Simple memory: a theory for archicortex

TLDR

The paper proposes that archicortex’s defining feature is a simple memorizing task, uses this insight to generate theories for various archicortical areas, and introduces a functional classification of typical archicortical cells. The authors develop a simple representation scheme that maps vast information into the firing of about 200 cells, numerically analyze a specific example to draw general conclusions, and provide a functional interpretation of key archicortical regions and a classification of their cells. Numerical constraints determine the size of mammalian memorizing models, yielding a general archicortex model; the model predicts that storing ~10⁵ simple representations requires minimal recall cues, and it generates numerous testable predictions that must hold if the theory is correct.

Abstract

It is proposed that the most important characteristic of archicortex is its ability to perform a simple kind of memorizing task. It is shown that rather general numerical constraints roughly determine the dimensions of memorizing models for the mammalian brain, and from these is derived a general model for archicortex. The addition of further constraints leads to the notion of a simple representation, which is a way of translating a great deal of information into the firing of about 200 out of a population of 105 cells. It is shown that if about 10 5 simple representations are stored in such a population of cells, very little information about a single learnt event is necessary to provoke its recall. A detailed numerical examination is made of a particular example of this kind of memory, and various general conclusions are drawn from the analysis. The insight gained from these models is used to derive theories for various archicortical areas. A functional interpretation is given of the cells and synapses of the area entorhinalis, the presubiculum, the prosubiculum, the cornu ammonis and the fascia dentata. Many predictions are made, a substantial number of which must be true if the theory is correct. A general functional classification of typical archicortical cells is proposed.