Abstract: The fundamental problem of episodic memory concerns linking items with
their temporal context (during study) and retrieving the context
associated with items (during recall). The reinstatement of mental
context is distinguished from the idea that remembering solely involves
a reactivation of content information that is specific to that event. I
will first present behavioral evidence for the idea associations in
episodic memory arise from this contextual encoding/retrieval process,
and that forgetting largely reflects the loss of effective contextual
cues at retrieval. I will then show how the Context Maintenance and
Retrieval model (CMR, Polyn et al., 2009)—a computational model of
episodic memory—can account for these data, along with data on the
role of semantic and source information in memory retrieval. Finally, I
will present direct neurophysiological evidence for context
reinstatement based on an analysis of intracranial recordings taken as
63 neurosurgical patients studied and recalled lists of words. We first
identified a global pattern of neural activity that exhibits a
fundamental property of temporal context: namely, that it changes
gradually over time. Upon recalling a studied item, we found that this
pattern of activity was not only similar to the pattern observed when
the item was studied, but was also similar to neighboring list items
with similarity decreasing reliably as a function of distance. This
finding provides direct neural evidence in support of the context
reinstatement hypothesis.
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