Shape Invariant Coding of Motion Direction in Somatosensory Cortex

Yu-Cheng Pei,James C Craig,Sliman J Bensmaia,Steven S Hsiao,Ford F Ebner

doi:10.1371/journal.pbio.1000305

Abstract

Author SummaryWhen we physically interact with an object, our hands convey information about the shape of the object, its texture, its compliance, and its thermal properties. This information allows us to manipulate tools and to recognize objects based on tactile exploration alone. One of the hallmarks of tactile object recognition is that it involves movement between the skin and the object. In this study, we investigate how the direction in which objects move relative to the skin is represented in the brain. Specifically, we scan a variety of stimuli, including bars and dot patterns, across the fingers of non-human primates while recording the evoked neuronal activity. We find that a population of neurons in somatosensory cortex encodes the direction of moving stimuli regardless of the shape of the stimuli, the speed at which they are scanned across the skin, or the force with which they contact the skin. We show that these neurons can account for our ability to perceive the direction of motion of tactile stimuli.

Highlights

In both vision and touch, information about form and motion is inferred from a spatio-temporal pattern of activation across a twodimensional sensory sheet
In previous studies of motion processing in primary somatosensory cortex (S1), a population of neurons has been identified whose responses are modulated by the direction of stimulus motion [7,8,9,10]
At the other extreme (100% coherence), all the dots move in the same direction, and the display yields a robust percept of motion direction

Summary

Introduction

In both vision and touch, information about form and motion is inferred from a spatio-temporal pattern of activation across a twodimensional sensory sheet (the retina and the skin). The early stages of form processing have been shown to be similar in these two modalities in that both involve decomposing the stimulus into a set of local oriented contours [1,2,3]. In previous studies of motion processing in primary somatosensory cortex (S1), a population of neurons has been identified whose responses are modulated by the direction of stimulus motion [7,8,9,10]. Sensitive neurons have been found in three areas of what is traditionally considered S1, namely 3b, 1, and 2. The question remains how representations of motion are elaborated in these three cortical areas

Objectives

Findings

Methods