Attention and Consciousness

Transcription

1 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

2 Sensory Systems modulated by Attentional Systems a Single Hair Cell-- pin drop a Single Photon a Single molecule

3 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

4 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

5 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

6 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

7 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

8 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

9 What Happens to the Lag? Reaction times can be 200 ms, recognition can take 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

10 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

11 Stroop Task xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx

12 Stroop Task Red Brown Blue Green Green Blue Yellow Black Brown Green Yellow Red Black Red Yellow Blue Black Yellow Brown Red Green Blue Black Brown

13 Stroop Task Red Brown Blue Green Green Blue Yellow Black Brown Green Yellow Red Black Red Yellow Blue Black Yellow Brown Red Green Blue Black Brown

14 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

15 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

16 END of MATERIAL FOR MIDTERM

17 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)

18 Central Attention: not just sensory/perceptual Message 1 Message 2 GREEN MARK EGGS BACK FINE AND RICE HAM Subjects occasionally reported green eggs and ham This shouldn t happen if message 2 were completely filtered out no central attention process..

19 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 RAS Arousal

20 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

21 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

22 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?

23 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)

24 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?

25 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

26 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

27 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

28 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)

29 Species Variation in Sleep (Figure adapted from Kripke et al., 1979)

30 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

31 EEG Stages of Sleep (Figure adapted from Cartwright, 1978)

32 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)

33 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

34 Altered States of Consciousness Changes in consciousness can be brought on by Meditation Hypnosis Drug ingestion Religious experiences

35 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.

36 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.

37 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.