Mixed selectivity 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 processing. Neural coding for complex episodic processing is however largely undocumented. 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 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 further discovered that the processing of category and feature information by these neurons is sustained by accumulation of temporal information over a long timescale, 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.

Posterior parietal cortex oscillatory activity shapes persistent spatial memory impairments induced by soluble amyloid-β oligomers

“…Furthermore, they support the potential use of PPC oscillatory activity as a valuable tool for early detection and intervention in AD.episodic memory retrieval and updating, in uencing new memories based on current experiences [12][13][14]. Furthermore, functional magnetic resonance imaging (fMRI) studies have revealed a positive correlation between the strength of the functional connectivity between the PPC and the hippocampus, and spatial memory performance accuracy [15]. Speci cally, the dPPC connects with the anterior hippocampus in humans (equivalent to the ventral hippocampus in rodents), while the vPPC is linked to the posterior (dorsal in rodents) hippocampus.In this context, effective communication between the hippocampus and cortical regions, and modulation of these memory processes, rely on neural oscillations, particularly theta and gamma rhythms, and the degree of synchronization between these regions, known as inter-regional coherence [16][17][18].…”

“…episodic memory retrieval and updating, in uencing new memories based on current experiences [12][13][14]. Furthermore, functional magnetic resonance imaging (fMRI) studies have revealed a positive correlation between the strength of the functional connectivity between the PPC and the hippocampus, and spatial memory performance accuracy [15]. Speci cally, the dPPC connects with the anterior hippocampus in humans (equivalent to the ventral hippocampus in rodents), while the vPPC is linked to the posterior (dorsal in rodents) hippocampus.…”