Hippocampal place fields: Relationship between degree of field overlap and cross-correlations within ensembles of hippocampal neurons

Robert E. Hampson, Douglas R. Byrd, Joanne K. Konstantopoulos, Terence Bunn, Sam A. Deadwyler
1996 Hippocampus  
The capacity to record from multiple neurons in awake freely moving animals provides a means for characterizing organizational principles of place field encoding within ensembles of hippocampal neurons. In this study, cross-correlations between pairs of hippocampal place cells and degree of overlap between their respective place fields were analyzed during behavioral performance of delayed matching (DMS) or nonmatching sample (DNMS) tasks, or while the same rats chased pellets in a different
more » ... ironment. The relationship between field overlap and crosscorrelations of neural spike activity within ensembles was shown to be a positive, exponentially increasing, function. Place fields from the same neurons were markedly "remapped" between the Delay and Pellet-chasing tasks, with respect to physical location and size of fields. However individual pairs of place cells within each ensemble retained nearly the same degree of overlap and cross-correlation even though the spatial environment and the tasks differed markedly. This suggested that place cells were organized in functional "clusters" which exhibited the same interrelations with respect to place field overlap and cross-correlations, irrespective of actual field location. When cross-correlations between place cells were compared to placement of the array recording electrodes within the hippocampus, the strongest correlations were found along previously defined posterior-projecting fiber gradients between CA3 and CAI subfields (Ishizuka et al. [1990] , J Comp Neurol 295580-623; Li et al. [1994] (J Comp Neurol 339:181-208). These findings suggest that the functional organization of place fields conforms to anatomical principles suspected to operate within hippocampal ensembles. 01996 Wiley-Liss, Inc. KEY WORDS: hippocampus, delayed-matchhonmatch-to-sample, multineuron recording, food pellet retrieval, CA3 to CA1 connectivity The notion that the hippocampus encodes a cognitive map of the environment (O'Keefe and Nadel, 1978; O'Keefe, 1990; Nadel, 1991) was a natural outgrowth of the demonstration that hippocampal cell firing was
doi:10.1002/(sici)1098-1063(1996)6:3<281::aid-hipo6>3.0.co;2-q pmid:8841827 fatcat:z6hzz2oykbfpzizn3jnvhczquy