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.

Keywords:

• Near-infrared spectroscopy
• NIRS
• hemodynamic response
• functional activation
• somatosensory cortex
• motor cortex

Acknowledgements

The authors express gratitude to MRI technologists Joanne Murray and Kerry Hartz for project support, and to the participants.

Disclosure statement

Dr Barlow is the principal inventor of the Galileo™ which is licensed to Epic Medical Concepts & Innovations (Mission, KS, USA) by the University of Kansas and the University of Nebraska. The authors alone are responsible for the content and writing of the paper.

Funding

This work was supported, in part, by the Barkley Trust Foundation at the University of Nebraska–Lincoln (Barlow).