title: Effects of Increasing Neuromuscular Electrical Stimulation Current Intensity on Cortical Sensorimotor Network Activation: A Time Domain fNIRS Study.
abstract: Neuroimaging studies have shown neuromuscular electrical stimulation (NMES)-evoked movements activate regions of the cortical sensorimotor network, including the primary sensorimotor cortex (SMC), premotor cortex (PMC), supplementary motor area (SMA), and secondary somatosensory area (S2), as well as regions of the prefrontal cortex (PFC) known to be involved in pain processing. The aim of this study, on nine healthy subjects, was to compare the cortical network activation profile and pain ratings during NMES of the right forearm wrist extensor muscles at increasing current intensities up to and slightly over the individual maximal tolerated intensity (MTI), and with reference to voluntary (VOL) wrist extension movements. By exploiting the capability of the multi-channel time domain functional near-infrared spectroscopy technique to relate depth information to the photon time-of-flight, the cortical and superficial oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin concentrations were estimated. The O2Hb and HHb maps obtained using the General Linear Model (NIRS-SPM) analysis method, showed that the VOL and NMES-evoked movements significantly increased activation (i.e., increase in O2Hb and corresponding decrease in HHb) in the cortical layer of the contralateral sensorimotor network (SMC, PMC/SMA, and S2). However, the level and area of contralateral sensorimotor network (including PFC) activation was significantly greater for NMES than VOL. Furthermore, there was greater bilateral sensorimotor network activation with the high NMES current intensities which corresponded with increased pain ratings. In conclusion, our findings suggest that greater bilateral sensorimotor network activation profile with high NMES current intensities could be in part attributable to increased attentional/pain processing and to increased bilateral sensorimotor integration in these cortical regions.
authors.affiliation: Movement To Health (M2H), EuroMov, University of Montpellier, Montpellier, France; Movement Neuroscience, IHBI, Queensland University of Technology, Brisbane, Australia.
authors.forename: Makii
authors.initials: M
authors.lastname: Muthalib
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, Milan, Italy.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Re
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, Milan, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Zucchelli
authors.affiliation: Movement To Health (M2H), EuroMov, University of Montpellier, Montpellier, France.
authors.forename: Stephane
authors.initials: S
authors.lastname: Perrey
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, Milan, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Contini
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Caffini
authors.affiliation: Istituto di Fotonica e Nanotecnologie, CNR, Politecnico di Milano, Milan, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Spinelli
authors.affiliation: Movement Neuroscience, IHBI, Queensland University of Technology, Brisbane, Australia.
authors.forename: Graham
authors.initials: G
authors.lastname: Kerr
authors.affiliation: Dipartimento di Medicina Clinica, Sanità Pubblica, Scienze della Vita e dell'Ambiente, Università degli Studi dell'Aquila, L'Aquila, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Quaresima
authors.affiliation: Dipartimento di Medicina Clinica, Sanità Pubblica, Scienze della Vita e dell'Ambiente, Università degli Studi dell'Aquila, L'Aquila, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Ferrari
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, Milan, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Torricelli
mesh_terms: D000328:Adult; D001931:Brain Mapping; D004558:Electric Stimulation; D005542:Forearm; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000000981:diagnostic imaging / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology; D009415:Nerve Net / Q000502:physiology*; D010108:Oxyhemoglobins / Q000378:metabolism; D010147:Pain Measurement; D017397:Prefrontal Cortex / Q000000981:diagnostic imaging / Q000502:physiology; D011859:Radiography; D066191:Sensorimotor Cortex / Q000000981:diagnostic imaging / Q000502:physiology*; D019265:Spectroscopy, Near-Infrared
chemical_list: D006454:Hemoglobins; D010108:Oxyhemoglobins