Recognition memory: familiarity signals increase selectively in the lateral entorhinal cortex following hippocampal lesions

Abstract

The sense of familiarity for events is crucial for successful recognition memory. However, the neural substrate and mechanisms supporting familiarity remain unclear. Some human and animal studies suggest that the lateral entorhinal (LEC) and the perirhinal (PER) cortices might be essential for familiarity judgments while others attribute this function to the hippocampus (HIP) and it is unclear whether LEC, PER and HIP interact within this frame. Here, we especially investigate if LEC and PERs contribution to familiarity depends on hippocampal integrity. Using a human to rat translational memory task and high resolution IEG imaging, we report that hippocampal lesions selectively enhance activity in LEC during familiarity judgments. These findings suggest that different mechanisms support familiarity in LEC and PER and, that HIP might exert a tonic inhibition on LEC during recognition memory that might be released when HIP is compromised, possibly constituting a compensatory mechanism in aging and amnesic patients.