Mixed Coding of Content-Temporal Detail by Dorsomedial Posterior Parietal Neurons

Abstract

The dorsomedial posterior parietal cortex is part of a higher-cognition network implicated in elaborate processes underpinning memory formation, recollection, episodes reconstruction, and temporal information processing. Neural coding for complex episodic processing is however under-documented. Here we revealed a set of neural codes of “neuroethogram” in the primate parietal cortex. Analyzing neural responses in macaque dmPPC to naturalistic videos, we discovered several groups of neurons that are sensitive to different categories of ethogram-items and to low-level sensory features. The amount of information coded within these multiplex representations in turn increases our trained classifier decodability for different video-types. We also discovered that the processing of category and feature information by these neurons is sustained by accumulation of temporal information over a long timescale up to 30 s, corroborating its role at the apex of the cortical hierarchy of temporal receptive windows. Taken altogether, these neural findings explain how dorsomedial PPC weaves fabrics of ongoing experiences together in real-time and realize a multiplex representation of an organism’s past. The high dimensionality of neural representations should motivate us to shift the focus of attention from pure selectivity neurons to mixed selectivity neurons, especially in increasingly complex naturalistic task designs.

Note:
Funding Information: This work received support from National Natural Science Foundation of China (32071060), Science and Technology Commission of Shanghai Municipality (201409002800), Jiangsu Provincial Department of Science and Technology (BK20221267), Jiangsu Qinglan Talent Program Award, and internal funding from School of Psychology and Cognitive Science (East China Normal University) (SCK).

Conflict of Interests: The authors declare no competing intere

Ethical Approval: All animal care, experimental, surgical procedures, and pre/post surgical care were approved by the Institutional Animal Care and Use Committee (permission code: M020150902 & M020150902-2018) at East China Normal University.

Keywords: Neuroethology, dorsomedial posterior parietal cortex, information accumulation, temporal receptive window, mixed representation