Neural adaptations in short-term learning of sign language revealed by fMRI and DTI

While vocal articulation is a unique feature of spoken languages, signed languages use facial expressions and hand movements for communication. Despite this substantial difference, neuroimaging studies show that spoken and sign language rely on similar areas of the brain in the frontal and parietal regions. However, little is known about the specific roles of these areas and how early they get involved. In the present study, we investigate the impact of short-term training-related changes in learners of British sign language (BSL). Pre- and post-training functional magnetic resonance imaging (fMRI) and diffusion tensor imaging scans were taken from twenty-six right-handed healthy volunteers. During the training course, participants were taught to discriminate and sign basic sentences using BSL for three consecutive days (1 h per day). fMRI results show increasing brain activity in the right cerebellum and cerebral brain areas including bilateral middle temporal gyrus, left angular gyrus, left middle and inferior frontal gyrus. Moreover, functional connectivity increased significantly after training between these areas. Microstructural findings show significant mean diffusivity and radial diffusivity reductions in the left angular gyrus, which are significantly correlated with behavioural improvement. These results reveal a high degree of similarity in the neural activity underlying signed and spoken languages. The rapid microstructural changes, identify the left angular gyrus as a structure that rapidly adapts to newly learnt visual-semantic associations.