Abstract
Neuroplastic changes induced by sensory learning have been recognized within the cortices of specific modalities as well as within higher ordered multimodal areas. The interplay between these areas is not fully understood, particularly in the case of somatosensory learning. Here we examined functional and structural changes induced by short-term tactile training based of Braille reading, a task that requires both significant tactile expertise and mapping of tactile input onto multimodal representations. Subjects with normal vision were trained for 3 weeks to read Braille exclusively by touch and scanned before and after training, while performing a same-different discrimination task on Braille characters and meaningless characters. Functional and diffusion-weighted magnetic resonance imaging sequences were used to assess resulting changes. The strongest training-induced effect was found in the primary somatosensory cortex (SI), where we observed bilateral augmentation in activity accompanied by an increase in fractional anisotropy (FA) within the contralateral SI. Increases of white matter fractional anisotropy were also observed in the secondary somatosensory area (SII) and the thalamus. Outside of somatosensory system, changes in both structure and function were found in i.e., the fusiform gyrus, the medial frontal gyri and the inferior parietal lobule. Our results provide evidence for functional remodeling of the somatosensory pathway and higher ordered multimodal brain areas occurring as a result of short-lasting tactile learning, and add to them a novel picture of extensive white matter plasticity.
Highlights
Neuroplastic changes accompanying the processes of new skill acquisition or associative learning have been studied in both humans and animals
We analyzed brain activation patterns accompanying discrimination of Braille characters performed by active touch, before and after a short-term intensive tactile training of Braille reading in sighted subjects (N = 21)
The Braille discrimination vs. finger movement comparison showed a similar pattern of activity across the brain with stronger activations after the training (Figure S1A); comparing Braille vs. rectangles revealed a massive reorganization of cortical activation within the left hemisphere (Figure S1B)
Summary
Neuroplastic changes accompanying the processes of new skill acquisition or associative learning have been studied in both humans and animals. Tactile sensory discrimination was reported to alter receptive fields and excitability of neurons of the primary somatosensory cortex, and induce representational plasticity in both humans and animals (Recanzone et al, 1992; Siucinska and Kossut, 1996 Pleger et al, 2003; Gebel et al, 2013; Ladda et al, 2014; Andrew et al, 2015). Only a few functional activation studies were combined with investigation of white matter integrity (Scholz et al, 2009; Taubert et al, 2010; Loui et al, 2011; Gebauer et al, 2012; Schlegel et al, 2012; Lövdén et al, 2013; Draganski et al, 2014; Chavan et al, 2015) and none of them focused on tactile learning
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