broca’s area is not solely responsible for speech production, as other areas may also play a role. 2b. Language Centres: Wernicke’s Area At a similar time, Carl Wernicke discovered another area of the brain that was involved in understanding language. Wernicke found that patients with lesions to Wernicke’s area were still able to speak, but were unable to comprehend language. Wernicke’s area is found in the left temporal lobe, and it is thought to be involved in language processing/comprehension. People with damage to this area struggle to comprehend language, often producing sentences that are fluent, but meaningless (Wernicke’s aphasia). Wernicke concluded that language involves a separate motor and sensory region. The motor region is located in Broca’s area, and the sensory region is located in Wernicke’s area. Extension: However, research by Saygin et al. (2003) found that some patients displayed symptoms of Wernicke’s aphasia without any damage to this area. This suggests that language comprehension is much more complex than originally thought. Further evidence has also been found which suggests some left-handed people process language in the right hemisphere.

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LOCATION FUNCTION LEFT, RIGHT OR BOTH

HEMISPHERES

MOTOR AREA

Frontal Lobe

The motor area is responsible for voluntary movements by sending signals to the muscles in the body.

Both The motor area on one side of the brain controls the muscles on the opposite side.

SOMATO-SENSORY AREA

Parietal Lobe

The somatosensory area receives incoming sensory information from the skin to produce sensations related to pressure, pain, temperature, etc.

Both The somatosensory area on one side of the brain receives sensory information from the opposite side of the body.

VISUAL AREA Occipital Lobe

The visual area receives and processes visual information. The visual area contains different parts that process different types of information including colour, shape or movement.

Both Information from the right-hand side visual field is processed in the left hemisphere, and information from the left-hand side visual field is processed in the right hemisphere.

AUDITORY AREA

Temporal Lobe

The auditory area is responsible for analysing and processing acoustic information.

Both Information from the left ear goes primarily to the right hemisphere and information from the right ear goes primarily to the left hemisphere.

BROCA’S AREA

Left Frontal Lobe

The Broca’s area is found in the left frontal lobe and is thought to be involved in language production.

Left

WERNICKE’S AREA

Left Temporal Lobe

The Wernicke’s area is found in the left temporal lobe and is thought to be involved in language comprehension.

Left

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Evaluating Localisation of Function The claim that functions are localised to certain areas of the brain has been

criticised. Lashley proposed the equipotentiality theory, which suggests that the basic motor and sensory functions are localised, but that higher mental functions are not. He claimed that intact areas of the cortex could take over responsibility for specific cognitive functions following brain injury. This therefore casts doubt on theories about the localisation of functions, suggesting that functions are not localised to just one region, as other regions can take over specific functions following brain injury.

There is a wealth of case studies on patients with damage to Broca’s and

Wernicke’s areas that have demonstrated their functions. For example, Broca’s aphasia is an impaired ability to produce language; in most cases, this is caused by brain damage in Broca’s area. Wernicke’s aphasia is an impairment of language perception, demonstrating the important role played by this brain region in the comprehension of language.

o However, although there is evidence from case studies to support the function of the Broca’s area and Wernicke’s area, more recent research has provided contradictory evidence. Dronkers et al. (2007) conducted an MRI scan on Tan’s brain, to try to confirm Broca’s findings. Although there was a lesion found in Broca’s area, they also found evidence to suggest other areas may have contributed to the failure in speech production. These results suggest that the Broca’s area may not be the only region responsible for speech production and the deficits found in patients with Broca’s aphasia could be the result of damage to other neighbouring regions.

Furthermore, psychologists suggest that it is more important to investigate how

the brain areas communicate with each other, rather than focusing on specific brain regions. Wernicke claimed that although the different areas of the brain are independent, they must interact with each other in order to function. An example to demonstrate this is a man who lost his ability to read, following damage to the connection between the visual cortex and the Wernicke’s area, which was reported by Dejerine. This suggests that interactions between different areas produce complex behaviours such as language. Therefore, damage to the connection between any two points can result in impairments that resemble damage to the localised brain region associated with that specific function. This reduces the credibility of the localisation theory.

o Also, critics argue that theories of localisation are biologically reductionist in nature and try to reduce very complex human behaviours and cognitive processes to one specific brain region. Such critics suggest that a more thorough understanding of the brain is required to truly understand complex cognitive processes like language.

Finally, some psychologists argue that the idea of localisation fails to take into

account individual differences. Herasty (1997) found that women have proportionally larger Broca’s and Wernicke’s areas than men, which can perhaps explain the greater ease of language use amongst women. This, however, suggests

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a level of beta bias in the theory: the differences between men and woman are ignored, and variations in the pattern of activation and the size of areas observed during various language activities are not considered.

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3. Hemispheric Lateralisation Lateralisation is the idea that the two halves of the brain are functionally different and that each hemisphere has functional specialisations, e.g. the left is dominant for language, and the right excels at visual motor tasks. The two hemispheres are connected through nerve fibres called the corpus callosum, which facilitate interhemispheric communication: allowing the left and right hemispheres to ‘talk to’ one another. Split-Brain Research Sperry and Gazzaniga (1967) were the first to investigate hemispheric lateralisation with the use of split-brain patients. Background: Split-brain patients are individuals who have undergone a surgical procedure where the corpus callosum, which connects the two hemispheres, is cut. This procedure, which separates the two hemispheres, was used as a treatment for severe epilepsy. Aim: The aim of their research was to examine the extent to which the two hemispheres are specialised for certain functions. Method: An image/word is projected to the patient’s left visual field (which is processed by the right hemisphere) or the right visual field (which is processed by the left hemisphere). When information is presented to one hemisphere in a split-brain patient, the information is not transferred to the other hemisphere (as the corpus callosum is cut).

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Sperry and Gazzaniga conducted many different experiments, including describe what you see tasks, tactile tests, and drawing tasks. In the describe what you see task, a picture was presented to either the left or

right visual field and the participant had to simply describe what they saw.

In the tactile test, an object was placed in the patient’s left or right hand and they had to either describe what they felt, or select a similar object from a series of alternate objects.

Finally, in the drawing task, participants were presented with a picture in either

their left or right visual field, and they had to simply draw what they saw. Findings: DESCRIBE WHAT YOU SEE Pictured presented to the right visual field

(processed by left hemisphere) Picture presented to the left visual field

(processed by right hemisphere) The patient could describe what they saw, demonstrating the superiority of the left hemisphere when it comes to language production.

The patient could not describe what was shown and often reported that there was nothing present.

TACTILE TESTS

Objects placed in the right hand (processed by the left hemisphere)

Objects placed in the left hand (processed by the right hemisphere)

The patient could describe verbally what they felt. Or they could identify the test object presented in the right hand (left hemisphere), by selecting a similar appropriate object, from a series of alternate objects.

The patient could not describe what they felt and could only make wild guesses. However, the left hand could identify a test object presented in the left hand (right hemisphere), by selecting a similar appropriate object, from a series of alternate objects.

DRAWING TASKS Pictured presented to the right visual field

(processed by left hemisphere) Picture presented to the left visual field

(processed by right hemisphere) While the right-hand would attempt to draw a picture, the picture was never as clear as the left hand, again demonstrating the superiority of the right hemisphere for visual motor tasks.

The left-hand (controlled by the right hemisphere) would consistently draw clearer and better pictures than the right-hand (even though all the participants were right-handed). This demonstrates the superiority of the right hemisphere when it comes to visual motor tasks.

Conclusion: The findings of Sperry and Gazzaniga’s research highlights a number of key differences between the two hemispheres. Firstly, the left hemisphere is dominant in

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terms of speech and language. Secondly, the right hemisphere is dominant in terms of visual-motor tasks. Evaluating Split-Brain Research It is assumed that the main advantage of brain lateralisation is that it increases

neural processing capacity (the ability to perform multiple tasks simultaneously). Rogers et al. (2004) found that in a domestic chicken, brain lateralisation is associated with an enhanced ability to perform two tasks simultaneously (finding food and being vigilant for predators). Using only one hemisphere to engage in a task leaves the other hemisphere free to engage in other functions. This provides evidence for the advantages of brain lateralisation and demonstrates how it can enhance brain efficiency in cognitive tasks.

o However, because this research was carried out on animals, it is impossible to conclude the same of humans. Unfortunately, much of the research into lateralisation is flawed because the split-brain procedure is rarely carried out now, meaning patients are difficult to come by. Such studies often include very few participants, and often the research takes an idiographic approach. Therefore, any conclusions drawn are representative only of those individuals who had a confounding physical disorder that made the procedure necessary. This is problematic as such results cannot be generalised to the wider population.

Furthermore, research has suggested that lateralisation changes with age.

Szaflarki et al. (2006) found that language became more lateralised to the left hemisphere with increasing age in children and adolescents, but after the age of 25, lateralisation decreased with each decade of life. This raises questions about lateralisation, such as whether everyone has one hemisphere that is dominant over the other and whether this dominance changes with age.

Finally, it could be argued that language may not be restricted to the left

hemisphere. Turk et al. (2002) discovered a patient who suffered damage to the left hemisphere but developed the capacity to speak in the right hemisphere, eventually leading to the ability to speak about the information presented to either side of the brain. This suggests that perhaps lateralisation is not fixed and that the brain can adapt following damage to certain areas.

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4. Plasticity and Functional Recovery The brain is not a static organ, and the functions and processes of the brain can change as a result of experience and injury. Brain plasticity refers to the brain’s ability to change and adapt because of experience. Research has demonstrated that the brain continues to create new neural pathways and alter existing ones in response to changing experiences (see evidence below). The brain also appears to show evidence of functional recovery: the transfer of functions from a damaged area of the brain after trauma to other undamaged areas. It can do this through a process termed neuronal unmasking where ‘dormant’ synapses (which have not received enough input to be active) open connections to compensate for a nearby damaged area of the brain. This allows new connections in the brain to be activated, thus recovering any damage occurring in specific regions. Evidence/Evaluation for Plasticity and Functional Recovery Kuhn et al. found a significant increase in grey matter in various regions of the

brain after participants played video games for 30 minutes a day over a two-month period. Similarly, Davidson et al. demonstrated the permanent change in the brain generated by prolonged meditation: Buddhist monks who meditated frequently had a much greater activation of gamma waves (which coordinate neural activity) than did students with no experience of meditation. These two studies highlight the idea of plasticity and the brain’s ability to adapt as a result of new experience, whether it’s video games or mediation.

There is further research to support the notion of brain plasticity. Maguire et al.

found that the posterior hippocampal volume of London taxi drivers’ brains was positively correlated with their time as a taxi driver and that there were significant differences between the taxi drivers’ brains and those of controls. This shows that the brain can permanently change in response to frequent exposure to a particular task.

o However, some psychologists suggest that research investigating the plasticity of the brain is limited. For example, Maguire’s research is biologically reductionist and only examines a single biological factor (the size of the hippocampus) in relation to spatial memory. This approach is limited and fails to take into account all of the different biological/cognitive processes involved in spatial navigation which may limit our understanding. Other psychologists suggest that a holistic approach to understanding complex human behaviour may be more appropriate.

There is research to support the claim for functional recovery. Taijiri et al. (2013) found that stem cells provided to rats after brain trauma showed a clear development of neuron-like cells in the area of injury. This demonstrates the ability of the brain to create new connections using neurons manufactured by stem cells.

While there is evidence for functional recovery, it is possible that this ability can

deteriorate with age. Elbert et al. concluded that the capacity for neural

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reorganisation is much greater in children than in adults, meaning that neural regeneration is less effective in older brains. This may explain why adults find change more demanding than do young people. Therefore, we must consider individual differences when assessing the likelihood of functional recovery in the brain after trauma.

A final strength of research examining plasticity and functional recovery is the

application of the findings to the field of neurorehabilitation. Understanding the processes of plasticity and functional recovery led to the development of neurorehabilitation which uses motor therapy and electrical stimulation of the brain to counter the negative effects and deficits in motor and cognitive functions following accidents, injuries and/or strokes. This demonstrates the positive application of research in this area to help improve the cognitive functions of people suffering from injuries.

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Possible Exam Questions 1. Explain what is meant by the term plasticity. (2 marks)

2. Briefly explain how split-brain patients could be examined in an experiment. (4

marks) 3. Briefly explain what split-brain research has shown. (4 marks) 4. Outline evidence in relation to brain plasticity. (4 marks)

5. Outline evidence in relation to functional recovery. (4 marks) 6. Evaluate research using split-brain patients to investigate hemispheric

lateralisation of function. (4 marks) 7. David is fourteen years old. Last year, he was hit by a bus when walking to school

and suffered from serious head injuries. While David made a full physical recovery, he has problems with his speech and comprehension of language. However, after one year, David had recovered nearly all of his language abilities. Use your knowledge of functional recovery and plasticity to explain David’s recovery. (4 marks)

8. Joseph suffered a stroke when he was 45-years-old. He could move his left arm and

leg but was paralysed down his right side. While Joseph could understand what was said to him, he was unable to speak. Referring to Joseph, discuss hemispheric lateralisation of language centres in the brain. (16 marks).

9. Describe and evaluate what research has shown about localisation of function in

the brain. (16 marks)

10. Describe and evaluate research into lateralisation and/or the split brain (16 marks).

11. Discuss evidence for plasticity and/or functional recovery after trauma. (16 marks) SA

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STUDYING THE BRAIN Specification: Ways of studying the brain: scanning techniques, including functional magnetic resonance imaging (fMRI); electroencephalogram (EEGs) and event-related potentials (ERPs); post-mortem examinations. WHAT YOU NEED TO KNOW 1. Outline and evaluate fMRI as a way of studying the brain 2. Outline and evaluate EEG & ERP as a way of studying the brain 3. Outline and evaluate post-mortem examinations as a way of studying the brain 4. Compare the different ways of studying the brain

KEY TERMS DEFINITIONS Functional Magnetic Resonance Imaging (fMRI)

Functional magnetic resonance imaging (fMRI) is a brain-scanning technique that measures blood flow in the brain when a person performs a task. fMRI works on the premise that neurons in the brain which are the most active (during a task), use the most energy. An fMRI creates a dynamic (moving) 3D map of the brain, highlighting which areas are involved in different neural activities.

Electroencephalogram (EEGs)

An electroencephalogram (EEG) works on the premise that information is processed in the brain as electrical activity in the form of action potentials or nerve impulses, transmitted along neurons. EEG ners measure this electrical activity through electrodes attached to the scalp. Small electrical charges that are detected by the electrodes are graphed over a period of time, indicating the level of activity in the brain.

Event-Related Potentials (ERPs)

Event-Related Potentials (ERP) use similar equipment to EEG, i.e. electrodes attached to the scalp. However, the key difference is that a stimulus is presented to a participant (for example a picture/sound) and the researcher looks for activity related to that stimulus.

Post-Mortem Examination A post-mortem examination is when researchers study the physical brain of a person who displayed a particular behaviour while they were alive that suggested possible brain damage. An example of this technique is the work of Broca, who examined the brain of a man who displayed speech problems when he was alive. It was subsequently discovered that he had a lesion in the area of the brain important for speech production. This area later became known as Broca’s area.

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Introduction – Studying the Brain Studying the brain allows psychologists to gain important insights into the underlying foundations of our behaviour and mental processes. A range of methods are available that involve scanning the living brain, and looking at patterns of electrical activity. However, a post-mortem examination is another possible approach. 1. Functional Magnetic Resonance Imaging (fMRI)

Functional magnetic resonance imaging (fMRI) is a brain-scanning technique that measures blood flow in the brain when a person performs a task. fMRI works on the premise that neurons in the brain that are the most active during a task use the most energy. Energy requires glucose and oxygen. Oxygen is carried in the bloodstream attached to haemoglobin (found in red blood cells) and is released for use by

these active neurons, at which point the haemoglobin becomes deoxygenated. Deoxygenated haemoglobin has a different magnetic quality from oxygenated haemoglobin. An fMRI can detect these different magnetic qualities and can be used to create a dynamic (moving) 3D map of the brain, highlighting which areas are involved in different neural activities. fMRI images show activity approximately 1-4 seconds after it occurs and are thought to be accurate within 1-2 mm. An increase in blood flow is a response to the need for more oxygen in that area of the brain when it becomes active, suggesting an increase in neural activity. Evaluation of fMRI Invasive or Non-Invasive: An advantage of fMRI is that is non-invasive. Unlike

other scanning techniques, for example Positron Emission Tomography (PET), fMRI does not use radiation or involve inserting instruments directly into the brain, and is therefore virtually risk-free. Consequently, this should allow more patients/participants to undertake fMRI scans which could help psychologists to gather further data on the functioning human brain and therefore develop our understanding of localisation of function.

Spatial Resolution: fMRI scans have good spatial resolution. Spatial resolution

refers to the smallest feature (or measurement) that a scanner can detect, and is an important feature of brain scanning techniques. Greater spatial resolution allows psychologists to discriminate between different brain regions with greater accuracy. fMRI scans have a spatial resolution of approximately 1-2 mm which is significantly greater than the other techniques (EEG, ERP, etc.) Consequently,

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psychologists can determine the activity of different brain regions with greater accuracy when using fMRI, in comparison to when using EEG and/or ERP.

Temporal Resolution: fMRI scans have poor temporal resolution. Temporal

resolution refers to the accuracy of the scanner in relation of time: or how quickly the scanner can detect changes in brain activity. fMRI scans have a temporal resolution of 1-4 seconds which is worse than other techniques (e.g. EEG/ERP which have a temporal resolution of 1-10 milliseconds). Consequently, psychologists are unable to predict with a high degree of accuracy the onset of brain activity.

Causation: fMRI scans do not provide a direct measure of neural activity. fMRI

scans simply measure changes in blood flow and therefore it is impossible to infer causation (at a neural level). While any change in blood flow may indicate activity within a certain brain area, psychologists are unable to conclude whether this brain region is associated with a particular function.

o In addition, some psychologists argue that fMRI scans can only show localisation of function within a particular area of the brain, but are limited in showing the communication that takes place among the different areas of the brain, which might be critical to neural functioning.

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2. Electroencephalogram & Event-Related Potentials Electroencephalogram (EEG) An electroencephalogram (EEG) works on the premise that information is processed in the brain as electrical activity in the form of action potentials or nerve impulses, transmitted along neurons. EEG scanners measure this electrical activity through electrodes attached to the scalp. Small electrical charges detected by the electrodes are graphed over a period of time, indicating the level of activity in the brain. There are four types of EEG patterns including alpha waves, beta waves, theta waves and delta waves. Each of these patterns has two basic properties that psychologists can examine:

1. Amplitude: the intensity or size of the activity 2. Frequency: the speed or quantity of activity

Also, EEG patterns produce two distinctive states: synchronised and desynchronized patterns. A synchronised pattern is where a recognised waveform (alpha, beta, delta and theta) can be detected, whereas a desynchronized is where no pattern can be detected. Fast desynchronized patterns are usually found when awake and synchronised patterns are typically found during sleep (alpha waves are associated with light sleep, and theta/delta waves are associated with deep sleep). Furthermore, EEG scanning was responsible for developing our understanding of REM (dream) sleep, which is associated with a fast, desynchronized activity, indicative of dreaming. EEG can also be used to detect illnesses like epilepsy and sleep disorders, and to diagnose other disorders that affect brain activity, like Alzheimer’s disease. Event-Related Potentials (ERP) Event-Related Potentials (ERP) use similar equipment to EEG, electrodes attached to the scalp. However, the key difference is that a stimulus is presented to a participant (for example a picture/sound) and the researcher looks for activity related to that stimulus. However, as ERPs are difficult to separate from all of the background EEG data, the stimulus is present many times (usually hundreds), and an average response is graphed. This procedure, which is called ‘averaging’, reduces any extraneous neural activity which makes the specific response to the stimulus stand out. The time or interval between the presentation of the stimulus and the response is referred to as latency. ERPs have a very short latency and can be divided into two broad categories. Waves (responses) that occur within 100 milliseconds following the presentation of a stimulus are referred to as sensory ERPs, as they reflect a

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sensory response to the stimulus. ERPs that occur after 100 milliseconds are referred to as cognitive ERPs, as they demonstrate some information processing. Evaluation of EEG & ERP Invasive or Non-Invasive: An advantage of EEG and ERP is that both techniques are

non-invasive. Unlike other scanning techniques, such as Positron Emission Tomography (PET), EEG and ERP do not use radiation or involve inserting instruments directly into the brain and are therefore virtually risk-free. Furthermore, EEG and ERP are much cheaper techniques in comparison with fMRI scanning and are therefore more readily available. Consequently, this should allow more patients/participants to undertake EEG/ERPs, which could help psychologists to gather further data on the functioning human brain and therefore develop our understanding of different psychological phenomena, such as sleeping, and different disorders like Alzheimer's.

Spatial Resolution: However, one disadvantage of EEG/ERP is that these

techniques have poor spatial resolution. Spatial resolution refers to the smallest feature (or measurement) that a scanner can detect, and is an important feature of brain scanning techniques. Greater spatial resolution allows psychologists to discriminate between different brain regions with greater accuracy. EEGs/ERPs only detect the activity in superficial regions of the brain. Consequently, EEGs and ERPs are unable to provide information on what is happening in the deeper regions of the brain (such as the hypothalamus), making this technique limited in comparison to the fMRI, which has a spatial resolution of 1-2mm.

Temporal Resolution: An advantage of the EEG/ERP technique is that it has

good temporal resolution: it takes readings every millisecond, meaning it can record the brain’s activity in real time as opposed to looking at a passive brain. This leads to an accurate measurement of electrical activity when undertaking a specific task.

o However, it could be argued that EEG/ERP is uncomfortable for the participant, as electrodes are attached to the scalp. This could result in unrepresentative readings as the patient’s discomfort may be affecting cognitive responses to situations. fMRI scans, on the other hand, are less invasive and would not cause the participants any discomfort, leading to potentially more accurate recordings.

EEG: Another issue with EEG is that electrical activity is often detected in

several regions of the brain simultaneously. Consequently, it can be difficult pinpoint the exact area/region of activity, making it difficult for researchers to draw accurate conclusions.

ERP: However, ERPs enable the determination of how processing is affected by

a specific experimental manipulation. This makes ERP use a more experimentally robust method as it can eliminate extraneous neutral activity, something that other scanning techniques (and EEG) may struggle to do.

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3. Post-Mortem Examination The final method of investigating the brain is post-mortem examination, where researchers will study the physical brain of a person who displayed a particular behaviour while they were alive that suggested possible brain damage. An example of this technique is the work of Broca, who examined the brain of a man who displayed speech problems when he was alive. It was subsequently discovered that he had a lesion in the area of the brain important for speech production. This later became known as Broca’s area. Similarly, Wernicke discovered a region in the left temporal lobe, which is important for language comprehension and processing, which is now known as Wernicke’s area. This method of investigation has successfully contributed to the understanding of many disorders. Iverson examined the brains of deceased schizophrenic patients and found that they all had a higher concentration of dopamine, especially in the limbic system, compared with brains of people without schizophrenia, highlighting the importance of such investigations. Furthermore, post-mortem studies allow for a more detailed examination of anatomical and neurochemical aspects of the brain than would be possible with other techniques. They also enable researchers to examine deeper regions of the brain such as the hypothalamus and hippocampus, something that is not as easy with other methods of investigation. Evaluation of Post-Mortem Examination Causation: One of the main limitations of post-mortem examination is the issue of

causation. The deficit a patient displays during their lifetime (e.g. an inability to speak) may not be linked to the deficits found in the brain (e.g. a damaged Broca’s area). The deficits reported could have been the result of another illness, and therefore psychologists are unable to conclude that the deficit is caused by the damage found in the brain.

o In additional, another issue is that there are many extraneous factors that can affect the results/conclusions of post-mortem examinations. For example, people die at different stages of their life and for a variety of different reasons. Furthermore, any medication a person may have been taking, their age, and the length of time between death and post-mortem examination, are all confounding factors that make the conclusions of such research questionable.

However, one strength of post-mortem examinations is that they provide a

detailed examination of the anatomical structure and neurochemical aspects of

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the brain that is not possible with other scanning techniques (e.g. EEG, ERP and fMRI). Post-mortem examinations can access areas like the hypothalamus and hippocampus, which other scanning techniques cannot, and therefore provide researchers with an insight into these deeper brain regions, which often provide a useful basis for further research. For example, Iverson found a higher concentration of dopamine in the limbic system of patients with schizophrenia which has prompted a whole area of research looking into the neural correlates of this disorder.

While post-mortem examinations are ‘invasive’, this is not an issue because the

patient is dead. However, there are ethical issues in relation to informed consent and whether or not a patient provides consent before his/her death. Furthermore, many post-mortem examinations are carried out on patients with severe psychological deficits (e.g. patient HM who suffered from severe amnesia) who would be unable to provide fully informed consent, and yet a post-mortem examination has been conducted on his brain. This raises severe ethical questions surrounding the nature of such investigations.

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4. Compare Ways of Studying the Brain

TECH

NIQ

UE

OUTLINE

INVA

SIVE

OR

NO

N-IN

VASI

VE

TEM

PORA

L RE

SOLU

TIO

N

SPAT

IAL

RESO

LUTI

ON

fMRI

fMRI measures blood flow when a person performs a task and creates a dynamic (moving) 3D map of the brain, highlighting which areas are involved in different neural activities.

Non-Invasive 1-4 s 1-2 mm

EEG

EEG measures electrical activity through electrodes attached to the scalp. Small electrical charges are detected by the electrodes that are graphed over a period of time, indicating the level of activity in the brain.

Non-Invasive (although

uncomfortable)

1-10 ms

Superficial general

regions only

ERP

ERP uses similar equipment to EEG. However, the key difference is that a stimulus is presented to a participant and the researcher looks for activity related to that stimulus.

Non-Invasive (although

uncomfortable)

1-10 ms

Superficial general

regions only

Post

-Mor

tem

Ex

amin

atio

n A post-mortem examination is when researchers study the physical brain of a person who displayed a particular behaviour while they were alive that suggested possible brain damage.

N/A (Invasive - although the person is no longer alive)

N/A N/A

Exam Hint: Questions 9 and 10 in the possible exam questions section are tricky, as they require you to compare/contrast different ways of studying the brain. The table above can help you find the similarities and differences between the different techniques.

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Possible Exam Questions 1. Short Answer: Outline fMRI as a way of studying the brain. (4 marks) 2. Short Answer: Outline EEGs as a way of studying the brain. (4 marks) 3. Short Answer: Outline ERPs as a way of studying the brain. (4 marks) 4. Short Answer: Outline post-mortem examinations as a way of studying the brain.

(4 marks) 5. Short Answer: Outline one strength and one limitation of fMRI. (6 marks) 6. Short Answer: Outline one strength and one limitation of EEGs. (6 marks) 7. Short Answer: Outline one strength and one limitation of ERPs. (6 marks) 8. Short Answer: Outline one strength and one limitation of post-mortem

examinations. (6 marks) 9. Short Answer: Outline one difference between EEG and ERP (2 marks) 10. Short Answer: Outline one difference between fMRI and EEG. (2 marks) 11. Essay: Discuss ways of studying the brain. (16 marks)

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BIOLOGICAL RHYTHMS Specification: Biological rhythms: circadian, infradian and ultradian and the difference between these rhythms. The effect of endogenous pacemakers and exogenous zeitgebers on the sleep/wake cycle. WHAT YOU NEED TO KNOW 1. Outline examples of, and evaluate circadian rhythms, with research support. 2. Outline examples of, and evaluate the role of endogenous pacemakers and

exogenous zeitgebers. 3. Outline examples of, and evaluate infradian and/or ultradian rhythms

KEY TERMS DEFINITIONS

Biological Rhythms

Biological rhythms are cyclical patterns within biological systems that have evolved in response to environmental influences, e.g. day and night. There are two key factors that govern biological rhythms: endogenous pacemakers (internal), the body’s biological clocks, and exogenous zeitgebers (external), which are changes in the environment.

Circadian

One biological rhythm is the 24-hour circadian rhythm (often known as the ‘body clock’), which is reset by levels of light. The word circadian is from the Latin ‘circa’ which means ‘about’, and ‘dian’, which means ‘day’. Examples of circadian rhythms include the sleep-wave cycle and body temperature.

Infradian

Another important biological rhythm is infradian rhythms, which last longer than 24 hours and can be weekly, monthly or annually. A monthly infradian rhythm is the female menstrual cycle, which is regulated by hormones that either promote ovulation or stimulate the uterus for fertilisation.

Ultradian

Ultradian rhythms last less than 24 hours and can be found in the pattern of human sleep. This cycle alternates between REM (rapid eye movement) and NREM (non-rapid movement) sleep and consists of five stages. The cycle starts at light sleep, progressing to deep sleep and then into REM sleep, where brain waves speed up and dreaming occurs. This repeats itself about every 90 minutes throughout the night and a person can experience up to five complete sleep cycles each night.

Endogenous Pacemakers

Endogenous pacemakers are internal mechanisms that govern biological rhythms, in particular the circadian sleep/wake cycle. Although endogenous pacemakers are internal biological clocks, they can be altered and affected by the environment. The most important

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endogenous pacemaker is the suprachiasmatic nucleus, which is closely linked to the pineal gland, both of which are influential in maintaining the circadian sleep-wake cycle.

Exogenous Zeitgebers

Exogenous zeitgebers influence biological rhythms. These can be described as environmental events that are responsible for resetting the biological clock of an organism. They can include social cues, such as meal times and social activities, but the most important zeitgeber is light, which is responsible for resetting the body clock each day, keeping it on a 24-hour cycle.

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Introduction Biological rhythms are cyclical patterns within biological systems that have evolved in response to environmental influences, e.g. day and night. There are two key factors that govern biological rhythms: endogenous pacemakers (internal factors), the body’s biological clocks, and exogenous zeitgebers (external factors), which are changes in the environment. Exam Hint: For each of the biological rhythms (circadian, infradian and ultradian) it is important you that you can define the term and provide at least one example. 1. Circadian Rhythms One biological rhythm is the 24-hour circadian rhythm (often known as the ‘body clock’), which is reset by levels of light. The word circadian is from the Latin ‘circa’ which means ‘about’, and ‘dian’, which means ‘day’. The sleep-wake cycle is an example of a circadian rhythm, which dictates when humans and animals should be asleep and awake. Light provides the primary input to this system, acting as the external cue for sleeping or waking. Light is first detected by the eye, which then sends messages concerning the level of brightness to the suprachiasmatic nuclei (SCN). The SCN then uses this information to coordinate the activity of the entire circadian system. Sleeping and wakefulness are not determined by the circadian rhythm alone, but also by homoeostasis. When an individual has been awake for a long time, homeostasis tells the body that there is a need for sleep because of energy consumption. This homeostatic drive for sleep increases throughout the day, reaching its maximum in the late evening, when most people fall asleep. Body temperature is another circadian rhythm. Human body temperature is at its lowest in the early hours of the morning (36oC at 4:30 am) and at its highest in the early evening (38oC at 6 pm). Sleep typically occurs when the core temperature starts to drop, and the body temperature starts to rise towards the end of a sleep cycle promoting feelings of alertness first thing in the morning. Evaluating Circadian Rhythms Research Support: Research has been conducted to investigate circadian

rhythms and the effect of external cues like light on this system. Siffre (1975) found that the absence of external cues significantly altered his circadian rhythm: When he returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was. This suggests that his 24-hour sleep-wake cycle was increased by the lack of external cues, making him believe one day was longer than it was, and leading to his thinking that fewer days had passed.

o Siffre’s case study has been the subject of criticism. As the researcher and sole participant in his case study, there are severe issues with generalisability. However, further research by Aschoff & Weber (1962) provides additional support for Siffre’s findings. Aschoff & Weber

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studied participants living in a bunker. The bunker had no windows and only artificial light, which the participants were free to turn on and off as they pleased. Aschoff & Weber found that the participants settled into a longer sleep/wake cycle of between 25-27 hours. These results, along with Siffre’s findings, suggest that humans use natural light (exogenous zeitgebers) to regulate a 24-hour circadian sleep-wake cycle, demonstrating the importance of light for this circadian rhythm.

Individual Differences: However, it is important to note the differences between

individuals when it comes to circadian cycles. Duffy et al. (2001) found that ‘morning people’ prefer to rise and go to bed early (about 6 am and 10 pm) whereas ‘evening people’ prefer to wake and go to bed later (about 10 am and 1 am). This demonstrates that there may be innate individual differences in circadian rhythms, which suggests that researchers should focus on these differences during investigations.

Additionally, it has been suggested that temperature may be more important than

light in determining circadian rhythms. Buhr et al. (2010) found that fluctuations in temperature set the timing of cells in the body and caused tissues and organs to become active or inactive. Buhr claimed that information about light levels is transformed into neural messages that set the body’s temperature. Body temperature fluctuates on a 24-hour circadian rhythm and even small changes in it can send a powerful signal to our body clocks. This shows that circadian rhythms are controlled and affected by several different factors, and suggests that a more holistic approach to research might be preferable.

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2. Endogenous Pacemakers & Exogenous Zeitgebers Biological rhythms are regulated by endogenous pacemakers, which are the body’s internal biological clocks, and exogenous zeitgebers, which are external cues, including light, that help to regulate the internal biological clocks. Exam Hint: It’s important to note that endogenous pacemakers and exogenous zeitgebers interact with one another to control and fine-tune biological rhythms and therefore it is necessary to consider these concepts together. Endogenous Pacemakers Endogenous pacemakers are internal mechanisms that govern biological rhythms, in particular, the circadian sleep-wake cycle. Although endogenous pacemakers are internal biological clocks, they can be altered and affected by the environment. For example, although the circadian sleep-wave cycle will continue to function without natural cues from light, research suggests that light is required to reset the cycle every 24 hours. (See Siffre and Aschoff & Weber, above) The most important endogenous pacemaker is the suprachiasmatic nucleus, which is closely linked to the pineal gland, both of which are influential in maintaining the circadian sleep/wake cycle. The suprachiasmatic nucleus (SCN), which lies in the hypothalamus, is the main endogenous pacemaker (or master clock). It controls other biological rhythms, as it links to other areas of the brain responsible for sleep and arousal. The SCN also receives information about light levels (an exogenous zeitgeber) from the optic nerve, which sets the circadian rhythm so that it is in synchronisation with the outside world, e.g. day and night. The SNC sends signals to the pineal gland, which leads to an increase in the production of melatonin at night, helping to induce sleep. The SCN and pineal glands work together as endogenous pacemakers; however, their activity is responsive to the external cue of light. Put simply:

Exogenous Zeitgebers As outlined above, exogenous zeitgebers influence biological rhythms: these can be described as environmental events that are responsible for resetting the biological clock of an organism. They can include social cues such as meal times and social activities, but the most important zeitgeber is light, which is responsible for resetting the body clock each day, keeping it on a 24-hour cycle. The SNC contains receptors that are sensitive to light and this external cue is used to synchronise the body’s internal organs and glands. Melanopsin, which is a protein in

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the eye, is sensitive to light and carries the signals to the SCN to set the 24-hour daily body cycle. In addition, social cues, such as mealtimes, can also act as zeitgebers and humans can compensate for the lack of natural light, by using social cues instead. Evaluating Endogenous Pacemakers & Exogenous Zeitgebers The importance of the SCN has been demonstrated in research. Morgan (1955)

bred hamsters so that they had circadian rhythms of 20 hours rather than 24. SCN neurons from these abnormal hamsters were transplanted into the brains of normal hamsters, which subsequently displayed the same abnormal circadian rhythm of 20 hours, showing that the transplanted SCN had imposed its pattern onto the hamsters. This research demonstrates the significance of the SCN and how endogenous pacemakers are important for biological circadian rhythms.

o However, this research is flawed because of its use of hamsters. Humans would respond very differently to manipulations of their biological rhythms, not only because we are different biologically, but also because of the vast differences between environmental contexts. This makes research carried out on other animals unable to explain the role of endogenous pacemakers in the biological processes of humans.

There is research support for the role of melanopsin. Skene and Arendt (2007)

claimed that the majority of blind people who still have some light perception have normal circadian rhythms whereas those without any light perception show abnormal circadian rhythms. This demonstrates the importance of exogenous zeitgebers as a biological mechanism and their impact on biological circadian rhythms.

There is further research support for the role of exogenous zeitgebers. When Siffre

(see above) returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was. This suggests that his 24-hour sleep-wake cycle was increased by the lack of external cues, making him believe one day was longer than it was. This highlights the impact of external factors on bodily rhythms.

Despite all the research support for the role of endogenous pacemakers and

exogenous zeitgebers, the argument could still be considered biologically reductionist. For example, the behaviourist approach would suggest that bodily rhythms are influenced by other people and social norms, i.e. sleep occurs when it is dark because that is the social norm and it wouldn’t be socially acceptable for a person to conduct their daily routines during the night. The research discussed here could be criticised for being reductionist as it only considers a singular biological mechanism and fails to consider the other widely divergent viewpoints.

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3. Infradian Rhythms & Ultradian Rhythms Infradian Rhythms Another important biological rhythm is the infradian rhythm. Infradian rhythms last longer than 24 hours and can be weekly, monthly or annually. A monthly infradian rhythm is the female menstrual cycle, which is regulated by hormones that either promote ovulation or stimulate the uterus for fertilisation. Ovulation occurs roughly halfway through the cycle when oestrogen levels are at their highest, and usually lasts for 16-32 hours. After the ovulatory phase, progesterone levels increase in preparation for the possible implantation of an embryo in the uterus. It is also important to note that although the usual menstrual cycle is around 28 days, there is considerable variation, with some women experiencing a short cycle of 23 days and others experiencing longer cycles of up to 36 days. Extension: A second example of an infradian rhythm is related to the seasons. Research has found seasonal variation in mood, where some people become depressed in the winter, which is known as seasonal affective disorder (SAD). SAD is an infradian rhythm that is governed by a yearly cycle. Psychologists claim that melatonin, which is secreted by the pineal gland during the night, is partly responsible. The lack of light during the winter months results in a longer period of melatonin secretion, which has been linked to the depressive symptoms. Exam Hint: While it is logical to assume that infradian rhythms, in particular the menstrual cycle, are governed by internal factors (endogenous pacemakers) such as hormonal changes, research suggests that these infradian rhythms are heavily influenced by exogenous zeitgebers. Evaluating Infradian Rhythms Research suggests that the menstrual cycle is, to some extent, governed

by exogenous zeitgebers (external factors). Reinberg (1967) examined a woman who spent three months in a cave with only a small lamp to provide light. Reinberg noted that her menstrual cycle shortened from the usual 28 days to 25.7 days. This result suggests that the lack of light (an exogenous zeitgeber) in the cave affected her menstrual cycle, and therefore this demonstrates the effect of external factors on infradian rhythms.

There is further evidence to suggest that exogenous zeitgebers can affect

infradian rhythms. Russell et al. (1980) found that female menstrual cycles became synchronised with other females through odour exposure.

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In one study, sweat samples from one group of women were rubbed onto the upper lip of another group. Despite the fact that the two groups were separate, their menstrual cycles synchronised. This suggests that the synchronisation of menstrual cycles can be affected by pheromones, which have an effect on people nearby rather than on the person producing them. These findings indicate that external factors must be taken into consideration when investigating infradian rhythms and that perhaps a more holistic approach should be taken, as opposed to a reductionist approach that considers only endogenous influences.

o Evolutionary psychologists claim that the synchronised menstrual cycle provides an evolutionary advantage for groups of women, as the synchronisation of pregnancies means that childcare can be shared among multiple mothers who have children at the same time.

There is research to suggest that infradian rhythms such as the menstrual

cycle are also important regulators of behaviour. Penton-Volk et al. (1999) found that woman expressed a preference for feminised faces at the least fertile stage of their menstrual cycle, and for a more masculine face at their most fertile point. These findings indicate that women’s sexual behaviour is motivated by their infradian rhythms, highlighting the importance of studying infradian rhythms in relation to human behaviour.

Finally, evidence supports the role of melatonin in SAD. Terman (1988) found that the rate of SAD is more common in Northern countries where the winter nights are longer. For example, Terman found that SAD affects roughly 10% of people living in New Hampshire (a northern part of the US) and only 2% of residents in southern Florida. These results suggest that SAD is in part affected by light (exogenous zeitgeber) that results in increased levels of melatonin.

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Ultradian Rhythms Ultradian rhythms last fewer than 24 hours and can be found in the pattern of human sleep. This cycle alternates between REM (rapid eye movement) and NREM (non-rapid movement) sleep and consists of five stages. The cycle starts at light sleep, progressing to deep sleep and then REM sleep, where brain waves speed up and dreaming occurs. This repeats itself about every 90 minutes throughout the night. A complete sleep cycle goes through the four stages of NREM sleep before entering REM (Stage 5) and then repeating. Research using EEG has highlighted distinct brain waves patterns during the different stages of sleep.

1. Stages 1 and 2 are ‘light sleep’ stages. During these stages brainwave patterns become slower and more rhythmic, starting with alpha waves progress to theta waves.

2. Stages 3 and 4 are ‘deep sleep’ or slow wave sleep stages, where it is difficult to wake someone up. This stage is associated with slower delta waves.

3. Finally, Stage 5 is REM (or dream) sleep. Here is the body is paralysed (to stop the person acting out their dream) and brain activity resembles that of an awake person.

On average, the entire cycle repeats every 90 minutes and a person can experience up to five full cycles in a night. Exam Hint: When providing an example of an ultradian rhythm, answers should explicitly mention that the cycle occurs more than once every 24 hours. Furthermore, specific details in relation to the distinctive characteristics of the different stages are required to demonstrate understanding.

Extension: Another ultradian rhythm is appetite or meal patterns in humans. Most humans eat three meals a day and appetite rises and falls because of food consumption.

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Evaluating Ultradian Rhythms Individual Differences: The problem with studying sleep cycles is the

differences observed in people, which make investigating patterns difficult. Tucker et al. (2007) found significant differences between participants in terms of the duration of each stage, particularly stages 3 and 4 (just before REM sleep). This demonstrates that there may be innate individual differences in ultradian rhythms, which means that it is worth focusing on these differences during investigations into sleep cycles.

o In addition, this study was carried out in a controlled lab setting, which meant that the differences in the sleep patterns could not be attributed to situational factors, but only to biological differences between participants. While this study provide convincing support for the role of innate biological factors and ultradian rhythms, psychologists should examine other situational factors that may also play a role.

Additionally, the way in which such research is conducted may tell us little

about ultradian rhythms in humans. When investigating sleep patterns, participants must be subjected to a specific level of control and be attached to monitors that measure such rhythms. This may be invasive for the participant, leading them to sleep in a way that does not represent their ordinary sleep cycle. This makes investigating ultradian rhythms, such as the sleep cycle, extremely difficult as their lack of ecological validity could lead to false conclusions being drawn.

An interesting case study indicates the flexibility of ultradian rhythms. Randy

Gardener remained awake for 264 hours. While he experienced numerous problems such as blurred vision and disorganised speech, he coped rather well with the massive sleep loss. After this experience, Randy slept for just 15 hours and over several nights he recovered only 25% of his lost sleep. Interestingly, he recovered 70% of Stage 4 sleep, 50% of his REM sleep, and very little of the other stages. These results highlight the large degree of flexibility in terms of the different stages within the sleep cycle and the variable nature of this ultradian rhythm.

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Possible Exam Questions 1. Short Answer Question: Outline one or more examples of circadian rhythms. (4

marks) 2. Short Answer Question: Outline one or more examples of ultradian rhythms. (4

marks) Exam Hint: Students often lose marks on short answer questions by not focusing their response. The most accessible example for this question is the alternation between NREM and REM sleep. However, top mark answers need to provide details of this alternation, including the number of episodes per night and the distinctive characteristics of each stage. Another example could include meal patterns in humans. Some students confuse ultradian and infradian rhythms and claim that temperature and the sleep/wake cycle is an example of ultradian, which is incorrect. 3. Short Answer Question: Outline one or more examples of infradian rhythms. (4

marks) 4. Short Answer Question: Outline what research into circadian rhythms has found.

(4 marks) 5. Short Answer Question: Outline what research into ultradian/infradian rhythms

has found. (4 marks)

6. Short Answer Question: What is meant by the terms endogenous pacemakers and exogenous zeitgebers. (4 marks)

7. Application: John is an electrician and has just started a new job where he works

shifts. He works 4 day shifts, then has 4 days off, and then works 4 night shifts. After working night shifts, John finds it difficult to sleep during the day and becomes very frustrated. Using your knowledge of endogenous pacemakers and exogenous zeitgebers, explain John’s experiences. (4 marks)

8. Essay: Outline and evaluate circadian rhythms. (16 marks)

9. Essay: Outline and evaluate infradian and/or ultradian rhythms. (16 marks) 10. Essay: Discuss research into the disruption of biological rhythms. (16 marks) Exam Hint: You can answer this question by considering the effects of shift work on mood, physical illness and productivity; the beneficial effects of altering shift work patterns; and the effects of jet lag on physical health. 11. Essay: Discuss the consequences of disrupting biological rhythms. (16 marks) Exam Hint: While this question may appear similar to the above, the focus of this question needs to be on ‘the consequences’ of disruption and not just a descriptive outline of the research.

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12. Essay: Outline and evaluate the effect of endogenous pacemakers and exogenous zeitgebers on the sleep-wake cycle. (16 marks)

Extension: Disruption of Biological Rhythms One of the more difficult sample questions is to discuss the consequences of disrupting biological rhythms and this section will focus on a different area that examines the disruption in the sleep-wake cycle for people who work at night (shift workers). People who work at night (shift work) often experience symptoms similar to jet lag. This is because the person’s work schedule (exogenous zeitgeber) is at odds with their circadian sleep-wave cycle, which is governed by powerful biological factors (endogenous pacemakers). Not surprisingly, people who work shift work often feel sleepy at work and suffer from insomnia at home. There are numerous consequences for people who work shifts, including: Sleep Deprivation: People who work at night and have to sleep during the day

often experience difficulties in sleeping. This is because their biological clocks (endogenous pacemakers) do not adjust completely. Furthermore, the daytime is associated with significantly more noise and other disturbances that can also affect sleep.

o Research suggests that daytime sleep is shorter than night-time sleep. Tilley and Wilkinson (1982) suggest that REM is particularly affected and this reduction in sleep results in sleep deprivation, which produces lower levels of energy and reduces alertness during the night time (awake period).

Heart Disease: There is a relationship between shift work and heart disease.

o Knutsson (1986) found that people who worked shift patterns for more than 15 years were significantly more likely to develop heart disease. This research highlights the negative health consequences of disrupting biological rhythms, in particular the sleep-wake cycle. However, it is worth noting that these findings are purely correlational and while the findings might indicate a link between the disruption of biological rhythms and heart disease, other factors may also play a significant role. For example, it may be that jobs that require night time working are inherently more stressful and it is the stress that is the major factor and not the shift work.

Social Consequences: Another issue that people who work shift patterns

experience is social disruption. People who work hours that are at odds with the hours worked by their family and friends find it difficult to spend quality time with significant others.

Practical Applications: While the research above highlights a series of negative

consequences associated with disrupting biological rhythms, Czeisler et al. (1982) used research on shift work to improve the health and performance of shift workers. They found that by using a phase system to make shift changes slower, workers reported increased satisfaction and increase productivity. This suggests

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that the negative impact of disrupting biological rhythms can be overcome by slowly introduce people to night work.

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