Identifying brain areas responsible for temporal order representations

Abstract

Remembering events in their correct order is fundamental to cognition, but how exactly the brain represents this is poorly understood. This thesis tested the specific hypothesis that temporal order is represented by tuned neural populations, using population receptive field (pRF) modelling of fMRI data to search for these populations. We scanned participants while they performed a sequence memory task, in which they encoded the order of a visual sequence and then recalled an item's original sequence position. We analysed the data using pRF models to test the predictions of the hypothesised voxel-wise tuning for temporal order. The results showed that temporal order-tuned models, which included a predictor for an item's sequence position, significantly outperformed our baseline, which lacked such a predictor. A logarithmic Gaussian tuning profile provided the best fit, offering a neural correlate for the primacy effect. However, while individual participants showed clear temporal order tuning in specific areas, these locations were not consistent across the group, and no single brain region was universally involved. Distinct signals for the recall of different positions were also not found. These findings point to a need for future research to focus on the sources of this inter-subject variability. This could allow for a better understanding of how temporal order is represented in the human brain, and how individual cognitive strategies influence that representation.