Russell J. Schachar

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The stop-signal procedure was used to examine the development of inhibitory control. A group of 275 participants, 6 to 81 years of age, performed a visual choice reaction time (go) task and attempted to inhibit their responses to the go task when they heard a stop signal. Reaction times to the stop and go signals were used to assess performance in(More)
Impulsivity is a primary symptom of the combined type of Attention Deficit/Hyperactivity Disorder (AD/HD). The Stop Signal Paradigm is premised upon a primary deficit in inhibitory control in AD/HD, whereas the Delay Aversion Hypothesis, by contrast, conceptualizes impulsivity in AD/HD, not as an inability to inhibit a response, but rather as a choice to(More)
BACKGROUND Findings from family and twin studies suggest that genetic contributions to psychiatric disorders do not in all cases map to present diagnostic categories. We aimed to identify specific variants underlying genetic effects shared between the five disorders in the Psychiatric Genomics Consortium: autism spectrum disorder, attention(More)
Two experiments investigated the development and pathology of inhibitory control in children. Inhibitory control was investigated with the stop-signal paradigm, which is based on a formal theory of inhibition and directly measures the mechanism of inhibition. The ability to inhibit developed little after Grade 2, but subjects with attention deficit disorder(More)
This study investigated the effects of methylphenidate (MPH) on inhibitory control in hyperactive children. A double-blind, placebo-control, within-subject (crossover) design was used in which 12 children, between 6 and 11 years of age, were each tested four times in each drug condition: 0.3 mg/kg and 1.0 mg/kg of methylphenidate, and placebo. Dependent(More)
The gene for the synaptic vesicle docking fusion protein, synaptosomal-associated protein of 25 kDa (SNAP-25), has been implicated in the etiology of attention-deficit hyperactivity disorder (ADHD) based on the mouse mutant strain coloboma. This neutron-irradiation induced mouse strain is hemizygous for the deletion of the SNAP-25 gene and displays(More)
A modification of the stop-signal task was used to investigate the development of selective inhibitory control. A group of 317 participants, age 6 to 82 years, performed a visual choice reaction time (go) task and attempted to selectively inhibit their response to the go task when hearing one of two randomly presented tones (1000 Hz, 250 Hz), each presented(More)
OBJECTIVE Long-term effects of psychostimulants on growth in height and in weight are investigated in children with attention-deficit/hyperactivity disorder. METHOD Participants were 79 children, 6 to 12 years of age, with attention-deficit/hyperactivity disorder, who were followed annually for up to 5 years, between the years 1993 and 1994 and 1998 and(More)
The objective of this study was to determine whether deficient inhibitory control distinguishes children with a diagnosis of attention-deficit/hyperactivity (ADHD) disorder, conduct disorder (CD), and comorbid ADHD + CD from normally developing children. Participants were rigorously diagnosed children (age 7 to 12 years) with ADHD (N = 72), CD (N = 13) or(More)