Somatosensory evoked potentials that index lateral inhibition are modulated according to the mode of perceptual processing: comparing or combining multi-digit tactile motion

Irena Arslanova,Keying Wang,Hiroaki Gomi,Patrick Haggard

doi:10.1080/17588928.2020.1839403

Irena Arslanova, Keying Wang + Show 2 more

Open Access

https://doi.org/10.1080/17588928.2020.1839403

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Journal: Cognitive Neuroscience	Publication Date: Dec 14, 2020
Citations: 3	License type: open-access

Affiliation: University College London, NTT (Japan)

Abstract

ABSTRACT Many perceptual studies focus on the brain’s capacity to discriminate between stimuli. However, our normal experience of the world also involves integrating multiple stimuli into a single perceptual event. Neural mechanisms such as lateral inhibition are believed to enhance local differences between sensory inputs from nearby regions of the receptor surface. However, this mechanism would seem dysfunctional when sensory inputs need to be combined rather than contrasted. Here, we investigated whether the brain can strategically regulate the strength of suppressive interactions that underlie lateral inhibition between finger representations in human somatosensory processing. To do this, we compared sensory processing between conditions that required either comparing or combining information. We delivered two simultaneous tactile motion trajectories to index and middle fingertips of the right hand. Participants had to either compare the directions of the two stimuli, or to combine them to form their average direction. To reveal preparatory tuning of somatosensory cortex, we used an established event-related potential design to measure the interaction between cortical representations evoked by digital nerve shocks immediately before each tactile stimulus. Consistent with previous studies, we found a clear suppression between cortical activations when participants were instructed to compare the tactile motion directions. Importantly, this suppression was significantly reduced when participants had to combine the same stimuli. These findings suggest that the brain can strategically switch between a comparative and a combinative mode of somatosensory processing, according to the perceptual goal, by preparatorily adjusting the strength of a process akin to lateral inhibition.

Highlights

Given the overwhelming flux of information and the brain’s limited processing capacity (Broadbent, 1958; Gallace et al, 2006; Luck & Vogel, 1997), incoming sen sory inputs need to be processed efficiently to guide behavior
Participants were pre sented with three choices on the computer screen positioned above right hand, and selected one with their left hand
We showed that the suppressive interaction between evoked responses to simultaneous stimulation of two digits was not fixed, but was strategically adjusted accord ing to the perceptual task at hand

Summary

Introduction

Given the overwhelming flux of information and the brain’s limited processing capacity (Broadbent, 1958; Gallace et al, 2006; Luck & Vogel, 1997), incoming sen sory inputs need to be processed efficiently to guide behavior. While an observer can isolate one particular bird’s movement, the observer is able to perceive the average movement of the flock as a whole. The ability to extract overall or average motion infor mation from multiple, simultaneous motion cues has been described in vision (Watamaniuk & McKee, 1998; Watamaniuk et al, 1989) under the idea of ensemble perception (for review see Alvarez, 2011; Whitney & Yamanashi Leib, 2018). When an object held between fingers begins to move, the overall motion direction of the object can be clearly perceived (Martin, 1992). Because the motion cues at each fingertip may not be redundant, the brain must aggregate individual motion direction cues from differ ent digits to extract the veridical average motion direc tion.

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