RESUMO
Event-related potential (ERP) studies report that the positive deflection following stimulus evaluation at 300 msec (P3) in hyperactive children is augmented by methylphenidate (MP). This study investigates P3 and preceding ERP components using an auditory oddball task in attention-deficit hyperactivity disorder (ADHD). Mismatch negativity, negativity at 100 and 200 msec, and positivity at 200 msec and 300 msec (P3) were obtained from 14 control and hyperkinetic children. ADHD children who responded to MP were tested on two separate days while receiving either MP or placebo. Controls were tested once. No differences were found between groups for ERP components preceding P3. P3 amplitude was significantly larger under MP than under placebo, but did not differ from controls. Under MP, differences in P3 amplitude unexpectedly occurred when no response was required. A P3 amplitude increase under MP and the unexpected P3 suggest that MP affects attention regulation.
Assuntos
Transtorno do Deficit de Atenção com Hiperatividade/tratamento farmacológico , Transtorno do Deficit de Atenção com Hiperatividade/psicologia , Estimulantes do Sistema Nervoso Central/uso terapêutico , Processos Mentais/efeitos dos fármacos , Metilfenidato/uso terapêutico , Comportamento/efeitos dos fármacos , Criança , Eletroencefalografia/efeitos dos fármacos , Potenciais Evocados P300/efeitos dos fármacos , Potenciais Evocados P300/fisiologia , Feminino , Humanos , Masculino , Escalas de Graduação PsiquiátricaRESUMO
This pilot study investigates electrophysiological correlates of methylphenidate (MP) treatment among hyperkinetic children who are clinical responders to therapy. Event-related potentials were obtained from a small sample (6 hyperactive and 5 controls) during an auditory "oddball" task. In the ignore condition, oddball tones elicited a frontocentral "mismatch" negativity (MMN) during the 100- to 200-msec latency range following stimulus presentation. In the attend condition, oddball target tones elicited a centroparietal P3 as well. MP significantly decreased hyperkinetic behaviors. Preliminary analyses of the electrophysiological data indicated a decreased amplitude of the P3 waveform among hyperkinetic children and a trend toward normalization on MP. Waveform abnormalities in the latency range of control MMN suggested either a decrease in MMN amplitude or an increase in MMN latency in hyperactive subjects along with a trend toward normalization by MP. The preliminary data are suggestive of information-processing abnormalities among hyperactive children that may be sensitive to MP therapy.
