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Consciousness > Task 6 - Brain and consciousness > Flashcards

Task 6 - Brain and consciousness Flashcards

1
Q

Left hemisphere

A

Temporal lobe: language comprehension and production (dominant hemisphere)
Parietal lobe: naming objects, STM of verbal information

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2
Q

Right hemisphere

A

a) Spatial perception (btw objects, navigating in space, recognizing objects and aiming movements)
b) STM of nonverbal information

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3
Q

Contralateral organization

A

Left hemisphere controls right side of the body and vice versa
Vision: the left lobe processes info from right visual field

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4
Q

Commissurotomy

A

Surgical transection of the corpus callossum
- done to control for severe epilepsy
CONS: not effective, so they also cut the anterior commissure –> effective

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5
Q

Split-brain test results must be interpreted with caution. Why?

A
  1. Brains are not normal - patients were suffering from severe epilepsy
  2. not many patients exist - small sample
  3. Individual differences - in some patients, the right hemisphere is relatively unresponsive
  4. Other hemisphere may take over: functional reorganization prior to surgery may have occurred
  5. Hemispheres might acquire functions post-surgery
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6
Q

Unilateral testing

A

Under normal conditions, split-brain patients can see the entire scene with each of the two hemispheres

TEST OF INDIVIDUAL HEMISPHERES:

  1. Ask to identify object by touch alone:
    a) right hand: able to name object
    b) left hand: could’t name object but could show how to use it. (right hemisphere can’t talk but still knows)
  2. T-scope: lateralize visual stimuli: subjects focused on a dot at the center of the screen. The stimulus is briefly flashed on one side, while not moving the eyes.
    a) left hemisphere: can name things in right visual field (RVF)
    b) right hemisphere: knows, but cannot name it. Person can select objects that go with the one seen (understands concept) and can show an emotional response to it

LEFT HEMISPHERE TRIES TO MAKE SENSE OF THE RESPONSE OF THE RIGHT HEMISPHERE

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7
Q

Visuospatial superiority of right hemisphere

A

Right hemisphere is superior in many non-verbal tasks

Block-design test: subjects used colored blocks to construct a pattern that match sample pattern shown in a picture
- right hand: almost impossible

Face recognition: right hemisphere is better than left
Chimeric figures: picture with half of a face was matched with other half. The face was flashed on T-scope screen and subject should chose the matching face seen from a set of 4 different faces
a) pointing response: controlled by the right hemisphere (almost always correct)
b) verbal response: controlled by the left hemisphere (not always correct)

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8
Q

Visual completion

A

Split-brain patients perceive incomplete figures as complete (not sure why that is)

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9
Q

Other minds problem

A

The speaking left hemisphere has no knowledge of the right hemisphere’s experience and can only make inferences based on overt responses.
- in real life, patients don’t experience this

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10
Q

Objective criterions to infer consciousness

  • dualism
  • Sperry’s interactionism theory
A
  1. Introspective verbal report: only possible for left hemisphere
    a) Dualism: left hemisphere receives knowledge from immaterial consciousness and can make verbal reports about it
  2. Intelligent action: behavior adaptive to current situation and controlled by flexible thought processes.
    a) Sperry’s interactionism theory: consciousness is identified with holistic properties of neural activity and plays a role in controlling behavior
    - Hypothesis: Due to separation, each hemisphere has its own center of consciousness (split consciousness)
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11
Q

Evidence for dual consciousness

A

When we use the criterion of intelligent action to infer consciousness, the right hemisphere shows perceptual awareness and conscious thinking.

COGNITIVE TASKS: intelligent action can also follow from visual-spatial images (mental):
Horse photo was flashed to right visual field (RH). Patient could draw what goes with it –> draw a saddle & then afterwards the left hemisphere could infer what the mental image was (horse), without seeing it.

VOLITION: Alien hand: independent actions from left hand (right hemisphere) = independent consciousness.
- left hand takes over when right hand is struggling with something (person does not try to do that)

CROSS CUING: LH infers what RH sees or feels by noticing RH overt response.
- picture flashed to left visual field (RH) and subject couldn’t name it. When guessing again, the subject frowned & shook head. PP changed the answer
RH can only show short-term goals, not long-tern plans
- it is relatively rare anyways

SELF-RECOGNITION AND SOCIAL VALUES: Self recognition is the minimal criterion for self-awareness

  • z-lense experiment: patients could recognize themselves when a picture of them was flashed to their right hemisphere: voice tone changed & patient said ‘something I would like to have’
  • sense of humor: man laughed and voted his picture with a thumbs down
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12
Q

Partial consciousness model (Ecces)

A

Only LH is conscious, RH is unconscious

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13
Q

Split consciousness model (Sperry)

A

Each hemisphere has its own consciousness

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14
Q

Challenges that are faced by Partial consciousness model &Split consciousness model:

A

3/5 hallmarks also exist in adults with unified consciousness

  1. RESPONSE-VISUAL FIELD INTERACTION: Stimulus to LVF, patient can only point with left hand and not say what is seen
    cons: doesn’t hold for all patients, in some patients conscious unity doesn’t break down
  2. HEMISPHERIC SPECIALIZATION: also observed in healthy adults
  3. POST-HOC CONFABULATIONS: LH interprets RH actions.
    cons: that happens also in healthy people: behavior that is caused by factors the subject doesn’t know of –> person makes confabulations
  4. SPLIT ATTENTION: Studies suggest that patients attention is split: object and space-based attention are situated in different hemispheres
    Cons: these findings don’t show disturbances of consciousness:
    a) similar phenomena for healthy patients: each hemisphere track information separately and only share info when necessary
    b) Attention can also be unified in split-brain patients (shown by attentional blink)
  5. INABILITY TO COMPARE STIMULI ACROSS THE VISUAL MIDLINE: patients fail to indicate whether both stimuli are the same –> only when both are presented in one visual field
    Cons: there are examples of patients who actually can
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15
Q

Conscious unity, split-perception model:

A

Consciousness is unified but visual perception is large unintegrated in split-brain patients:

  • that’s why they often cannot make comparisons across the midline
  • explains hemispheric specialization: as visual info isn’t shared, the contralateral hemisphere does all the processing (max hemispheric specialization)
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16
Q

Integrated information theory:

A

Consciousness arises when a system has a rich representation repertoire and when its subsystems are strongly interconnected.
When the integration of a subsystem is larger than the connection between the subsystems: consciousness arises as a function of the subsystems

Split brain: intrahemispheric connectivity is bigger than interhemispheric connectivity –> each hemisphere has its own consciousness

17
Q

Recurrent processing theory

A

Consciousness can arise though local recurrent processing btw cortical modules even in the absence of a global integrative process. Such local processing only leads to phenomenal consciousness, that is otherwise inaccessible und unreportable.
-For unified reportable consciousness, integration between the hemispheres is needed

It is more compatible with the new ‘Conscious unity, split-perception model’, as the basic non-reportable consciousness is not dependent on inter hemispheric integration

18
Q

Global workspace theory

A

cerebral hemispheres house a global workspace & only information processed by that workspace reach consciousness
- if both hemispheres are split: no integration of GW. Either one GW in one hemisphere or 2 independent ones in each hemisphere

19
Q

Gazzaniga & LeDeoux- right hemisphere language ability

A

Right hemisphere is unconscious in most split-brain patients, but some patients have a conscious RH depending on right hemisphere language ability
- those without that ability can’t carry out complex cognitive tasks

PATIENT P.S.: RH couldn’t speak first but learned to speak some years after surgery

  • RH arranged scrabble letters to answers about self-concept. Mostly RH and LH agreed about answers
  • RH was able to understand and carry out action verbs
  • RH show emotional reactions to words and evaluate them
20
Q

Interpreter system (Gazzaniga)

A 
More recently (compared to right hemisphere language ability theory) Gazzaniga identified consciousness with a LH-interpreter system: 
The interpreter system interprets the action of a number of modules which are independent functional units that retrieve memories, compute & store them, receive info & trigger emotional reaction 
- why do they occur 
- tries to fit them into narrative sequence of our life 
- it is not the same as the language system

SUPPORT:

  • eight choice pictures: chose the one that goes best with pics on screen: LH couldn’t understand choices of RH
  • series of words flashed: couldn’t read them from left to right but sequentially for each hemisphere. Afterwards first only able to report what LH read, but after a while PP could integrate LH and RH into one story

CONCLUSION:

  1. Actions are controlled by non-conscious modules. The interpreter system only gives us an illusion of mental unity.
  2. RH is not conscious, even in patients with a RH language ability

CONS: limiting consciousness to the interpreter systems a criterion that is too narrow

SOLUTION: Reflective consciousness is similar to the interpreter system (NOT SAID BY GAZZANIGA)

a) maybe primary consciousness can be found in both hemispheres but reflective only in the LH
b) RH could be conscious from itself, but unconscious from viewpoint of LH

21
Q

Subcortical areas are still unified

A

if consciousness is linked to subcortical processing, then consciousness may still be unified and unaffected by splitting the brain

22
Q

Conscious unity related to functional unity

A

Consciousness would remain unified if a minimal amount of synchronization btw subsystems is preserved (even if they aren’t directly linked)

23
Q

medical consciousness /awareness

A

consciousness on a global level

24
Q

Content consciousness

A

subjective experience

25
Q

Consciousness paradigms

A
  1. Illusions: endogenously created
    a) phosphenes - perception of light without light being there
    b) hallucinations
    c) phantom pain
  2. Multi-stable paradigms: repeated perceptual alternations btw 2 possible perceptions (e.g. ambiguous figures)
  3. On-off paradigm: exact same stimuli used in all trials. Brain activity is strictly related to endogenous processes differentiating stimulus perceived vs non perceived
    a) visual masking
    b) attentional blink - attention works in chunks
    c) phosphenes induced by TMS: find threshold in which subjects don’t experience anything anymore
26
Q

Oscillatory rhythms & parameters

A

Oscillatory rhythms are thought to indicate conscious percept:

a) frequency: how often signal goes up and down in a second
b) Amplitude: how strong the signal is (how many neurons fire
c) phase: were signal finds itself at a particular moment of time

27
Q

Signal analysis

A

Take a lot of same trials and average it

a) frequency analysis
b) time frequency analysis: how frequency change over time
c) phase locking analysis: where is smith at a certain moment in time
d) phase coherence: activity in 2 different brain areas & compare them.
l. coherence: same bands
ll. synchronized: go up and down at same times

28
Q

Gamma Band activity

A

Gamma band activity: cross-modality processing

Occipital lobe fires in response to aligned light bars 
Mooney faces (face seen in one direction but not in the other) elicits much stronger gamma responses (supraliminal stimuli)

Conscious perception is linked to distributed activity of both local and global synchronization in the brain
- increase in gamma activity for emotional stimuli irrespective of availability to conscious access

GAMMA BAND ACTIVITY IS RELATED BUT NOT SUFFICIENT FOR CONSCIOUSNESS

29
Q

Alpha band activity

A

using TMS to induce phosphenes:

a) could see phosphenes = low alpha activity
b) couldn’t see phosphenes = high alpha activity –> reflects momentary cortical excitability

30
Q

How do we know of oscillations are actually important for consciousness?

A
  1. Entrainment: alignment of system (brain) with the environment (TMS)
  2. Sensory entrainment: reaction time faster when stimuli are presented in a regular manner
  3. Nibs entrainment:
    a) tms
    b) tACS
    induce certain frequency on brain to see if brain can change activity (when inducing 10 Hz, stimulus detection is worse).
31
Q

Global neuronal workspace

A

brain processes are constantly active and process stimuli unconsciously: only if top-down processing is active, the stimulus becomes conscious

32
Q

Window to consciousness

A

Alpha activity is needed for consciousness. Brain processes stimuli unconsciously with low level waves, but then these interact with other areas, alpha waves are needed

33
Q

Oscillatory prerequisites

A

There is something that is always there so that consciousness can arise, but don’t underly consciousness. There are consequences of consciousness arising afterwards

Consciousness (5 decks)

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