Sleep to Retrieve: Sleep’s role in memory retrieval and underlying neural correlates

• Applicant: Dr. Nicolas Lutz
• Subject Area: Biological Psychology and Cognitive Neuroscience ; General, Cognitive and Mathematical Psychology
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 572500983

While sleep is known to benefit memory encoding and, particularly, memory consolidation, the role of sleep in memory retrieval is unclear. Retrieval is an essential aspect of memory which, in the “sleep and memory” literature, has mostly been considered as an output measure for successful memory encoding and/or consolidation. However, accessibility to stored information represents a critical individual factor in the process leading to expressed memory performance. The overall aim of the present project is to uncover this previously largely overlooked function of sleep and its underlying neural correlates. Based on the Synaptic Homeostasis Hypothesis (SHY), I propose a new theoretical framework in which sleep and wakefulness continue to change synaptic strength even after the critical consolidation period through processes of synaptic down-selection and synaptic potentiation, respectively. Accordingly, during slow-wave sleep, weak synapses (contributing to “noise” accumulated during the previous wake period) are down-selected, thereby increasing the signal-to-noise ratio and improving access to stored information. Based on this framework as well as own preliminary data, my framing hypothesis is that sleep (particularly slow-wave sleep) benefits memory retrieval in both declarative and procedural memory systems. To test this hypothesis, participants’ sleep will be experimentally manipulated by introducing an extra period of sleep (afternoon nap) vs. natural daytime wakefulness just prior to memory retrieval but separated in time from initial encoding and the critical consolidation period. We will scrutinize behavioural effects and electrophysiological correlates of sleep-dependent memory retrieval in both declarative and procedural memory systems by employing polysomnography and wake electroencephalography during and following the sleep/wake manipulation. In additional experiments, we will investigate whether different brain structures involved in memory retrieval are differentially affected by sleep vs. wakefulness by employing functional magnetic resonance imaging (fMRI) during retrieval testing. By scrutinizing the largely overlooked role of sleep in memory retrieval, the present project will make an important contribution to fully understanding the memory function of sleep and provides a promising direction also for future basic and translational research.

• DFG Programme: Research Grants