Consciousness Flashcards
consciousness
What is the definition of consciousness?
- The state of being aware of and responsive to one’s surroundings - Awareness or perception of an inward psychological or spiritual fact
Objective definitions of consciousness
Ability to respond to stimuli: sensation (pain, touch proprioception), auditory (verbal, non-verbal), visual, olfactory and taste The ability to speak, the ability to orientate in time and place
Subjective definitions of consciousness
The experience of sensory stimuli
the experience of emotion, memory, thought, self and non-self, experience of free will
Key aspects & requirements of human consciousness
Arousal Input: - sense organs - proprioception -interoception -emotion
Output and control:
Motor: speech, locomotion, dexterity
Cognitive: differentiation of awareness (naming, defining, recognising unique features) integration of awareness (categorising, semantics), perception and conception, memory, reasoning/logic/rationality, representation of space and time, representation of self & non-self, language, agency
Emotional system: drive/instinct - to percieve, think act
Sensory - subjective experience of emotion motor - e.g. expression of anger, laughter, pain
Physiological & pathological states and consciousness
Sleep, coma, death PVS, MCS, locked in syndrome
Describe sleep
-Decreased arousal (and hence awareness & therefore consciousness) -physiological -active process -reversible and cyclical
Describe slow wave sleep
Stage 3 sleep, full of delta waves waves less than 4Hz Deep, slow brain waves known as delta waves begin to emerge during stage 3 sleep. This stage is also sometimes referred to as delta sleep. During this stage, people become less responsive and noises and activity in the environment may fail to generate a response. It also acts as a transitional period between light sleep and a very deep sleep.
Describe Stage 2 sleep
Stage 2 is the second stage of sleep and lasts for approximately 20 minutes. The brain begins to produce bursts of rapid, rhythmic brain wave activity known as sleep spindles. Body temperature starts to decrease and heart rate begins to slow.
REM sleep
The brain becomes more active
Body becomes relaxed and immobilized
Dreams occur
Eyes move rapidly
Most dreaming occurs during the fourth stage of sleep, known as rapid eye movement (REM) sleep.
REM sleep is characterized by eye movement, increased respiration rate, and increased brain activity.
REM sleep is also referred to as paradoxical sleep because while the brain and other body systems become more active, muscles become more relaxed.
Dreaming occurs due to increased brain activity, but voluntary muscles become immobilized.
Coma
- characterised by a complete loss of wakefulness and reactivity
- a state of unresponsiveness to external stimuli with eyes closed
- pathological but usally reversible -prolonged unconsciousness
Causes of coma
sedation/anaethesia
epilepsy
electrolyte/metabolic
disturbance of thermoregulation
structural damage to brainstem/thalamus/cortex e.g. stroke, trauma, tumour
inflammation, infection
metabolic coma
triphasic theta hepatic, uraemia, diabetic, pancreatic, adrenocorticoid failure
Name this stage of sleep?
slow stage of sleep
Name this stage of sleep
Stage 2 sleep
Name this stage of sleep
REM sleep
Name this EEG pattern
Triphasic theta - in metabolic coma
Outcomes of metabolic coma
Reversal and recovery
survival into vegetative state or minimally conscious state
irreversible cessation of function of brainstem (brainstem death), cerebral cortex (neocortical death), body
Glasgow coma scale
Max 15, min 3
coma of 8 (e.g. E2, M5, V1 - just conscious)
Eye opening (E) - spontaneous (4), to speech (3), to pain (2), no response (1)
Eye opening is an index of arousal
Absent eye opening distinguishes coma/brainstem death from PVS and MCS
Best motor response to verbal command (M) - obeys commands (6), localises to pain (5), flexion-withdrawal to pain (4), flexion-abnormal to pain (3), extension to pain (2), no response (1)
Best verbal response (V), oriented and converses (5), disoriented and converses (4), inappropriate words (3), incomprehensible sounds (2), no response (1)
Vegetative state
Awake but unaware
Absent awareness (& hence consciousness)
Preserved arousal (preserved sleep/wake cycle)
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
ØPermanent Vegetative State
Categories of vegetative state
Continuing vegetative state (4 weeks)
Permanent vegetative state
- after a non-traumatic brain injury 6 months in the UK
- after traumatic brain injury 1 year
Unresponsive wakefulness syndrome (UWS)
- proposed by the European Task Force on Disorders and Consciousness, yet to be fully defined
RCP guidelines for coma
A state of unrousable unresponsiveness, lasting more than 6 hours in which a person:
- cannot be awakened
- fails to respond normally to painful stimuli, light or sound
- lacks a normal sleep-wake cycle and
- does not initiate voluntary actions
RCP guidelines for vegetative state
a state of wakefulness without awareness in which tehre is preserved capacity for spontaneous or stimulus-induced arousal, evidenced by sleep-wake cycles and a range of reflexive and spontaneous behaviours
VS is characterised by complete absence of behavioural evidence for self- or environmental awareness
Minimally conscious state (MCS)
A state of severely altered consciousness in which minimal but clearly discernible behavioural evidence of self- or environmental awareness is demonstrated.
MCS is characterised by inconsistent, but reproducible, responses above the level of spontaneous or reflexive behaviour, which indicate some degree of interaction with their surroundings
Continuing VS
A state of VS lasting for more than 4 weeks
May be classified as permanent VS if it has persisted for:
>6 months following anoxic or other metabolic brain injury
>1 year following traumatic brain injury
in cases of genuine clinical uncertainty, a further period of targeted monitoring (6-12 months) may be required to make a diagnosis of permanent VS
Recovery from permanent VS may be regarded as highly improbable
