Adaptive Cortical Organization for Distributed Working Memory Storage

• Applicant: Dr. Thomas Christophel
• Subject Area: Biological Psychology and Cognitive Neuroscience ; Human Cognitive and Systems Neuroscience
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 439471997

We are capable of retaining almost any form of stimulus in working memory. In day to day life, however, we only need to retain some information every given moment while readily ignoring or forgetting irrelevant percepts. The cortical organization of working memory has been debated for decades. We have recently put forth a view of working memory which attributes storage to a distributed system of cortical regions that jointly store working memory contents. In particular, we hypothesized that the cortical sheet represents a gradient of abstraction where posterior-sensory regions encode sensory detail and frontal regions carry more semantic, invariant and response-related representations. This research program describes three lines of research, which test three central postulates of this distributed view: First, we aim to use behavioral modelling, fMRI and MVPA to directly test the prediction of a sensory-to-frontal gradient of abstraction during working memory. To this end, we will ascertain whether voxel-level delay-period response patterns in posterior and frontal regions are best explained by cellular tuning functions which are capable of representing sensory detail (sensory-continuous encoding models) or by encoding models which reflect more categorical representations. Second, we want to test whether the localization of working memory storage is dependent on what kind of other contents are held in memory. In particular, we will assess whether the representation of a visual feature (orientation) is reallocated to more anterior regions when another visual feature is memorized while no reallocation would occur when the other stimulus is auditory. Thereby, we asses a view of working memory where representations are continuously transferred between different neural circuits harboring varying neural coding schemes to minimize interference with other contents. Third and finally, we want to localize processes that exert control over working memory stores. To this end, we will trace the representation of instructive cues which tell subjects what items are relevant in a given trial from their sensory representation over a putative executive control stage to their effect on working memory storage. Thereby, we evaluate whether working memory is controlled by a central executive in frontal regions or whether the mechanism which exerts control over the distributed memory stores is itself distributed.

• DFG Programme: Independent Junior Research Groups