Attention and Consciousness “Millions of items … are present to my senses which never properly enter into my experience. Why? Because they have no interest for me. My experience is what I agree to attend to … each of us literally chooses, by his ways of attending to things, what sort of a universe he shall appear to himself to inhabit”

William James, 1890, Principles of Psychology

Sensory Systems modulated by Attentional Systems

a Single Photon

a Single molecule

a Single Hair Cell--”pin drop”

What is Attention’s Goal?

Truthful perception of the world is neither required nor necessarily attempted

Conscious experiences focus on gathering information quickly

Details are filled-in to give a sense of continuity to our perceptions

This is the point of attention in general, i.e., to concentrate on what is important

A distinction between attention and consciousness

A common sense distinction between attention and consciousness:

We can ask someone to ‘please pay attention’ but not to ‘please be conscious’. In general, however, when people pay attention to something, they generally become conscious of it.

The common sense distinction between attention and consciousness suggests that there are attentional control mechanisms that often determine what will or will not become conscious …

A distinction between attention and consciousness

A common sense distinction between attention and consciousness:

We can ask someone to ‘please pay attention’ but not to ‘please be conscious’. In general, however, when people pay attention to something, they generally become conscious of it.

The common sense distinction between attention and consciousness suggests that there are attentional control mechanisms that often determine what will or will not become conscious …

Selective attention: voluntary and automatic

In the real world, voluntary and automatic attention are generally mixed. For example, we can train ourselves to pay attention to the new ringtone we found for our cell phone.

When it rings and we suddenly pay attention to it, is that voluntary or automatic?

Visual areas involved in active and passive viewing extend to the parietal lobe

Consciousness William James (1890):

Consciousness is a constantly moving stream of thoughts, feelings, and emotions

Consciousness can be viewed as our subjective awareness of mental events

Functions of consciousness: Monitoring mental events Control: consciousness allows us to formulate and

reach goals Consciousness may have evolved to direct or

control behavior in adaptive ways

Libet’s Half-second Delay

Electrically stimulated patients’ somatosensory cortices during surgery Minimum level of stimulation necessary At this intensity, ½ second of continuous

stimulation before any perception Shorter stimulation requires greater intensity

What Happens to the Lag?

Reaction times can be 200 ms, recognition can take 300-400 ms, but Libet’s delay is 500 ms… Our body responds before we are conscious

of why it is responding Subjective referral: after neuronal

adequacy is reached, the event is referred back to the point at which it occurred

Cortex and Consciousness The dorsolateral prefrontal cortex is

activated during conscious control tasks Subjects asked to name the ink color in the

Stroop task below have difficulty when the word name and color are different

This color-naming task was associated with activation of the dorsolateral prefrontal cortex

Stroop Task

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Stroop Task

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Stroop Task

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Attention Our conscious awareness is limited in capacity

and we are aware of only a small amount of the stimuli around us at any one time

Attention refers to the process by which we focus our awareness

Three functions of attentional processes: Orienting function toward the environment Control of the content of consciousness

• I will think about this issue but not that one…

Maintaining alertness

The brain basis of conscious experience

Binding features into conscious objects

The concept of feature binding -- combining color, location, shape, and the like into a single neuronal assembly -- is often necessary for visual consciousness. Treisman suggested that an attentional spotlight was required to combine different aspects of a stimulus into a reportable event.

Treisman’s spotlight for binding visual features

END of MATERIAL FOR MIDTERM

Divided Attention Divided attention refers to a

task in which a person is asked to attend to two tasks at the same time Subject may be asked to listen to

one conversation (shadowing) delivered via the left ear

Some information on the other channel (right ear) is processed (as shown in priming tasks)

Central Attention: not just sensory/perceptual

Message 1 Message 2GREEN MARKEGGS BACKFINE ANDRICE HAM

Subjects occasionally reported“green eggs and ham”

This shouldn’t happen if message 2 were completely filtered out—no central attention process..

Attention and the Brain

Michael I. Posner Two attention systems; two functions

Anterior frontal lobe system• Tasks requiring awareness (planning or writing)

Posterior parietal lobe system• Tasks involving visuospatial abilities (playing Tetris,

vigilance tasks)

Reticular Activating System RASArousal

Flow of Consciousness Day-dreams are shifts in attention

toward internal thoughts and imagined scenarios College students may spend as much as

50% of their waking time in a day-dream Beeper studies of high-school students

have noted the predominance of negative thoughts when students are with their families as opposed to others

Psychodynamic View of Consciousness

Freud argued that three mental systems form consciousness Conscious: mental events that you

are aware of Preconscious: Mental events that

can be brought into awareness Unconscious: Mental events that are

inaccessible to awareness; events are actively kept out of awareness

TOT Demonstration

Heavy, broad-bladed knife or hatchet used especially by butchers

Crystalline sugar occurring naturally in fruits, honey, etc.

The independent candidate that ran against Clinton and Bush I.

Do any of these questions put the answer on the tip of your tongue?

Subliminal Perception Notion that brief exposure to sub-threshold stimuli can

influence awareness Study: subjects are shown aggressive (A) or positive (B)

stimuli and then rate a neutral stimulus (C) Subjects shown panel A first subsequently rated the boy in

panel C more negatively

(Figure adapted from Eagle, 1959)

Unconscious Cognitive Processes Information-processing view can be extended to

analyses of unconscious processes Notion is that many brain mechanisms operate

in parallel Some of these mechanisms operate outside of the

level of consciousness Functional significance of unconscious

mechanisms: Are efficient and rapid Can operate simultaneously Operate in the absence of consciousness?

The brain basis of conscious experience

Unconscious comparisons

How can we investigate conscious experience?

Consciousness has been used a a variable, with experiments designed to compare conscious and unconscious conditions in the same experiment using the same stimuli.

Backward masking is used to compare conscious and unconscious perception. Subjects do not perceive the smiling face, but the unconscious face still primes behavior and brain activity

Blindsight People with damage to the central portion

of the occipital cortex are blind in the sense that they are unable to

see objects placed before them are able to provide partial information about

the geometric shape of an object (blindsight) Blindsight may involve a primitive visual

system in the midbrain

Neurology of Consciousness Consciousness is distributed

throughout the brain Hindbrain and midbrain are

important for arousal and for sleep

Damage to the reticular formation can lead to coma

Prefrontal cortex is key for conscious control of information processing

Sleep and Dreaming Behavioral characteristics of sleep

Minimal movement Stereotyped prone posture Require a high degree of stimulation to

arouse organism Physiological characteristics of sleep

Brain wave activity (seen in the EEG) Paralysis of muscles (seen in the EMG) Cardiovascular changes (alternating cycles

of arousal)

Species Variation in Sleep

(Figure adapted from Kripke et al., 1979)

Function of Sleep

Memory consolidation Energy conservation Preservation from predators Restoring bodily functions

Sleep deprivation can alter immune function and lead to early death

Sleep deprivation can also lead to hallucinations and perceptual disorder

EEG Stages of Sleep

(Figure adapted from Cartwright, 1978)

REM Sleep

Characteristics of REM sleep Presence of rapid-eye-movements Presence of dreaming Increased autonomic nervous system activity EEG resembles that of awake state (beta

wave) Motor paralysis (except for diaphragm)

Dreaming

Psychoanalytic view: Dreams represent a window into the unconscious The latent content (meaning) can be inferred from the

manifest content (the actual dream) Cognitive view: Dreams are constructed from the

daily issues of the dreamer Biological view: Dreams represent the attempt of

the cortex to interpret the random neural firing of the brain during sleep

Altered States of Consciousness

Changes in consciousness can be brought on by Meditation Hypnosis Drug ingestion Religious experiences

The brain basis of conscious experience

Conscious events recruit widespread brain activation

There are many sources of evidence suggesting that the more we are conscious of some event, from visual perception to motor control, the more cortical activity we are likely to find.

Results of an fMRI experiment: brain activation during a sensorimotor task where subjects were asked to tap along with the sound of a metronome. Once trained on the task, the scientists varied the pace of the metronome by 3, 7, or 20%. Cortical activity increased dramatically as a function of the unpredictability of the tapping task.

The brain basis of conscious experience

Fast cortical interactions may be needed for conscious events

It is believed that rhythmic synchrony between different brain regions may signal cooperative and competitive interactions between neuronal populations needed to perform tasks, particularly those that are conscious and under voluntary control.

A summary and some hypotheses

Selective attention to a visual stimulus seems to be guided by parts of the frontal and parietal lobes

Conscious cognition can be shown to recruit frontoparietal regions

Thus selective attention can be thought of as an act of focusing brain resources on visual cortex -- particularly the region where feature analysis and construction seems to take place.

Conscious cognition can be seen as going in the opposite direction, a visual object serving to mobilize cortical regions far beyond visual cortex alone.