Differential effects of aging and epilepsy in discriminating and reactivating memories

Pattern separation and pattern completion are distinct neurocognitive processes involved in encoding and retrieval of memories. However, there is currently no robust behavioural task in humans to measure both processes within the same paradigm. We describe the Memory Pinhole task, a novel paradigm which offers a distinct measure of each process, applied to healthy young, healthy older and people with epilepsy. Both pattern separation and pattern completion are observed in healthy younger individuals. A pattern completion deficit is seen in people with epilepsy, while the healthy older cohort show a deficit in pattern separation. To understand the neural mechanisms, we simulated human performance using an auto-associative neural network. Modelling indicated that disruption in different neuronal populations could explain the distinct memory profiles observed in ageing and epilepsy. These results demonstrate that pattern separation and pattern completion are distinct processes that can be measured from a single behavioural task and are differentially affected by ageing and epilepsy. ### Competing Interest Statement The authors have declared no competing interest.