Coexistence of tics and hyperactivity in children: no additive at the psychophysiological level.

The objective of the present work was to study the effects of tic disorder (TD) and hyperactivity (HA) on slow cortical potentials in children with combined TD + HA symptoms. Being related to different processes of frontal lobe control over preparatory cortical activity, early and late components of the slow negative potentials (eSNP, ISNP) were examined. SNP amplitude was analyzed as reflecting the sufficiency of preparatory cortical activation; scalp distribution of SNP and relationships to reaction times were studied as revealing the efficiency of task-related region-specific activation. It was hypothesized that if the effects of TD and HA were independent, additive effects on SNP amplitudes would be observed in children with coexisting TD and HA symptoms (TD + HA). Differences in SNP scalp distribution between control and patient groups were predicted to occur mainly over the frontal brain areas. Four groups of children (n = 10/11 in each group) were studied: healthy controls, pure TD, pure attention deficit hyperactivity disorder (ADHD), and combined tic and hyperactivity symptoms. SNPs were recorded in an auditory warned reaction time task (S1-S2-RT) from 8 electrode locations. According to the results, the effects of TD and HA on the sufficiency of task-dependent cortical activation were different, with only the TD factor related to lower SNP amplitudes. Nevertheless, deviant patterns of scalp distribution were found for pure ADHD patients, which suggested an inefficiency in involving the adequate task-related areas. For TD + HA children, like pure TD, lower SNP amplitudes and similar distribution and correlation patterns were present. Thus, according to amplitude, topography, and correlation criteria, TD + HA does not appear to be a subgroup of HA disorder but seems more similar to pure tic disorder.