Executive functions and methylphenidate response in subtypes of attention-deficit/hyperactivity disorder.
BACKGROUND
Oculomotor tasks are a well-established means of studying executive functions and frontal-striatal functioning in both nonhuman primates and humans. Attention-deficit/hyperactivity disorder (ADHD) is thought to implicate frontal-striatal circuitry. We used oculomotor tests to investigate executive functions and methylphenidate response in two subtypes of ADHD.


METHODS
Subjects were boys, aged 11.5-14 years, with ADHD-combined (n = 10), ADHD-inattentive (n = 12), and control subjects (n = 10). Executive functions assessed were motor planning (tapped with predictive saccades), response inhibition (antisaccades), and task switching (saccades-antisaccades mixed).


RESULTS
The ADHD-combined boys were impaired relative to control subjects in motor planning (p < .003) and response inhibition (p < .007) but not in task switching (p > .92). They were also significantly impaired relative to ADHD-inattentive boys, making fewer predictive saccades (p < .03) and having more subjects with antisaccade performance in the impaired range (p < .04). Methylphenidate significantly improved motor planning and response inhibition in both subtypes.


CONCLUSIONS
ADHD-combined but not ADHD-inattentive boys showed impairments on motor planning and response inhibition. These deficits might be mediated by brain structures implicated specifically in the hyperactive/impulsive symptoms. Methylphenidate improved oculomotor performance in both subtypes; thus, it was effective even when initial performance was not impaired.
O'Driscoll
Gillian A
GA
Department of Psychology, McGill University, Montreal, Quebec, Canada. Gillian@hebb.psych.mcgill.ca
Dépatie
Lana
L
Holahan
Anne-Lise V
AL
Savion-Lemieux
Tal
T
Barr
Ronald G
RG
Jolicoeur
Claude
C
Douglas
Virginia I
VI
D000293:Adolescent; D000704:Analysis of Variance; D001289:Attention Deficit Disorder with Hyperactivity / Q000145:classification / Q000188:drug therapy* / Q000503:physiopathology*; D000697:Central Nervous System Stimulants / Q000627:therapeutic use*; D002648:Child; D003710:Demography; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D008774:Methylphenidate / Q000627:therapeutic use*; D009043:Motor Activity / Q000187:drug effects; D009483:Neuropsychological Tests; D011237:Predictive Value of Tests; D011340:Problem Solving / Q000187:drug effects*; D011569:Psychiatric Status Rating Scales; D011597:Psychomotor Performance / Q000187:drug effects; D011930:Reaction Time / Q000187:drug effects; D015203:Reproducibility of Results; D012438:Saccades / Q000187:drug effects; D014145:Trail Making Test; D014792:Visual Acuity / Q000187:drug effects
D000697:Central Nervous System Stimulants; D008774:Methylphenidate