Episodic Memory Formation via Cortico-Hippocampal Interactions

[Lokendra Shastri]

Dear Connectionists,

The following article may be of interest to you.

Best wishes,

-- Lokendra Shastri
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http://www.icsi.berkeley.edu/~shastri/psfiles/shastri_em.pdf

	  From Transient Patterns to Persistent Structures:
 A model of episodic memory formation via cortico-hippocampal interactions

                              Lokendra Shastri
                  International Computer Science Institute
                             Berkeley, CA 94704
 
				Abstract
We readily remember events and situations in our daily lives and 
rapidly acquire memories of specific events by watching a telecast or 
reading a newspaper. There is a broad consensus that the hippocampal 
system (HS), consisting of the hippocampal formation and neighboring
cortical areas, plays a critical role in the encoding and retrieval of
such ``episodic'' memories. But how the HS subserves this mnemonic
function is not fully understood. This article presents a computational
model, SMRITI, that demonstrates how a cortically expressed transient
pattern of activity representing an event can be transformed rapidly 
into a persistent and robust memory trace as a result of long-term pot-
entiation within structures whose architecture and circuitry resemble
those of the HS. Memory traces formed by the model respond to partial
cues, and at the same time, reject similar but erroneous cues. During
retrieval these memory traces, acting in concert with cortical circuits
encoding semantic, causal, and procedural knowledge, can recreate
activation-based representations of memorized events. The model
explicates the representational requirements of encoding episodic
memories, and suggests that the idiosyncratic architecture of the HS is
well matched to the representational problems it must solve in order to
support the episodic memory function. The model predicts the nature of
memory deficits that would result from insult to specific HS components
and to cortical circuits projecting to the HS. It also identifies the
sorts of memories that must remain encoded in the HS for the long-term,
and helps delineate the semantic and episodic memory distinction.

(Submitted to Behavioral and Brain Sciences)