We used the psychotomimetic phencyclidine (PCP) to investigate the relationships among cognitive behavior, coordinated neural network function, and information processing within the hippocampus place cell system. We report in rats that PCP (5 mg/kg, i.p.) impairs a well learned, hippocampus-dependent place avoidance behavior in rats that requires cognitive control even when PCP is injected directly into dorsal hippocampus. PCP increases 60-100 Hz medium-freguency gamma oscillations in hippocampus CA1 and these increases correlate with the cognitive impairment caused by systemic PCP administration. PCP discoordinates theta-modulated medium-frequency and slow gamma oscillations in CA1 LFPs such that medium-frequency gamma oscillations become more theta-organized than slow gamma oscillations. CA1 place cell firing fields are preserved under PCP, but the drug discoordinates the subsecond temporal organization of discharge among place cells. This discoordination causes place cell ensemble representations of a familiar space to cease resembling pre-PCP representations despite preserved place fields. These findings point to the cognitive impairments caused by PCP arising from neural discoordination. PCP disrupts the timing of discharge with respect to the subsecond timescales of theta and gamma oscillations in the LFP. Because these oscillations arise from local inhibitory synaptic activity, these findings point to excitation-inhibition discoordination as the root of PCP-induced cognitive impairment.SIGNIFICANCE STATEMENT Hippocampal neural discharge is temporally coordinated on timescales of theta and gamma oscillations in the LFP and the discharge of a subset of pyramidal neurons called "place cells" is spatially organized such that discharge is restricted to locations called a cell's "place field." Because this temporal coordination and spatial discharge organization is thought to represent spatial knowledge, we used the psychotomimetic phencyclidine (PCP) to disrupt cognitive behavior and assess the importance of neural coordination and place fields for spatial cognition. PCP impaired the judicious use of spatial information and discoordinated hippocampal discharge without disrupting firing fields. These findings dissociate place fields from spatial cognitive behavior and suggest that hippocampus discharge coordination is crucial to spatial cognition.

Center for Neural Science New York University New York New York 10003

Department of Physiology and Pharmacology State University of New York Downstate Medical Center Joint Graduate Program in Biomedical Engineering SUNY Downstate Medical Center and New York University Polytechnic University State University of New York Downstate Medical Center Brooklyn New York 11203 Center for Neural Science New York University New York New York 10003

Department of Physiology and Pharmacology State University of New York Downstate Medical Center The Robert F Furchgott Center for Neural and Behavioral Science Center for Neural Science New York University New York New York 10003 Neuroscience Institute New York University Langone Health New York New York 10016

Graduate Program in Neural and Behavioral Science State University of New York Downstate Medical Center Department of Physiology and Pharmacology State University of New York Downstate Medical Center Center for Neural Science New York University New York New York 10003

Graduate Program in Neural and Behavioral Science State University of New York Downstate Medical Center Department of Physiology and Pharmacology State University of New York Downstate Medical Center National Institute of Mental Health Klecany 25067 Czech Republic

Institute of Physiology Czech Academy of Sciences Prague 14220 Czech Republic and

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