How General Is The Concept Of A Receptive Field?

1. How General Is The Concept Of A Receptive Field? Gregg Rosenberg April 7, 2004 Towards A Science of Consciousness

2. Talk Outline Foundations • The classic example of a receptive field • A rough attempt at generalizing the classic definition of receptive field • An attempt at precision in the generalized definition The ontology of consciousness • Hypothesis 1: The field of conscious experience is determined by the contents of a receptive field at the level of the whole person. • Hypothesis 2: The subjective phenomenal contents of consciousness are Russellian intrinsic contents within the receptive field. • Summary

3. The Classic Example of a Receptive Field Visual Field

4. Definition(s) of the Classic Receptive Field For the prototypical retinal example: • Proximate cause definition: A retinal cell’s receptive field is the area of the retina where stimulation elicits a response in the cell. • Ultimate cause definition: A retinal cell’s receptive field is the area in the visual field where a stimulus elicits a response in the cell.

5. Definition(s) of the Classic Receptive Field For the prototypical retinal example: • Proximate cause definition: A retinal cell’s receptive field is the area of the retina where stimulation elicits a response in the cell. • Ultimate cause definition: A retinal cell’s receptive field is the area in the visual field where a stimulus elicits a response in the cell. For arbitrary neural cells: • Proximate cause definition: A neuron’s receptive field is the map of neurons in the brain where stimulation elicits a response in the cell. • Ultimate cause definition: A neuron’s receptive field is the area or feature in the organism’s stimulus field where a stimulus elicits a response in the cell.

6. Generalization of the concept of receptive field From here: I will focus on the Proximate Cause definition. For arbitrary kinds of entities: • Proximate cause definition: An entity’s receptive field consists of the entities in its immediate environment whose interactions with the receiving entity elicit responses from it.

7. An attempt at precision in the generalized concept • What kinds of entities are candidates for having receptive fields? • What is a “response”? • What is an “immediate environment”? • What kinds of “interactions”?

8. Defining characteristics of “entities” What kinds of entities? How are they identified? • A receptive entity must be an entity that can take on a “single” state. • CAS criteria relevant (Holland 1996, 1998): • CAS mechanisms: Tags, building blocks, internal models. • CAS properties: Aggregation, Flows, Diversity, Non-linearity.

9. Defining characteristics of “entities” • Self/non-self recognition – Tagging that enables the aggregation of components within a boundary. • Selectively permeable boundary – Tagging that enables selective interaction with environment. • Attractor states – A set of stable states towards which neighboring states in a given basin of attraction asymptotically approach in the course of the entity’s dynamic evolution. • Lever points – Points of interaction where small amounts of input can produce large, directed changes.

10. Defining characteristics of a “response” • Stable state – Prior to the response the entity is evolving within the basin of attraction of an attractor state. • Controlled trigger – The response is a reaction to validly tagged signals received through the permeable boundary. • Detectable difference – The trigger causes the entity to move sharply away from the attractor it had been approaching in a way that makes a difference to its interactions with its environment. • Cycles through one or more limit cycles. • Jump to a new basin of attraction. • Jump to a qualitatively different traversal path within its existing basin.

11. Example: Persons • Coarse grained stable states – At the most coarse grain, a living person has a limit cycle of two state attractors: Waking and sleeping. • Controlled trigger – Human beings cycle between these two states reliably in response to circadian rhythms or external stimuli. Circadian rhythms are good examples of hormones being injected into the system as tagged messages right at structured lever points. • Detectable difference – The response consists of the person moving sharply away from the attractor he or she had settled near. • Person cycles from waking to sleeping or sleeping to waking.

12. Defining an “immediate environment” An entity’s immediate environment is the set of other entity’s at the same level from which signals flow to the receiving entity without having to flow through any other entity at the same level as the receiving entity. Not Immediate Not Immediate Receiving Entity Immediate Immediate

13. The definition of a receptive field understood precisely • Proximate cause definition (original): An entity’s receptive field consists of the entities in its immediate environment whose interactions with the receiving entity elicit responses from it. • Sharpening: An entity B is in the receptive field of an entity A at time t if, and only if, B is in the immediate environment of A at time t and is capable of contributing to a possible perturbation wave with respect to A.

14. Example: Neural firing • Token responses – Neural firings. A typical neural activation is a response to a set of convergent signals received through its dendritic boundary. • Perturbation waves – This set of signals constitutes a perturbation wave, a wave of tagged causal influence, eliciting a firing response from the neuron. • Immediate environment – Every perturbation wave must come through a set of entities in the receiving neuron’s immediate environment.

15. How general? Example 1: Atoms? • Entity – • Self/non-self recognition – The integrity of nuclear forces in a nucleus. • Selectively permeable boundary – Orbital shells. • Attractor states – Stable orbital configurations. • Lever points – Conditions under which orbital configurations can change. • Responses – Changes in ionic configurations. • Immediate environment – Other atoms. • Perturbations – Collisions.

16. How general? Example 2: Cells other than neurons? • Entity – • Self/non-self recognition – The selectivity of transport and messenger proteins. • Selectively permeable boundary – Cell walls. • Attractor states – Energy production states and message release via proteins. • Lever points – Protein and ionic concentrations. • Responses – Cell division? Release of proteins into bloodstream? • Immediate environment – Other cells. • Perturbations – Hormones and proteins absorbed through the cell wall.

17. How general? Example 3: Neural columns and assemblies? • Entity – • Self/non-self recognition – Harmony of wave characteristics. • Selectively permeable boundary – The cloud of neurotransmitter junctions associated with its dendrite and axon projections to other neural columns/assemblies. • Attractor states – Discrete frequency ranges in its group firing characteristics. • Lever points – Neurotransmitter imbalances. • Responses – Changes in the group harmonics of its neural firings. • Immediate environment – Other neural columns/assemblies. • Perturbations – Waves with competing harmonics.

18. Do Persons Have Receptive Fields? • Entity – • Self/non-self recognition – Immune system. • Selectively permeable boundary – An epidermal layer with sensory receptors. • Attractor states – The Sleep/wake cycle. More importantly, the wakefulness attractor is a very complex landscape composed of a variety of sub-attractors and limit cycles we can identify with motor and attentional programming. • Lever points – An integrated control system with person level responses modulated by attentional focus & emotional salience within consciousness. • Responses – Changes in the priming of motor programming. • Immediate environment – The array of perceptual and introspectible objects capable of being represented in the global workspace of consciousness. • Perturbations – High saliency changes in the contents of the global workspace.

19. Ontology of Consciousness: Hypothesis 1 The field of conscious experience is determined by the contents of a receptive field at the level of the whole person.

20. Ontology of Consciousness:Hypothesis 2 Thesubjective phenomenal contents of consciousness are Russellian intrinsic contents within a person’s receptive field. • These intrinsic contents carry the convergent influences active at the personal level. • These perturbation waves are composed of signals defined by, and structured according to, their command content for the person, not their micro constitution. • The person receives perturbation waves as unified command structures converging on it through its receptive field. • There is no “combination problem”.

21. Summary • The concept of having a “receptive field” can be generalized so that it includes persons. • The contents of consciousness may be determined by the contents of a person’s receptive field. • The qualitative content of consciousness may be the Russellian intrinsic content of perturbation waves received by the person. • The metaphysics of how all this may occur is explained in detail in my book, A Place For Consciousness to be published by OUP later this year (2004).