Figure 4.

Group results with and without white matter regressor. In our main analysis, we included realignment parameters and a white matter mean signal time course as regressors of no interest in the individual design matrices. The white matter regressor in particular could have induced artificial signal changes by itself. Therefore, we additionally analyzed our data without the white matter regressor. The top row of the figure shows the results for Experiment 2 (left arm reaching); the bottom row shows the results for Experiment 1 (right arm reaching). Left, Results of the contrast reaching > saccades from the original analysis including realignment parameters (RP) and the white matter (WM) regressor. The data are thresholded at the same value as in Figure 3 (t > 4). Middle, Results of the the same contrast, reaching > saccades, including the same regressors of no interest without a threshold (t > 0) to illustrate the full pattern of positive signals. Right, The same contrast based on a conventional analysis including only the realignment parameters as regressors of no interest. The color scale was set to an identical range for both analyses, and the transversal slice is located at z = −6 mm. Scale bar, 10 mm.