7T laminar fMRI reveals the microcircuitry underpinning recall of remote autobiographical memories

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

Alice L. Hickling¹, Nadine N. Graedel¹, Ian A. Clark¹, Oliver Josephs¹, Vahid Malekian¹, Peter Kok¹, Martina F. Callaghan¹, Eleanor A. Maguire¹; ¹University College London

The ability to retrieve remote autobiographical memories from many years ago is important for maintaining the narrative of our lives. Previous neuroimaging research suggests that individual remote autobiographical memories are represented in the medial prefrontal cortex (mPFC) and hippocampal subfield CA3. However, the cortical and subcortical microcircuits involved in autobiographical memory retrieval are largely unexplored. To address this issue, we used 7T laminar functional MRI to test whether representations of individual remote autobiographical memories were present in particular hippocampal subfields and/or in the cortical layers (superficial, middle, deep) of brain areas typically involved in autobiographical memory recall, including parahippocampal, temporal, medial parietal and medial prefrontal cortices. Healthy adult participants retrieved six remote (2-5 year old) autobiographical memories six times each while being scanned. Using representational similarity analysis, we found that individual remote autobiographical memory representations were detectable in one brain area, the deep layer of the mPFC. We then examined whether the trial-by-trial strengths of these remote autobiographical memory representations were correlated with those in any other cortical layer or hippocampal subfield – so-called informational connectivity. We found that mPFC deep layer memory representation strengths were correlated with those in one brain area, namely CA3. This finding suggests that there may be sharing of memory-related information specifically between the mPFC deep layer and CA3 during recall of remote autobiographical memories. Overall, these results highlight the involvement of feedback processing pathways, which typically travel in the deep cortical layers, when recollecting autobiographical memories from the remote past.

Topic Area: LONG-TERM MEMORY: Episodic