Interdigitated Columnar Representation of Personal Space and Visual Space in Human Parietal Cortex

TL;DR

This study reveals that the human parietal cortex contains interdigitated columns that encode personal space and visual disparity, transforming sensory information into social and spatial perceptions related to personal boundaries.

Contribution

It demonstrates the existence of distinct, interdigitated columnar representations for personal space and disparity distance in the parietal cortex, advancing understanding of spatial and social processing in the brain.

Findings

PD columns respond selectively to face proximity near personal space boundary.

BOLD responses in PD columns correlate with discomfort and arousal levels.

DD columns encode disparity-based distances, interdigitated with PD columns.

Abstract

Personal space (PS) is the distance that people prefer to maintain between themselves and unfamiliar others. Interpersonal intrusion into a given persons PS evokes discomfort, and an urge to move further apart. We hypothesized that in parietal cortex: 1. PS processing involves a previously-described threat-sensitive brain circuit, and 2. the spatial encoding of distance is transformed accordingly, from purely sensory to PS-related. These hypotheses were tested using 7T fMRI at high spatial resolution. In response to images of different visual stimuli across a range of virtual distances, we found two categories of distance encoding in functionally corresponding columns within parietal cortex. First, PD (personal distance) columns responded selectively to moving and stationary face images presented at virtual distances nearer (but not further) than each subjects behaviorally-defined PS boundary. In the majority of PD columns, BOLD response amplitudes increased monotonically and nonlinearly with increasing virtual face proximity. In the remaining PD columns, BOLD responses decreased with increasing proximity. These fMRI response functions appear related to previously-reported variations in subjective discomfort levels, and physiologic arousal, during intrusion into but not beyond personal space. Secondly, DD (disparity distance) columns in parietal cortex responded selectively to disparity-based near or far distances, in random dot stimuli, like disparity-selective columns described previously in occipital cortex. In parietal cortex, maps of DD columns were systematically non-overlapping (interdigitated) with the PD columns. These results suggest that the transformation of spatial information, from visual to higher-order, may be computed in multiple small sites, rather than across a larger cortical gradient, in parietal cortex.