philosophy

PH101, Summer Semester 2021

Handout #4

Christof Koch: Consciousness (ch. 8)

· ‘The hard problem’ of consciousness

· Suppose some given theory about how consciousness is caused is true

· E.g. Crick/Koch hypothesis: layer 5 cortical neurons’ firing in the visual cortex every 20 milliseconds is the neural correlate of consciousness

· How is this proposal different from Descartes’ contention that the pineal gland is the seat of the soul?

· Emergence

· It seems that the complexity of a creature’s conscious states is correlated to the complexity of the creature’s brain (consider various animals)

· Consider e.g. the wetness of water, the laws of heredity, or a traffic jam

· In each case, the phenomenon is the result of a complex interaction of constituent parts

· In the case of consciousness, it emerges out of the interactions of a large network of cells

· According to this theory, very basic organisms would not be conscious

· But how can the addition of more of the same (neurons and their interactions) make a difference?

· The Immanence of Consciousness in Complexity

· Consciousness is an elementary property of living matter

· Consider electrical charge: an electron has one negative charge, a proton has one positive charge

· Charge is an intrinsic properties of these particles

· Consciousness is an intrinsic property of organised chunks of matter

· Information Theory

· ‘Information’: consider a light switch that has two positions, ‘on’ and ‘off’

· Knowing which state it is in corresponds to one bit of information

· Information as difference in total state of a system

· The Theory of Integrated Information

· Two properties of consciousness:

· 1. Information is ‘reduction of uncertainty’

· Each conscious experience is such a reduction

· 2. Conscious states are integrated

· Each conscious state is a ‘single apprehension’: you cannot reduce it into component parts

· Therefore, any conscious system must be a single, integrated entity with a large repertoire of highly differentiated states (‘integration and differentiation’)

· The quantity of a system’s conscious experience in a particular state is equal to the amount of integrated information generated by the system above and beyond the information generated by is parts

· The more integrated and differentiated the system is, the more conscious it is

· Consider split-brain patients: the brain as a whole has no more conscious experiences

· Its integrated information is zero

· Ɵ quantifies the reduction of uncertainty that occurs in a system in a particular state (over and above the information generated independently by its parts)

· Integrated information arises from causal interactions within the system

· When those interactions can’t take place, Ɵ shrinks even though the actual state of the system remains unchanged

· Consider seeing the Burj Khalifa tower when it’s quiet, and consider seeing it when your auditory cortex is silenced by a barbiturate

· Integration theory predicts that even though brain activity is the same in both cases, Ɵ and therefore perceptual experience will differ in both cases

· The fact that neurons could fire but do not is meaningful

· Computing Ɵ

· All possible ways the system can be divided have to be considered

· Synchronous firing of action potentials among neurons is a means of integration

· But maximal integration can go with minimal differentiation

· E.g. epileptic seizures: all of the brain’s neurons firings are synchronized

· But maximal integration can go with minimal differentiation

· Conversely, Ɵ is low for networks composed of numerous small, quasi-independent modules

· Critical questions

· Why should evolution favour systems with high Ɵ?

· Ability to combine data from different sensors to contemplate and plan future course of action

· How do you explain the possibility of unconscious states?

· The theory captures not only the quantity but also the quality of an experience

· ‘Qualia space’: dimensionality identical to number of different states a system can occupy

· State of any physical system can be mapped onto a shape in a multidimensional qualia space

· Its surface are facets: it is a polytope

· Panpsychism

· Any system with a Ɵ value greater than 0 has experience

· As soon as a system has both differentiated and integrated states of information, it feels like something to be such a system

· It has an internal perspective

· On this view, consciousness is a fundamental feature of the universe

· This theory is called ‘panpsychism’

· ‘Consciousness is in the air we breather, the soil we tread on, the bacteria that colonize our intestines, and the brains that enable us to think’

· Teilhard de Chardin:

· “We are logically forced to assume the existence in rudimentary form…of some sort of psyche in every corpuscle, even in those whose complexity is of such a low or modest order as to render it (the psyche) imperceptible”