Abstract
The cortical representations of orofacial pneumotactile stimulation involve complex neuronal networks, which are still unknown. This study aims to identify the characteristics of functional connectivity (FC) evoked by three different saltatory velocities over the perioral and buccal surface of the lower face using functional magnetic resonance imaging in twenty neurotypical adults. Our results showed a velocity of 25 cm/s evoked stronger connection strength between the right dorsolateral prefrontal cortex and the right thalamus than a velocity of 5 cm/s. The decreased FC between the right secondary somatosensory cortex and right posterior parietal cortex for 5-cm/s velocity versus all three velocities delivered simultaneously (“All ON”) and the increased FC between the right thalamus and bilateral secondary somatosensory cortex for 65 cm/s vs “All ON” indicated that the right secondary somatosensory cortex might play a role in the orofacial tactile perception of velocity. Our results have also shown different patterns of FC for each seed (bilateral primary and secondary somatosensory cortex) at various velocity contrasts (5 vs 25 cm/s, 5 vs 65 cm/s, and 25 vs 65 cm/s). The similarities and differences of FC among three velocities shed light on the neuronal networks encoding the orofacial tactile perception of velocity.
Highlights
The human somatosensory system decodes tactile stimuli from peripheral sensory receptors through a complex process involving interactions between bottom-up thalamocortical and topdown corticocortical/cortico-thalamo-cortical pathways (Avivi-Arber et al, 2011; Lundblad et al, 2011; Zembrzycki et al, 2013; Hwang et al, 2017)
Comparing 5 and 25 cm/s task conditions, increased functional connectivity (FC) was identified between the right DLPFC and the right thalamus
The present study examined FC evoked by the orofacial tactile perception of velocity using functional magnetic resonance imaging (fMRI) in 20 neurotypical adults
Summary
The human somatosensory system decodes tactile stimuli from peripheral sensory receptors through a complex process involving interactions between bottom-up thalamocortical and topdown corticocortical/cortico-thalamo-cortical pathways (Avivi-Arber et al, 2011; Lundblad et al, 2011; Zembrzycki et al, 2013; Hwang et al, 2017). Brain Connectivity Evoked by Orofacial Stimuli located in the postcentral gyrus, processes complex information about the location, velocity, and other characteristics of tactile stimulation from the thalamus through the thalamocortical axons. A type of cutaneous mechanoreceptors that usually detect rapid vibrations (about 200–300 Hz) in both glabrous and hairy skin (e.g., palm and arm, respectively), were considered to be virtually absent from the facial skin based on psychophysical methods (Barlow, 1987), and the cutaneous mechanoreceptors in the facial skin have high densities and are slow adapting, with small receptive fields (Johansson and Olsson, 1976; Johansson et al, 1988)
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