Neural substrates of cognitive impairment in a NMDAR hypofunction mouse model of schizophrenia and rescue by risperidone

In mice with NMDAR hypofunction induced by subchronic phencyclidine (PCP), memory and auditory perception impairments are linked to disrupted connectivity between the medial prefrontal cortex and the dorsal hippocampus. Short-term memory relies on high gamma connectivity from the prefrontal cortex to the hippocampus, while long-term memory retrieval depends on theta connectivity from the hippocampus to the prefrontal cortex. Subchronic PCP impairs both short-term and long-term memory, increases prefrontal activity, decreases hippocampal activity, and disrupts this connectivity. Two weeks of daily risperidone rescues memory deficits, attenuates hippocampal desynchronization, and also ameliorates auditory perception impairments and their neural correlates.

Study at a glance

Abstract

NMDAR hypofunction is a pathophysiological mechanism relevant for schizophrenia. Acute administration of the NMDAR antagonist phencyclidine (PCP) induces psychosis in patients and animals while subchronic PCP (sPCP) produces cognitive dysfunction for weeks. We investigated the neural correlates of memory and perceptual impairments in mice treated with sPCP and the rescuing abilities of the atypical antipsychotic drug risperidone administered daily for two weeks. We recorded neural activities in the medial prefrontal cortex (mPFC) and the dorsal hippocampus (dHPC) during memory acquisition, short-term, and long-term memory in the novel object recognition test and during auditory perception and mismatch negativity (MMN) and examined the effects of sPCP and sPCP followed by risperidone. We found that the information about the new object and its short-term storage were associated with mPFC→dHPC high gamma connectivity whereas long-term memory retrieval depended on dHPC→mPFC theta connectivity. sPCP impaired short-term and long-term memory, which was associated with increased mPFC and decreased dHPC neural network activities, and disrupted mPFC-dHPC connectivity. Risperidone rescued the memory deficits and attenuated hippocampal desynchronization. sPCP also impaired auditory perception and its neural correlates (evoked potentials and MMN) in the mPFC, which were also ameliorated by risperidone. Our study suggests that during NMDAR hypofunction the mPFC and the dHPC disconnect possibly underlying cognitive impairment in schizophrenia, and that risperidone targets this circuit to ameliorate cognitive abilities in patients.