Visual object and visuospatial cognition in Huntington's disease: implications for information processing in corticostriatal circuits

The primate visual system contains two major streams of visual information processing, The ventral stream is directed into the inferior temporal corte x and is concerned with visual object cognition, whereas the dorsal stream is directed into the posterior parietal cortex and is concerned with visuos patial cognition, Both of these processing streams send projections to the basal ganglia, and the ventral stream may also receive reciprocal connectio ns from the basal ganglia, Although a role for the basal ganglia in visual object and visuospatial cognition has been suggested, little work has been carried out in this area in humans, The primary site of neuropathology in H untington's disease is the basal ganglia, and hence Huntington's disease pr ovides an important model for the role of the human basal ganglia in visual object and visuospatial cognition, and its breakdown in disease, We examin ed performance on a wide battery of tests of both visual object and visuosp atial recognition memory, working memory, attention, associative learning a nd perception, enabling us to specify more fully the role of the basal gang lia in visual object and visuospatial cognition, and the disruption of thes e processes in Huntington's disease, Huntington's disease patients exhibite d deficits on tests of pattern and spatial recognition memory; showed impai red simultaneous matching and delay-independent delayed matching-to-sample deficits; showed spared accuracy but impaired reaction times in visual sear ch; were impaired in spatial but not visual object working memory; and show ed impaired pattern-location associative learning, The results of our inves tigations suggest a particular role for the striatum in context-dependent a ction selection, in line with current computational theories of basal gangl ia function.