Background Impulsive and irritable behaviour have been reported in HD from the earliest clinical descriptions of the condition, and abnormalities on various measures of impulsive behaviour have been demonstrated. However these studies had small sample sizes, and did not account for potential confounding effects in the HD population such as IQ and medication. Furthermore, the links between impulsive and irritable behaviour in HD remain unclear.
Determine which cognitive mechanisms contribute to irritable behaviour in HD
Determine which aspects of impulsive behaviour are seen in HD
Methods/Techniques We recruited HD patients and familial controls from the South Wales HD Service and performed a battery of established and novel cognitive tasks, including questionnaire measures of impulsive behavour and irritability (UPPSP, Barrett Impulsivity Scale, PBAs and Snaith), motor inhibition (stop signal task), delay discounting (Kirby instrument) and cognitive impulsivity (Iowa Gambling task). We also performed tasks of provocation (a previously reported task, and a novel task) to determine the relative contributions of impaired inhibition and excessive response to provocation in mediating irritability in HD.
Results We recruited 51 HD patients and 26 controls. We found differences in response to provocation and also impaired motor inhibition on the stop signal task in the HD population, even after correcting for relevant confounders such as IQ, medication, motor impairment and psychiatric comorbidity. However, only the response to provocation was associated with irritability in HD. The tasks of delay discounting, and cognitive impulsivity did not demonstrate any differences between HD patients and controls after controlling for relevant confounders.
Conclusions Irritability in HD is mediated by excessive response to provocation rather than the known impairments in motor inhibition. Other aspects of impulsivity to contribute to impulsive behaviour in HD.
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