Electrophysiological evidence for abnormal preparatory states and inhibitory processing in adult ADHD

Gráinne Mcloughlin,Aribert Rothenberger,Philip Asherson,Tobias Banaschewski,Jonna Kuntsi,Daniel Brandeis,Bjoern Albrecht

doi:10.1186/1744-9081-6-66

Abstract

BackgroundAttention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder that starts in childhood and frequently persists in adults. Several theories postulate deficits in ADHD that have effects across many executive functions or in more narrowly defined aspects, such as response inhibition. Electrophysiological studies on children, however, indicate that ADHD is not associated with a core deficit of response inhibition, as abnormal inhibitory processing is typically preceded or accompanied by other processing deficits. It is not yet known if this pattern of abnormal processing is evident in adult ADHD.MethodsThe objective of this paper was to investigate event-related potential indices of preparatory states and subsequent response inhibition processing in adults with ADHD. Two cued continuous performance tasks were presented to 21 adults meeting current criteria for adult ADHD and combined type ADHD in childhood, and 20 controls.ResultsThe ADHD group exhibited significantly weaker orienting attention to cues, cognitive preparation processes and inhibitory processing. In addition, we observed a strong correlation between the resources allocated to orienting to cues and the strength of the subsequent response strength control processes, suggesting that orienting deficits partly predict and determine response control deficits in ADHD.ConclusionsThese findings closely resemble those previously found in children with ADHD, which indicate that there is not a core response inhibition deficit in ADHD. These findings therefore suggest the possibility of developmental stability into adulthood of the underlying abnormal processes in ADHD.

Highlights

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder that starts in childhood and frequently persists in adults
Given the limited existing eventrelated potentials (ERPs) data on Adult ADHD (AD-ADHD), this study aimed to provide a detailed investigation of key ERP indices, previously reported as affected in childhood ADHD, in adults with ADHD, to investigate possible developmental stability in the associated deficits
Performance measures Repeated-measures ANCOVA of the reaction time measures indicated no significant effects of age as a covariate, so it was subsequently dropped from analyses, [MRT: F(1, 37) = 3.20, p = 0.08; SD-reaction times (RTs): F(1, 37) = 1.69, p = 0.20; F(1, 37) = 0.60, p = 0.44] nor were there group-by-task interactions for MRT [F(1,39) = 0.36, p = 0.55], SD-RT [F(1,39) = 0.16, p = 0.70] or CV [F(1,39) = 0.20, p = 0.66]

Summary

Introduction

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder that starts in childhood and frequently persists in adults. Electrophysiological studies on children, indicate that ADHD is not associated with a core deficit of response inhibition, as abnormal inhibitory processing is typically preceded or accompanied by other processing deficits It is not yet known if this pattern of abnormal processing is evident in adult ADHD. In contrast to performance measures such as speed and accuracy, which provide indirect indices of underlying processes, eventrelated potentials (ERPs) provide a direct measure of covert brain activity and its precise timing. This is especially true for neuronal processes occurring in the absence of overt behaviour, such as preparatory and inhibitory processes. ERPs can distinguish between different covert processes and elucidate whether behavioural impairments are preceded or potentially caused by certain neuronal deficits

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