Changes of the brain electrical fields during the continuous performance test in attention-deficit hyperactivity disorder-boys depending on methylphenidate medication

Objective: The continuous performance test (CPT) is successfully applied to evaluate attentional performance in attention-deficit hyperactivity disorder (ADHD)-children. The aim of the present study was to investigate the changes of the topographic P300-features in relation to methylphenidate-medication and to different attentional processes in primer- and distractor-conditions. Methods: Twenty-one-channel-ERPs of 17 ADHD-boys were analyzed with reference-independent methods. Four quasi stable microstates within the time frames of conventional P100, P200, P3a and P3b components were identified by means of a data-driven segmentation procedure. Results: In segment 3 topographical assessment yielded a significant occipital and right-shift of the positive centroid, longer centroid distance and higher amplitudes in primer- than in distractor conditions. MPH increased the amplitude and distance in primer and distractor-condition, without changing the topography. In segment 4 the electric fieldstrength of distractor-conditions collapsed, whereas the primer condition showed a strong fronto-parietallly oriented potential-field. There was a tendency to higher amplitudes due to MPH-medication. Conclusions: These results indicate a robust neurophysiologic differentiation of cognitive processes. MPH activates an early (P3a) covert attention process indicated by increased amplitudes and centroid. No effects were seen in later processes. Based on these effects, we propose to use the amplitude- and distance-increase in microstate 3 as an indicator of MPH efficacy in ADHD-boys.