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
Minimally Conscious state
Like vegetative state but with at least 1 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 signaled by at least one of two items:
functional communication
object use
Locked in syndrome
conscious (Aroused and aware)
unable to respond (de-efferented)
most cases are partially locked in:
- preserved vertical eye movements
- reserved eye opening
Causes:
- ventral pontine damage
- severe Guillian Barre syndrome
Brain stem reflexes
Corneal blink reflex -trigeminal (opthalmic branch) afferent, pons, facial efferent
Pupillary light reflex
Reflex conjugate eye movement to the side when turning patient’s head (vestibulo-occular reflex)
Brain stem death
Irreversible cessation of brainstem function
Such that consciousness could never be regained
- Absent Reflexes
- Pupils
- Ice Calorics
- Corneals
- Pain
- Gag
- Cough
- Apnoea - 5 min test after pre-oxygenation and allowing CO2 to reach 6Kpa
- No arousal
Legal requirements
Presence of an irreversible cause e.g. anoxia, structural damage
Absence of reversible cause e.g. drugs, hypothermia, alcohol, posions, 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
Macroscopic structures which correlate anatomically with consciousness
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 which correlate anatomically with consciousness
Von Economo neurones
Crown of Thorns neurons
What are Von Economo neurons and where are they found?
Large spindle-shaped soma (or body), gradually tapering into a single apical axon, with only a single dendrite facing opposite.
Found in 2 very restricted regions in the brains of hominids (humans and other great apes)
- Anterior cingulate cortex (ACC)
- Fronto-insular cortex (FI)
Also 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
?represents convergent evolution due to adaptation to larger brains
allows rapid communication across relatively large brains
Which is the von economo neuron and the normal pyramidal neuron?
Cerebral cortex
Creation of maps of the self and environment
Processing to integrate the maps and to respond appropriately
Intralaminar thalamic nuclei (including centro-median nucleus)
General anaesthetics suppress activity in ILN
Bilateral lesions of C-M nucleus
- Coma or severe delirium
- Death
- Persistent vegetative state
- Mutism
Unilateral lesions of C-M nucleus
- Unilateral neglect
Ascending reticular activating system
Serotonergic nuclei: dorsal raphe & median raphe
Dopaminergic nuclei: ventral tegmental area & substantia nigra pars compacta
Noradrenergic nuclei: locus coeruleus & related brainstem nuclei
Histaminergic nuclei: tubero-mamillary nucleus
Cholinergic nuclei
- Basal Nucleus of Meynert (attention)
- Pontine tegmentum: laterodorsal tegmental nucleus & pedunculopontine nucleus
What are some individual arousal systems?
Midbrain
- Dorsal raphe nucleus – 5HT
- Parabrachial nucleus glutamate, CRGP, dynorphin
- Pretectal area
- Periaqueductal grey
- Ventral Tegmental area - Dopamine
Pons
- Locus coeruleus – Noradrenaline
- Latero-dorsal tegmental nucleus – Acetyl Choline
- Pedunculopontine nucleus – Acetyl Choline
- Pontine raphe nuclei – 5HT
- Intralaminar centro-median nucleus - glutamate
Hypothalamus
- Tuberomammillary nucleus - Histamine
- Lateral hypothalamus – Hypocretin, glutamate
Basal Forebrain
- Substantia Innominata - Acetyl Choline
Functional imaging in disorders of consciousness
Coordinate-based meta-analysis
SPECT, PET & fMRI
Decreased activity (compared with healthy controls)
Default mode network (DMN)
Medial prefrontal cortex (mPFC)
Ventral medial prefrontal cortex (vMPFC)
Medial temporal lobes (mTL)
Posterior cingulate cortex (PCC)
Precuneus and posterior inferior parietal lobule (pIPL)
When is the default mode network activated?
DMN Components activated in:
Self-Reference:
- Autobiographical information (episodic memory) Detailed memory related to specific events in time
- Self-reference: traits and descriptions
- Reflecting about one’s own emotional state
- Remembering the past and envisioning the future (?free will)
Reference to other conscious entities:
- Theory of Mind
- Moral reasoning
- Social evaluations & social categorization / status
- Story comprehension
What is the role of the anterior cingulate cortex?
Role in consciousness?
Error detection and conflict monitoring
Sense of volition
Registration of pain
Social evaluation
Reward-based learning
Claustrum
Electrode between the left claustrum & anterior-dorsal insula.
Stimulation reproducibly resulted in:
- complete arrest of volitional behaviour
- unresponsiveness
- Amnesia
No negative motor symptoms or mere aphasia.
Disruption of consciousness did not outlast the stimulation
No epileptiform discharges.
Crown of thorns
Giant neurons encircling the brain
Three neurons stretched across both brain hemispheres, and one of the three wrapped around the organ’s circumference like a ‘crown of thorns’, Koch says
Phyisiolohical correlates of consciousness
Surface EEG
- High frequency, de-synchronized waking rhythm
- Alpha rhythm
- Gamma synchronization around 40Hz esp visual cortex
- High band gamma synchrony (85-150hz) – fronto-parietal
Event-Related Potentials
- Sensory
- P300 (P3a & P3b) - attention
- N400 – response to meaningfulness of stimuli
- Late positive complex (LPC) – explicit recognition memory
- Motor
- Bereitschafts-Potential – conscious preparation for voluntary movement (“free will”?)
Functional and theoretical correlates of consciousness
fMRI activation patterns during stimulation (especially in response to spoken questions)
Perturbational Complexity Index (PCI – Transcranial Magnetic Stimulation- evoked potentials
MEG Indices
- Lempel-Ziv Complexity (LZc) - quantifies the number of distinct patterns present in data
- Amplitude Coalition Entropy (ACE) - reflects the entropy over time of the set of most active channels
- Synchrony Coalition Entropy (SCE) - reflects the entropy over time of the constitution of the sets of synchronous channels
Phi (Integrated information theory) - ? how measured
The observations of Glasgow Coma Score testing might be described as the physical or somatic correlates of consciousness
Neuro-scientific theories of consciousness
Seek to explain consciousness purely in terms of neural events occurring within the brain (physicalism)
- Gerald Edelman (re-entrant circuits)
- Daniel Dennett
- Francis Crick & Christof Koch (The Claustrum)
- Dehaene & Changeaux (2001) Global Workspace
- Integrated information theory Tononi et al. (2008/2014)
- Antonio Damasio (“Self comes to Mind” 2010)
Quantum Theories of Consciousness
- Eg Penrose & Hameroff (1998)
Inattentional blindness
inattentional blindness, also known as perceptual blindness, is a psychological lack of attention that is not associated with any vision defects or deficits. It may be further defined as the event in which an individual fails to perceive an unexpected stimulus that is in plain sight.
Conscious perceptions
are constructions
e.g. neon spreading illusion
virtual reality can induce artificial out of body experiences
Subjective qualities of human consciousness
What is it like to be me or you?
Ability to experience sensory stimuli
Ability to experience emotion
Ability to experience memories
Ability to experience self
Ability to exert Free Will
- to direct the flow of thought
- to make decisions to act or think
The hard problem of consciousness
Nobody has the slightest idea how anything material could be conscious. Nobody even knows what it would be like to have the slightest idea how anything material could be conscious - Jerry Fodor
Trying to explain what it is like to be me or you
arises from brain structure and electrochemical activity
Leibniz’s mill
Leibniz’s mill
One is obliged to admit that perception and what depends upon it is inexplicable on mechanical principles, that is, by figures and motions.
Imagining that there is a machine whose construction would enable it to think, to sense, and to have perception, one could conceive it enlarged while retaining the same proportions, so that one could enter into it, just like into a windmill.
Supposing this, one should, when visiting within it, find only parts pushing one another, and never anything by which to explain a perception.
Thus it is in the simple substance, and not in the composite or in the machine, that one must look for perception
Philosophy of mind - dualism and monism
Dualism
- Socrates, Plato & Aristotle
- Decartes
- Res Extensa & Res Cogitans
Monism
- Pre-Socratic
- Heraclitus, Parmenides
- Post-Socratic
- Stoics & Plotinus - one substance, identified as God
- Spinoza
- Leibniz
- Hegel
Modern Materialism– The Theory of everything
Consciousness as an illusion
the self as a construction
- buddhism
- Metzinger - the transparent avatar
Difficult problems of consciousness
The hard problem - why is it like something to be a conscious organism
binding - integrating all the aspects into a single unified perception - senses (especially vision), memory, emotions, sense of self, sense of free will to direct thought and action
location of consciousness
splitting of consciousness
unconscious awareness
other minds
dreams
