In patients with atypical dementia, cognitive dysfunctions other than amnesia predominate. It remains to be established how to examine these cognitive dysfunctions in the systematic way. "Action" deficit in dementia can occur at any stage from perception of objects to motor control. We examined the mechanism of "action" deficit in a patient with posterior cortical atrophy and that with progressive supranuclear palsy. The former demonstrated impaired control of visual attention, which seems to be related to dysfunction of the dorsal visual pathway. The latter showed poor control of ballistic action with a tool. Dysfunction of the supplementary motor area might be related to poor control of context-dependent ballistic action in this patient. Combined use of neuropsychological and neuroradiological data could clarify the underlying functional impairment and their neuronal bases, which will help understand pathological progression of atypical dementia.
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