On the epistemic role of hippocampal cells: the case of splitter cells

Abstract

AbstractOver the past decades, the hippocampal formation has undergone extensive study leading researchers to identify a vast array of cells with functional properties (place cells, splitter cells, etc). In the present work, we aim at investigating whether the activity of those cells derives from the anatomy and inner circuitry of the hippocampal formation or derives instead from the actual behavior of the animal. To do so, we simulated an agent navigating inside an 8-shaped track, making alternating choices (T-maze alternating task). We designed a random network, based on the reservoir computing paradigm, that processes distance-based sensors and outputs a direction change (constant speed). Despite its simplicity, the model successfully solved the task while bearing no structural similarity with the hippocampal formation. We subsequently followed the comprehensive and recent review on splitter cells byDuvelle et al. (2023), and applied the exact same analysis onto the activity on the cells composing our model. We were able to identify splitter cells (as well as place cells, head direction cells and decision cells) and confirm a significant portion of the theoretical hypotheses of Duvelle et al. regarding splitter cells. Beyond these results, this work strongly suggests that the activity of such cells originates from the actual behavior of the agent as opposed to any structural or anatomical origin: any model doing the same task might exhibit the same cell activity. From a broader point of view, this work questions the epistemic role of such cells in our understanding of the hippocampal formation.