Verbal Fluency in Children: Developmental Issues and Differential Validity in Distinguishing Children with Attention-Deficit Hyperactivity Disorder and Two Subtypes of Dyslexia

Archives of Clinical Neuropsychology, Vol. 14, No. 5, pp. 433–443, 1999 Copyright © 1999 National Academy of Neuropsychology Printed in the USA. All rights reserved 0887-6177/99 $–see front matter PII S0887-6177(98)00038-9 Verbal Fluency in Children: Developmental Issues and Differential Validity in Distinguishing Children with Attention-Deficit Hyperactivity Disorder and Two Subtypes of Dyslexia Morris J. Cohen Medical College of Georgia Allison M. Morgan and Melanie Vaughn University of Georgia Cynthia A. Riccio Texas A&M University Josh Hall Ball State University Previous research studies have shown that in adults, verbal fluency is impaired after lesion to the frontal lobes and left temporal lobe. More recently, there have been a few studies reported which indicated that in children, like adults, left hemisphere and frontal lesions result in pronounced effects on verbal fluency. The present study examined developmental differences in verbal fluency within a sample of 130 normal children, aged 6 to 12 years. Additionally, the same verbal fluency test was administered to two subgroups of children with developmental dyslexia and a group of children with attention-deficit/hyperactivity disorder (ADHD). Analysis of variance (ANOVA) revealed significant between-group differences by age in the normal children. Further, ANOVA demonstrated that the verbal fluency measure was clinically useful in differentiating the Language Disorder/Dysphonetic Dyslexic subgroup from the Visual-Spatial/Dyseidetic Dyslexic subgroup and the ADHD group, with the latter two groups performing within the average range © 1999 National Academy of Neuropsychology. Published by Elsevier Science Ltd Acknowledgment is given to Harry Davis, Office of Research and Computing, The Medical College of Georgia, for his valuable assistance in data analysis. Address correspondence to Morris J. Cohen, EdD, Department of Neurology, Section of Child Neurology, The Medical College of Georgia, Augusta, GA 30912-3255. 433 434 M. J. Cohen et al. INTRODUCTION Previous research with adult populations has shown measures of verbal fluency (rapid verbal naming) to be sensitive to brain integrity, particularly in the left frontal lobe. For example, several studies have reported differential effects on verbal fluency depending on the laterality of the lesion. Research has indicated that subjects with left hemisphere lesions, primarily frontal, have significantly lower verbal fluency scores than those with right hemisphere lesions (Benton, 1968; Borkowski, Benton, & Spreen, 1967; Miller, 1984; Milner, 1964; Newcombe, 1969; Pendleton, Heaton, Lehman, & Hulihan, 1982; Perret, 1974). Other studies have found lateralization effects after temporal lobectomies, with left temporal patients having significantly lower verbal fluency scores both preoperatively as well as 1 week postoperatively (Martin, Loring, Meador, & Lee, 1990), with greater improvement in verbal fluency found at 6 months (Hermann & Wyler, 1988) and 1 year (Loring, Meador, & Lee, 1994) following surgery. However, Loring et al. (1994) reported that both right and left temporal lobectomy patients had decreases in verbal fluency immediately after surgery and that the patterns in performance were similar for patients regardless of which temporal lobe had been resectioned. Studies have also examined the differential effects of anterior and posterior lesions on verbal fluency. Within the left hemisphere, subjects with prefrontal lesions have been found to have greater impairments in verbal fluency than subjects with temporal lesions (Crowe, 1992; Milner, 1964). Similarly, results in a study by Ramier and Hécaen (1970) indicated that while subjects with left frontal impairments had the greatest deficits in verbal fluency, individuals with right frontal lesions had significantly lower verbal fluency than those with other right-sided lesions. Further, research suggests that individuals with frontal lesions are more impaired in verbal fluency, as compared with controls with extracranial nervous system pathology or no neurological impairment (Miller, 1984), and controls with psychiatric disorders even when covarying for intelligence quotient (IQ), age, and education (Crockett, Bilsker, Hurwitz, & Kozak, 1986). Thus, while there appears to be strong evidence in adults that left hemisphere lesions impair verbal fluency performance to a greater degree than right hemisphere lesions, and that anterior lesions are more damaging than posterior lesions, measures of verbal fluency cannot be used in isolation to localize brain lesions. VERBAL FLUENCY IN CHILDREN Similar to the adult literature, brain lesions appear to negatively impact verbal fluency in children/adolescents; however, a direct relationship between lesion site and verbal fluency has not been established. For example, Levin et al. (1993), investigated various cognitive impairments in head-injured children and adolescents and found that severely head-injured subjects (Glasgow Coma Scale #8) (GCS; Teasdale & Jennett, 1974), but not those with less severe injuries (GCS .8), produced fewer correct words than normals on a verbal fluency measure. Frontal, but not extrafrontal, lesion size was found to significantly increase the GCS scores’ accuracy at predicting verbal fluency. In addition, the prediction accuracy of verbal fluency performance was significantly improved based on the size of orbital-frontal lesions. Using the Rapid Automatized Naming Test (RAN; Denckla & Rudel, 1976), a related fluency measure requiring the rapid naming of digits, colors, letters, and objects, children with left hemisphere lesions have been found to respond at a significantly slower rate than matched normal controls Verbal Fluency 435 (Aram, Ekelman, & Whitaker, 1987) and children with unilateral right hemisphere lesions, perhaps reflecting slower lexical retrieval (Aram, Meyers, & Ekelman, 1990). Given that the vast majority (approximately 90%) of children with developmental dyslexia exhibit deficits in phonological processing and language development (see Hynd & Cohen, 1983; Lombardino, Riccio, Hynd, & Pinheiro, 1997 for review), research studies have investigated the rapid verbal naming performance of children with neurodevelopmental disabilities on measures of verbal fluency. For example, studies have shown that children with developmental dyslexia are characterized by deficits in verbal fluency and rapid automatized naming (Denckla & Rudel, 1976; Felton & Wood, 1989; Felton, Wood, Brown, Campbell, & Harter, 1987; Korhonen, 1991, 1995; Levin, 1990; Rudel, 1985; Wolf, 1986; Wolf & Obregon, 1992). Korhonen (1995) also reported that although initially, 9-year-old children with dyslexia and deficits in rapid naming did not differ significantly from controls on a verbal fluency measure (Korhonen, 1991), they did differ significantly at age 18, with the dyslexic children being less productive. In addition, there is now a growin (...truncated)