[Mathematical structure of episodic memory].
The hippocampus, which is a part of the old brain, has been considered responsible for the formation of episodic memory. Atrophy of the hippocampus can lead to Alzheimer disease. Alzheimer disease is a problem of the society. It is also expected to pose a serious problem in future societies composed of large numbers of elderly people. Therefore, it has become the focus of considerable attention. Motivated by the rehabilitation process of Alzheimer's patients, we mathematically studied the coding scheme in the hippocampus. We show that a mathematical model for CA3 exhibits successive recalls of memories which follow the emergent chaotic dynamics, where chaotic dynamics means ordered but comple and unpredictable neural activity. We also show that a network consisting of two-compartment model neurons for CA1 produces Cantor sets, by which the input time series of CA1 can be hierarchically encoded. We called this coding scheme Cantor coding. Predictions obtained from the model study have been partially verified by experiments using rat hippocampal slices.
Tsuda
Ichiro
I
Research Institute for Electronic Science, Hokkaido University, Kita-ku, Sapporo 060-0812, Japan.
D000544:Alzheimer Disease / Q000209:etiology; D000818:Animals; D001284:Atrophy; D006624:Hippocampus / Q000166:cytology / Q000473:pathology / Q000502:physiology*; D006801:Humans; D008568:Memory / Q000502:physiology*; D008954:Models, Biological; D008962:Models, Theoretical; D009415:Nerve Net / Q000502:physiology; D017966:Pyramidal Cells / Q000502:physiology; D051381:Rats