A review of the perceptual and attentional-executive characteristics of dementia with Lewy bodies relative to Alzheimer’s and Parkinson’s disease

Dementia with Lewy bodies (DLB) is the second most prevalent neurodegenerative dementia disorder, after Alzheimer’s disease (AD). DLB is characterised clinically by cognitive fluctuations, visual hallucinations, rapid-eye-movement sleep behaviour disorder, and Parkinsonism. Differentiating DLB from AD and related disorders of Parkinson’s disease (PD) and Parkinson’s disease with dementia (PDD) can be difficult at early disease stages due to overlapping clinical and pathological features. Nevertheless, it has been shown that visuoperceptual, attention and executive deficits, relative to memory impairments, are especially prominent in the early stages of DLB compared with AD or PD. The importance of these impairments is reflected in the recent revision of the diagnostic consensus guidelines of DLB. As the last reviews of cognitive impairments in DLB were conducted over a decade ago (Collerton, Burn, McKeith & O’Brien, 2003; Metzler-Baddeley, 2007; Ralph, 2001), we provide an up-to-date review of the literature into perceptual and attention-executive functions in DLB. There is a need for better controlled studies into cognitive deficits, their neural correlates, and relationships to clinical symptoms in DLB, that go beyond standard clinical assessments. Evidence regarding visuoperception suggests that low-level functions may be relatively preserved while mid- and higher-level functions, that require the recruitment of attention and executive functions are disproportionally affected in DLB. Cognitive fluctuations and visual hallucinations may arise from a desynchronization of top-down attention and bottom-up sensory networks.