Visual evoked potential changes induced by methylphenidate in hyperactive children: dose/response effects

Abstract

Visual event related potentials (ERP) were recorded from 21 hyperactive children aged 7-13 years under two attention conditions at 4 levels of methylphenidate dose (placebo, low, medium and high). ERP measures were very sensitive to age (under or over 10 years) and attention condition, but less sensitive to drug dose. There appeared to be two classes of drug dose effect on ERP amplitude, those that changed monotonically with dose and those from which dose interacted with attention non-monotonically. Drug effect on ERP amplitude may also depend on age so that opposite effects may occur in young and old children. No latency measures showed a dose effect. It appears that methylphenidate can speed reaction times without shortening ERP latency. This suggests the drug acts more on response-related processes than on stimulus evaluation.