Walter J.Freeman
How Brains Make Up Their Mind
Phoenix 1999pg 40
Self OrganisationWhat do pragmatists have that can replace these compelling metaphors of energy driving us from outside?
They have self organisation, meaning that the self organises itself. We drive ourselves?
Humans evolved from simpler creatures, and these earlier forms exhibit precursors of our rich varied intentional behaviour.
Evolution has given us the capacity to detect intentionality in others without needing to define it. We recognise directed behaviour almost instantly when we see it. When we encounter an object of a certain kind, we ask whether it is alive or dead, likely to attack or ready to escape if we try to capture it. If it is still, we ask if it is watching us. If it is moving, we ask if the motion is directed towards or away from us, or two other parts of its environment.
In the modern world, we have little difficulty in distinguishing the behaviour is of intelligent machines that do not know what they are doing from those of intentional animals that do. There are many examples in the zoological literature of intelligent behaviour exhibited by other vertebrates.
My approach has been to study the brains of vertebrates that are simpler than humans, but not too simple or too different, because the appropriate simpler brains can start us on a well marked trail in stages to human brains. The brains of the tiger salamander is being closer to that of our earliest vertebrate ancestors than any other existing brain. It's simple structure provides us with an introduction to brain function.
The salamander brain
There are three main parts of the salamander brain: the fore brain, with its two hemispheres; midbrain; and hind brain, with its rudimentary cerebellum.
The midbrain and the hindbrain form the brain stem, which connects the forebrain into the spinal cord, which connects the sensory and motor nerves to the skeletal muscles, as well as the collections of neurons making up the autonomic nervous system, which regulates our vegetative functions. Intentional action is directed by internally generated goals and takes place in the time and space of the world shared with other intentional beings.
The materialist and cognitivist terms for these space-time processes of the short-term memory and cognitive map. In the pragmatist view, these terms are misleading, because there is no temporary storage of images, and there's no representation all map.
One of the problems faced by pragmatists is to give biological content of the metaphors of memory, cognitive map, command and feature. These combined functions, however they are labelled and conceived, provide the brain with its space-time field of action, which is built into each of the intentional states it constructs. That field enables it to go to sites of expected reward, track a moving prey, or spot a hidden refuge.
This association area in the salamander's brain is the forerunner of our hippocampus, which has prominent roles and learning, spatial orientation, and remembering.
Taken together, the sensory, motor and association cortices form a ring of interconnected neural tissue called the "transitional zone". These three primitive parts of the hemisphere have persisted as the limbic system (from the Latin "limbus" meaning belt) around the stalk of each hemisphere connecting it to the midbrain.
Researchers have studied the effects on behaviour of damage from disease or experimental surgery in many vertebrates, including salamanders, frogs, dogs and humans. The results show that the limbic system is essential for all intentional actions, including perception and most forms of learning.
When a surgeon cuts the connections between the brain stem and the hemispheres and isolates the limbic system, an animal loses all intentional behaviour. It retains the capabilities for chewing and swallowing food put in its mouth, for locomotion with its several types of gait, and for a variety of other regulatory functions called homeostasis, but it does not do anything or go anywhere intentionally. The parts of the brain that produce the patterns that orient activity into the environment are lost, and the capacity to execute the motor patterns remain without direction.
On the other hand, when the surgeon removes any or all other parts of the forebrain, the behaviour of the animal is severely impoverished, because the animal is deaf, blind or partially paralysed, but its remaining behaviour is unmistakably intentional.
The relations among the three parts of the simple brain are crucial for understanding how they create intentional behaviour. In each hemisphere the sensory cortex receives input, the motor cortex implements action, and the hippocampus provides multisensory integration and orientation in space and time. Each part has reciprocal connections to the others.
Preafference
The entire hemisphere constructs goal states through its interactive neural activity patterns. Those patterned activities guide the body through complex sequences of actions, and prime the sensory cortex to select the smells, sights, sounds and tastes that are predicted as the consequences of the impending goal directed actions.
This is a central process that we call preafference, and it provides the basis for what we experience as attention and expectation.
It enables the sensory cortex to predict specifically how the action to be taken will change the relations to the eyes, knows, ears and fingers to the world. The messages are called corollary discharges. Together they help us to distinguish between changes in the environment and the apparent changes that are due to the internal movement of our bodies, so that when we move our eyes, we do not perceive the world to move. They tell us whether the voice we hear, the hand we see or the odour we smell is our own or someone else's.
The somatosensory cortex also receives messages from the muscles and joints, confirming whether an intended action has been performed. This process of feedback is called proprioception, to distinguish it from exteroception of the world and interoception of the internal organs.
Proprioception and interoception differ from preafference and corollary discharge by going from the brain through the body, instead of remaining entirely within the brain. For all cortices, preafference is the process by which we imagine what things may be like, if or when they come.
The primary sensory cortices transmit their activity constantly and, if they have nothing to report, they transmit to our limbic system whatever their priming has led them to construct.
The sensory receptors do not have that kind of selective autonomy for pattern formation. Cortices give visions and hallucinations. Receptors give itches and ringing in the ears.
The burning of fuel to maintain the metabolic ground state of your body and brain depletes your reserves and makes you hungry. As a hungry animal, you seek an odour of food by sniffing. When you locate it, you hold that smell, move your head and body, take another sample, and compare it with the first. Is it stronger or weaker? Do you go left, right or straight ahead? To decide that, you must know where you were, where you are now, what you did to get from there to here, and how long you took.
Even this simple intentional task requires your brain to direct all sensory-induced activity patterns into the space-time field in the hippocampus to confirm or deny the expected consequences of each action, so each part of the brain is constantly interacting with the others. The assembled activity is unified, whole and purposive (intentional).
As animals evolve in competition for resources, their success depends on increasing the range and complexity of their possible courses of action and constructions of meaning. Brains increase in size and the complexity of connections.
The dynamics of the activity comprising meanings require increasingly elaborate stages between the primary sensory cortices and limbic system, while preserving the basic feedback interactions.
In humans, these new stages may become well known because of their accessibility by non-invasive brain imaging: the cingulate, inferotemporal and orbitofrontal cortices.
The new parts and connections provide ever greater sophistication, forming the basis for language, mainly in the left lateral hemisphere, and for social behaviour, through enormous expansion of the ventral frontal lobes.
Singular destruction of these "add-ons" can lead to blindness, deafness, partial paralysis, loss of language, and the social blindness that is characteristic of damage in the frontal lobes. Yet intentional behaviour persists, albeit with impoverished meanings, unless there is also destruction in the limbic system, as in advanced Alzheimer's disease, which has a particularly virulent predilection for destroying the final link of the sensory cortices to the hippocampus.
But singular destruction of the medial temporal lobes in both hemispheres does not abolish all aspects of intentionality. Instead, it results in loss of space-time orientation and the ability to add new episodic memories, that is, unity and wholeness. Goal-directedness is not restricted to the limbic system by any means.
These are the issues I raise in this book: how patterns of brain activity are directed intentionally towards external objects, leading to the creation and assimilation of meaning through learning. The specific properties of neuron populations explain how the patterns arise and how they guide behaviour into the world by coordinating the firings of microscopic motor neurons. I view the neural populations that compose the limbic system as the key to understanding the biology of intentionality.
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