Brain and Consciousness What the class is about:

• The Scientific Study of Consciousness

• A central problem is science: ‘Consciousness is the major unsolved problem in biology’

[Francis Crick]

• Different from all other problems is science– Cannot be measured objectively – Yet we know it exists

Brain and Consciousness

• Ignored for many years • ‘Does it really exist?’

– The most secure knowledge: – ‘I think therefore I am’

• Renewed interest in neuroscience, psychology, physics

• Empirical studies ‘Consciousness is now largely a scientific problem’

• Philosophy: will not cover directly

Requirements • Come to class

• Check web site – No class: March 25, April 15

• Final project (extra credit) – Term paper

Web site: http://www.wisdom.weizmann.ac.il/~lior/Course07/

Forum: additional points, ideas for experiments, refs.

Partial Descriptions

• Our own awareness of ourselves and the world; mental processes that include perception, thoughts and feelings.

• Being aware of one’s environment, one’s own existence, sensations and thoughts, to be mentally perceptive or alert, awake, and capable of thought, will and perception

• Including: perceptual awareness, sensations, thoughts and understanding, feelings, free will and choice.

• ‘Impossible to define…without a grasp of what consciousness means’ Int. Dictionary of Psychology

Some of the questions:

• What is consciousness? • What are the brain mechanisms related to

consciousness?

Even if we identify them:

• ‘How can the flow of sodium potassium, calcium, and electrical activity, cause a terrible tooth ache?’

The physical equations do not predict any of this

Some of the questions:

• Do animals have awareness, what species, what sort?

Can animals be just

‘…a superior race of marionettes, which eat without pleasure, cry without pain, desire nothing, know nothing, and only simulate intelligence?’

[Thomas Henry Huxley]

Evolution and epiphenomenon

Some of the questions:

• Can artificial devices have consciousness?

• ‘How can a physical device feel anything?’

• Does consciousness serve any functional role?

• How is choice and free will compatible with physics? (classical, quantum)

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Some Topics

• The neural correlates of consciousness (NCC) • Which cortical areas and brain events are

correlated with perceptual awareness

– Rivalry – Blindsight – Low / high areas and awareness – Brain stimulation – fMRI, single-unit, lesions

Binocular Rivalry

Blindsight: Seeing without awareness

OR:

• http://www.echalk.co.uk/amusements/OpticalIllusions/illusions.htm

• http://www.michaelbach.de/ot/mot_mib/index.html

• (Alt-tab)

Motion-induced Blindness

Esc to return to presentation

Behavioral Studies

• Developing new perceptions (magnetic north, ‘auditory images’)

• Controlling devices by brain activity

• Re-mapping sensory events – Rubber hand, phantom perception

Rubber Hand Illusion

Computational Aspects

• The cognitive science approach

• Strong and weak AI

• The Chinese room (Searle)

• Consciousness and information (Chalmers)

Relation to physics (QM)

• Properties of QM which have possible relevance

• Collapse of the wave function (Shimoni).

• The brain as a non-Turing device (Penrose)

On Brain and Consciousness

• Brain • Behavior • Computation • Physics

• Brain:The neural correlates of consciousness (NCC) Which cortical areas and brain events are correlated with perceptual awareness

On Brain and Consciousness Some history and classical examples

• The brain is the source of mental phenomena

• The ancient Greeks

• Descartes: the pineal gland

‘seat of the soul’

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Origin of the Brain Doctrine

• Brain Theory:Alcmaeon, Hippocrates, Plato → Alexandria → Rome (Galen)

• Heart Theory: Aristotle

• Until middle ages, Galen vs. Aristotle

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The Early Greek on the Brain:

• Hippocrates:

‘..The eyes and the ears and the tongue and the hands and feet do whatsoever the brain determines…it is the brain that is the messenger to the understanding’

• In Plato, Socrates says: ‘…It is the brain that conveys sensations like hearing, seeing and smelling, so that memory and opinion are produced and, once they had firmly settled, knowledge is generated in such way.’

On brain and mental phenomena

• Some classical cases and examples – – Early history of BS MS

• Phineas Gage

• Fronto-limbic tumor

• Elliot, patient of Damagio

• Amygdala stimulation

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Phineas Gage

Before: well-balanced mind, a shrewd, smart businessman, very energetic and persistent in executing all his plans of operation.

After: fitful, irreverent, indulging at times in the grossest profanity… with animal passions

His mind was radically changed, his friends said he was 'no longer Gage'.

First evidence that damage to the frontal lobes could alter aspects of personality and social interactions .

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Fronto-limbic tumor and pornography

A Virginia man who at 40 became obsessed with child pornography

No previous history of pedophilic inclinations

Completely disappeared with the surgical removal of a tumor of the fronto-limbic system, which had invaded the hypothalamic region

When the tumor grew back, his preoccupation with pornography returned, only to vanish again with repeat surgery.

Reported by P. Churchland

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Elliot: Emotions and decision making

Perceptual, learning, language and mathematical abilities, memory intact .Disastrous business and personal decisions .

Inability to solve the problems of everyday lifeIn the past, felt sensations and emotions that he no longer experienced

Damasio: role of emotions in decisions Natural problem solving by ‘images of alternative scenarios’Communication frontal lobe amygdala

Descartes’ Error (Damasio 1994)

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Oxytocin

Secretion regulated by the electrical activity of neurosecretory oxytocin cells in the hypothalamus.

Maternal-offspring attachment in mammals mediated by oxytocin.

Mate-attachment in females. (In males: vasopressin related to monogamous behavior)

Oxytocin involved in social recognition and bonding, and appears to be involved in the formation of trust between people .

Amygdala and Fear

Electrical stimulation of the human amygdala produces fear

Amygdala Stimulation: Fear, Rage, Aggression

• Sustained stimulation invokes fear, panic, rage.• Up to several minutes after the stimulation• emotional expression: crying, baring teeth, pupil

dilation, sniffing, licking, and chewing • rage can gradually build up, attacks directed at

something real or imaginary.

• Damage to the amygdala can have similar results in terms of rage, fear, abnormal emotional behavior.

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• ‘subjective experience of fear relies upon amygdala-medial frontal activity’

• What is the relation between fear and neural activity in the

amygdala (and related structures)?

• This activity appears as the only difference between the state of having these affects and not having them.

• Can we equate the two? (identity theory) • Is one the cause of the other?

(useful but insufficient)

The Case of Charles Whitman

Born in 1941, IQ in the 99.9%, loved animals, athletic, ‘all American boy ’Marines: ‘the kind of guy you would want around if you went into combat ’

Gradual change of behavior: headaches, attacks of rage, increasingly religious, hyper energetic, hypergraphia

Autopsy: ‘tumor the size of a walnut, erupting from beneath the thalamus, impacting the hypothalamus, extending into the temporal lobe and compressing the amygdaloid nucleus ’

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"It was after much thought that I decided to kill my wife, Kathy, tonight....I love her dearly… I cannot rationally pinpoint any specific reason for

doing this "...

NCC

Neural Correlates of Consciousness – NCC • Physicalism: Mental states = brain states • Cannot be strictly true.• Which brain mechanisms and events ‘produce’ awareness?

• The NCC PROGRAM: BSi CSi

• An important question, but not an explanation • What are the facts, and what they mean

• Special Brain areas?• Different qualia in different regions? (motion, faces..) • Special populations of neurons? • Synchrony? (40 Hz oscillations)?

NCC

Rivalry

Relation between activity and awareness

Was studied with psychophysics, single-unit, fMRI

Face – House Rivalrly fMRI

Bi-Stability

Binocular Rivalry Gabor patches

Local Rivalry

Kovacs et al PNAS 1996

Rivalry: Neurophysiology

Rivalry neurophysiology

Rivalry -- neurophysiology

Percentage of cells changing responses with perception

‘perceptual’ cells in deep layers only

Many cells with intermediate responses

Logothetis and Leopold in TICS 1999

V1 Ocular Dominance

Rivalry – fMRI in V1

Heeger et at Nature Neuroscience 2000

fMRI in V1

Rivalry changes are similar to monocular, but less pronounced

Dominance in rivalry is partial

Rivalry changes spread throughout areas (V1, V2, V3, V3a, V4)

Rivalry – fMRI Face vs Grating

Used face in one eye and drifting gratings in the other

Lumer Friston & Rees, Science 1998

Rivalry fMRI

Perceptual switches (red) and monocolar replay (green)

The Control of Rivalry

Small regions in fronto-parieltal activated during perceptual switches

Face – House Rivalrly fMRI

Face-Place Rivalry

Tong, Nakayama, Kanwisher Neuron, Vol. 21, 753–759, October, 1998,

Face-Pace Rivalry

House-Face fMRI Transitions

Rivalry differences similar to monocular but less pronounced

Activity is higher for the perceived stimulus

Dominance is partial, significant activity for the non-dominant stimulus .

Complementary images

• Specific activation without awareness– (could tell the stimulus ‘from the outside’)

• Similar in a parietal hemifield neglect• FFA is active in prosopagnosia • No other areas of distinction where observed• Stronger BOLD activation with awareness• ‘Sufficient level of activation’?

– Can this be tested further?