Memory enhancement via targeted reactivation

The aim of the project is to use post-learning rest periods as a new window for enhancing memory formation in humans. Episodic memory, our ability to vividly recollect past experiences, sensations and thoughts, lies at the core of human cognition. On the flipside, the debilitating effects of memory loss are apparent in healthy ageing as well as in neurodegenerative diseases such as Alzheimer’s Disease. How are these memories created? From the brain’s perspective, forming new memories is a complex and multi-faceted process. While much research has thus far been dedicated on the initial learning experience (‘encoding’), recent findings suggest that the time interval after learning, including sleep and awake rest, may be just as important for successful learning and may represent a hitherto underexplored window into human memory enhancement and control.

A striking series of recent studies has shown that presenting olfactory or auditory cues to sleeping or resting participants can be used to bolster memory formation. In particular, re-presenting to the sleeping participant a smell that was present during learning was shown to improve later memory for the learning material, without participants being aware of that manipulation.

A number of important questions have remained open however. For instance, does such experimental cueing equally benefit all expressions of memory? Does it generalise to all kinds of learning material? When is the optimal time point for cueing (awake rest vs. different stages of sleep)? And importantly, what are the underlying brain mechanisms? Does experimental cueing lead the brain to ‘bring back’ the previous learning experience? Indeed, we know from animal research that the brain spontaneously reactivates previous learning experiences during sleep (a phenomenon called ‘replay’) and that the extent of this replay predicts how well information will be retained after sleep. This begs the question whether cued reactivation may serve to facilitate the brain’s natural reactivation/’replay’ mechanisms.

To address these questions, the PhD project will systematically investigate how memory performance can be bolstered via targeted experimental cueing and what the underlying brain mechanisms are. During his/her training, the student will accomplish three main tasks:

1. Design a novel experimental paradigm that uses auditory cueing of different stimuli during post-learning rest to selectively enhance episodic memory performance.
2. Apply auditory cueing during natural sleep and compare the effects to cueing during awake rest.
3. Use simultaneous Electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) during sleep to investigate whether cueing leads to neural reinstatement/replay of the initial learning experience.

This project will not only to provide a better understanding of how the brain creates new memories, but also holds promise for opening a new window for experimental memory control and therapeutic intervention. In particular, once we understand how new memory traces are laid down after the initial experience, we may block this process in the case of adverse experiences which may otherwise lead to debilitating long-term conditions such as post-traumatic stress disorder (PTSD).