Characterising the hippocampal response to perception, construction and complexity

Abstract

The precise role played by the hippocampus in supporting cognitive functions such as episodic memory and future thinking is debated, but there is general agreement that it involves constructing representations comprised of numerous elements. Visual scenes have been deployed extensively in cognitive neuroscience because they are paradigmatic multi-element stimuli. However, questions remain about the specificity and nature of the hippocampal response to scenes. Here, we devised a paradigm in which we had participants search pairs of images for either colour (perceptual) or layout (spatial constructive) differences. Importantly, images depicted either naturalistic scenes or phase-scrambled versions of the same scenes, and were either simple or complex. Using this paradigm during functional MRI scanning, we addressed three questions: 1. Is the hippocampus recruited specifically during scene processing? 2. If the hippocampus is more active in response to scenes, does the cognitive process (perception or construction) being engaged influence its activation? 3. If the hippocampus is upregulated during scene processing, does the complexity of the scenes affect its response? We found that, compared to phase-scrambled versions of the scenes, the hippocampus was more responsive to scene stimuli. Moreover, a clear anatomical distinction was evident, with scene perception engaging the posterior hippocampus and scene construction recruiting the anterior hippocampus. The complexity of the scenes did not influence hippocampal activity. These findings seem to align with perspectives that propose the hippocampus is especially attuned to scenes, and its involvement occurs irrespective of the cognitive process or the complexity of the scenes.

Hippocampal representations switch from errors to predictions during acquisition of predictive associations

“…In the current study, both prediction error and prediction signals seem to have been driven by the posterior rather than the anterior hippocampus. This finding is in line with suggestions that hippocampal representations increase in complexity and scale along the long axis 55 ; simple cue-stimulus associations as studied here may therefore be encoded in posterior hippocampus 56 , whereas more complex representations such as narratives 55 and scenes [83][84][85] are encoded in anterior hippocampus.…”

New insights into anatomical connectivity along the anterior–posterior axis of the human hippocampus using in vivo quantitative fibre tracking

“…There is long-standing agreement that the hippocampus is essential for supporting episodic long-term memory (1) and for facilitating spatial navigation (2). The hippocampus has more recently been linked with other roles including imagination of fictitious and future experiences (3,4), visuospatial mental imagery (5), visual perception (6,7) and decision making (8). It is a complex structure containing multiple subregions (referred to as subfields) including the dentate gyrus (DG), cornu ammonis (CA) 4-1, subiculum, presubiculum and parasubiculum.…”

Conjunctive and complementary CA1 hippocampal cell populations relate sensory events to immobility and locomotion

“…Such cell-behavior relations are congruent with reports of the relationship between hippocampal field potentials and behavior. Given this complementary and conjunctive cell subpopulation organization, it is not surprising that subpopulations of cells can be secondarily related to features of spatial behavior (O'Keefe and Dostrovsky, 1971;O'Keefe and Nadel, 1978), episodic learning and memory (Eichenbaum, 2004;Eichenbaum and Cohen, 2014), context representation (Bulkin et al, 2020;Rudy, 2009;Smith and Bulkin, 2014), and scene construction (McCormick et al, 2021), as the hippocampus is downstream from the many cortical and subcortical systems that are also involved in these processes.…”