Hemodynamic changes in cortical sensorimotor systems following hand and orofacial motor tasks and pulsed pneumotactile stimulation

Abstract

We performed a functional near-infrared spectroscopy (fNIRS) study of the evoked hemodynamic responses seen in hand and face sensorimotor cortical representations during (1) active motor tasks and (2) pulsed pneumotactile stimulation. Contralateral fNIRS measurements were performed on 22 healthy adult participants using a block paradigm that consisted of repetitive right hand and right oral angle somatosensory stimulation using a pulsed pneumotactile array stimulator, and repetitive right-hand grip compression and bilabial compressions on strain gages. Results revealed significant oxyhemoglobin (HbO) modulation across stimulus conditions in corresponding somatotopic cortical regions. Of the 22 participants, 86% exhibited a decreased HbO response during at least one of the stimulus conditions, which may be indicative of cortical steal, or hypo-oxygenation occurring in channels adjacent to the primary areas of activation. Across all conditions, 56% of participants' HbO responses were positive and 44% were negative. Hemodynamic responses most likely differed across hand and face motor and somatosensory cortical regions due to differences in regional arterial/venous anatomy, cortical vascular beds, extent and orientation of somatotopy, task dynamics, and mechanoreceptor typing in hand and face. The combination of optical imaging and task conditions allowed for non-invasive examination of hemodynamic changes in somatosensory and motor cortices using natural, pneumatic stimulation of glabrous hand and hairy skin of the lower face and functionally relevant and measurable motor tasks involving the same structures.

Vibrography: Single-Interval Up/Down (SIUD) Adaptive Vibrotactile Threshold Estimation of the Glabrous Hand and Perioral Face in Neurotypical Adults

“…The activity patterns of single primary SA afferents with large receptive fields were influenced by tangential skin stretch associated with voluntary contraction of facial muscles [60]. These findings suggest that trigeminal mechanoreceptors in hairy and glabrous perioral skin can contribute to facial kinesthesia and proprioception for motor control by signaling small variations in stretching and contraction [50,64]. Hand.…”

Dynamic causal modeling of sensorimotor networks elicited by saltatory pneumotactile velocity in the glabrous hand

“…The Galileo system uses the pneumatic stimulator probes, called as TAC‐Cells (6 mm ID, 15 mm sealing flange), which are machined from acetyl thermoplastic homopolymer (Delrin ® ), to rapidly deform (∼10 milliseconds rise/fall times) the surface of the skin using tiny volumes of compressed air 37 . The TAC‐Cell is a small capsule with a sealing flange and can be adhered to virtually any skin surface (ie, face and glabrous hand) 23,24,38–40 . The saltatory pneumotactile velocity stimuli were delivered through 18’ long polyurethane tubing with 0.09‐inch internal diameters from the Galileo system positioned near the waveguide outside the MRI suite to the participant's right glabrous hand.…”

“…37 The TAC-Cell is a small capsule with a sealing flange and can be adhered to virtually any skin surface (ie, face and glabrous hand). 23,24,[38][39][40] The saltatory pneumotactile velocity stimuli were delivered through 18' long polyurethane tubing with 0.09-inch internal diameters from the Galileo system positioned near the waveguide outside the MRI suite to the participant's right glabrous hand. The detailed illustration figure has been published in our previous work.…”

Real‐Time Cerebral Hemodynamic Response to Tactile Somatosensory Stimulation

“…6 Very few studies have directly measured the effect of sensory stimulation of the hands or lips on CBFV in the basal cerebral arteries, 7 although the effects of sensory stimulation of the hand on local or regional CBF have been studied by various modalities, including PET, 8,9 functional MRI (fMRI), 10–12 and functional near-infrared spectroscopy (fNIRS). 13 Each of these modalities has drawbacks and limitations. For example, PET has limited spatial 14 and temporal 8,15 resolution and involves radiation exposure, 16 fMRI has limited temporal resolution, 17 and fNIRS has relatively low spatial resolution.…”