7T laminar fMRI responses during encoding and retrieval of naturalistic virtual experiences

Poster Session C - Sunday, April 14, 2024, 5:00 – 7:00 pm EDT, Sheraton Hall ABC

Yan I. Wu¹, Alice L. Hickling¹, Nicholas A. Alexander¹, Nadine N. Graedel¹, Robert A. Seymour¹, Oliver Josephs¹, Vahid Malekian¹, Martina F. Callaghan¹, Eleanor A. Maguire¹; ¹University College London

Previous research has consistently identified a set of brain regions, including the hippocampus and medial prefrontal cortex (mPFC), that supports recollection of our past experiences. What happens in the brain during the initial formation of such autobiographical memories is less clear. To address this issue, we had healthy adult participants embark upon an interactive guided tour through a virtual reality town during which they had a range of naturalistic experiences while being scanned using 7T fMRI. They returned later that day and recalled the virtual experiences first silently during fMRI, followed by retrieval aloud outside the scanner. We investigated fMRI responses in the layers (superficial, middle, deep) of the mPFC and other cortical areas, along with the hippocampal subfields, when encoding and recalling these everyday experiences. Analyses included examination of whether the initial formation of autobiographical memories was supported by specific cortical layers, with a particular interest in the deep layer and also the hippocampal subfields CA3 and dentate gyrus. In addition, the encoding data were interrogated with respect to whether experiences were well or poorly remembered during subsequent retrieval. Because recall took place approximately 12 hours after encoding, this dataset also afforded us the opportunity to examine laminar and subfield responses during an early phase of systems-level consolidation of (virtual) autobiographical memory representations, something that has rarely been reported. Overall, this rich 7T fMRI dataset has started to expose how memories more akin to real life might be formed and represented at the level of neural microcircuits.

Topic Area: LONG-TERM MEMORY: Episodic