Thesis defense Ruud Berkens (Donders series 390)

28 August 2019

Promotor: prof. dr. G. Fernández, co-promotor: dr. M. van der Linden

Modulation of Memory Integration in the Human Brain: Experimental Investigations of Memory Encoding & Consolidation

This thesis addresses the question of how the human brain selectively integrates information from experience into the long-term memory store and the neocortical memory system, either during initial encoding or during subsequent consolidation  First, I show that associations with a negative valence are encoded in a less specific manner, and this reduced memory specificity was related to increased connectivity between the medial prefrontal cortex and hippocampus. Second, I demonstrate that the application of transcranial magnetic stimulation in order to down-regulate neural excitability in the medial prefrontal cortex results in a subsequent reduction in false memories.  Third, I studied how participants gradually acquire a generalized associative structure across repeated trials. Using a computational learning model,  I relate the updating and accumulation of a linguistic associative structure to specific learning-related activity in several cortical and subcortical brain regions.  In a fourth study, I studied whole-brain connectivity changes in response to the presentation of auditory cues during slow-wave sleep, which supposedly serves to reactivate previously acquired visuospatial memories. We show that in response the visual cortex displays an increased integration with the rest of the brain, and in particular mnemonic regions related to memory reprocessing during sleep. This increase in integration of the visual cortex was related to overall memory stabilization, supporting a potential functional role of such memory reprocessing in memory consolidation. These studies employing various methodologies, tasks and analysis techniques shed a light on the myriad ways in which the brain adaptively regulates the how incoming information is encoded and consolidated within hippocampal-neocortical and neocortical networks.