Week 2 Psych 169 PDF

Today’s Lecture:  Neural correlates of consciousness (NCC)  Locked-in syndrome  Persistent Vegetative State (PVS)  Minimally Conscious State (MSC)  Phantom limbs  Neural correlates of consciousness (NCC):  Does not try to tackle the hard problem: – Qualia – Theoretical and philosophical...

Today’s Lecture:  Neural correlates of consciousness (NCC)  Locked-in syndrome  Persistent Vegetative State (PVS)  Minimally Conscious State (MSC)  Phantom limbs  Neural correlates of consciousness (NCC):  Does not try to tackle the hard problem: – Qualia – Theoretical and philosophical problems  Instead, lets study neural processes and correlate them with conscious experience r  NCC: Usual caution about causality  When a correlation is found between neural events and conscious experience, we must consider all possibilities: – 1) Neural event caused conscious experience – 2) Neural event caused by conscious experience – 3) Something else caused both  Confound between neural activity coding the stimulus and coding the conscious experience of color  Confound between neural activity coding the stimulus and coding the conscious experience of color How to study NCC?  Keep stimulus constant  Record brain events as conscious state changes  Example: Necker cube  Another example of how to study NCC?  Binocular rivalry  Different images presented to the two eyes  Stimulus does not change, but the percept flips  Where in the brain does it happen?  V1 activity changes in sync with flip of the percept  Originates in monocular neurons in V1 (inhibitory action) V1 – But, higher cortical centers are also involved To Left Eye To Right Eye Perception that flips – Single cell recordings in monkeys  Increasingly larger proportion of neurons sync to image flip as you go to higher brain areas:  V1/V2 = 20%  V4/V5 = 40%  Hgher centers: inferior temporal cortex (IT) & superior temporal sulcus STS = 90%  Another approach: Finding neural correlates for disorders of consciousness  Locked-in syndrome – Part of the brainstem is damaged from accident, disease, or stroke – Higher functioning areas are spared – All muscles are paralyzed except for the eyes – Communicate by blinking or computer interface Jean-Dominique Bauby Diving bell  “My heels hurt, my head weighs a ton, and something like a giant invisible diving bell holds my whole body prisoner.” “…the life I once knew was snuffed out Friday, the eight of December, last year. Up until then, I had never even heard of the brain stem. I’ve since learned that it is an essential component of our internal computer, the inseparable link between the brain and the spinal cord. I was brutally introduced to this “…vital piece of anatomy when a cerebrovascular accident took my brain stem out of action.”  Locked-in syndrome  Using EEG and EOG to communicate  Persistent vegetative state (PVS) – Wakefulness without awareness – PVS is between coma and minimally conscious state (MCS) – Coma: eyes closed and non-responsive to stimuli – MCS: inconsistent signs of consciousness (may understand simple commands)  PVS is caused by damage to higher areas of brain (trauma, virus, tumor,…)  Brainstem is relatively intact  Patient may fully recover or remain in PVS  If a patient remains in vegetative state for more than 4 weeks, the condition becomes classified as persistent vegetative state  Some PVS patients are chronically awake  Most show regular sleep-wake cycles  Most also show REM sleep, though REM sleep duration is shorter than normal controls  No correlation between REM sleep duration and likelihood of recovery from PVS  Better chance of recovery if PVS is caused by head injury than if it is caused by lack of oxygen to the brain  Do they feel pain?  Electrical stimulation to PVS patients  Brainstem, thalamus, primary somatosensory cortex were activated  Higher centers of the brain did not respond  Loud sounds: Activity in primary auditory cortex (A1) but not higher centers  PVS is due to dissociation between primary sensory areas and fronto-parietal network So are PVS patients conscious?  Terri Schiavo case  At age 26 went into cardiac arrest  Massive brain damage due to lack of oxygen to brain  PVS for 5 years  Series of court and legislative actions  Owen et al. (2006): Detecting awareness in PVS  Maybe “Islands” of preserved brain functions exist  Spoken instructions: – “imagine playing a game of tennis” – “imagine walking to all the rooms in your house starting from the front door” Playing tennis: activated the supplementary motor area Walking: parahippocampal place area (PPA), posterior parietal cortex, premotor cortex  PVS patient understood spoken commands and responded through brain activity  Patient’s decision to cooperate with the authors shows a clear act of intention  Terminology: PVS is starting to be called: unresponsive wakefulness syndrome  Do patients who recover from PVS, remember what happened during their vegetative state?  28 year old male was in a car accident resulting in PVS  Recovered after 20 months in PVS  Could correctly recollect his previous life  Could not consolidate new information during PVS  Had anterograde amnesia (could not form new memories during PVS) Phantom Limbs  Over 90% experience phantom limbs after losing an arm or leg  Onset could be the same day, or develop days or weeks later  Could last for years or decades  Pain sensations: Phantom leg can cramp up  Phantom hand involuntarily clenched  There could be other sensations: itching, roughness (walking on gravel), cold, hot, …  Pain mostly affects parts of body farthest from the body, like foot of an amputated leg  The exact cause of pain is unclear  May be a response to mixed signals to brain  Triggers the basic message: Something is not right.  Broadcasts this message using pain  Common explanation?  Severed nerves still pass signal to brain  Brain interpretation: limb is still there  What happens to cortical areas representing the missing limb? – Heat, cold, or touch on face is sometimes perceived as heat, cold, or touch on phantom hand – Somatosensory cortex: Face area is near hand area – Face area takes over Neural Correlates of Pain  Perception of pain  Pain is always subjective (qualia)  Larger areas of activity in anterior cingulate cortex (ACC) when pain is more intense Cingulate Cortex Anterior Cingulate Cortex  Ramachandran’s treatment of phantom pain  Phantom hand clinched and painful  Patient sees reflection of normal hand  Task: move both hands together  Visual feedback resulted in reduction of pain  Virtual arms also ease phantom pain  Patient can see and move a virtual arm  Electric signals from the muscles in the amputated arm sent to computer  Creates real-time movement  Today’s Lecture:  Where in the brain does consciousness “happen”?  Theories of consciousness  Global Workspace Theory (GWT)  Integrated Information Theory (IIT)  Quantum Physics Theory Where does consciousness happen in the brain?  Is there a “consciousness center” in the brain?  There is no single place  No stream of neural activity going to this central place  No commands coming out from this central place  Massive parallel processing  Feedback loops  Complex cell assemblies forming and dissolving  Interactions between distant areas (corticocortical & corticothalamic)  Plenty of interaction, but no center  An interesting discovery Giant Neurons in the Claustrum Claustrum Claustrum giant neurons  We can safely say that distributed processing in various parts of the brain are involved in consciousness  An interesting discovery:  ”The disunity of consciousness” published in TICS (Trends in Cognitive Sciences)  Demonstrated that consciousness happens in different places in the brain and at different times (not synchronized) Semir Zeki (University College London)  Examined two area of the brain: – V4: color processing – V5 (MT): motion processing  Color and motion systems occupy geographically distinct locations in the brain  Damage to V4 results in achromatopsia (color blindness)  Damage to V5 leads to akinetopsia (visual motion blindness)  Processing sites are also conscious sites  Color qualia is generated in V4  Motion qualia is generated in V5  fear qualia generated in amygdala  Olfactory qualia (smell of coffee) generated in olfactory cortex  These are called micro-consciousness  How do we know that processing sites are where consciousness happens?  Patient GY blinded in one hemifield in childhood (damage to V1)  Cannot see object (apple) on left side  Is correctly able to tell if it is moving or not Lesion to visual cortex  Direct input to V5 (bypassing V1)  If you can directly send visual information (motion) to the specialized area (V5) then it can result in a conscious correlate of motion  Further evidence:  If the object (apple) is not moving in left hemifield, then GY is not conscious of it  But moving the apple makes GY conscious of its existence  GY goes from not-conscious to conscious…  What happens in GY’s brain (fMRI)?  Activity increases only in V5 and nowhere else  Implication: – V5 is where consciousness happens (for motion) – V4 is where consciousness happens for color  When does consciousness happen?  You become conscious of the color and motion of an object at different times  Color is perceived before motion by 80 milliseconds  Then why does everything seem in sync? – Brain ignores mismatched times – Perceptually synchronizes everything  Theatre of the Mind (What does being conscious feel like?)  What does it feel like being you now? – Somewhere inside my head – Looking out through my eyes – Feel the position of my body – Can hear sounds around me – Ideas come in and glide away – If I shut my eyes, I can imagine things (as if looking at images)  Some have compared this to a theatre  Dennett calls this the “Cartesian theatre”  This theatre has a mental screen  Images are projected on screen for viewing by my “mind’s eye”  Images and feelings in this place are in consciousness  The rest are unconscious  The show: “stream of consciousness”  The audience: “me”  Experiments with the mental screen  Roger Shepard (Stanford U.)  Mental rotation of 3D objects  Made objective measurements  Time to reach decision is correlated with time it takes to physically rotate the object in space Mental rotation Mental Rotation  Conclusion from Shepard’s experiments  Mental images are like pictures  Mental rotations can happen unconsciously – Key in a door – Reach for a cup handle  Where in the brain does mental rotation occur?  Right posterior parietal lobe Harris, I. M., et al. Selective right parietal lobe activation during mental rotation: A parametric PET study. Brain, 123, pp. 65-73.  Who is looking at the metaphorical mental screen?  The “inner” you, has “inner eyes”  Homunculus problem  Infinite regress  Crick and Koch: – There is no infinite regress if frontal parts of the brain are “looking at” sensory systems in the back Theories of Consciousness  Global Workspace Theory (GWT)  Integrated Information Theory (IIT)  Quantum physics theory of consciousness Global Workspace Theory (GWT) Bernard Baars Stanislas Dehaene  GWT: Think about consciousness as a theatre – Consciousness is like a “bright spot” on stage – Directed to different actors by spotlight of attention  Different actors (players) compete for access to consciousness  Who are the players? Ideas, visual imagery, hearing, seeing, thoughts, feelings,… – Bright spot surrounded by fringe events (vaguely conscious) = working memory – Backstage: numerous unconscious systems that shape the events happening in the bright spot (language, autobiographical memory, learned skills) – Unconscious audience is sitting in dark getting information broadcast to them from stage  GWT: Brain is structured so that only a few items at a time are dealt with in the Global Workspace (7 plus or minus 2)  Baars: “Consciousness is not mysterious. It is a working part of the cognitive system”  GWT avoids dealing with the hard problem Integrated Information Theory (IIT)  Integrated information theory (IIT) Giulio Tononi and Christof Koch  A system is conscious to the extent that it has “integrated information”  Φ (phi) is a measure of the system’s integration of information  Φ is measured in bits  The larger the value of Φ the more conscious a system is  According to IIT, consciousness is graded Increasing Φ less More Conscious Conscious  What about a camera image sensor?  1 megapixel camera (1,000,000 pixels)  Number of different patterns = 21,000,000  Number of atoms in the universe = 2266  Camera is obviously not conscious  Why not?  Camera sensor is a collection of one million individual, completely independent photodiodes, each with two states  Collectively no smarter than one photodiode  When you see an image, you experience it as an integrated whole  You cannot experience properties independently (color, shape, location) Quantum Physics Theory of Consciousness  Quantum Theory  Sir Roger Penrose  2020 Nobel Prize  Conscious understanding is completely different than computation  Brains are completely controlled by physics  It requires a completely new kind of physics that can deal with non-computable problems  Elementary particles “They behave in a way that is like nothing that you have seen before. Your experience with things that you have seen before is incomplete. The behavior of things on a very Richard Feynman tiny scale is simply different. An (Nobel Prize) atom does not behave like a …miniature representation of the solar system with little planets going around in orbits.”  Quantum Theory  Penrose: Consciousness emerges from quantum processes in microtubules  Tiny tube-like proteins found in all cells  Superposition: Something exist in two states (card falling both face down/up)  Superposition: Schrodinger’s cat  How do we deal with this absurd result? From Erwin Schrodinger’s 1935 paper: The present situation in quantum mechanics. “One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following device (which must be secured against direct interference by the cat): in a Geiger counter there is a tiny bit of radioactive substance, so small, that perhaps in the course of the hour one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer which shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The psi-function of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts.”  Copenhagen Interpretation  Macroscopic objects are made up of atomic particles, so why don’t we see superposition in real world?  We observe a single outcome  The multiple states collapse into a single state when observed (not computable)  Completely random The Copenhagen interpretation Werner Niels Bohr Heisenberg But… there is another interpretation  Many Worlds Interpretation  No collapse  Superposition: alternative parallel worlds Many Worlds Interpretation Relevance to consciousness  Free will  Quantum Randomness: Which state a system collapses into is truly random (to which side the playing card will fall)  Quantum indeterminacy (randomness) explains existence of free will  Entanglement: The state of one particle determines that of the other entangled particle no matter how far away they are from each other  Entanglement can bring about this sense of unity of the self  Criticisms:  Some drugs damage microtubules but have no effect on consciousness  Some drugs (anesthetics) have no effect on microtubules but cause unconsciousness  Microtubules: not involved in sleep-wake cycle  Microtubules are not isolated enough  How does subjective experience (qualia) arise from microtubules (green, pain, joy,…)  Chalmers’ mocking criticism: Consciousness is mysterious, quantum theory is mysterious, therefore they must be related