Inhibitory deficits in ocular motor behavior in adults with attention-deficit/hyperactivity disorder.
BACKGROUND
Many of the symptoms of attention-deficit/hyperactivity disorder (ADHD) have been attributed to deficits in behavioral inhibition mediated by the frontostriatal system. The ability to suppress unwanted saccadic eye movements is mediated by prefrontal cortex-basal ganglia circuitry and thus constitutes a useful measure of inhibitory ability.


METHODS
To evaluate the functional integrity of this circuitry in ADHD, adult ADHD subjects unmedicated for at least 48 hours and normal comparison adults were studied by means of a comprehensive battery of ocular motor paradigms.


RESULTS
On a prosaccade task, in which subjects were required to generate saccades toward a peripheral visual target after a short stimulus-free interval, ADHD subjects generated significantly more of anticipatory (premature) saccades (reaction time <90 msec) and of saccades toward the target on catch trials, in which they were supposed to inhibit eye movements. On the antisaccade task, in which they were required to inhibit gazing toward the target while moving their eyes in the opposite direction, ADHD subjects made significantly more directional errors than normal adults. The performance of ADHD adults was consistent with deficits in saccadic inhibition.


CONCLUSIONS
Given the recent evidence for the interdependence between the brain systems mediating visual attention and ocular motor behavior, these findings support the notion that deficits in inhibitory mechanisms might underlie the inattention characteristic of ADHD. These results also implicate abnormalities in prefrontal cortex-basal ganglia circuitry in ADHD.
Feifel
David
D
Adult ADHD Program, Department of Psychiatry, University of California, San Diego, La Jolla, California, USA. dfeifel@ucsd.edu
Farber
Robert H
RH
Clementz
Brett A
BA
Perry
William
W
Anllo-Vento
Lourdes
L
D000328:Adult; D000704:Analysis of Variance; D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology*; D004585:Electrooculography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009433:Neural Inhibition / Q000502:physiology*; D009483:Neuropsychological Tests; D010775:Photic Stimulation / Q000379:methods; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012438:Saccades / Q000502:physiology*; D013647:Task Performance and Analysis