Egocentric and allocentric visuospatial working memory in premotor Huntington's disease: A double dissociation with caudate and hippocampal volumes

Abstract Our brains represent spatial information in egocentric(self-based) or allocentric(landmark-based) coordinates. Rodent studies have demonstrated a critical role for the caudate in egocentricnavigation and the hippocampus in allocentricnavigation. We administered tests of egocentricand allocentric working memoryto individuals with premotor Huntington's disease(pmHD), which is associated with early caudate nucleusatrophy, and controls. Each test had 80 trials during which subjects were asked to remember 2 locations over 1-sec delays. The only difference between these otherwise identical tests was that locations could only be coded in self-based or landmark-based coordinates. We applied a multiatlas-based segmentation algorithm and computed point-wise Jacobian determinants to measure regional variationsin caudate and hippocampal volumes from 3 T MRI. As predicted, the pmHD patients were significantly more impaired on egocentric working memory. Only egocentricaccuracy correlated with caudate volumes, specifically the dorsolateralcaudate head, right more than left, a region that receives dense efferents from dorsolateral prefrontal cortex. In contrast, only allocentricaccuracy correlated with hippocampal volumes, specifically intermediate and posterior regions that connect strongly with parahippocampal and posterior parietal cortices. These results indicate that the distinction between egocentricand allocentricnavigation applies to working memory. The dorsolateralcaudate is important for egocentric working memory, which can explain the disproportionate impairment in pmHD. Allocentric working memory, in contrast, relies on the hippocampus and is relatively spared in pmHD.