Attention Deficit Hyperactivity Disorder (ADHD) – further advances in uncovering the neural dysfunction underlying the disorder

Orateur : Paul OVERTON (University of Sheffield, GB)

Attention Deficit Hyperactivity Disorder (ADHD) is a prevalent neurodevelopmental disorder characterised by (inter alia) an increase in distractibility. The current front-line pharmacotherapies for the treatment of ADHD, namely the psychostimulants methylphenidate and amphetamines, have clear abuse potential, hence there is a strong need to develop new drug treatments for this disorder. However, the therapeutic mechanism of action of current psychostimulant medications in ADHD is far from clear, in large part because the pathophysiological changes underlying ADHD are uncertain. A few years ago I gave a talk at GIN where I outlined my idea about the possible role of the superior colliculus, a sensory structure intimately linked with distractibility, in ADHD. I presented evidence for collicular sensory hyper-responsiveness in an animal model of ADHD, and evidence that amphetamine depresses sensory responsiveness in normal rats. Here, I will develop the story further, presenting additional evidence from animal models, and more recent work in humans showing that subjects with high levels of ADHD-like traits show evidence of abnormal collicular function, demonstrated via multisensory integration, microsaccade and fMRI data. Finally, the functional implications of collicular hyper responsiveness will be explored. If correct, sensory hyper-responsiveness in the SC may represent a new model system for use in the development of non-addictive pharmacotherapies for ADHD, as well as representing a potential biomarker for the disorder.

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