Error corrections in children with ADHD and DCD

The present study examines the ability of 10 to 12 year old ADHD, DCD and comorbid ADHD/DCD children to update discrete step tracking responses to a superseding stimulus. These groups were compared to a comparison group for responses to crossed or uncrossed step stimuli. In crossed step situation, target stepped to 101.60 mm of either side of homebase and then to the opposite side. In uncrossed step situation, target first stepped to a position 203.20 mm to the right and then to either 101.60 mm or 50.80 mm from homebase. Interstep intervals were 40, 140 and 220 msec. Data were analysed in relation to amplitude transition function. When responding to crossed step stimuli, all groups produced a bimodal reaction time (RT) distribution. Responses made directly to the second step position were associated with longer RTs. This result suggests that these children were able to inhibit a response in one direction and reprogrammed the response in the opposite direction. For uncrossed stimuli, initial response amplitude varied systematically as a function of determinant time interval (DTI). For intermediate amplitude responses, DTI did not change as a function of the amplitude of the second step. The results are consistent with the continuous updating or averaging of error information. Since the corrective response was accurate with respect to second target, the results suggest all groups had recourse to an efference copy. The results are discussed in terms of the mechanisms available to children for updating visuo-spatial error information.