Pubblicazioni

Neurophysiological Correlates of HD-tDCS-induced modulation of cortical sensorimotor networks a stimultaneous fNIRS-EEG study

M, Muthalib; A, Dutta; P, Besson; S, Perrey

Abstract:

INTRODUCTION. Non-invasive anodal transcranial direct current stimulation (atDCS) increases neuronal excitability and activity. Recent physiological and modelling studies have shown that a 4x1 high definition atDCS (HD-atDCS) montage can constrain the electric field between the active electrode and four surrounding return electrodes, and thus focally stimulate a target cortical region (Edwards et al., 2013; Muthalib et al., 2015). For HD-atDCS to be applied optimally to stimulate a target cortical region, a neurophysiological correlate of the strength of the applied electric field should be measured during the stimulation. The temporal and spatial changes of cortical neurovascular dynamics can be measured non-invasively during the stimulation using fNIRS (hemodynamics) and EEG (neuronal activity) neuroimaging methods. The aim of this study was to measure and model using combined fNIRS-EEG neuroimaging the time course of bilateral sensorimotor network hemodynamics and neural activity during HD-atDCS targeting the left sensorimotor cortex (SMC). METHODS. Fifteen healthy subjects received 10min, 20min and Sham HD-atDCS (2mA; Startstim, Neuroelectrics) targeting the left SMC via a 4x1 HD-atDCS electrode montage (anode on C3 with four return cathode electrodes ~4cm apart, see Fig.1) in a randomized, cross-over study design. Simultaneous EEG (23 channels; Active 2, Biosemi) and fNIRS (16 channels; Oxymon MkIII, Artinis Medical Systems) was used to measure changes in bilateral sensorimotor network neuronal activity (EEG frequency) and hemodynamics (fNIRS: oxy-O2Hb and deoxy-HHb hemoglobin concentrations). RESULTS. In general, the O2Hb time course showed a biphasic increase in the stimulated left sensorimotor network during only the 10min and 20min HD-atDCS sessions, with a more rapid increase during the first 2-5min for the fNIRS channels surrounding the anode (Ch3,4,5,6) than those outside the perimeter of the return electrodes (Ch1,2,7,8) or contralateral channels (Ch9-16), which was followed by a relative plateau for the rest of the stimulation period. The time course of HHb signals were more variable between subjects. In a subsample of 5 subjects the EEG power spectrum analysis showed that HD-atDCS primarily modulated EEG power in the Theta (4-7Hz) and Alpha (7-12Hz) frequency bands. A Kalman filter using an autoregressive exogenous (ARX) model was able to appropriately track O2Hb signals using EEG band-power signals. CONCLUSION. The temporal and spatial increase of O2Hb in the stimulated left sensorimotor network by HD-atDCS could represent the strength of the induced electrical field, and thus provide an indication of the dose of cortical neuromodulation. The ARX model using neuronal (EEG) and hemodynamic (fNIRS) responses can lend to closed-loop control of HD-atDCS for optimised neuromodulation in various neuroergonomic applications

Patologie/Applicazioni:

• Stimolazione elettrica transcranica (TES)

Anno:

2016

Tipo di pubblicazione:

Articolo

Parola chiave:

neuromodulazione; ossigenazione cerebrale; hd-tdcs

Testata scientifica:

International Conference of Neuroergonomics