The Westend Lectures on Brain and Cognition with Nikolai Axmacher:
Engram reinstatement and the role of representational format

Memories of specific events are represented by distributed neural assemblies, or engrams. In humans, these engrams can be tracked by time-frequency patterns in EEG and intracranial EEG recordings and via distributed patterns of BOLD responses. We propose that individual engrams consist of a multitude of representational formats that correspond to different processing steps of these events. Reinstatement of engrams in different representational formats supports different memory functions, from short-term memory maintenance to long-term memory retrieval and memory consolidation. The presentation provides an overview about recent studies investigating the brain regions and oscillatory signatures that support reinstatement of engrams in these various representational formats. We also suggest that neurological and psychiatric diseases specifically impair individual representational formats of engrams that can explain distinct memory dysfunctions.