Functional Connectivity Evoked by Orofacial Tactile Perception of Velocity

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.

Dynamic Causal Modeling of Neural Responses to an Orofacial Pneumotactile Velocity Array

“…The present study aimed to identify effective connectivity in 20 neurotypical adults' fMRI data using DCM during orofacial pneumotactile stimuli through a 5-channel array at three saltatory velocities (5, 25, and 65 cm/s). This work is an extension of our previous studies (Custead et al, 2017;Wang et al, 2020) and will provide new information on the causal relationships between brain regions within the sensorimotor systems responsible for encoding the velocity tactile stimulation. We aimed to address the following questions on 1) whether orofacial pneumotactile stimuli (5, 25, and 65 cm/s) are processed serially from the contralateral SI to the contralateral SII or parallelly to both contralateral SI and SII, 2) how orofacial pneumotactile stimuli (5, 25, and 65 cm/s) influence interhemispheric connections between the contralateral SII and the ipsilateral SII, 3) how passive orofacial pneumotactile stimuli (5, 25, and 65 cm/s) influence the contralateral M1, and 4) what is the role of the right lobule VI in the sensorimotor networks during orofacial pneumotactile stimuli (5, 25, and 65 cm/s).…”

“…This study used a dataset that has been described in previous publications (Custead et al, 2017;Wang et al, 2020), which provides additional details regarding participants, paradigms, and fMRI data preprocessing.…”

“…Our group previously identified a putative neuronal somatosensory network with bilateral SI, left M1, and the right lobule VI using a univariate generalized linear model (GLM) on functional magnetic resonance imaging (fMRI) data of 20 neurotypical adults when perceiving moving stimulation on the right lower face (Custead et al, 2017). A subsequent functional connectivity (FC) analysis on the same data revealed that the medium velocity (25 cm/s) tactile stimulation evoked stronger FC in the ipsilateral cortical regions than the low velocity (5 cm/s) (Wang, Sibaii, Custead, Oh, & Barlow, 2020). Nevertheless, there is still much to learn about the complex neuronal networks involved in orofacial pneumotactile velocity processing.…”

“…Recent evidence has supported that the cerebellum can be subdivided into several specialized functional regions (Witter & De Zeeuw, 2015). Previous work has demonstrated that the right lobule VI was a part of the sensorimotor somatotopic representations for the face (Custead et al, 2017;Grodd et al, 2001;Wang et al, 2020). The effective connectivity of the cortico-cerebral networks elicited by passive orofacial pneumotactile stimulation has not yet been studied, which will provide unique insights into the feedforward and feedback pathways of tactile processing in the cortico-cerebral networks.…”

“…Our previous study identified similarities and differences of functional connectivity in the sensorimotor system during orofacial pneumotactile stimuli of different velocities (5, 25, 65 cm/s) and shed light on the functional networks encoding the orofacial pneumotactile perception of velocity (Wang et al, 2020). However, the functional connectivity is limited to undirected connections among regions, and the causal relationships within the sensorimotor network cannot be examined.…”