Response inhibition in Huntington's disease-a study using ERPs and sLORETA

Huntington's disease (HD) is an autosomal dominant inherited neurodegenerative disorder, with neurodegeneration mainly affecting the striatum. We investigated executive functions related to response inhibition in (HD) and healthy controls by means of event-related potentials (ERP) in a simple Go/Nogo-task. In Nogo as opposed to Go trials two fronto-central ERP components are elicited: the Nogo-N2 and Nogo-P3. These components are supposed to depend on (medial) prefrontal regions, especially the anterior cingulate cortex (ACC). The results show that the Nogo-N2 did not differ between the groups, while the Nogo-P3 demonstrated a strong attenuation in the HD-group, which also showed more false alarms in the Nogo-condition. Using sLORETA it is shown that this attenuation was related to the medial frontal cortex, especially the ACC, and superior frontal cortex areas. Moreover, the attenuation was related to the underlying genetic disease load (CAG-index). The decline in inhibition is likely mediated via a dysfunction in the ACC, which is known to be dysfunctional in HD. Moreover, the results may be interpreted that the decline in response inhibition in HD is gene-associated. The differentially affected Nogo-components suggest that they rely on different neuronal circuits, even within the ACC. For HD this suggests that this structure is not entirely dysfunctional.