Functional reorganization of the conceptual brain system after deafness in early childhood.

Cosimo Urgesi,Natalie M Trumpp,Markus Kiefer

doi:10.1371/journal.pone.0198894

Abstract

The neurodevelopmental consequences of deafness on the functional neuroarchitecture of the conceptual system have not been intensively investigated so far. Using functional magnetic resonance imaging (fMRI), we therefore identified brain areas involved in conceptual processing in deaf and hearing participants. Conceptual processing was probed by a pictorial animacy decision task. Furthermore, brain areas sensitive to observing verbal signs and to observing non-verbal visual hand actions were identified in deaf participants. In hearing participants, brain areas responsive to environmental sounds and the observation of visual hand actions were determined. We found a stronger recruitment of superior and middle temporal cortex in deaf compared to hearing participants during animacy decisions. This region, which forms auditory cortex in hearing people according to the sound listening task, was also activated in deaf participants, when they observed sign language, but not when they observed non-verbal hand actions. These results indicate that conceptual processing in deaf people more strongly depends on language representations compared to hearing people. Furthermore, additionally enhanced activation in visual and motor areas of deaf versus hearing participants during animacy decisions and a more frequent report of visual and motor features in the property listing task suggest that the loss of the auditory channel is partially compensated by an increased importance of visual and motor information for constituting object knowledge. Hence, our results indicate that conceptual processing in deaf compared to hearing people is more strongly based on the language system, complemented by an enhanced contribution of the visuo-motor system.

Highlights

Investigations of early onset deafness allow us to study experience-dependent influences on the neurodevelopment of higher-level cognition functions such as memory and language
In order to assess whether functional cortical reorganization in deafness is based on functional properties of the stimuli or stimulus modality, we identified in deaf participants brain areas sensitive to observing verbal signs and to observing non-verbal visual hand actions compared to baseline
The present study indicated neuro-plastic changes in the conceptual system of early onset deaf individuals: Compared with hearing participants, conceptual processing during the animacy

Summary

Introduction

Investigations of early onset deafness allow us to study experience-dependent influences on the neurodevelopment of higher-level cognition functions such as memory and language. In individuals, who became deaf in early childhood before or during language development and did not receive cochlear implants, sign language is typically used instead of spoken language. Due to the lack of the acoustic channel, deaf individuals have to rely on vision, action or touch to gain information about objects and events in the environment [2,3].

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