Perception, attention, and working memory are disproportionately impaired in dementia with Lewy bodies compared with Alzheimer's disease

Objective-To test the hypotheses that visuoperceptual and attentional abili ty are disproportionately impaired in patients having dementia with Lewy Bo dies (DLB) compared with Alzheimer's disease (AD). Methods-A comprehensive battery of neuropsychological tasks designed to ass ess working, episodic, and semantic memory, and visuoperceptual and attenti onal functions was given to groups of patients with DLB (n=10) and AD (n=9) , matched for age, education, and mini mental state examination (MMSE), and to normal controls (n=17). Results-Both patient groups performed equally poorly on tests of episodic a nd semantic memory with the exception of immediate and delayed story recall , which was worse in the AD group. Digit span was by contrast spared in AD. The most striking differences were on tests of visuoperceptual/spatial abi lity and attention. Whereas patients with AD performed normally on several subtests of the visual object and space perception battery, the DLB group s howed substantial impairments. In keeping with previous studies, the AD gro up showed deficits in selective attention and set shifting, but patients wi th DLB were more impaired on virtually every test of attention with deficit s in sustained, selective, and divided attention. Conclusions-Patients with DLB have substantially greater impairment of atte ntion, working memory, and visuoperceptual ability than patients with AD ma tched for overall dementia severity. Semantic memory seems to be equally af fected in DLB and AD, unlike episodic memory, which is worse in AD. These f indings may have relevance for our understanding of the genesis of visual h allucinations, and the differential diagnosis of AD and DLB.