Dementia in Huntington's disease is associated with neurochemical deficits in the caudate nucleus, not the cerebral cortex.

Choline acetyltransferase (ChAT) and the neurotransmitter amino acids gamma-aminobutyric acid (GABA) and glutamic acid were measured in brain tissue taken post-mortem from control subjects and from patients with Huntington's disease (HD). Two subgroups of HD patients were defined with either severe dementia or no dementia. It was found that ChAT exhibited no greater decrease in cortical tissue from severely demented patients. While there were also no significant deficits associated with dementia in cortical concentrations of the amino acids, a substantial and regionally-specific decrease in both GABA and glutamate was observed in the caudate nucleus of severely demented HD patients.