Ch 14 1st set of notes

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Ch 14 (1st set of notes)

• Psyc 317B

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Consciousness as Perceptual Awareness

• How different is imagining a scene and seeing it?
• Are the same sorts of brain processes involved?
• How different is inward imagining and outward
  perceiving?
• Note that, traditionally (prior to the cognitive
  revolution) it has been assumed that
  introspection (looking within) is a lot like
  exteroception (looking without)
• Causal theory of perception if a perceptual
  experience is caused in the right way by an
  object, then we are perceiving it we perceive an
  object when that object causes our experience.
• Indirect Perception we are only ever aware
  immediately of the contents of our own mind
• These are the overarching questions of the
  chapter
• How does perception give rise to consciousness
  (perceptual awareness)?
• Is consciousness necessary to process and respond
  to sensory stimuli?
• Does consciousness serve a genuine function
  (like linking perception to action)?
• Are there identifiable brain locations/pathways/st
  ates that give rise to consciousness?

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What is Consciousness?

• Subjective awareness of internal and external
  events
• The essence of mind as Descartes mind-body
  dualism
• W. James continuous, unbroken stream of
  consciousness
• Like flashing a light to see the darkness
• Consciousness does not exist as a thing, but as a
  process, as event
• The meaning of consciousness can often be
  revealed by the associated system of contrasting
  or opposite concepts
• Conscious vs. subconscious (or subliminal) vs.
  unconscious (or not-conscious)
• Consider these categories of knowledge about
  your self

Based on Carl Jung
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Consciousness as a mongrel concept

• Freud distinguishes subconscious id, ego and
  superego (the unconscious conscience)
• Toulmin (1982) distinguishes four senses of
  conscious
• being aware (responsive, awake)
• being attentive (concentration, focus, selective)
• being articulate (can report or describe
  experience)
• knowing together (literally, con-scious a form
  of collective, group, class or cultural
  awareness ideological conviction)
• Block (1995) four meanings of consciousness
• phenomenal consciousness
• a subjective awareness of what our mind is
  currently doing
• monitoring consciousness
• one's ability to reflect on one's own thinking
  processes (metacogntion)
• self consciousness
• one's general knowledge about oneself
• access consciousness (the opposite the
  cognitive unconscious)
• the manipulation of representations which has the
  potential to influence your reasoning,
  communication, or behavior

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perceptual awareness

• We are perceptually aware of X when we can report
  its presence either verbally or through some
  prearranged signal.
• This perceptual awareness (the main subject of Ch
  14) is treated as a form of access consciousness.
• In fact, it is perhaps most accurately called
  phenomenal consciousness, but, unlike access
  consciousness, that is not subject to direct
  observation.
• Other terms
• Preconscious contains all those perceptual
  stimuli that are present for you to direct your
  attention to should you choose to.
• You are said to be inattentionally blind to those
  perceptual stimuli which you could, but are not
  presently attending to (inattentional blindness).
• Illusion of Complete Perception we feel we can
  see everything at a glance in a scene, but we
  cannot (wheres waldo?)
• not if you take as a criterion of perception the
  ability to report

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Some Philosophical Issues

• Monism there is only one kind of thing
  (substance) in the world (usu. mind or matter
  ideal or real).
• Dualism There are two kinds of substances in the
  world (usu. mind and matter).
• consciousness depends on different form of
  reality than the material facts observable by
  the senses (suitably equipped).
• Substance Dualism arose with Descartes, but is
  intuitive to many.
• Property Dualism asserts merely that, while
  everything that exists is made of matter,
  consciousness only arises when matter is so
  arranged as to yield emergent properties,
  properties that emerge from but are not reducible
  to lower level physical properties.
• E.g. wetness of water loudness of sound (even
  water itself? Whirlpools?)
• Some people are eliminative materialists they
  deny that consciousness will figure in any way in
  a complete scientific theory that it will go the
  way of pholgiston, caloric fluid, or élan vital.
• Or text takes an opposite view that,
  operationally defined, consciousness can enter
  scientific investigation

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William James (1842-1910)

• James founded the first US experimental
  laboratory in psychology in 1875.
• Deeply influenced by Darwin, he sought to find a
  middle position between (soft-hearted) idealists
  and realists (tough-minded) he called it
  pragmatism, then radical empiricism
• He coined the term stream of consciousness to
  capture his observations that perceptions and
  thoughts were constantly changing and without
  any gap or dead-time.
• He distinguished
• Substantive states consciousness is occupied by
  a particular object or thought (as in careful
  scrutiny, concentration, focus)
• Transitive states consciousness has a shifting
  object, e.g. while transitioning from one object
  to another (as in rushing to work).

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Binocular Rivalry an instance of multistable
or alternating consciousnessTry this yourself
with two cardboard tubes!

• Normally, each eye has a slightly different view
  of the visual scene.
• But we do not see two images our mind-brain
  fuses them together in a process known as
  stereopsis or binocular fusion.
• By manipulating the images sent to each eye
  (making them very different and therefore
  un-fuseable), scientists can create rivalry
  between the two eyes
• We become conscious of, first what one eye
  reveals to us, then what another does. One eye is
  give precedence (dominance), while the other is
  actively suppressed.

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Binocular Disparity and Stereopsis

• The two retinal images are not normally seen
  independently.
• But we do not experience two worlds or two
  images.
• We can experience the retinal disparity
  (difference in retinal image between two eyes)
  see exercise top right.
• The 3D ViewMaster stereoscope also facilitates 3D
  viewing
• compare these exercises to beta-phenomenon of
  apparent motion.
• This raises the question of where and how the two
  arrays of 2D information become fused (binocular
  fusion)

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Binocular Fusion
Get a 4x6 card and place it between your eyes
along your nose and also between the two stairs.
Walk up the 3D staircase!

• Without self-injury, point a pencil straight at
  your nose from directly in front of your face
• Look through each eye to compare then compare
  with look though both eyes. Only with both eyes
  does the pencil look straight (unangled).
• Or, line up both fingers before your nose (at say
  6 and 10 out). See them as lined up with both
  eyes, but as misaligned from each eye
  individually.

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Stereoscopic photo Can you see the 3D

• These images are not quite alike they differ
  much as two retinal images of the same scene
  might differ.
• It is possible to fuse these mentally and see a
  3D image.

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• Stereopsis is the experienced impression of 3D
  from two non-3D images.
• Microbiologists routinely use binocular fusion to
  visual the structure of complex protein molecules.

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• Stereoscopic photography was a fad in the late
  1800s.
• To calculate the disparity in such image pairs,
  the brain must compare incoming information from
  each retina.
• The (unsolved) correspondence problem is to
  discover how this is done.

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Binocular/Representational Rivalry

• When distinct (un-fuseable) images are present to
  each eye, there is a competition as to which
  image will get into consciousness.
• The images tend to alternate in consciousness,
  popping in and out.
• Greater luminance contrast in stimuli can make a
  difference to how well they do in the rivalry.
• Greater psychological significance in stimuli
  also makes a difference
• Stronger stimuli presented to one eye is able to
  counteract the suppression by the other eye.
• Suppression is thought to be caused by inhibitory
  signals from neighboring ocular dominance slabs
  of neurons.
• Neuron fatigue rates affect the switch between
  eyes.

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Representation Rivalrysometimes the rivalry is
not between images per se but between features of
images, and involves feature detectors.

• Logothetis and colleagues studied representation
  rivalry in an attempt to find where in the brain
  the competition took place.
• Monkeys were trained to distinguish rivalry
  stimuli.
• Many monocular V1 neurons were found to change
  when the stimulus was switched (as expected)
• But when the dominant view switched, relatively
  monocular few V1 neurons changed response
  patterns.
• In this case, many binocular neurons in V4
  changed their response patterns.
• Also, when these stimuli were switched between
  eyes, so rapidly that subjects did not notice,
  they reported a slow binocular rivalry effect.

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Duck or Rabbit?
Representational Rivalry? Perhaps this is why it
is impossible to see both the duck and the rabbit
at the same time.
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Masking, Attention and Consciousness

• It turns out that masking a briefly-presented
  stimulus can effectively remove it from
  phenomenal consciousness, but not nec. from
  access consciousness.
• That is, people are not aware of (and cannot
  report) the prime or masked stimulus, but it
  influences their behavior.
• Thus people cant report a masked prime dog,
  but can more rapidly identify semantically
  related terms like puppy
• In the above experiment, researchers asked
  subjects to complete the target word-stem with
  any word except the prime stimulus word.
• They were better able to succeed in this if the
  mask came slowly than if it came quickly, even
  compared to baseline condition (target prime
  unrelated)

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Can you trust what he says?

• This is an ambiguous figure, but it only appears
  as such when the less obvious representation has
  been pointed out (or found).
• Ambiguity within perception depends on attention
• Suggestions consciousness is involved in
  creating a (consistent) global or overall
  interpretation of perceptual experience
• Once that is accomplished, there is no felt need
  to look for ambiguities that may be present.
• What enters consciousness is apparently in part
  under voluntary control.

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What takes Consciousness so long?

• When the eyes are in motion (saccades) conscious
  awareness is actively suppressed.
• Exception tracking motion
• In this experiment, one of three rods is
  illuminated and the subject must quickly reach
  for the lit rod and call out tah!
• Sometimes the lit rod changes, and the subject
  must call out tah! again and redirect arm (they
  must report the change)
• The change in target is made to occur during a
  saccade
• Result movement correction occurs before subject
  can report it!

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Agnosia(not-knowing)
Asked to copy the horse drawing, a patient with
simultagnosia produced the image on the right

• Besides blindness (complete or partial loss of
  visual function), there are various forms of
  perceptual disturbances where very special or
  complex aspects of visual function are lost
  (often die to trauma, stroke, injury, disease,,
  etc.)
• Sometimes these seem to involve a malfunction of
  attention
• Agnosias break apart integrated experience they
  separate what is inseparable in ordinary
  consciousness
• E.g. only color, shape, orientation, texture or
  movement perception is lost
• Color agnosia cones are fine V1 may be fine
  people can recognize colors and recognize
  objects but they cant tell the color of
  objects.
• Shape and orientation must be coded separately,
  for they can come apart in agnosia they can be
  doubly dissociated (while object recognition
  remains!)
• Patients can tell it is an X, but cant say if it
  is upright or angled they cant distinguish 6
  and 9. If an known object is presented in an
  unusual orientation, it cant be recognized.

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Simultagnosia

• Normals can readily identify all the objects
  depicted here, even though they are all presented
  at once, overlapping, simultaneous.
• Patients with simultagnosia will typically report
  only one object, and deny they see others.
• Such patients also show a decrease in attention
  span (i.e., the number of obejcts that can be
  held in consciousness at once).
• Such agnosics cannot place a dot in the centre of
  a circle, since that requires holding the dot and
  the circle in mind simultaneously.
• Focusing on one part of the image, they loose
  awareness of its spatial relations with other
  parts.

Visual Integrative Agnosia refers to the combined
condition of simultagnosia and object agnosia
(inability to recognize objects)
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Hemi-neglect

• Visual hemi-neglect (aka visual
  hemifield-neglect) refers to the inability to pay
  attention to or notice stimuli from one-half of
  the visual field (i.e., the right or left side of
  a scene or object) even though more basic visual
  field abilities are intact.
• Often, the loss occurs on the left side of the
  visual world as the result of right parietal lobe
  damage.
• As represented in the image at right, a patient
  with hemi-neglect might perceive the only the
  right half of an object, and if asked to copy a
  drawing, they are likely to omit the material on
  the left.
• Similarly, such patients often eat only the food
  on the right half of the plate, leaving that on
  the left.
• But when the plate is rotated 180 degrees they
  perceive, and may then consume the food that was
  initially on the left.

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Hemi-neglect

• The images on the left below were presented to a
  patient with visual hemineglect, who was asked to
  copy them.
• The images below on the right are the copies
  produced.
• Notice that the leftmost figure is missing
  entirely, and the left sides of the others are
  partial and incomplete.
• A 1997 study of 602 stroke patients in Copenhagen
  found that 23 suffered some degree of
  hemineglect.
• Visual hemineglect is typically the result of
  damage to the right visual cortex (as is evident
  in the case below)

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visual form agnosia

• Patient D.F. with visual form agnosia (ventral
  damage) could not recognize the apple or the book
  in the drawings, and could not copy them.
• But she could draw apples and books from memory.
  Later, however, she could not recognize what she
  had drawn. She could also verbally describe
  images
• D.F., if asked, could not orient a card to match
  the orientation of a slot
• But she could, if asked, insert the card through
  the slot, as if mailing a letter, no matter what
  the orientation of the slot.
• D.F. shows single dissociation between judging
  orientation (ventral) and coordinating vision and
  action (dorsal)
• other dorsal damage cases, taken with DF,
  establish a double dissociation

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Blindsight

• DF was also surprisingly good at other visually
  guided actions (like mailing a letter), even
  though she reported being unaware of the
  perceptual basis of her actions.
• Asked to indicate the size of a block with her
  fingers, she did poorly.
• But when she went to pick up the object, she
  adjusted her fingers appropriately.
• Similar phenomena in other sense modalities have
  been found
• Blindsmell deaf hearing numbsensse.

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These illusions fool the perceptual (ventral)
system, but not the action (dorsal) system

• Visual-geometrical illusions have been used to
  show that there are separate and relatively
  independent visual pathways in the brain.
• It was found that
• This suggests that consciousness, involved with
  global interpretation, is helpful in action
  planning, but that the action system does not
  need this global analysis.
• However, normally movements are also guided by
  online control, which involves integration
  between the perceptual and the action systems.

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Function of ConsciousnessGlobal interpretation
and global hypothesis testing

• Intuitively, the function of consciousness is
  perceptual integration.
• If information about parts of our environment
  could be accessed individually, without
  integration of the parts, we might have
  difficulty assessing overall advantage or
  disadvantage of a situation.
• It may even be that consciousness (e.g. visual
  awareness) is responsible for integrating the
  various features that specialized parts of the
  visual system process
• Color, shape, texture, movement
• Consciousness as the mechanism that bind
  perceptual qualities together.

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Neural Synchrony or Coordination

• Synchronous neural firing may be the glue that
  binds together the activity regions of the brain
• Visual cortex neurons fire in phase if responding
  to the same object, out of phase if different
  objects are involved.
• Widespread synchronous brain activity also occurs
  in response to presented ambiguous figures (like
  duck-rabbit) but not in response to presented
  meaningless stimuli (EEG)
• Correlated activity levels have also been found
  when subjects were aware of the relationship
  between a visual and an auditory event but not
  when they were unaware (PET)
• Dynamic Core a large group of synchronously
  firing neurons thought to be necessary and
  sufficient for conscious awareness (Edelman)
• For vision dorsal, ventral, thalamus, amygdala,
  frontal, parietal, etc. all become time-locked as
  we become conscious

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Binocular Rivalry and Synchrony

• Rivalry stimuli were line patterns that were
  moving in different directions
• Under conditions of no rivalry, neurons
  responding to a pattern fired in synchrony,. As
  indicated in the amplitude of sine wave patterns
  at left.
• In rivalry condition, those neurons responding to
  the seen pattern were highly synchronous while
  those responding to unseen or suppressed
  stimuli were far less synchronized.