Physiological Basis of Hyperkinesis Treated With Methylphenidate

Abstract

The study attempted to determine the primacy of physiological arousal or motor activation levels in predicting the number of developmental problems, current symptoms, and response to methylphenidate in 12 hyperkinetic children when compared with 12 unmedicated normal controls. Auditory evoked responses (EVC) and galvanic skin conductance (GSR) gauged physiological arousal level, while the sensorimotor EEG rhythm (SMR) and electromyogram (EMG) indexed both arousal and motor activation. Before medication, hyperkinetic children differed from normal control children in showing more severe developmental amid current symptom profiles and reduced SMR. The dearth of SMR is consistent with the rhythm's association with immobility in lower aninials. Although physiological measures failed to distinguish hyperkinetic children in general, four children consistently revealed hypoaroused physiological patterns relative to other hyperkinetic and normal control children. Low arousal characteristics included higher amplitude EVC as well as reduced GSR conductance, EMG, and SMR. Low arousal subjects also showed a history of poor sensorimotor development with the most severe current symptomatologies and benefited most from methyiphenidate. A concurrent trend toward a normalization of all physiological measures with medication is consistent with the arousal hypothesis. However, initial SMR incidence alone accurately predicted the severity of pretreatment motor symptoms and individual response to medication, suggesting a basis for these findings in motor functions.