Working memory in ADHD: prefrontal/parietal connections.
Current theories of dopaminergic and noradrenergic mechanisms, which are thought to be of importance in the regulation of attention are reviewed. A biphasic model of dopaminergic function is described, in which tonic dopamine exerts a suppressive influence on subcortical dopamine systems by altering tonic/phasic dopaminergic relationships. Noradrenergic mechanisms are of importance in modulating sensory processing at the prefrontal cortical level. The work of Silberstein and colleagues utilizing Steady-State Visually Evoked Potential, during the course of an A-X Continuous Performance Task enables examination of the spatial distribution and dynamics of electrical brain activity during the task. The maintenance of activation in the interval between A and X provides a measure of working memory, thought to be related to prefrontal-parietal activation, which is facilitated by administration of methylphenidate to children with ADHD, suggesting that working memory may be a core deficiency in children with ADHD. While tonic dopamine activity in ventral striatum/accumbens gates inhibitory activity, dorsolateral prefrontal-parietal connections allow maintenance of working memory required for goal completion.
Levy
F
F
School of Psychiatry, University of New South Wales, Sydney, Australia.
Farrow
M
M
D000818:Animals; D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology*; D002648:Child; D004298:Dopamine / Q000502:physiology; D005074:Evoked Potentials, Visual; D006801:Humans; D008568:Memory / Q000502:physiology*; D009483:Neuropsychological Tests; D018377:Neurotransmitter Agents / Q000502:physiology; D009638:Norepinephrine / Q000502:physiology; D010296:Parietal Lobe / Q000502:physiology* / Q000503:physiopathology; D017397:Prefrontal Cortex / Q000502:physiology* / Q000503:physiopathology; D011597:Psychomotor Performance; D009435:Synaptic Transmission / Q000502:physiology*
D018377:Neurotransmitter Agents; D004298:Dopamine; D009638:Norepinephrine