Functional Connectivity Evoked by Orofacial Tactile Perception of Velocity

Abstract

The cortical representation of orofacial pneumotactile stimulation involves a complex network, which is still unknown. This study aims to identify the characteristics of functional connectivity (FC) elicited by different saltatory velocities over the perioral and buccal surface of the lower face using functional magnetic resonance imaging (fMRI) in twenty neurotypical adults. Our results showed 25 cm/s evoked more functional coupling in the right hemisphere, suggesting 25 cm/s might be optimal velocity if bilateral brain damages occur. The decreased FC between the right secondary somatosensory cortex and right posterior parietal cortex for 5 cm/s versus All-on showed that the relatively slow velocity evoked less coupling in the ipsilateral hemisphere, which suggesting functional coupling in the contralateral hemisphere is in charge of orofacial tactile perception of velocity. The increased FC between the right thalamus and bilateral secondary somatosensory cortex for 65 cm/s versus All-on indicated that the neural encoding of relatively fast tactile velocity is more coupling between the right thalamus and bilateral secondary somatosensory cortex. Our results have shown different characteristics of FC for each seed at various velocity contrasts (5 > 25 cm/s, 5 > 65 cm/s, and 25 > 65 cm/s), suggesting the neuronal networks encoding the orofacial tactile perception of velocity. The difference of functional connectivity among three velocities may indicate the optimal stimulation setting for better therapeutic effects on stroke recovery.