Invited reviewA review of electrophysiology in attention-deficit/hyperactivity disorder: II. Event-related potentials
Introduction
This paper reviews the field of event-related potentials (ERPs) in attention-deficit/hyperactivity disorder (AD/HD). Together with our companion paper reviewing the field of electroencephalography (EEG) in AD/HD (Barry et al., 2003), it aims to provide a wide overview of the electrophysiology of AD/HD.
AD/HD refers to a variable cluster of hyperactivity, impulsivity, and inattention symptoms, which substantially affects the individual's normal cognitive and behavioural functioning. Over the last 30 years, substantial changes have occurred in conceptualizations of AD/HD (see Barry et al., 2003 for a systematic description of the symptomatology associated with each categorization). Early accounts used terms such as ‘minimal brain dysfunction’ (MBD) syndrome (Strauss and Lehtinen, 1947) and ‘hyperkinetic impulse disorder’ (Laufer and Denhoff, 1957). The disorder was first listed in the second edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-II; American Psychiatric Association, 1968) as ‘hyperkinetic reaction of childhood’. DSM-III (American Psychiatric Association, 1980) renamed it ‘attention-deficit disorder’ (ADD), with two types: with hyperactivity (ADDh) and without hyperactivity (ADDwo). In the DSM-III-R (American Psychiatric Association, 1987), it was renamed ‘attention-deficit hyperactivity disorder’ (ADHD), and considered unidimensional; a second category, ‘undifferentiated attention-deficit disorder’ (U-ADD) featured marked inattention. The DSM-IV (American Psychiatric Association, 1994) lists 3 main types: predominantly inattentive (AD/HDin); predominantly hyperactive-impulsive (AD/HDhyp); and combined type (AD/HDcom). Hyperkinetic disorder (HKD) in the tenth revision of the International Classification of Diseases (ICD-10; World Health Organisation, 1993) lists similar criteria.
In this paper we report data using the diagnostic categories of the research under discussion, but attempt to separate out the systematic effects relatable to symptom clusters in the modern diagnostic categories.
Section snippets
ERPs in AD/HD
ERPs allow examination of electrical representations of the underlying sensory and cognitive processes occurring in the brain in response to stimuli. The ERP contains a number of characteristic peaks and troughs which basic research has shown to correspond to certain underlying processes. Determination of the functional significance of a particular ERP component involves simultaneous consideration of its eliciting conditions, polarity (positive or negative), timing (latency) and scalp
Specificity of ERP differences
The extent to which reported ERP differences are specific to AD/HD has been addressed by several studies. The reduced auditory P3 at Pz was specific to AD/HD children when compared to those with autism and dyslexia (Kemner et al., 1998). An auditory SA investigation of ADHD alone and with comorbid conduct and tic disorders reported that while P300 and the negative difference wave (Nd) did not differentiate the groups, MMN was smaller in all ADHD groups, but only the group with comorbid conduct
Problems with past ERP research
Several methodological problems may be identified in past ERP investigations of AD/HD. For example, many suffer from small subject numbers, restricting the generalizability of their results. Some suffer methodological flaws. As an example, the combined-modality oddball task used by Satterfield et al., 1988, Satterfield et al., 1990, Satterfield et al., 1994 included intensity differences to discriminate target from standard stimuli. This may be problematic, as it has been reported previously
Future directions
In the context of the studies reviewed above and in Barry et al. (2003), we briefly sketch future directions for research and development in electrophysiology in the AD/HD field.
Acknowledgements
The authors thank Aneta Dimoska, Carly Pleffer and Janette Smith for their contributions to this paper.
References (121)
- et al.
A review of electrophysiology in attention-deficit/hyperactivity disorder: I. Qualitative and quantitative electroencephalography
Clin Neurophysiol
(2003) - et al.
Neuroelectric mapping reveals precursor of stop failures in children with attention deficits
Behav Brain Res
(1998) - et al.
The effects of age on the N200 component of the auditory event-related potentials
Cog Brain Res
(1993) - et al.
ERP components in go/nogo tasks and their relation to inhibition
Acta Psychol
(1999) - et al.
Endogenous brain potentials associated with selective auditory attention
Electroenceph clin Neurophysiol
(1980) - et al.
Separate brain potential characteristics in children with reading disability and attention deficit disorder: II. Color and letter relevance effects
Brain Cogn
(1988) - et al.
Intensity dependence of auditory evoked potentials as an indicator of central serotonergic neurotransmission: a new hypothesis
Biol Psychiatry
(1993) - et al.
Time-on-task analysis using wavelet networks in an event-related potential study on attention-deficit hyperactivity disorder
Clin Neurophysiol
(2001) - et al.
Auditory event-related potentials in attention and reading disabled boys
Int J Psychophysiol
(1986) - et al.
Auditory event-related potentials to a two-tone discrimination paradigm in attention deficit hyperactivity disorder
Psychiatry Res
(1996)