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RESPONSE CHOICE AND INHIBITION IN ADULTS, CONTROL AND ADHD CHILDREN
 

COMMUNICATION
TOPIC: NEUROPEDIATRICS

Authors:
Michelle Bourassa, Philippe Robaey, Frini Karayanidis, Gilles Pelletier & Guy Goeffroy

Cognitive Psychophysiology and Neuropsychiatry Laboratory,
Department of Psychiatry, Sainte-Justine Hospital, University of Montréal
3100 Ellendale, Montréal, Québec, Canada  H3S 1W3
e-mail: bourassa@vif.com

Introduction: Attention Deficit Hyperactivity Disorder (ADHD) is one of the most prevalent childhood psychiatric disorders. Although the name of the disorder suggests a deficit in the input stages of information processing, recent studies locate the deficit in response choice and inhibition of motor processes.

Methods: A very carefully selected group of 21 6 to 9 year-old right-handed ADHD subjects was compared to 21 control children and 17 control adults on two tasks requiring response inhibition in different contexts. In the stimulus-response compatibility (SRC) task, subjects responded to arrows with the compatible (same direction as arrow, 66% of trials) or the incompatible hand (opposite to arrow, 33%). Stimulus/hand compatibility was determined by stimulus color. The same stimuli were presented in the go-nogo task with different instructions. Subjects were asked to respond in a compatible way in 66% of trials or to withhold response, again depending on stimulus color.

Results: In the SRC task, all children showed more correct responses with the right hand in both conditions. Reaction times to incompatible trials were longer for the right hand, suggesting that more control was needed to maintain the level of performance.

ADHD children showed more false alarms in the nogo condition of the GNG task, associated with a lower control of the right hand. In the SRC task, the response choice deficit hypothesis in ADHD was not verified. However, ADHD children showed difficulties in shifting to new SRC instructions  after a GNG task, when a right hand incompatible response was expected.

Conclusion:  These results underline the importance of  hand dominance in motor development. ADHD childrenís difficulties in shifting to new instructions for right hand responses are interpreted in terms of a more encompassing regulation deficit.