Week 1 Psych 169 Consciousness & the Brain PDF

Consciousness & the Brain Psychology 169 Dr. Kourosh Saberi Teaching Assistant: Kathleen Medriano  Text: Consciousness: An Introduction, 3rd Edition Susan Blackmore & Emily Troscianko  Chapters 1-12, 15  Recommended Text: – Consciousness and the Brian: D...

Consciousness & the Brain Psychology 169 Dr. Kourosh Saberi Teaching Assistant: Kathleen Medriano  Text: Consciousness: An Introduction, 3rd Edition Susan Blackmore & Emily Troscianko  Chapters 1-12, 15  Recommended Text: – Consciousness and the Brian: Deciphering How the Brain Codes Our Thoughts.  Topics:  Theories of consciousness  Attention & its relation to consciousness  Dorsal and ventral cortical streams  What do perceptual illusions tell us about consciousness  Split-brain patients – Split consciousness?  Damaged brains: – locked-in syndrome – Persistent vegetative states (fMRI) – Anosagnosia paralysis – Blindsight (Damage to V1)  When did consciousness arise during evolution? – Adaptive value for survival (natural selection)  Are animals conscious? – Self-recognition  Transitional states:  What can we learn from sleep? – dreaming – Waking up – Sleepwalking  Anesthesia  Could a machine be conscious? – Recent developments in quantum computing  How to build a conscious machine  Can quantum physics explain consciousness? Course requirements  Grading:  Midterm 1 (1/3 of course grade)  Midterm 2 (1/3 of course grade)  Final: (1/3 of course grade)  50 questions, multiple choice  Grades will be curved based on class performance  Grading:  You may drop one exam  Each of the 2 remaining exams: 50% of course grade  Today’s Lecture: The Problem of Consciousness  Defining the problem  Qualia  The explanatory gap  The “hard problem”  First vs. third-person problem  Defining the problem:  No generally accepted definition of “consciousness”  Defining the problem:  Everyday usage: “awake”, “knowing something”, “attending to something”  Often contrasted with “unconscious”  In scientific study of consciousness, it often refers to “subjective experience” Qualia  Qualia are qualities that are experienced subjectively  Singular: quale (pronounced qua-lay) – smell of coffee – the experience of color – pitch of a sound  Qualia: emphasis on perceptual experience instead of physical/neural mechanisms How odorants stimulate receptors in the olfactory bulb How rods/cones in the retina are stimulated by different wavelengths of light How hair cells in the cochlea encode different sound frequencies  A quale is what something is like  Problem of consciousness: how objective (physical) brains produce subjective qualia  The history of consciousness is the history of explaining a gap  But what sort of gap is this?  Mary the color scientist  Australian Philosopher Frank Jackson  One of the best know thought experiments  Are qualia something separate from the brain?  Mary lives far in the future  Neuroscience is complete  Scientists know everything there is to know about the physical processes in the brain and how they produce behavior  Mary specializes in color vision  Mary knows everything there is to know about mechanisms of color vision: Retinal mechanisms Optics of the eye Different wavelength Physics of light Central Neural Pathways  Mary has been brought up all her life in a black and white room Retinal mechanisms Optics of the eye Different wavelength Physics of light Central Neural Pathways  She has never seen any colors at all  Observing the world through black & white TV monitor  One day, Mary finally leaves her black & white room and sees colors for the first time  What happens?  “Wow…I never realized red would look like that”  Or will she say “That’s red, that’s green, nothing new of course”  Frank Jackson: When Mary comes out, she obviously learns something fundamentally new – what red is like  Now she has color qualia as well as physical facts  Chalmers: No amount of knowledge about physical facts could have prepared her for what it feels like to see a blue sky or green grass  …Physical facts about the world are not all there is to know (Chalmers)  Objections: – Mary does experience something surprising, but its because she comes to know an old fact in a new way – Or, she learned a new skill not a new fact  Daniel Dennett says Mary will not be surprised: – The premise of the story is false – We did not follow instructions – We failed to allow Mary to know everything there is to know about color  Dennett’s alternate ending: – Mary’s captors give her a blue banana – She is not fooled – “Hey, you tried to trick me. Bananas are yellow, but this one is blue” – Mary: I know everything about color vision – I know exactly what impressions yellow and blue objects would make on the nervous system – I know exactly what thoughts they would induce in me – This is what it means to know all physical facts  Frank Jackson (Mary’s inventor) later changed his mind – “Mary will not be surprised by color” – “If you think Mary will learn something new, you are biased by your own current limited knowledge”  What do you think?  If you believe that Mary will be surprised, then you believe that qualia (subjective experience) is something additional to knowledge of the physical world  If you think she will not be surprised, then you believe that knowing all facts tells you everything, including what it is like to experience something The Explanatory Gap  American Philosopher Joseph Levine coined the phrase: “The Explanatory Gap” (1984)  Defined as the gap between physical brain activity and conscious experience  The Explanatory Gap  William James (1890): the “chasm between the inner and the outer worlds”  Tyndall (Irish Physicist) “The passage from the physics of the brain to …consciousness”  Behaviorists didn’t worry about this “great gap” because they simply avoided mentioning consciousness or subjective experience Stimulus Response  Australian Philosopher David Chalmers: – “Easy” problems – “Hard” problem  Easy problems: Studied using standard research methods in cognitive science Attention Memory Motor Control – Solved by understanding neural or computational mechanisms  Hard problem: subjective experience – To experience the quality of deep blue – Or sensation of middle C  Hard problem:  Chalmers: Even when you’ve explained all neural mechanisms and functions related to experience, two questions remain: – Why are these functions accompanied by experience (why not a zombie or a robot)? – How physical processes in the brain give rise to subjective experience? The first-person third-person problem in the study of consciousness  Scientific study of consciousness based on empirical findings and testable theories  Consciousness is our first-person view of the world  Most science: third-person view, things that can be verified and agreed on by others.  Is it possible, in principle, to gain access to another person’s experience (qualia)?  Conjoined Twins (sharing parts of the brain)  Conjoined twins (British Columbia)  Brains connected by a "thalamic bridge" Krista and Tatiana Hogan  Light flashed to eyes of one twin causes activity in visual cortex of other twin Tatiana and Krista Hogan  Scrape ketchup off her tongue  Laugh at things together without speaking, as if they have the same thought Tatiana and Krista Hogan  Tatiana controls 3 arms and a leg, while Krista controls 3 legs and an arm  Tatiana can see out of both of Krista’s eyes, Krista can see out of one of Tatiana’s  They say they know one another’s thoughts without needing to speak (“We talk in our heads”) The first-person third-person problem: Neural networks associated with concepts Jennifer Aniston Neurons Jennifer Aniston Neurons in the Hippocampus Jennifer Aniston Neurons in the Hippocampus  Jennifer Aniston Cells – Hippocampus Halle Berry Neuron Halle Berry Neuron  Other neurons selectively responded to:  The Beatles  Michael Jordan  Bill Clinton  The Simpsons Cartoon  Sydney Opera House  Such examples, conjoined twins and concept specific networks, can potentially provide insight into solving the hard problem  Today’s Lecture:  Early theories  Philosopher’s zombie  What is it like to be a bat (reductionism)  Veridical perception (Visual system’s representation of the external world)  Early theories:  Broadly divided into Monist (one kind of stuff in the world), and Dualist (two kinds)  Monist: – Mental world is fundamental (George Berkeley) – Physical world is fundamental Berkeley (1685-1753)  Epiphenomenalism: Mind is produced by physical events, but has no causal role (cannot affect the physical)  Sound of a locomotive whistle can’t influence its machinery Thomas Huxley (1825-1895)  Dualism: mind & brain are two different stuff  French Philosopher René Descartes (1596- 1650)  Wanted to base his philosophy on a firm foundation (what am I absolutely sure of?)  “I think, therefore I am”  Substance Dualism  Descartes: the mind and physical world interact in the pineal gland  Problem?  Proposing a site doesn’t solve the question of how this interaction happens  Very few dualists today  Most neuroscientists & psychologists: “Minds are simply what brains do”  How does each approach deal with qualia?  Substance Dualist: qualia (e.g., smell of coffee) are part of a separate mental world from physical objects (the brain)  Epiphenomenalists: qualia exist but have no causal properties  Idealists: everything is qualia  Materialists/physicalists: qualia is a brain process. It’s what the brain does. Is consciousness essential? The Philosopher’s Zombie  The Philosopher’s Zombie  Looks and acts like you, in every way a physical twin, but is not conscious  The Philosopher’s Zombie  No view from within, no qualia  Easy to imagine, and obviously possible  John Searle (UC Berkeley): there could be identical behavior in two systems, one conscious, the other totally unconscious  Sleepwalking  Stage 3 NREM  Slow wave (deep sleep)  No awareness (dark inside)  No memory The Somnambulist, 1871 John Everett Millais  A silicon version of you (but all dark inside)  This creature would be unconscious  Consciousness inessentialism: The idea that if zombies are possible, then consciousness is optional (or inessential) Can qualia be explained by looking at the function of individual neurons? (reductionism)  Thomas Negal  Philosophical Review (1974)  Argued against reductionism  Reductionism: Explanation of entire systems in terms of their individual, constituent parts  We can understand the function of watch from interaction of its parts  Bats perceive the world through sonar  Hearing for bats is like seeing is for us  What is perception like for a bat?  There is something it is like to be a bat  Negal distinguishes between two uses of the term “consciousness”:  “Phenomenal consciousness” or P-Consciousness = experience – There is something “it is like” to be you  “Access Consciousness” or A-Consciousness: When you attend to something, it enters your consciousness – It is the functional aspect of consciousness Visual system’s representation of the world  Visual system generates an internal model (representation) of the world  Two questions: – 1) How accurately is the world represented? – 2) How detailed is this representation?  Perceptual Illusions  Illusion: something that is not what it appears to be  Café wall illusion  Café wall illusion Hermann Grid Illusion Retinal ganglion cells Ganglion cell receptive field (RF)  Retinal ganglion cells have a center-surround receptive field More inhibition (darker) Less inhibition (brighter) Hermann Grid Illusion  Is visual perception veridical?  Veridical Perception: Direct Perception of stimuli as they exist  Visual world is not always accurately mapped (internally represented)  Other evidence that visual perception is not veridical:  Visual “filling in” of missing information  Blind spot: Where the optic nerve leaves the retina  6˚ visual angle  What do you see at the blind spot?  Not a blank space  If background is boring gray, you see gray  If background is blue/Yellow stripes, you see blue/yellow stripes at blind spot  What if it’s a complex scene: population of people/faces  Pebbles on the beach  It is filled in with the appropriate stimulus (people/pebbles)  Note: blind spot is 15˚ away from fovea  The brain paints in properties at this location  Active cognitive processes: – Interpretation – Filling in  How does filling in work?  Two views:  Isomorphic: low level visual processes fill in the details (V1)  Symbolic: filling in occurs higher up in the visual system and is more conceptual (Visual Association Cortex)  V. S. Ramachandran (UCSD)  Blind spot experiments  Two lines crossing with a gap  Gap falls on blind spot  Subjects report continuous lines  Yellow doughnuts  Doughnut or a Solid disk?  “Pop out” effect  Josh (patient): right primary visual cortex (V1) injured by steel rod in industrial accident  Large scotoma (blind spot) in left visual field  Position scotoma on a solid line  First, I see a gap  After a few seconds, gap closes and I see a continuous line  Filling in did not work for column of large Xs  Worked for column of small x  Different levels of processing:  Large “X”s activated object recognition area (ventral/temporal)  Column of small “x” activated lower level texture coding  Twinkling black dots on red background  Josh reported: – First the red color bled into the scotoma  Twinkling black dots on red background  Josh reported: – First the red color bled into the scotoma – Then the dots appeared – Finally, all dots (even in scotoma) began to twinkle  Artificially induced scotoma  Flickering “snow” (noise)  After 5s, gray square fills with flickering “snow”  fMRI studies show that early visual areas (V1, V2) are not involved in “filling in”  Areas V3 and V4 are largely involved Mendola et al. (2006). Journal of Cognitive Neuroscience.  Gray is perceptually filled in with letters  …but you can’t read them  Oliver Sacks  Tumor destroyed much of the retina of his right eye Sacks (1933-2015)  Scotoma: large blind spot  Spot would take on the color of the sky if he looked at it for a while Sacks (1933-2015)  Flock of birds disappear and reappear on the other side Sacks (1933-2015)  Sacks: – Plain colors fill in quickly – Patterns on carpet in his office: 10 to 15 seconds  Sacks: – Size of pattern mattered – 2 feet from brick wall: scotoma filled with the brick’s red color, but no details – 20 feet from brick wall: perfectly formed bricks  Sacks: – Place scotoma on foot (“visually amputate it”) – Wiggled toes  First a stump appeared  One minute later, a complete phantom foot  Change blindness A demonstration of the sparseness of visual representation  Eye saccades cause massive blur  Trans-saccadic memory is very poor 200 20 ms ms Saccades while freely Saccades during reading scanning a picture  Early vision theories: successive pictures (from multiple saccades) must be integrated into one big representation  Requires massive computations  Claim: we have a detailed view of the world  Change blindness challenged this assumption Examples of change blindness  Change blindness shows that we overestimate our ability to detect change  No need to store large amounts of visual information  Inattentional blindness  If you are not directly paying attention to something, will you see it?  Easy to miss something obvious (does not enter your consciousness)  Inattentional blindness  The most important factor affecting inattentional blindness is a person’s own attentional goals  Hard to see something that is truly unanticipated