AUDITORY EVENT-RELATED POTENTIALS (ERPS) AND MISMATCH NEGATIVITY (MMN) IN HEALTHY-CHILDREN AND THOSE WITH ATTENTION-DEFICIT OR TOURETTE TICSYMPTOMS/

The study compares 5 auditory event-related potential (ERP) components (P1 to P3) after 3 tones differing in pitch and rarity, and contrasts the mismatch negativity (MMN) between them in 12 children with attent ion-deficit hyperactivity disorder (ADHD; mean 10.2 years of age), 12 healthy controls pairwise matched for age (controls), and 10 with Chro nic Tic or Tourette Syndrome (TS). Topographic recordings were derived from 19 scalp electrodes. Four major effects are reported. (a) Shorte r latencies in ADHD patients were evident as early as 100 ms. (b) Both ADHD and TS groups showed very large P2 components where the maxima w ere shifted anteriorly. The differences in the later potentials were o f a topographical nature. (c) Frontal MMN was non-significantly larger in the ADHD group but normalized data showed a left rather than a rig ht frontal bias as in control subjects. Maxima for TS were usually pos terior. (d) ADHD patients did not show the usual right-biased P3 asymm etry nor the frontal versus parietal P3 latency difference. From these results it is suggested that ADHD patients process perceptual informa tion faster from an early stage (N1). Further, along with the TS group , ADHD patients showed an unusually marked inhibitory phase in process ing (P2), interpreted as a reduction of the normal controls on further processing. Later indices of stimulus processing (N2-P3) showed a fro ntal impairment in TS and a right hemisphere impairment in ADHD patien ts. These are interpreted in terms of the difficulties in sustaining a ttention experienced by both ADHD and TS patients.