No representation of allocentric space has been found in the brain

A detailed Summary of No representation of allocentric space has been found in the brain

"No representation of allocentric space has been found in the brain"

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The question of how animals and humans navigate is a fundamental research problem upon which there has been much experimentation and debate, and so it is necessary to refine the title to a specific point. As Tolman (1948) established that rats can solve spatial problems too complex for a purely stimulus-response system to solve, and that therefore some kind of neural map is necessary for navigation, this essay will basically address the question of whether the brain forms an allocentric (which is independent of the organism) or an egocentric (based on the organism's own perception of the surroundings) view of the environment. For the purpose of simplicity this essay will concern itself with only the brain of a rat.

This essay will thus discuss the evolution of relevant behaviourist and neurophysiological theories, the most important being O'Keefe (1991); Muller, Kubie, Bostock, Taube and Quirk (1991); and Rolls (1991).

The behaviourist theories proposed that a reward or aversive object/event will motivate a rat to move towards or away from the location along a reward gradient, and this has been shown to be the c

Morris, R.C. (1981) Spatial localization does not depend on the presence of local cues. Learning and motivation, 12, 239-60.

Rolls (1991) used further anatomical details to suggest how this system could provide an allocentric or egocentric concept of the environment. He hypothesised that as place-coded neurones on the upper layers of the antorhinal cortex are the route of entry of information into the system the CA3 pyramidal cells could make possible calculations of vectors to the location of objects, this is a neurophysiological basis for how animals might represent and navigate in their egocentric environment using the hippocampal region of the brain. Rolls (1991) also suggested that as the subiculum region also receives inputs from brain regions associated with incentives e.g. the amygdala and anterior thalamus, this is a good candidate for the structure responsible for performing goal and aversive movement vectors. This gives credence to behavioural factors involved in map formation, and implies that as this behavioural is goal-oriented, it may also be egocentric.

Rolls (1991) examined the functional anatomy of the CA3 cells and suggests an auto-associative matrix memory system. The CA3 system is highly interconnected and there is a relatively high probability (about 3.9%) that a neurone will connect with a neighbouring cell, and the cells respond to a stimulus only from a certain location and then fire others which could then provide an overall map of the environment. This is useful as the a snapshot of a scene will allow retrieval all the relevant locations of objects within the environment, allowing completion in recall. This anatomy also allows Hebbian learning, that is, strongly activated cells will form stronger links with other cells. This means that as the rat learns about its environment different synaptic weights can be attached to different objects or locations.

Tolman, E.C. (1948) Cognitive maps in rats and men. Psychology Review, 40, 60-70.

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Approximate Word count = 1805
Approximate Pages = 7 (250 words per page double spaced)

Category: Science