The nature of unilateral motor commands in between‐hand choice tasks as revealed by surface Laplacian estimation

Abstract

From electroencephalographic recordings, we estimated the surface Laplacian over motor areas in a Stroop-like between-hand choice reaction time task in humans. Response-locked averages showed a (negative) "motor potential" over the primary motor areas contralateral to the response. At the same time, a positive wave was observed over the primary motor areas ipsilateral to the response. These data suggest that, when a between-hand choice is required, an inhibition of the primary motor cortex ipsilateral to the nonresponding hand is implemented. This observation is relevant to the interpretation of the lateralized readiness potential (LRP) because the LRP is blind to the respective contribution of the contralateral and ipsilateral motor cortices. In addition, a negative wave beginning about 200 ms before EMG onset and peaking about 50 ms before it occurred over the supplementary motor areas (FCz). This wave preceded the motor potential, which supports the view that the supplementary motor areas are upstream in a hierarchy of the motor command.

Disentangling Neural Sources of the Motor Interference Effect in High Functioning Autism: An EEG-Study

“…Atypical motor preparation abilities in ASD have primarily been related to disturbances in the supplementary motor area circuity (Rinehart et al, 2001), the neural area which is thought to underlie the RP Laplacian (Rigoni et al, 2013;Vidal et al, 2003). It should be noted that the original imitation inhibition paradigm we used (Brass et al, 2000;Brass, Zysset, & von Cramon, 2001) does not include a non-social control condition.…”

“…For the stimulus-locked P3, we pooled the activity at electrodes CPz, Pz and POz per condition in the time window from 350 to 400 ms. Based on earlier research (Leuthold & Schröter, 2011;Rigoni et al, 2013;Shibasaki & Hallett, 2006), we identified the RP component in the response-locked segments as the gradient shift preceding the steep negative slope before response onset at electrode FCz (i.e., from -400 to -100 ms for the current dataset). To disentangle the activity of the supplementary motor area, related to motor preparation processes, from contaminating activity related to motor execution processes in the M1, we increased the spatial resolution of the EEG-signal by means of Laplacian transformations (Rigoni et al, 2013;Tandonnet et al, 2005;Vidal et al, 2003). Due to the poor spatial resolution of the EEG-signal, volume conduction effects smear the distribution of the potentials at the scalp level, therefore producing overlapping effects of motor execution and motor preparation processes within the RP (Rigoni et al, 2013).…”

“…First, we interpolated the signal with the spherical spline interpolation procedure, and then computed second derivatives in the two dimensions of the space (degree of spline = 3, maximum degrees the Legendre Polynomial = 15. Conform earlier studies (e.g., Rigoni et al, 2013;Vidal et al, 2003) and the observed topography (figure 2), we conducted the RP-analyses on electrode FCz.…”

“…Third, we found a congruency-related difference in the Readiness Potential (RP; with the spatial resolution of the EEG-signal increased by means of Laplacian transformations; Rigoni et al, 2013;Tandonnet et al, 2005;Vidal et al, 2003, see also Methods). This is a component which typically magnifies with increasing complexities of motor preparation (Rigoni, Brass, Roger, Vidal, & Sartori, 2013;Tandonnet, Burle, Hasbroucq, & Vidal, 2005;Vidal, Grapperon, Bonnet, & Hasbroucq, 2003). The congruency effect in RP might reflect an influence of perception on action.…”

Movement-related changes in cortical excitability: A steady-state SEP approach

“…Vidal et al (2003) and Praamstra and Seiss (2005) have suggested, on the basis of current source density transformation of EEG data, that the LRP during movement preparation and execution involves contralateral activation and ipsilateral inhibition. The bi-hemispheric involvement in the preparation of a unimanual response underlines the limitations of the LRP and the potential value of complementing it with ssSEPs.…”