Response inhibition deficits in externalizing child psychiatric disorders: An ERP-study with the Stop-task

Björn Albrecht,Daniel Brandeis,Tobias Banaschewski,Aribert Rothenberger,Hartmut Heinrich

doi:10.1186/1744-9081-1-22

Abstract

BackgroundEvidence from behavioural studies suggests that impaired motor response inhibition may be common to several externalizing child psychiatric disorders, although it has been proposed to be the core-deficit in AD/HD. Since similar overt behaviour may be accompanied by different covert brain activity, the aim of this study was to investigate both brain-electric-activity and performance measures in three groups of children with externalizing child psychiatric disorders and a group of normal controls.MethodsA Stop-task was used to measure specific aspects of response inhibition in 10 children with attention-deficit hyperactivity disorder (AD/HD), 8 children with oppositional defiant disorder/conduct disorder (ODD/CD), 11 children with comorbid AD/HD+ODD/CD and 11 normal controls. All children were between 8 and 14 years old. Event-related potentials and behavioural responses were recorded. An initial go-signal related microstate, a subsequent Stop-signal related N200, and performance measures were analyzed using ANCOVA with age as covariate.ResultsGroups did not differ in accuracy or reaction time to the Go-stimuli. However, all clinical groups displayed reduced map strength in a microstate related to initial processing of the Go-stimulus compared to normal controls, whereas topography did not differ. Concerning motor response inhibition, the AD/HD-only and the ODD/CD-only groups displayed slower Stop-signal reaction times (SSRT) and Stop-failure reaction time compared to normal controls. In children with comorbid AD/HD+ODD/CD, Stop-failure reaction-time was longer than in controls, but their SSRT was not slowed. Moreover, SSRT in AD/HD+ODD/CD was faster than in AD/HD-only or ODD/CD-only. The AD/HD-only and ODD/CD-only groups displayed reduced Stop-N200 mean amplitude over right-frontal electrodes. This effect reached only a trend for comorbid AD/HD+ODD/CD.ConclusionFollowing similar attenuations in initial processing of the Go-signal in all clinical groups compared to controls, distinct Stop-signal related deficits became evident in the clinical groups. Both children with AD/HD and ODD/CD showed deficits in behavioural response-inhibition accompanied by decreased central conflict signalling or inhibition processes. Neither behavioural nor neural markers of inhibitory deficits as found in AD/HD-only and ODD/CD-only were additive. Instead, children with comorbid AD/HD+ODD/CD showed similar or even less prominent inhibition deficits than the other clinical groups. Hence, the AD/HD+ODD/CD-group may represent a separate clinical entity.

Highlights

Evidence from behavioural studies suggests that impaired motor response inhibition may be common to several externalizing child psychiatric disorders, it has been proposed to be the core-deficit in Attention-deficit hyperactivity disorder (AD/HD)
There were no differences between inhibition-functions (group (F(3,35) = 1.60, p > .20) and group*SSD (F(6,70) = 1.61, ε = .95, p > .16)). Groups differed in their Stop-failure-reactiontimes (F(3,35) = 3.70, p = .02) with control children being faster than all clinical groups; no differences were found among the clinical groups
There were group-differences in Stop-signal reaction times (SSRT) (F(3,35) = 3.41, p > .03) with slower SSRT for the pure AD/HD and oppositional defiant disorder/conduct disorder (ODD/CD) groups compared to controls, but not for the comorbid AD/ HD+ODD/CD which displayed faster SSRT than AD/HD and ODD/CD

Summary

Introduction

Evidence from behavioural studies suggests that impaired motor response inhibition may be common to several externalizing child psychiatric disorders, it has been proposed to be the core-deficit in AD/HD. According to Barkley's theory of AD/HD [2,3], deficient behavioural inhibition is the core deficit of the disorder, and may lead to impairments of executive functions. Impaired behavioural response inhibition is observed in children with other disruptive disorders such as ODD/CD [9], which is the most prevalent comorbidity of AD/HD and poses significant additional clinical and public health problems. Further deficits which are not likely to result from deficient inhibition are present in children with AD/HD, as evident from their poor performance in a variety of executive functions tasks such as the Continuous Performance Test (CPT) [10,11], Wisconsin Card-Sorting-Task [12,13,14], Tower-of-Hanoi [13,14] and Stroop-Test [12,15]; for a review see [16,17]

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