Hippocampal-dependent episodic memory and its relation to visual-perceptual processing

Abstract

Our understanding of the mechanisms by which the human hippocampus mediates the relationship between episodic autobiographical memory and visual imagery remains limited. There is growing interest and further evidence on how the hippocampus supports the recollection of past personal experiences and influences the vividness of the images we visualize in our mind’s eye. <br /> In this thesis, the first study (Leelaarporn et al., 2024) investigates the neural processes involved in retrieving episodic autobiographical memory in healthy individuals. It utilizes a novel ultra-high field 7 Tesla fMRI sequence at submillimeter voxel size to capture the functional differentiation of the hippocampal subfields and their interactions with neocortical structures during memory retrieval. The second study (Monzel, Leelaarporn et al., 2024) investigates neural correlates of autobiographical memory in individuals with Aphantasia, who are characterized by absent or dim visual mental imagery. Furthermore, the third study (Hansen et al., 2022) explores the lymphocyte population as possible biomarkers for limbic encephalitis patients with memory dysfunction. <br /> Taken together, the results suggest a complex relationship between autobiographical memory, visual-perceptual scene processing, and its dependence on the hippocampus. We propose specifically that the pre-/parasubiculum in the anterior body of the hippocampus may interact with the visual-perceptual cortex to orchestrate the recall of autobiographical memory retrieval. Damage to the hippocampal structure may be conducive to the deficits in episodic memory functions, highlighting the critical role of the hippocampus in maintaining the integrity of visual-perceptual processing. Future studies in individuals with hippocampal pathology are necessary to relate and map the functional and structural connectivity of this specific hippocampus-dependent processing.