Long-term visual-to-tactile stimulation induces functional reorganization of thalamic pathways to achieve visual...

Sensory substitution devices (SSDs) have shown promising results in restoring basic visual function in blind subjects by translating visual information into tactile stimuli. However, the specific neuroplastic changes enabling this process remain poorly defined. Although cross-modal plasticity has been widely described through a range of intermediate cortical steps from somatosensory regions to the primary visual cortex, the brain's ability to search for a direct route makes the thalamo-occipital pathway the most viable reorganization option after long-term passive tactile stimulation. In this study, we use resting-state fMRI to investigate whether SSD training could redirect functional connections from the somatosensory thalamic nuclei to the primary occipital areas. After 6 months of training, blind children showed increased connectivity between the somatosensory thalamic nuclei and the occipital regions. This stronger connectivity was associated with improved performance in identifying tactile stimuli. These findings support the hypothesis that long-term passive tactile training leads to subcortical functional reorganization rather than cortical changes. Specifically, the results showed an increase in connectivity between somatosensorial and multimodal integration thalamic nuclei and the visual cortical regions.