Disorders of conscious awareness

Question 1

Define the terms Conscious Awareness, Body Ownership, Agency and Volition

Answer 1

CONSCIOUS AWARENESS - self acknowledgement of own self and response to environment
BODY OWNERSHIP - Ability to identify own body parts and ability to control them
AGENCY - Ownership of own actions
VOLITION - will and intention for conducting an action

Question 2

What did Turk et al find with regards to conscious awareness in split-brain patients (following collosotomy)?

Answer 2

Severing the corpus collosum –> hemispheres work essentially independently of each other
When own face morphed with the face of a stranger along a continuous spectrum, from complete self to complete non-self, found that left hemisphere showed preference for recognising self, while the right processed basic senses of familiarity
So face information is available to both hemispheres but functionally processing appears lateralised

Question 3

What is Capgras syndrome?

Answer 3

Atypical perception of identity recognition (demonstrative of the need for emotional input for successful face recognition)
Can perceive a face and know who the face represents, but view the person as an imposter wearing a mask
Lack of emotional connection leads to assumption that it can’t be the real person

Question 4

What did Ramachandran suggest regarding a potential cause of Capgras syndrome?

Answer 4

Malfunction between brain’s visual cortex and the emotional feeling of “familiarity” which can occur in brain injury or diseases such as Alzheimer’s

Question 5

How does Prosopagnosia different from Capgras Syndrome?

Answer 5

Better-known form of facial misidentification - causes total inability to recognise previously familiar faces
Capgras is easy recognition but disagreement about person’s true identity

Question 6

What is Phantom Limb syndrome?

Answer 6

Disorder of body ownership - lost limb still felt following amputation, most commonly felt as pain

Question 7

What is an explanation for Phantom Limb syndrome?

Answer 7

Neural connections still project from the brain to where the limb used to be (residual memory of the limb and its connections) and the associated brain area is still present in the somatosensory cortex
Cortical reorganisation can occur such that phantom pain can occur after stimulation of another body part (neighbouring cortical areas take over the redundant region)

Question 8

Define phantom limb pain

Answer 8

Hallucination in the subconscious that a missing limb still exists - involves a very realistic perception of the missing limb even though the conscious mind clearly conceptualises the fact that the limb is lost

Question 9

What is particularly interesting about phantom limb pain?

Answer 9

Exists in those missing limbs due to birth defects - suggests that brain is disposed to an interaction with its limbs, hardwired to send and receive neurotransmissions from them.

Question 10

Briefly describe Melzack’s concept of a “neuromatrix”

Answer 10

Nociception does not equal pain - there are times when tissue damage –> nociceptive signals –> no pain and there are also times such as in phantom limb when there is no nociceptive input but pain occurs.
Suggests that pain is an active construct of the brain and central nervous system - sometimes stems from INTERPRETATION of nociceptive signals but sometimes doesn’t

Question 11

What is the somatosensory homunculus?

Answer 11

Certain parts of the brain are responsible for innervation of certain parts of the body e.g. the hand and arm occupy a significant portion of the homunculus

Question 12

What does the structure of the somatosensory homunculus mean for amputees?

Answer 12

In the case of upper extremity amputation, a large region of the brain once designated to innervate the arm now has no arm to interact with
Nature abhors a vacuum
So the neuromatrix fills the vacuum by actively creating the missing perceptions and sensations that the arm may feel - satisfies the body’s need to account for that body part

Question 13

In addition to phantom limb pain, why may amputees also experience hypersensitivity of adjoining body parts within the somatosensory homunculus?

Answer 13

For example, the face is located next to the upper extremity on the homunculus, and the genitals are located next to the leg
After amputation the adjacent area melds with the area for the missing limb and this results in increased sensitivity for that remaining body parts
Ramachandran demonstrated this using light stimulation of patients’ faces

Question 14

Where does a strong connection exist?

Answer 14

Between brain’s body awareness and sight - perception of self is coordinated through combining senses of proprioception and sight

Question 15

What is the basis of Ramachandran’s Mirror Therapy?

Answer 15

Conflict between sight and proprioception and the reality of a missing limb is what leads to the phantom pain.
This non-pharmaceutical treatment method works by replacing the missing physical feedback from the limb with visual feedback from a mirror image of the remaining arm

Question 16

What was the basis of Botvinick and Cohen’s rubber hand illusion?

Answer 16

Another illusion of body ownership - tactile sensation and visual feedback combining to give a sense of ownership to something that is actually not part of the body
Visual feedback actually overrides physical feedback and a degree of cortical remapping occurs

Question 17

What does the rubber hand illusion rely on?

Answer 17

Congruency - efforts to integrate fake arm into body construct, and also need synchronous stroking to allow for the congruency mapping
(Generally only works with objects resembling body parts as easier to integrate)

Question 18

What is a bottom-up theory for how body ownership is created?

Answer 18

Perceptual building of a construction from integration of multiple senses and use of inductive reasoning (inferencing and probability)
BAYESIAN PERCEPTUAL LEARNING THEORY (Armel and Ramachandran) -
- Visuotactile correlation necessary and sufficient for construction of ownership
- Need spatiotemporal coincidence and repeated patterns of afferent input

Question 19

What is the basis of top-down theories of body ownership?

Answer 19

Use of past body maps - internal template of the body and where it is/should be in space
Experience-based - reapply template to current sights/sensations

Question 20

What is Tsakiris’s neurocognitive model of body ownership?

Answer 20

We make comparisons with a pre-existing body template via integration from different sources
Comparisons happen on 3 levels:
- Visual input - body parts and where they should be
- Current body schemata - position, configuration, anatomy
- Comparison of sensory inputs e.g. visual and tactile
This explains the rubber hand illusion and why it works best when the object looks like a limb - works with the mental template everything is being compared to

Question 21

What was Weiskratz’s blindsight procedure?

Answer 21

Patient has damage to V1 (eyes still work)
Lack conscious visual awareness but still have subconscious awareness
LGN acts as bypass
Eye movement even still occurs, especially when cued, but no consciousness involved

Question 22

What are the properties of volition?

Answer 22

Not immediate/reflexive - more an active and conscious choice
Stimulus independent so hard to empirically test

Question 23

How did Libet et al attempt to study volition?

Answer 23

Used EEG over supplementary motor area (involved in planning and initiating movement)
EMG measured their finger movement
They watched a clock and pressed a button at will - reported time they decided to press button and time they were aiming for

Question 24

What were Libet et al’s findings?

Answer 24

BEREITSCHAFTS/readiness potential was 400ms before they reported having decided to press the button - Libet used this to conclude that free will does not exist
Awareness of movement initiation was 150ms before movement onset - brain prepares action before we become consciously aware of it

Question 25

Why was Libet et al’s study criticised?

Answer 25

Subjective report - measurements not fully precise
Attention divided during task - clock, button, task goal
Results may be more reflective of demand artefacts
Not natural volition as attention focused on the clock

Question 26

How did Haggard and Eimer replicate Libet et al’s study?

Answer 26

Controlled for different hemispheric responses and naturalised the set up of the experiment
Lateralised readiness potential - corresponded to finger being used to press the button
Specific body movements

Question 27

What were the stages of Haggard and Eimer’s model

Answer 27

Motivations and reasons for action guide the early “whether” decision
The “what” decision is based on task selection and action selection
The late “whether” decision is otherwise called the final predictive check (forward model)
This is followed by action execution –> acts on the external environment –> feedback to the early “whether” and motivations etc

Question 28

What is meant by a “vegetative” state and what did Owen et al do?

Answer 28

Lack of response to external stimuli
Used MRI to investigate awareness in coma patients - found simulation of tasks without seemingly being aware/able to respond (activity in SMA)

Question 29

What is alien/anarchic limb syndrome and what did Brion and Jedynak find?

Answer 29

Loss of agency
Hands functioning seemingly independent of volition, opposing a willed action
FRONTAL LESION - reflexive grabbing utilisation behaviour
COLLOSAL LESIONS - Intermanual conflict
–> ANTERIOR - Awareness of action initiation with respect to goal
–> POSTERIOR - Limb ownership

Question 30

What are the 5 components of Feinberg’s Comparator Model of Agency?

Answer 30

1) Make intention and motor plan –> establish motor command
2) From motor command, make prediction of sensory output
3) Execute action from motor command to create actual sensory outcome
4) Compare actual and predicted sensory outcomes
5) Outcome is phenomenological - if actual and predicted match –> sense of agency, if there is mismatch it is purely an action observation

Question 31

Summarise the 5 key aspects of conscious awareness and its disorders

Answer 31

1) Consciousness is not a unitary construct (more of an inference)
2) Pre-SMA and Corpus Callosum are important in building a sense of agency and body ownership
3) Body ownership is a multi-sensory construct
4) There is a combination of bottom-up and top-down factors influencing conscious awareness
5) Comparator models are important for conscious perceptions

Question 32

Define intermanual conflict

Answer 32

A disorder in which a person’s hand or limb acts as if it has autonomous, voluntary activity independent of the individual. For example, the hand which is under the person’s normal voluntary control might put a cigarette in the mouth, and the alien hand might knock it out.

Question 33

Why is alien hand syndrome fairly rare?

Answer 33

Results from infarction of the Corpus Callosum, which has an abundant blood supply