ADHD with or w/o OCD - response inhibition

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Response inhibition deficits in externalizing child psychiatric disorders:

An ERP-study with the Stop-task

http://www.behavioralandbrainfunctions.com/content/1/1/22/abstract

Bjorn Albrecht , Tobias Banaschewski , Brandeis , Hartmut Heinrich

and Aribert Rothenberger

Behavioral and Brain Functions 2005, 1:22 doi:10.1186/1744-9081-1-22

Published 9 December 2005

Abstract (provisional)

Background

Evidence from behavioural studies suggests that impaired motor response

inhibition may be a common deficit in 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

brain-electric-activity in combination with performance measures in three

groups of children with externalizing child psychiatric disorders and a

group of normal controls.

Methods

A Stop-task was conducted 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.

Results

Groups 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.

Conclusions

Following similar attenuations in initial processing of the Go-signal in

all clinical groups compared to controls, distinct inhibitory control

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 inhibition processes. These behavioural and neural

signs of inhibitory deficits found in AD/HD-only and ODD/CD-only were not

additive, and children with comorbid AD/HD+ODD/CD showed similar or even

fewer signs of inhibition deficits than the other clinical groups. Hence,

the AD/HD+ODD/CD-group may represent a separate clinical entity.