Invited Symposium: What Can Genetic Models Tell Us About Attention-Deficit Hyperactivity Disorder (ADHD)?
Attention Deficit Hyperactivity Disorder (ADHD) is characterized by inattention, hyperactivity and impulsivity. The neuropsychological deficits involve higher order executive functions. Two important functions necessary to control the motor output and which have shown to be deficient in children with ADHD are the abilities to inhibit and time a motor response (Rubia et al., 1998, Rubia et al., in submission). Inappropriate temporal and inhibitory control of the motor output may account for a wide range of symptoms, including motor clumsiness, inability to delay responses, poor protection of interference, disruptive social behaviour and emotional dyscontrol. Not much is known about the brain basis of hyperactivity. Structural neuroimaging studies have described volumetric abnormalities of frontal lobes, basal ganglia, corpus callosum and parietal lobes. Functional imaging studies have not been entirely consistent but have shown reduced brain activiy using Positron Emission Tomography (PET), Single Photon Emission Tomography (SPET) and electroencephalography (EEG) in superior and inferior prefrontal brain areas, caudate nucleus and parietal brain regions (Swanson et al., 1998).
Here we apply a stop task and a motor timing task in functional magnetic resonance imaging (fMRI) to compare blood flow dynamics during performance of healthy adults, healthy adolescents and adolescents with ADHD. The comparison of the two adolescent groups should reveal differences in blood flow dynamics in ADHD pathology compared to health. The comparison between adults and adolescents should reveal the development of blood flow dynamics with age in order to illuminate the hypothesis of a maturational lag in ADHD.
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|Rubia, K; Overmeyer, S; Taylor, E; Brammer, M; Williams, S; Simmons, A; Bullmore, E; (1998). Hypofrontality in Attention Deficit Hyperactivity Disorder (ADHD) During Higher Order Motor Control: a Study with fMRI. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Invited Symposium. Available at URL http://www.mcmaster.ca/inabis98/sadile/rubia0583/index.html|
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