Temporal evolution of oscillatory activity predicts performance in a choice-reaction time reaching task

Abstract

In this study, we characterized the patterns and timing of cortical activation of visually guided movements in a task with critical temporal demands. In particular, we investigated the neural correlates of motor planning and on-line adjustments of reaching movements in a choice-reaction time task. High-density electroencephalography (EEG, 256 electrodes) was recorded in 13 subjects performing reaching movements. The topography of the movement-related spectral perturbation was established across five 250-ms temporal windows (from prestimulus to postmovement) and five frequency bands (from theta to beta). Nine regions of interest were then identified on the scalp, and their activity was correlated with specific behavioral outcomes reflecting motor planning and on-line adjustments. Phase coherence analysis was performed between selected sites. We found that motor planning and on-line adjustments share similar topography in a fronto-parietal network, involving mostly low frequency bands. In addition, activities in the high and low frequency ranges have differential function in the modulation of attention with the former reflecting the prestimulus, top-down processes needed to promote timely responses, and the latter the planning and control of sensory-motor processes.

Fig. 1.

A: target array with 3 examples of trajectory (back- forward movement, gray- return). Representation of hand path area, movement extent, peak velocity and the points of onset, reversal, and end. B: velocity profile of a representative out and back movement with the 5 temporal windows used in the electroencephalographic (EEG) analysis.

Fig. 2.

Findings obtained in the event related spectral perturbation (ERSP) analysis. A: group-mean ERSP for the 5 selected frequency bands are plotted on the scalp at the different time intervals of interest. B: the 9 scalp regions of interest (S-ROIs) that were selected on the basis of the ERSP activation patterns. The S-ROIs are depicted in gray along with the corresponding electrodes. C: time course of the ERSP calculated on the group for the 9 scalp S-ROIs and significance limits (in gray) obtained with bootstrap statistic (P < 0.01).

Fig. 3.

Findings obtained in the phase coherence analysis. The different line plotted on the scalp indicates those channel pairs showing significant increase or decrease of coherence values in comparison to the baseline. The coherence variations are plotted for the different time intervals of interest. Gray lines, a significant decrease; black lines, a significant increase (Statistical nonparametric procedure using suprathreshold cluster analysis for multiple comparisons, P < 0.05). Asterisk, for the beta frequency bands, the lines show significant increase/decrease of coherence values in comparison to both the baseline and PreStim time intervals.