The Brain

How is the Brain studied?

CASE STUDIES•Study patients w/ brain damage (case studies)

LESION METHOD•damaging an animal’s brain and observing

EEG• Electroencephalogram • uses Electrodes • measures brain waves• Needle electrodes (this wires inserted into brain)

• Microelectrodes (can fit into one single cell)

MRI• magnetic resonance imaging• uses magnetic fields to produce

vibrations in the center of atoms • these are then picked up by special

receivers. • A computer then analyzes the

signals.

GREAT TECHNOLOGY

BUT WHAT DOES IT REALLY TELL

US?

•Only where things are happening. Still much to be learned.

Joseph Gall –•Phrenology •parts of brain serving different functions

• ideas totally wrong•But concept is valid

Localization of function

•particular functions for certain parts of the brain

BRAIN STEM•Located at base of the skull

•Two main structures include:

Brain Stem (in yellow & green)

Reticular activating system (RAS)

BRAIN STEM• Pons—sleeping, waking, &

dreaming (& other things)• Medulla—breathing & heart

rate & other things not consciously controlled {medulla is severed in hangings}

BRAIN STEM• Reticular Activating System

(RAS)—screens info, demands that things get done, connects with higher areas, (could not be alert w/o RAS)

CEREBELLUM•On top of brain stem

•Controls balance or coordination (may have other functions too)

cerebellum (in yellow)

Reticular activating system (RAS)

LIMBIC SYSTEM•Group of brain areas which are involved in emotional reactions & behavior

Limbic System

Reticular activating system (RAS)

THALAMUS• Deep in the

interior• traffic officer of

the brain• relays motor

impulses from higher centers to spinal cord

THALAMUS• relays sensory

messages to higher centers

• smell is only sense that by passes thalamus

HYPOTHALAMUS• & PITUITARY

GLAND

• located under the thalamus

• regulates drives in the human body (thirst, hunger, sex, body temperature, sweating, etc)

HYPOTHALAMUS• pituitary gland hangs from hypothalamus

• master gland

• secretes hormones (which send messages)

Amygdala• evaluates sensory

information• helps mediate

depression & anxiety (PET scans show high activity here in depressed people)

Hippocampus• looks like a seahorse

• compares sensory info with what the brain has learned to expect about the world (when something is familiar it does not get activated, but the unknown stimulates it—example, one cant’ get excited everytime a car goes by)

Hippocampus• Gateway to

memory (helps brain store info)

• Example H.M. had it removed and could no longer remember new info (old stuff he could)

CEREBRUM• Looks like cauliflower

• higher order activity takes place here

• contains two cerebral hemispheres

• connected by the corpus callosum

Cerebral Cortex• protects the cerebrum

• thin layers of dense cells75% of all brain cells are in cortex

• crimpled look provides enough room for all cells (without having giant heads)

Lobes of the Cortex

Occipital lobes• lower back of brain

• receive visual info

Frontal Lobe

Temporal Lobe

Parietal Lobe

Occipital Lobe

Parietal lobes• top of the brains cortex, receive info on pressure, pain,

touch, & temperature

• messages from hands & face are especially sensitive thus more signals are used for them

Frontal Lobe

Temporal Lobe

Parietal Lobe

Occipital Lobe

Temporal lobes• sides of the brains cortex (above ears), involved in

hearing, memory, perception, emotion, (language comprehension usually in left lobe)

Frontal Lobe

Temporal Lobe

Parietal Lobe

Occipital Lobe

Frontal lobes• front of brain’s cortex, short term memory, higher order

thinking, initiative, creativity, social judgment, * (speech production usually in left lobe)

Frontal Lobe

Temporal Lobe

Parietal Lobe

Occipital Lobe

Frontal lobes• motor cortex is here

• Broca’s Area (speech production)

Frontal Lobe

Temporal Lobe

Parietal Lobe

Occipital Lobe

INTERESTING FACTS ABOUT LOBES

• Bilingualism in early childhood is stored in same area (Broca’s Area),

• but if 2nd language learned later in life it is not stored here.

INTERESTING FACTS ABOUT LOBES

• If stimulated, the lobes would produce the same effects as when they receive the info from the body.

• (example, if parietal lobe stimulated you might feel tingling or mild sensation)

INTERESTING FACTS ABOUT LOBES

• But many areas are “silent” and do not do anything when stimulated

INTERESTING FACTS ABOUT LOBES

• The PREFRONTAL CORTEX appears to be what separates humans from other species. – area barely exists in mice– 3.5% in cats– 7% in dogs– 17% in chimps– but almost 30% in humans.

INTERESTING FACTS ABOUT LOBES

• Phineas Gage • (spike in head through

frontal lobes)• retains cognitive

functioning but personality changed forever.