Awareness and Abnormal States of Consciousness

Question 1

What is sentience?

Answer 1

Awareness of internal or external existence
Feeling/ sensing not reason
Therefore consciousness is not intelligence

Question 2

What are the two dimensions of awareness?

Answer 2

Wakefulness/ alertness

Complexity of representation/ representational capacity of consciousness (low= sleepwalking)

Question 3

Clusters of states

Answer 3

Continuous state

• Conscious wakefulness state
• Drowsiness
• Sleepwalking, complex
• REM sleep (low arousal and high representational)
• Deep sleep (low arousal)
• Coma= loss of sleep-wake cycle
• Persistent vegetative state= sleep-wake
• Minimally conscious= partial awareness
• Locked in syndrome= brainstem strokes

Question 4

Sleep-wake cycling

Answer 4

-Circadian Process= spontaneous 24 hour cycles, measured by melatonin level, blood cortisol, body temperature
=Master clock inputs from retina in light
=restore homeostatic and energy balance
-Sleep process
-Cognitive Pressure= top down influences from cognitive and emotional state

Question 5

Changes in sleep wake cycle throughout the day

Answer 5

C process= cycling with peaks in day and troughs at night, smooth cycle
-Gap between process C and process S called sleep pressure- increases throughout day

Question 6

The hypothalamic switch is sleep wake cycles

Answer 6

• Ventrolateral pre-optic area (VLPO)= GABA inhibitory neurones= sending off to sleep, project to centres involved in arousal
• Tuberomammillary nucleus in posterior hypothalamus switches in histamine switches on cortex
• Posterior lateral= Orexin/Hypocretin= switches on centres such as reticular activating system (dopamine, ACh, cholinergic)

Question 7

What is Narcolepsy?

Answer 7

Low levels of CSF Orexin

-Sudden onset of sleep

Question 8

What are the stages of sleep?

Answer 8

• Lighter
• Deeper (arousal state)
• 4 stages
• 90 min cycles
• REM sleep (dreaming) increases in proportion as we sleep longer

Question 9

What are the disorders of sleep?

Answer 9

-Non REM sleep
=Stage 3 and 4 (deep levels)
=Sleepwalking, Confusional arousals, night terrors
-REM sleep (reflect problems with system normally present in inhibitory corticospinal tract, act out conscious experience so act out dreams)
=behavioural disorder strongly predictable of alpha-synucleinopathy (Parkinson’s)
=Isolated sleep paralysis failure of CorticoST inhibition to be switched off when waking

Question 10

What structures are involved in arousal?

Answer 10

• Posterolateral hypothalamus (“wake up” switch)= diencephalon
• Reticular activating system (ACh – nicotinic)/ VTA (mesolimbic and mesocortical Dopamine)= brainstem
• Both thalami intact (the railway station)= bilateral thalamus (stroke)
• Neocortex intact (global cortex)

Question 11

Presentation of brain without fuel

Answer 11

Oxygen and glucose

A BP high enough to overcome gravity, pumping blood through the brain and back to the heart

Question 12

Presentation of brain with a problem (arousal)

Answer 12

Metabolic / Toxic (build up of urea, systemic inflammation)
BS/thalamic stroke
Raised ICP that compromises cerebral perfusion (Monro-Kelly doctrine)
Electrical failure (post-seizure)

Question 13

Criticism of GCS

Answer 13

Elides capacity, content and response in the GCS

-Best interpreted as holistic measure

Question 14

What are the pre-requisites for modelling of the world?

Answer 14

Arousal (is the patient awake and alert?) Pathways / systems for arousal

Capacity to generate percepts Perceptual & Attentional mechanisms

Question 15

What are the reality modelling and predictive values?

Answer 15

Capacity to model objective reality, set goals, and predict outcomes from possible interventions (intelligence)

  Memory & PFC/limbic function

Question 16

How do we act in the world?

Answer 16

Capacity to generate behaviour that acts-out predictive models in reality

 (Language & motor pathways)