Decoding Spatial Memory Retrieval in Cubical Space Using fMRI Signals

Abstract

The way spatial memory retrieval is represented in the brain remains unclear to date. Previous studies have displayed a hippocampus-centered navigation network using functional magnetic resonance imaging (fMRI) analysis. There have been some studies on the representation of navigation behavior by signal distribution patterns, but only in the hippocampus and adjacent structures. In this study, we aimed to determine (1) the brain regions that represent information in both intensity and distribution patterns during spatial memory retrieval and (2) whether the patterns of neural responses represent spatial memory retrieval behavior performance. Both univariate analysis [general linear model (GLM)] and multivariate pattern analysis (MVPA) were employed to reveal the spatial distributions of brain responses elicited by spatial memory retrieval. Correlation analyses were performed to detect the correspondences between brain responses and behavior performance. We found that spatial memory retrieval occurred in widespread brain regions, including the bilateral hippocampi, bilateral superior frontal gyrus, bilateral superior parietal lobules, bilateral occipital lobes, and cerebellum. The amplitude of activation in the left hippocampus showed a significant negative correlation (r = −0.46, p = 0.039) with the number of task completions. Additionally, within-subject classification accuracies based on the blood oxygenation level-dependent (BOLD) signal patterns of the right middle temporal gyrus (rMTG) rostral areas in the Brainnetome Atlas showed a significant positive correlation (r = 0.78, p < 0.0001) with retrieval accuracy. In summary, our findings have implications for understanding the separation between navigational and non-navigational states and emphasizing the utility of MVPA in the whole brain.

Proximity to Boundaries Reveals Spatial Context Representation in Human Hippocampal CA1

“…The second key difference was that each spatial context (i.e., each house) consisted of two rooms, whereas previous studies, to our knowledge, examined activity associated with open environments (Deuker et al, 2016;Kyle et al, 2015;Peer and Epstein, 2021;Steemers et al, 2016;Stokes et al, 2015;L. Zheng et al, 2021), single rooms (Guo et al, 2021), or adjoining rooms within a single context (Hassabis et al, 2009;Kim and Maguire, 2018). This distinction turned out to be important because PS values in CA1 were greater for pairs of objects that were located in the entry room of the same house than for pairs of objects in the inner room or objects encountered in different rooms.…”