T1 L15. Consciousness (AN)(1).pptx

Consciousness Dr Angus Nisbet Consultant Neurologist & Sleep Physician Etymology of Consciousness  Latin:  con "together" and scio "to know" “knowing together” - orign  Origin  Possibly introduced into English by Ralph Cudworth, Cambridge Platonist (1617 – 1688)  Todays  meaning From...

Consciousness Dr Angus Nisbet Consultant Neurologist & Sleep Physician Etymology of Consciousness  Latin:  con "together" and scio "to know" “knowing together” - orign  Origin  Possibly introduced into English by Ralph Cudworth, Cambridge Platonist (1617 – 1688)  Todays  meaning From John Locke’s Essay Concerning Human Understanding 1690 Definitions of Consciousness  Oxford English Dictionary   John Locke, Essay Concerning Human Understanding 1690   “The state of being aware of and responsive to one's surroundings” “The perception of what passes in a man's own mind”- (Book 2, Chap 1, Sect 19) • ‘Mind’ is arguably an alternative word for consciousness • • The origin of the modern concept of consciousness is often attributed to John Locke He doesn’t seem to include emotions Thomas Nagel 1974  If there is “something that it is like” to be that creature [ie subjectivity], then it is conscious • •  Ted Honderich, Actual Consciousness 2014   “The appearance of a world – a subjective world” – sounds pretentious, but good 3 components in his full theory (‘actualism’) • • •  The word ‘like’ implies a comparison with another (previous) conscious experience Therefore circular Perceptual Consciousness: “seeing and the like” Reflective Consciousness: “thinking and the like” Affective Consciousness: “desiring, feeling and the like” Modern Concepts   Consciousness: The property of ‘experiencing’ anything at all Human Consciousness: The property of ‘experiencing’ sensations, perceptions, thoughts, emotions • • Substitutes the word ‘experiencing’ for consciousness – therefore circular Illustrates that one can’t define consciousness by reference to anything else How do you know somebody is conscious?  Responsiveness (sensori-motor) • Eye movements • Head turning • Protective movements (blinking, withdrawal, defensive postures and movements) • Spontaneous voluntary actions (the appearance of) • Vocalization   Eg to pain Verbal Report • • • •  of sensation of perception (recognition) of orientation of memory The problem of other minds  Are ‘philosophical zombies’ conceivable? Definitions of Consciousness Medical vs Philosophical Objective  Ability to respond to stimuli  Sensory stimuli Subjective  The experience of sensory stimuli  Sensation      Pain  Touch  Proprioception  Auditory stimuli   Verbal  Non-verbal Visual Stimuli  Olfactory and gustatory stimuli Ability to Spontaneously Move      Eyes Head Limbs Ability to speak The ability to orientate in time & place     Awareness of environment Self-awareness Memory & Recognition Ability to reason Auditory  Verbal  Non-verbal   Pain Touch Proprioception Interoception Visual Olfactory and taste The experience of emotion The experience of memory The experience of thought The experience of self & non-self Agency: The experience of free will to:  Act  Speak  Direct Attention  Think        Red Highlight Indicates use in the Glasgow Coma Score     Imagine Conceive Calculate Plan Key Requirements for Human Consciousness   Arousal / Attention Input Sources - Embodiment  Having a body  External Input   Internal Input       Proprioception Interoception Emotion Connectivity Memory Processing Capacity  Rationality  Integration of information    Binding Categorising, semantics, binding of experience Differentiation of information   Sense organs Naming, defining, recognizing unique features Output Pathways? Key Aspects of Human Consciousness  Content            Cognition Differentiation of information – naming, defining, recognizing unique features Integration of information – categorising, semantics, binding of experience Perception & Conception – requires abstraction Memory (& hence recognition) Reasoning / Logic / Rationality eg law of non-contradiction Representation of Space & Time Representation of self & non-self (including other ‘selves’) Language – coded representation Agency: purpose-driven direction of thought (& action) Output / Control  Motor      Speech Locomotion Dexterity Eye Movements / head movements / other orientating movements Emotional    Autonomic responses: parasympathetic and sympathetic output Expression eg expression of anger, laughter, pain Drive /Instinct – to perceive, think and act Consciousness is an active process:  The Stream of Consciousness How Far Does Consciousness Extend?  The tree of Life How Far Does Consciousness Extend? Could Non-Living Things Become Conscious? Physiological States of Consciousness & Disorders of Consciousness         Sleep (various stages) Psychedelic states General Anaesthesia Coma PVS MCS Locked in Syndrome (Death) Sleep  Decreased Arousal  Decreased awareness • ie decreased conscious level    Physiological Active process Reversible & Cyclical Slow Wave Sleep Stage 3 (AASM) > 20% delta of >75mv in frontal leads Stage 2 Sleep REM Sleep Coma  Pathological  Complete prolonged loss of wakefulness & awareness (unconsciousness)  Unresponsiveness to external stimuli  Eyes usually closed  Often reversible Coma  Causes:       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 Metabolic Coma Triphasic Theta      hepatic uraemia diabetic pancreatic adrenocorti coid failure Coma Outcome 1. 2. Reversal and recovery Vegetative state or minimally conscious state (severely damaged neocortex) 3. Brainstem death (Irreversible cessation of brainstem function) Glasgow Coma Scale  Max 15, Min 3  GCS 8 (eg E2, M5, V1) - just conscious  Absent eye-opening distinguishes:   Coma / brainstem death from PVS and MCS Vegetative State “Unresponsive Wakefulness Syndrome”  Wakefulness     Absent awareness (& hence consciousness) Unresponsiveness:      No voluntary response to environment Variably preserved reflex responses to environment Cause:   Preserved arousal Preserved sleep/wake cycle widespread neocortical damage esp anoxia, head injury Persistent Vegetative State Permanent Vegetative State Vegetative State “Unresponsive Wakefulness Syndrome”  Continuing (persistent) vegetative state   4 weeks Permanent (chronic US) vegetative state  After a non-traumatic Brain Injury • 6 months in the UK • 3 months in the US  After Traumatic Brain Injury • 1 year  ‘Unresponsive wakefulness syndrome’ (UWS)  Proposed by the European Task Force on Disorders of Consciousness. Minimally Conscious State  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 signaled by at least one of 2 items:   functional communication object use. Detecting Awareness in the ‘Vegetative State’ (ie MCS) Tennis: Supplementary motor area (SMA) activity Imagining moving around a house: Parahippocampal gyrus (PPA) Posterior parietal-lobe (PPC) Lateral premotor cortex (PMC). Detecting Awareness in the Vegetative State Adrian M. Owen, Martin R. Coleman, Melanie Boly, Matthew H. Davis, Steven Laureys, John D. Pickard Science 08 Sep 2006: Vol. 313, Issue 5792, pp. 1402 Locked In Syndrome  Conscious   Unable to respond   de-efferented Most cases partially locked in:    aroused & aware preserved vertical eye movements preserved eye-opening Causes  Ventral Pontine Damage • UMN de-efferented  Severe Guillain Barre Syndrome • LMN de-efferented 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    allowing CO2 to reach 6Kpa after pre-oxygenation No arousal Spot 2 mistakes Brainstem reflexes Brain Stem Death Legal Requirements  Presence of an irreversible cause   Absence of reversible cause   eg anoxia, structural damage drugs, hypothermia, alcohol, poisons, metabolic (pupils react) or electrolyte disturbances, circulatory dysfunction  Irreversible cessation of function of Brainstem (brainstem death) – confirmed by 2 doctors Must be repeated after 24 hours of ongoing life support  Organ donation Where is Consciousness? Anatomical Correlates of Consciousness  Macroscopic Structures    Cerebral Cortex Brainstem and diencephalic arousal systems ‘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 Anatomical Correlates of Consciousness  Von Economo Neurons      Large spindle-shaped soma (or body) Gradually tapering into a single apical axon Only a single dendritic tree facing opposite Allow long-distance rapid communication across relatively large brains Found in very restricted brainsregions of hominids (humans and other great apes) • • •  Anterior cingulate cortex Fronto-insular cortex Dorsolateral prefrontal cortex (humans only) Also in brains of whales, killer whales, dolphins, elephants and raccoons • • 3 times higher concentrations of VENs in cetaceans in comparison to humans ? convergent evolution due to adaptation to larger brains Von Economo Neuron (right) Normal pyramidal Neuron (left) 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 thalamic intra-laminar nuclei Bilateral lesions of centro-median nucleus      Coma or severe delirium Death Persistent vegetative state Mutism Unilateral lesions of centro-median nucleus  unilateral neglect Arousal Systems by Neurotransmitter  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:   Latero-dorsal tegmental nucleus Pedunculo-pontine nucleus Arousal Systems by Brain Region  Midbrain       Pons       Locus coeruleus – Noradrenaline Latero-dorsal tegmental nucleus – Acetyl Choline Pedunculopontine nucleus – Acetyl Choline Pontine raphe nuclei – 5HT Intralaminar centro-median nucleus glutamate Hypothalamus    Dorsal raphe nucleus – 5HT Parabrachial nucleus glutamate, CRGP, dynorphin Pretectal area Periaqueductal grey Ventral Tegmental area - Dopamine Tuberomammillary nucleus - Histamine Lateral hypothalamus – Hypocretin, glutamate Basal Forebrain  Substantia Innominata - Acetyl Choline Anterior Cingulate Cortex  Role in consciousness?      Error detection and conflict monitoring Sense of volition Registration of pain Social evaluation Reward-based learning Claustrum Stimulation 2014 • 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. Claustrum Giant Neurons Encircling The Brain (Koch, Feb 2017 - unpublished)  Densely connected structure:  Cortex • esp fronto-parietal cortex, cingulate and precuneus.  Thalamus “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” Resting brain activity in disorders of Consciousness Hannawi et al (2015)   Meta-analysis - coordinate-based SPECT, PET & fMRI resting state studies  In disorders of consciousness (DOC)      coma minimally conscious state emergence from minimally conscious state vegetative state Reduced activity within ,       bilateral medial dorsal thalamic nucleus left cingulate posterior cingulate (DMN) precuneus (DMN) middle frontal gyri medial temporal gyri The Neural Correlate of (Un)Awareness: Laureys 2005 Large Scale Brian Networks    Collections of widespread brain regions showing functional connectivity by statistical analysis of the fMRI, PET, EEG, MEG, or fNIRS signal Overlapping Debated terminology Default Mode Network (DMN)   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 Active when not focused on the outside world DMN activity negatively correlated with activity in attentional and other networks Default Mode Network (DMN) Binding of the self?  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 Brain Networks in Disorders of Consciousness  PET    Global brain metabolism not a sensitive marker of consciousness Fronto-parietal network and their connectivity with thalamus breaks down in disorders of consciousness fMRI   Connectivity within DMN Connectivity between DMN & executive control network breaks down in disorders of consciousness Brain Network Studies in Chronic Disorders of Consciousness: Advances and Perspectives Ming Song, Yujin Zhang,Yue Cui, Yi Yang and Tianzi Jiang Neurosci Bull. 2018 Aug; 34(4): 592–604. Physiological Correlates of Consciousness  Surface EEG High frequency, de-synchronized waking rhythm  Alpha rhythm (8-13hz)  Depth  EEG Gamma (30–150 Hz) synchronization • visual cortex & sensory cortex • higher cortex, during working memory & learning • gamma power increases with sensory drive, perceptual grouping & attention. Physiological Correlates of Consciousness  Event-Related Potentials EEG averaged over repeated events Measurable, stereotyped, electro-magnetic brain correlates of sensory, cognitive, or motor events Sensory     • P300 (P3a & P3b)  • N400  • reflects processing of meaningfulness of stimulisemantic Late positive complex (LPC)   Attention to cognitively salient stimuli from any sense • P3a – novelty • P3b – un-expectability explicit recognition memory (400–500 ms) Motor • Bereitschafts-Potential – conscious preparation for voluntary movement (“free will”?) Functional Correlates of Consciousness  Transcranial magnetic stimulation TMS with MEG or EEG  Perturbational Complexity Index (PCI)  complexity of electroencephalographic (EEG) responses to transcranial magnetic stimulation (TMS), PCI cut-off value 92% sesnsitivty in detecting minimal signs of consciousness  Conscious Perceptions Are Constructions Neon Spreading Illusion Botvinick & Cohen. (1998) Virtual reality can induce Artificial ‘out-of-body’ experiences Blanke et al. (2007) Theories of Consciousness  Global workspace theory – Baars 1989  Global neuronal network theory - Dehaene & Changeux 1998  Integrated information theory - φ (Phi) Tononi 2004  Quantum theories of consciousness    Illusionism    Phillip Goff Idealism   Consciousness is an illusion ‘Consciousness is not what you think it is’ (Dennett) Panpsychism   Orchestrated objective reduction (Penrose & Hammeroff) Consciousness field Bernado Kastrup Psycho-physical parallelism & dual aspect ontology  Interactionist Dualism & (traditional religious views) Subjective Qualities of Human Consciousness  “What it is 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  How do we explain this? “The Hard Problem of Consciousness” Chalmers 1995 “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 (1992) “The Hard Problem of Consciousness” Chalmers 1995  Trying to explain how “what it is like to be me (or you)” arises from the brain structure and electro-chemical activity 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. In 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 Illusion  Consciousness as an illusion  The self as a construction   Buddhism Metzinger • The Transparent Avatar Difficult Problems of Consciousness  The Hard Problem (Chalmers)   Binding - integrating all the aspects into a single unified percept           Split brains Dissociative disorders Unconscious or pre-conscious   Senses (especially vision) Memory Emotions Sense of self Sense of free will to direct thought & action Location of Consciousness Splitting of Consciousness   How consciousness is related to brain structure & function perception emotion Other Minds Dreams Psycho-Physical Parallelism  Arnold  Geulincx (1624—1669) Les Deux Horloges: “corps et ame se comportent comme deux horloges qu'un aurait synchroniseees”  Gottfried Wilhelm (von) Leibniz (1646-1716) Monadology 78-81 – The PreEstablished Harmony    78. The soul follows its own laws, and the body likewise follows its own laws. They are fitted to each other in virtue of the pre-established harmony between all substances 79. Souls act in accordance with the laws of final causes through their desires, ends and means. Bodies act in accordance with the laws of efficient causes or of motion. The two realms, that of efficient causes and that of final causes, are in harmony, each with the other. 81. Bodies act as if (to suppose the impossible) there were no souls at all, and souls act as if there were no bodies, and yet both body and soul act as if the one were influencing the other.  John  Hughlings Jackson (1835 –1911) Father of English Neurology The doctrine I hold is : first, that states of consciousness (or, synonymously, states of mind) are utterly different from nervous states; second, that the two things occur together - that for every mental state there is a correlative nervous state ; third, that, although the two things occur in parallelism, there is no interference of one with the other. This may be called the doctrine of Concomitance. Conclusion However fine-grained (in time and space) the neural correlates of consciousness are, the explanatory gap between mind & matter remains (‘the hard problem of consciousness’) The End