Decreased callosal thickness in attention-deficit/hyperactivity disorder.
BACKGROUND
Neuroimaging studies of attention-deficit/hyperactivity disorder (ADHD) have revealed structural abnormalities in the brains of affected individuals. One of the most replicated alterations is a significantly smaller corpus callosum (CC), for which conflicting reports exist with respect to the affected callosal segments.


METHODS
We applied novel surface-based geometrical modeling methods to establish the presence, direction, and exact location of callosal alterations in ADHD at high spatial resolution. For this purpose, we calculated the thickness of the CC at 100 equidistant midsagittal points in an age-matched male sample of 19 individuals with ADHD and 19 typically developing control subjects.


RESULTS
In close agreement with many prior observations, the CC was shown to be significantly thinner in ADHD subjects in anterior and, particularly, posterior callosal sections. Covarying for intelligence did not significantly alter the observed ADHD effects. However, group differences were no longer present in anterior sections when covarying for brain volume and after excluding ADHD subjects comorbid for oppositional defiant disorder.


CONCLUSIONS
Decreased callosal thickness may be associated with fewer fibers or a decrease in the myelination of fibers connecting the parietal and prefrontal cortices. This might affect interhemispheric communication channels that are necessary to sustain attention or motor control, thus contributing to symptoms of hyperactivity and impulsivity, or inattention, observed in ADHD. Future studies are necessary to determine whether callosal abnormalities reflect maturational delays or persist into adulthood.
Luders
Eileen
E
Laboratory of Neuro Imaging, Department of Neurology, University of California--at Los Angeles School of Medicine, Los Angeles, California 90095-7334, USA.
Narr
Katherine L
KL
Hamilton
Liberty S
LS
Phillips
Owen R
OR
Thompson
Paul M
PM
Valle
Jessica S
JS
Del'Homme
Melissa
M
Strickland
Tony
T
McCracken
James T
JT
Toga
Arthur W
AW
Levitt
Jennifer G
JG
D000293:Adolescent; D000367:Age Factors; D001288:Attention; D001289:Attention Deficit Disorder with Hyperactivity / Q000473:pathology*; D019958:Attention Deficit and Disruptive Behavior Disorders / Q000150:complications; D001931:Brain Mapping; D002648:Child; D003337:Corpus Callosum / Q000473:pathology*; D006801:Humans; D006948:Hyperkinesis; D007175:Impulsive Behavior; D008279:Magnetic Resonance Imaging; D008297:Male; D008953:Models, Anatomic