Neuronal activity in the hippocampus during delayed non‐match to sample performance in rats: Evidence for hippocampal processing in recognition memory

Abstract

Neuronal activity in the CA1 of rats was explored with regard to functional correlates of performance in an odor-guided continuous delayed non-match to sample task. Although different CA1 cells fired in association with each identifiable trial event, these analyses focused on cells that fired selectively during the period of odor cue sampling and response generation. The firing patterns of many of these cells reflected the match or non-match comparison between current and previous odor cues independent of the particular stimuli that composed those comparisons. Such cells were more prevalent in sessions when performance was highly accurate. Hippocampal cells did not demonstrate stimulus-evoked firing that persisted through the memory delay, nor did they fire differentially to session-novel vs. repeated odor presentations. These results suggest that the hippocampus contributes to recognition memory by processing comparisons between current information and representations of previous stimuli stored in parahippocampal and neocortical structures.

The complementary brain: unifying brain dynamics and modularity

“…Neurobiological data have elsewhere been reviewed i n support of the ART hypothesis that the attentive-learning system includes such 'what' processing regions as inferotemporal cortex and its projections in prefrontal cortex, whereas the orienting-search system includes circuits of the hippocampal system 45 . Data about mismatch cells in the hippocampal system are particularly relevant to this hypothesis 70 . ART predicts that these interactions between inferotemporal cortex and the hippocampal system during a mismatch event offset the inability of the 'what' processing stream to search for and learn appropriate new recognition codes on its own.…”

The hippocampal debate: are we asking the right questions?

“…By this point, it is pretty much accepted that under certain conditions, hippocampal pyramidal cells show correlations to non-spatial aspects [48,69,71,101,109,157,238,239,246,247,250] (see [33,173] for reviews, but see [147] for an alternative viewpoint). These non-spatial aspects include when animals change task within an environment [101], in response to components of a task in which goals change [48,69,157,247], even after salient events [202].…”

“…These non-spatial aspects include when animals change task within an environment [101], in response to components of a task in which goals change [48,69,157,247], even after salient events [202]. In addition, hippocampal cells show place field changes with changes in environments or the available constellation of cues [17,90,93,129,148,181,219,223,250].…”

“…All non-spatial hippocampal correlates have been measured along categorized dimensions: specific odors [48,246], whether a cue is black or white [17], whether the goal is to the left or right of a T-maze [54,247], whether a lever is to the left or to the right [71], whether two sequential cues match or not [69,157,[193][194][195], which behavior is to be elicited [101], etc. In contrast, studies of spatial dimensions have shown conclusively that the representation changes continuously (e.g.…”

“…This happens when animals change environments [93,223], when animals reverse direction on repeated paths [101,109], when animals change task within an environment [101], in response to components of a task in which goals change [48,157,247], with changes in salient cues [17], and in response to incompatible cue manipulations [89,175,202,204,219].…”