Consciousness Flashcards
1
Q
What are the difference between the medical and philosophical definitions of Consciousnesses
A
- Medical approach is objective: relies on the response to stimuli
- Alertness
- Verbal
- Pain
- Unresponsive
- Philosophical approach is subjective: relies on the experience of the above
- sensation of pain touch proprioception and interoception
- experience of emotion, memory, though, self and non-self etc.
2
Q
What are the aspects and & requirements of full human consciousness
A
- Arousal/ activation
- Connectivity
- Input
- Sense organs
- Proprioception
- Interoception/ emotion
- Output/Control
- Motor: speech, locomotion, dexterity, eye/ head movements and other orientating movements
- Attention
- Cognition
- Emotional
3
Q
What are the physiological states of consciousness and disorders of consciousness
A
- Sleep (various stages)
- Psychedelic states
- General Anaesthesia
- Coma
- PVS
- MCS
- Locked-in Syndrome
- (Death)
4
Q
Give an overview of Sleep and it’s different stages
A
- state of decreased arousal
- physiological, reversible, cyclical and active process
- Awake: high-frequency, low amplitude beta activity
-
Stage 1-4 Sleep: reducing frequency, increasing amplitude
- Stage II: sleep spindles- 10-20Hz oscillations
- Stage III-IV: slower delta waves
- REM Sleep: low-voltage, high frequency similar to the awake state
5
Q
What is a Coma?
A
- this is a pathological complete prolonged loss of wakefulness and awareness (eyes usually closed)
- there is unresponsiveness to external stimuli but is often reversible
6
Q
Causes of a Coma
A
- Sedation / anaesthesia
- Epilepsy
- Electrolyte / metabolic disturbance
- Disturbance of thermoregulation
- Raised intracranial pressure
- Structural damage to brainstem / thalamus / cortex
- Stroke
- Trauma (brain injury)
- Tumour (compressive)
- Inflammation
- Infection
7
Q
What is a metabolic coma?
A
- more likely to have associated brain seizures and usually leave pupillary light reflexes intact
- Triphasic theta waves
Causes
- hepatic
- uraemia
- diabetic
- pancreatic
- adrenocorticoid failure
8
Q
What are the typical outcomes of comas?
- and what assessment can be done to distinguish them?
A
- Reversal and recovery
- Survival into vegetative state or minimally conscious state
- Irreversible cessation of function
- of
- Brainstem (brainstem death)
- Cerebral cortex (neocortical death)
- Glasgow coma scale: max 15, min 3
- absent eye-opening distinguishes coma/ brainstem death from PVS and MCS
9
Q
What is a Vegetative State
- description
- causes
- permenance
“Unresponsive Wakefulness Syndrome”
A
- Wakefulness
- Preserved arousal (preserved sleep/wake cycle)
- Absent awareness (& hence consciousness)
- Unresponsiveness:
- No voluntary response to environment
- Variably preserved reflex responses to environment
- Cause: widespread damage to cerebral cortex (esp anoxia, head injury) – Neocotical Brain death
- Persistent Vegetative State >4 weeks, can be permanent:
- After a non-traumatic Brain Injury
- 6 months in the UK
- 3 months in the US
- After Traumatic Brain Injury
- 1 year
- After a non-traumatic Brain Injury
10
Q
What is a Minimally Conscious State?
A
A state of severely altered consciousness in which minimal but clearly discernable behavioural evidence of self or environment awareness is demonstrated
Like Vegetative State, but with at least one of 11 items
- consistent movement to command
- reproducible movement to command
- object recognition
- object localization
- reaching
- visual pursuit
- fixation
- automatic motor response
- object manipulation
- localization to noxious stimulation
- intelligible but non-functional verbalization
- Emergence from MCS signalled by at least one of 2 items:
- functional communication
- object use.
11
Q
How can you detect awareness in VS (and MCS)
A
- Tennis: supplementary motor area activity
- Imaging moving around a house:
- Parahippocampal gyrus (PPA)
- Posterior Parietal Lobe (PPC)
- Lateral premotor cortex (PMC)
12
Q
What is Locked-in Syndrome?
A
- Conscious (aroused & aware)
- Unable to respond (de-efferented)
- Most cases are partially locked in:
- preserved vertical eye movements
- reserved eye-opening
- Causes
- Ventral Pontine Damage
- Severe Guillain Barre Syndrome
13
Q
What is Brain Stem death?
A
- Irreversible cessation of brainstem function
- Such that consciousness could never be regained
- Absent Reflexes
- Pupils, Corneals
- Ice Calorics: slow deviation of eye towards ear that is being irrigated shows an intact brainstem
- Pain
- Gag
- Cough
- Absent Reflexes
- Apnoea
- 5 min test after pre-oxygenation and allowing CO2 to reach 6Kpa
- No arousal
14
Q
What are the legal requirements to call brainstem death?
A
- Presence of an irreversible cause (eg anoxia, structural damage)
- Absence of reversible cause; drugs, hypothermia, alcohol, poisons, metabolic (pupils react) or electrolyte disturbances
- Irreversible cessation of function of
- Brainstem (brainstem death) – confirmed by 2 doctors
- Cerebral cortex (neocortical death)
- Body
- Must be repeated after 24 hours
- Ongoing life support?
- Organ donation
15
Q
What anatomical structures correlate to consciousness?
- Macro and Micro
A
Macroscopic Structures
- Cerebral Cortex
- Reticular activating system
- Thalamus
- Motor & sensory nuclei (cortical relay)
- Thalamic reticular nucleus (gabaergic, indirect: inhibitory on thalamus)
- Intralaminar nucleus esp centro-median nucleus
- Claustrum
- Default Mode Network (subjective consciousness)
- Anterior Cingulate Cortex
- Prefrontal Cortex
- Inferior Temporal Cortex
Microscopic Structures
- Von Economo Neurones
- Crown of Thorns Neurones
16
Q
What are Von Economo Neurons?
A
- Large spindle-shaped soma (or body) that gradually tapering into a single apical axon, there is only a single dendrite facing opposite. F
- Found in 2 very restricted regions in the brains of hominids (humans and other great apes)
- Anterior cingulate cortex (ACC)
- Fronto-insular cortex (FI)
- Found in the dorsolateral prefrontal cortex of humans.
- Also found in the brains of the humpback whales, fin whales, killer whales, sperm whales, bottlenose dolphin, Risso’s dolphin, beluga whales, African and Asian elephants, to a lesser extent in macaque monkeys and raccoons
- 3 times higher concentrations of VENs in cetaceans in comparison to humans
- potentially represents convergent evolution due to adaptation to larger brains
- allow rapid communication across relatively large brains
18
Q
What is the clinical significance of the Intralaminar Thalamic Nuclei and the Centro-median nucleus?
A
- General anaesthetics suppress activity in ILN
- Bilateral lesions of C-M nucleus result in
- Coma or severe delirium
- Death
- Persistent vegetative state
- Mutism
- Unilateral lesions of C-M nucleus
- unilateral neglect
23
Q
What is the role of the Anterior Cingulate Cortex in consciousness?
A
- Error detection and conflict monitoring
- Sense of volition
- Registration of pain
- Social evaluation
- Reward-based learning
25
Q
What is the Default Mode Network (DMN)
A
- A large-scale brain network primarily composed of
- medial prefrontal cortex
- posterior cingulate cortex/precuneus
- angular gyrus (part of the TPJ)
- hippocampus and para-hippocampus
- DMN activity negatively correlated with activity in attentional and other networks
- Active when not focused on the outside world: Self-reference and reference to other conscious entities
- autobiographical information (episodic memory), self-reference traits etc.
- reflecting about one’s own emotional state, remembering the at and envisioning the future
- Theory of mind, moral reasoning, social evaluation & social categorization/ status
- story comprehension
26
Q
How do Brain Networks fair in Disorders of Consciousness according to scans?
A
- PET
- Global brain metabolism not a sensitive marker of consciousness
- fronto-parietal networks and their connectivity with thalamus breaks down in disorders of consciousness
- fMRI
- there is connectivity within DMN
- Connectivity between DMN & ECN breaks down in disorders of consciousness
28
Q
What functional measures can be used to correlate to consciousness?
A
- TMS with MEG or EEG
- Perturbational Complexity Index (PCI)
- Lempel-Ziv Complexity (LZc) - quantifies the number of distinct patterns present in data
- Amplitude Coalition Entropy (ACE) - reflects the entropy over time in set of most active channels
- Synchrony Coalition Entropy (SCE) - reflects the entropy over time of the constitution of the sets of synchronous channels.
