L3 - Levels of Consciousness

Question 1

How can we describe levels of consciousness?

Answer 1

• Changes in intensity or degree of consciousness.
• All or none? Graded in intensity? Breadth of experience? or both?
• We still won’t be able to know about the quality or content of one’s conscious experience.

eg. what does less consciousness feel like? would pain be more intense due to limited variety of things in consciousness?

Question 2

Are babies conscious?

Answer 2

EEG using backward masking showed that babies

Question 3

What is a problem in assessing consciousness?

Answer 3

consciousness can exist with undeveloped or impaired sensory processing and/or motor output - so we need a measure of consciousness that does not rely on sensory processing or behaviour

Question 4

What are some disorders of consciousness?

Answer 4

• Brain death - irreversible end of all brain activity
• Coma - no response to pain, light, sound or voluntary action, eyes do not open and there are no sleep/wake cycles
• Vegetative State - non responsive, alternate b/w sleep/wake, if it lasts >1 month it’s termed ‘persistent’, and after 1 year only 1:100 improve.
• Minimally Conscious State - minimal but clear behavioural evidence of awareness of self/environment, evidence of awareness if often intermittent.
• Locked in syndrome - normal awareness and cognition but paralysed and voiceless, eyemovements may be inconsistent due to impaired vigilance, diagnosis often takes months - years

Question 5

what are ways that evidence has been found for consciousness in those in vegetative states?

Answer 5

• fMRI showed little difference between healthy and VS patient when asked to imagine playing tennis or visiting rooms in your house
• pupil signals
  limitation: all or none - those who fail these tests may still have minimal consciousness

Question 6

How can pupils signal decisions?

Answer 6

• Pupil will open and close due to release of NTs in the brain, particularly NA which is involved in consolidation of decisions/hard thinking
• use pupil dilation to communicate wit minimally conscious/locked in patients, by using repeated yes/no questions

Question 7

How can we assess consciousness using EEG?

Answer 7

• The greater the complexity of the neural signal, the greater the consciousness.
• Can be seen on EEG after a TMS shock
• Conscious EEG also shows more complex and PROLONGED waves
• Can also reduce the measure of complexity to a single score and to seperate those that are conscious from those that aren’t. (zip file)

Question 8

What are some mechs of anesthetics and consciousness drugs?

Answer 8

• all decrease integration, but can decrease or increase excitation in brain. - supports Tononi’s IIT theory
• Unclear mechanism but anaesthetics impact the thalamus - this area is also deactivated in vegetative state and first to come back when people recover.

Question 9

How has deep brain stimulation helped those in comas?

Answer 9

Electrical stimulation to the thalamus has been used to sucessfully jump-start consciousness in people in vegetative or minimally conscious states.