Encoding and storing experience in hippocampal-cortical networks

Speaker

Dr Jai Yu, Howard Hughes Medical Institute, Department of Physiology, University of California, San Francisco, USA

Abstract

While ongoing experience proceeds continuously, memories of past experience are often recalled as episodes with defined beginnings and ends. The neural mechanisms that transform the stream of neural activity patterns representing ongoing experience into discrete episodes are unknown. To investigate these mechanisms, we recorded neural activity in the hippocampus and prefrontal cortex, both of which are critical for memory processes. We show that during spatial navigation, hippocampal CA1 place cells maintain a continuous spatial representation across different states of motion (movement and immobility). In contrast, during sharp-wave ripples, when stored representations of experience are transiently expressed, movement and immobility-associated activity patterns are most often reactivated separately. Moreover, hippocampal reactivations of movement or immobility experiences are accompanied by distinct patterns of modulation in prefrontal cortex. These findings demonstrate a continuous representation of experience can be separated into independently reactivated memory representations across the hippocampal-cortical network.