Figure 1.
Time-course and topography of response-locked movement-related potentials (initial movement related potential peak - iMP) including the topography of iMP lateralization ([C3−C4]/2).
For control children, averages of all responses are illustrated together with a separate presentation of averages of fast (below median reaction time) and slow responses (above median reaction time). For children with ADHD, responses on and off methylphenidate are presented. For effects of response speed in ADHD see Figure 4. Note how the rather symmetrically distributed stimulus-related P300 shadowed MRP in the topography before the subtraction of symmetrically distributed potential components by the calculation of lateralization. iMP time-course (thick black arrows) and lateralized topography around C3 (grey arrows) are in good agreement with previous literature. mPINV (lateralized negativity at C3 in the time interval 500–800 ms) was not shadowed by P300 any more. Its topography is presented in Figure 2.
Figure 2.
Motor PINV topography for healthy control children.
(top; from left to right: all responses, fast responses below median reaction time, slow responses above median reaction time) and children with ADHD (bottom; from left to right: responses off and on methylphenidate) for the motor PINV time interval (500–800 ms after the response trigger, motor post-processing).
Table 1.
Lateralized motor potential (iMP’) and motor postimperative negative variation (mPINV’) amplitudes for the ADHD and the healthy control group ([C3−C4]/2).
Table 2.
ANOVA results (comparison children with ADHD versus healthy control children).
Table 3.
ANOVA results (effects of methylphenidate).
Figure 3.
Group effects and effects of stimulant medication.
Grand average of lateralized motor potentials ([C3−C4]/2) for children with ADHD and healthy control children. In ADHD children, the potential waveform before and after intake of 10 mg methylphenidate are shown – the order in which the sessions were recorded was counterbalanced.
Figure 4.
Grand average of lateralized motor potentials ([C3−C4)/2] of a) all responses time-locked to motor response; *: p<0.05; b) fast responses below median reaction time; c) slow responses above median reaction time. Lateralisation of the initial motor potential peak (iMP) was diminished in ADHD children especially during short, but not during long reaction time.
Figure 5.
Scatterplot showing the correlation between response speed and lateralized initial motor potential peak amplitude (iMP’) for children with ADHD and healthy control children ([C3−C4]/2).