Biophysical simulations of memory must choose which aspects of known neurophysiology and neuroanatomy to model. Relevant aspects were constrained by functional requirements determined for on-line acquisition in context dependent memory, memory that is retrieved by contextual cues. In an on-line task, the protocol of data presentation and the tunes at which encoding or retrieval in memory is needed are not predetermined. A sequence of neuronal spike patterns representing items may be presented only once. Yet, episodic memory of the sequence immediately encodes the temporal context of familiar items, a process known to depend on hippocampal function. For this, interference caused by overlapping spike patterns must be avoided, a requirement that suggested the relevance of coincidental spiking. Overlap in the input to the hippocampus was reduced by recruiting such spikes in a model of encoding in dentate gyrus. Durable encoding is required in the hippocampus, since hippocampal damage can cause retrograde amnesia in context dependent memory that spans years. Long-lasting synaptic changes involved modeling relevant neurophysiology concerning protein production elicited by the spaced reactivation of spike patterns. The likelihood of reactivation was increased by the well-known process of long-term potentiation of synaptic transmission. Such potentiation is elicited when a presynaptic spike precedes a postsynaptic spike within a specific time window repeatedly. The intervals in a sequence of spike patterns must be compressed and the sequence repeated, requirements that were achieved with a model of short-term memory based on persistent spiking. Retrieval may be concurrent with these encoding processes due to effects of different phases of a brain rhythm at theta frequency (3-12 Hz) that modulate transmission and plasticity. A model of short-term memory by Lisman and Idiart (Science 267:1512-15), extended by Jensen et al. (Learning and Memory 3:243
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.85561 |
| Date | January 2005 |
| Creators | Koene, Randal A. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Psychology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002209349, proquestno: AAINR12872, Theses scanned by UMI/ProQuest. |
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