Fig. 4.

Evidence and urgency effects on effector-selective and motor-independent decision signals. a–d Motor preparation. a Topography of the decrease in Mu/Beta-band amplitude at response, relative to pre-evidence baseline. Topography for left-hand responses is collapsed with a left-right-reversed topography for right-hand responses. b Stimulus-locked and c response-locked timecourses of Mu/Beta activity reflecting temporally increasing motor preparation (reduced spectral amplitude; note reversed y-axis) for the executed (solid) and the withheld (dashed) response. Spectral amplitudes for each time point are computed in a 300 ms window centered on that time point, resulting in a temporal smoothing effect. The gray vertical line indicates the time point for measurement of pre-response motor preparation (center of 300-ms time window). d Pre-response motor preparation at response plotted over RT. The level reached by the motor preparation towards the executed response (solid) is independent of evidence strength (light vs. dark), Speed/Accuracy regime (red vs. blue), and RT. As expected, motor preparation for the withheld response alternative reached significantly lower levels than that of the executed response (main effect of Executed/Withheld response, ANOVA F(1,15) = 14.3; p = 0.0018 Supplementary Table 5e). Error bars indicate S.E.M. across 16 subjects. e–h Motor-independent evidence accumulation. e ERP topography around the time of response commitment (−130 to −70 ms with respect to the button press, gray horizontal bar in g), showing a clear centro-parietal positivity. f Stimulus-locked and g response-locked centro-parietal traces for different evidence levels and Speed/Accuracy regimes, after subtraction of auditory evoked potential (see Methods, Supplementary Fig. 3). h CPP amplitude around the time of decision commitment, plotted over RT. Error bars indicate S.E.M. across 16 subjects. Note that y-axis scaling is identical across panels for each of the two decision signals, shown in b and f, respectively