Fig. 3.

Detection of the presence or absence of the SLR, for each of the three representative subjects. A: mean target-aligned EMG activity associated with the short or long reaction time (RT) movements, based on division of trials below or above the median RT (blue or green lines, respectively; solid or dashed lines show ipsilaterally or contralaterally directed movements, respectively). Scale values in μV. B: separate time-series receiver operating characteristic (ROC) analyses were performed on the short or long RT groups, segregated by the side of target presentation. For each ms, the ROC value quantifies the separation of the distribution of EMG activity, segregated by the side of target presentation; a value of 0.5 or 1.0 means the distributions either overlap completely (hence an ideal observer could not determine the side of the target based on EMG activity) or are completely segregated (hence an ideal observer could perfectly determine the side of the target based on EMG activity). See results for how the discrimination time (dotted vertical line) is determined based on the intersection of a linear regression spanning a baseline interval (red dashed line) and a linear regression running from an inflection point to the first peak of the ROC curve (red diagonal solid line and square). C: for each of the short and long RT groups, we plotted the mean RT as a function of the discrimination time, and calculated the slope of a line connecting these points; an SLR was determined to be present if the slope of this line exceeded 67.5° (as was the case bilaterally for subject A, and for left SPL from subject C).