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The first step in building our initial working theory of brain is to assert the essential link between the physical brain and cognition, what we usually consider to be mental activity. This is starting roughly in the middle between mind and brain, so we will be working in two directions from here.
Hypothesis 0: The physical correlate of a mental concept is a configuration of networked neurons.
We will wait until later to define mental and concept; until then, the everyday notions that we have will do just fine. Working upward from this central link between mental and physical, we add Hypothesis 1.
Hypothesis 1: The concept is an element of which all mentality is constructed.
This is a large leap, and we expect to add many working hypotheses above this one as the theory evolves. Together with Hypothesis 1, it defines the task of building a mind as putting together a network of concepts in the physical form of assembled or trained configurations of neurons. The bulk of our work will be to identify what kinds and what combinations of these atomic configurations it takes to reproduce brain functions.
Working downward, we add two more hypotheses, which we label with negative numbers to indicate their subordinate position relative to Hypothesis 0, the initial linking hypothesis.
Hypothesis -1: A brain and its peripheral sensory and motor nervous systems are a network of nested networks of neurons whose functional elements are discrete configurations of neurons and the electro-chemical systems that modulate neural behavior.
Hypothesis -2: The natural, and only meaningful, situation of a brain is as a intermediate processing system between a sensory system and a motor system in a motivated organism.
Hypothesis -3: Sensory neurons detect and signal states or events in an organism's environment or within the organism itself.
Hypothesis -4: Motor neurons effect events or states in the organism which may effect events or states in the environment.
Hypothesis -5: The sensible or knowable world is objective and is knowable through the detection of events and states.
These last five hypotheses ground the theory in an objective reality and provide the rationale for testing the theory in the behavior of real and modeled systems. They also outline what we will call the survival loop, the foundation structure upon which our program will build a brain-mind.
The survival loop
Our initial hypotheses state that the context of the mind is the brain, that the context of the brain is an organism which can sense and act, and that the context of an organism is an objective reality which the organism can know subjectively and interact with to survive and reproduce with more or less success.
Let's look at the concepts of organism and environment in more detail.
Definition: An organism is system whose states and processes interact with each other and the system's environment such that the system survives.
Living things and quasi-living things are examples of natural organisms. An artificial organism is a machine constructed to behave as a natural organism.
Definition: The environment of an organism is all of reality, other than the organism itself, that affects the organism. An environment is always defined relative to a particular subjective organism. Environment implies a discernable boundary that separates it from the organism.
The survival loop is the process by which an active, resource-consuming organism interacts with its environment to attain dynamic stability, which is to say to survive in a dynamic environment. The process begins with an event in the environment that is detected by a sensor of the organism. The sensor signals a processing unit that interprets the signal in the context of other signals, and in turn signals a motor function. The motor function produces an action that produces an event in the environment, the effect of which is beneficial to the organism. This cycle is basically the same as the Funktionskreis first suggested to the science of biology by Jakob von Uexkull in 1920, but we need to emphasize that the ultimate result of the functioning is survival. The role of the survival loop in this developing theory is to bind brain function to the success of an organism, where success is measured by survival of individuals or genotypes in a competitive environment.
A general abstract organism with a brain
We are going to skip over some of the simpler forms of organism and start with a general abstract organism that has a brain, of sorts. We will have to stretch our notion of brain quite a bit, here, but I think the notion will benefit from the stretching. Our basic organism is an abstraction of a natural organism that is equipped with a rudimentary nervous system.
Let's visualize our abstract organism in two dimensions, starting with, say, a circle (Fig.3). The circle and everything inside it is the organism; everything outside the circle is the environment. Some parts of the circle perimeter are special; they are sensors that detect certain classes of events or states in the environment. There are sensors and effectors inside the organism as well; they detect and cause events within the organism itself. Some other special parts on the circle are effectors, which produce specific classes of events in the environment. Inside the organism is a network of neurons that connects the sensors to the effectors.
Figure 1. Abstract Organism
The entire neural system has a basic three-layer structure. One is a layer of sensory neurons that has inputs which are triggered by specific events. The output of the sensory layer is input to a layer of interneurons, a neural net that integrates and processes the sensory layer output. The interneuron layer outputs to the motor layer, whose output activates effector mechanisms that cause things to happen within the organism or in the environment. The sensory and motor layers correspond to the peripheral nervous system of animals. The interneuron layer is what will develop into the central nervous system, a brain and spinal cord.
The part of the survival loop that lies within the organism, from sensor to effector, we will call the behavior arc. This abstract organism will serve as our basic template for creating real instances of intelligent organisms powered by brains.
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