Do Quantitative EEG Measures Differentiate Hyperactivity in Attention Deficit/Hyperactivity Disorder?

Article excerpt

Attention Deficit/Hyperactivity Disorder (AD/HD) can occur with or without hyperactivity. However, much of the existing research collapses both AD/HD and AD/HD without hyperactivity participants into the AD/HD category, possibly confounding the samples with a heterogeneous population comprised of people with different disorders. The purpose of the present study was to examine the external validity of AD/HD without hyperactivity as a diagnostic category. Quantitative electroencephalogram (EEG) analysis was used to examine possible differences in brain wave activity of the two subtypes of AD/HD while completing the Test of Variables of Attention (TOVA), a computerized task that measures a variety of constructs associated with attention and impulsivity. Although behavioral ratings confirmed differential characteristics of both subtypes of AD/HD, EEG findings did not differentiate between AD/HD with and without hyperactivity. Implications to cognitive models of AD/HD are discussed.

Attention Deficit/Hyperactivity Disorder (AD/HD) is one of the most common childhood behavior disorders and is estimated to affect 3 to 5% of school-age children (DSM-IV; American Psychiatric Association, 1994). However, the disorder has a long and confusing history, having been referred to as the Hyperkinetic Reaction of Childhood Disorder (American Psychiatric Association, 1968), Hyperactivity (Zentall, 1975), Minimal Brain Dysfunction (Bloomingdale & Bloomingdale, 1980), and Childhood Hyperkinesis (Mattes, 1980).

The predominant symptoms of AD/HD are inattention, excessive impulsivity, and/or hyperactivity. Two subtypes of the disorder were included in the Diagnostic and Statistical Manual of Mental Disorders (DSM-III; American Psychiatric Association, 1980): Attention Deficit Disorder with Hyperactivity (ADD/H) and Attention Deficit Disorder without Hyperactivity (ADD/WO). With the publication of the DSM-III-R (American Psychiatric Association, 1987), the distinction between these two subtypes was effectively removed by adopting a unidimensional category referred to as ADHD. Instead, a new diagnosis called Undifferentiated Attention Deficit Disorder (UADD) was created that included some of the disturbances that were previously classified as ADD/WO.

After considerable debate, the publication of the DSM-IV (American Psychiatric Association, 1994) reinstated the diagnosis by establishing three subtypes of AD/HD: the Predominately Inattentive Type, the Combined Type, and the Predominately Hyperactive-Impulsive Type. Most of the evidence supporting the validity of attention deficit without hyperactivity as a subtype of AD/HD comes from observations of overt behavior, comorbid diagnoses, and familial patterns of psychiatric disturbances (see Stewart, 1994). In spite of the specificity in diagnostic criteria the DSM-IV provides, it is still unclear whether attention deficit without hyperactivity warrants recognition as a separate disorder.

From a theoretical and clinical standpoint it is important to establish the external validity of AD/HD without hyperactivity as a disorder that can be clinically differentiated from AD/HD. Presently, most research collapses both subtypes of AD/HD, possibly confounding the samples with a heterogeneous population comprised of people with different disorders (Castellanos, 1999; Hynd et al., 1991).

In recent years, electroencephalogram (EEG) analysis has been used in the diagnosis of AD/HD. Compared to normal controls, children who are described as hyperactive typically exhibit excessive slow wave activity (typically in the theta band) and/or concomitant decrease in fast wave (primarily alpha and beta) activity (Callaway, Halliday, & Naylor, 1983; Dykman, Holcomb, Oglesby, & Ackerman, 1982; Harper, Deering, Cavernos-Gonzales, McNeil, & Ulam, 1996; Mann, Lubar, Zimmerman, Miller, & Muenchen, 1992; Matsuura et al., 1993). Excessive slow wave activity in AD/HD is a neurophysiological response consistent with a hypoarousal hypothesis of hyperactivity (Klove, 1989; Zentall, 1975; Zentall & Zentall, 1983) and provides evidence that AD/HD is a neurophysiological disorder. …