Is place the (only) functional correlate?

Abstract

To assess whether “place” is necessary and sufficient to account for the functional correlates of hippocampal neuronal activity, we examined several spatial and behavioral parameters associated with unit activity in rats performing both a place-guided navigation task and an odor-guided sensory-discrimination task. In the place task, most cells had place fields, but were also activated selectively in relation to speed, direction, or turning angle of movements the rat made in the field. In the odor task, most cells fired selectively either during the period of odor sampling and response generation or as the rat initiated the trial or approached the reward. Some of these cells fired preferentially in association with the presentation of particular stimulus configurations. Often the same cells had clear, but unrelated, spatial correlates in the place task and behavioral correlates in the odor task. These results suggest that we must view spatial coding as only one form of cognitive processing performed by the hippocampus, and that both spatial and behavioral variables must be considered in a complete account of hippocampal neuronal activity.