Enhancement of visual biological motion recognition in early-deaf adults: Functional and behavioral correlates

Abstract

Deafness leads to brain modifications that are generally associated with a cross-modal activity of the auditory cortex, particularly for visual stimulations. In the present study, we explore the cortical processing of biological motion that conveyed either non-communicative (pantomimes) or communicative (emblems) information, in early-deaf and hearing individuals, using fMRI analyses. Behaviorally, deaf individuals showed an advantage in detecting communicative gestures relative to hearing individuals. Deaf individuals also showed significantly greater activation in the superior temporal cortex (including the planum temporale and primary auditory cortex) than hearing individuals. The activation levels in this region were correlated with deaf individuals' response times. This study provides neural and behavioral evidence that cross-modal plasticity leads to functional advantages in the processing of biological motion following lifelong auditory deprivation.

Fig 1. Stimuli and behavioural results.

(A) example of a communicative gesture/emblems « calm down » (B) example of a non-communicative gesture/pantomimes « playing guitar » (C) example of a scrambled versions (D) Behavioral results illustrating the reaction times (RT) according to both groups. Errors bars denote standard deviation.

Fig 2. fMRI data.

The conjunction of cortical activations implicated in biological motion processing [(Emblems + Pantomimes)—scrambled] by the group, deaf (Red) and hearing participants (Blue), Overlap (Purple).

Fig 3. fMRI data.

(A) The cortical activations implicated in Emblems only (Yellow), Pantomime only (Blue), and the Overlap (Green) by the group. (B) Significant difference between deaf and hearing participants in the biological motion condition, the image in the maximum global coordinate (66.0–28.0 7.0). (C) Significant difference between deaf and hearing participants in the pantomime condition, the image in the maximum global coordinate (66.0–28.0 7.0). (D) Significant difference between deaf and hearing participants in the emblem condition, the image in the maximum peak activation at coordinates (66.0–28.0 7.0). Color scale represents T values (B,C, D).

Fig 4. fMRI data.

Covariation between cortical activity triggered by biological motion (Emblems—Pantomimes) and behavioral discrepancy (on reaction times) in the deaf group only. MNI coordinates for global maximum (66.0–28.0 7.0). Graphs: Correlation plots of the blood oxygen level-dependent Emblems-Pantomimes responses in this region against reaction times (RT). Each data point represents a single subject, Red for the deaf group and Green for the hearing group. Color scale represents F values.