Oscillatory Dynamics and Place Field Maps Reflect Hippocampal Ensemble Processing of Sequence and Place Memory under NMDA Receptor Control

Abstract

Place coding in the hippocampus requires flexible combination of sensory inputs (e.g., environmental and self-motion information) with memory of past events. We show that mouse CA1 hippocampal spatial representations may either be anchored to external landmarks (place memory) or reflect memorized sequences of cell assemblies depending on the behavioral strategy spontaneously selected. These computational modalities correspond to different CA1 dynamical states, as expressed by theta and low- and high-frequency gamma oscillations, when switching from place to sequence memory-based processing. These changes are consistent with a shift from entorhinal to CA3 input dominance on CA1. In mice with a deletion of forebrain NMDA receptors, the ability of place cells to maintain a map based on sequence memory is selectively impaired and oscillatory dynamics are correspondingly altered, suggesting that oscillations contribute to selecting behaviorally appropriate computations in the hippocampus and that NMDA receptors are crucial for this function.

Losing Control Under Ketamine: Suppressed Cortico-Hippocampal Drive Following Acute Ketamine in Rats

“…However, like knockout of NMDA-R on parvalbumin-expressing interneurons, pyramidal neuronselective ablation of functional NMDA-R also leads to enhanced CA1 gamma rhythms in addition to impaired CA1 pyramidal cell spatial information coding (Cabral et al, 2014;McHugh et al, 1996). These latter results are in keeping with our DCM-based predictions, and suggest that the relative contributions of NMDA-R at different synaptic locations to ketamine-induced activity remain to be fully resolved.…”

Chlorovirus ATCV-1 is part of the human oropharyngeal virome and is associated with changes in cognitive functions in humans and mice

“…Exposure of mice to ATCV-1 also resulted in changes in gene expression within the hippocampus, the region of the brain most associated with spatial memory and navigation (22,34,35). Of particular interest in light of the cognitive assays were alterations in the Cdk5 pathway (Fig.…”

Internally generated sequences in learning and executing goal-directed behavior

“…Lesion studies indicate that VS activity is not required per se to meet this more stringent criterion. However, we propose that, during IGSs, joint HC and VS representations do establish a contingency between potential paths, conceived as behavioral sequences or plans in the HC [34,36,119] and a rewarding outcome, coded in the VS. The specific association of an IGS-coded action sequence and reward expectation may meet this second criterion for goal-directed behavior.…”