Rethinking a right hemisphere deficit in ADHD.
BACKGROUND
Early observations from lesion studies suggested right hemisphere (RH) dysfunction in ADHD. However, a strictly right-lateralized deficit has not been well supported. An alternatively view suggests increased R > L asymmetry of brain function and abnormal interhemispheric interaction. If true, RH pathology in ADHD should reflect interhemispherically networked and overactivated functioning. The authors evaluated these assertions.


METHODS
Four elements of lateralized brain function were measured: LH specialized, RH specialized, LH with interhemispheric processing (LH/IH), and RH with interhemispheric processing (RH/IH). Next, the authors tested their association with cognitive ability, psychiatric comorbidity, and sibling correlations in 79 children with ADHD.


RESULTS
RH/IH processing was uniquely associated with other outcome measures. There were no associations for independent RH or LH function alone.


CONCLUSIONS
Interhemispherically networked RH processing is critical in ADHD. In addition, lack of association between LH specialized processing and cognitive ability (especially for verbal cognitive tasks) supports increased RH mediation of task processing.
Hale
T Sigi
TS
UCLA Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA 90024, USA. sig@ucla.edu
Loo
Sandra K
SK
Zaidel
Eran
E
Hanada
Grant
G
Macion
James
J
Smalley
Susan L
SL