The cognitive and non-cognitive symptoms of dementia have traditionally been investigated separately, though they may be expressions of the same functional impairments and underlying pathological processes. Dementia with Lewy bodies (DLB) is diagnosed by the coexistence of cognitive (a progressive dementia) and non-cognitive (fluctuations, visual hallucinations, and parkinsonism) symptoms. It therefore provides an ideal test disorder for an integrative model. We recently systematic reviewed 21 comparisons of the cognitive profile of DLB with those of Alzheimer’s (AD) and Parkinson’s diseases (PD). This showed that DLB is notable for the severity of its attentional, executive, and visual perceptual impairments. Other cognitive impairments are relatively less pronounced, and do not distinguish it from AD and PD. Using this data, and drawing on evidence from a range of other dementing illnesses, illustrates how a core non-cognitive symptom, visual hallucinations, may result from a combination of impairments in the cognitive domains of attention and visual perception. This can be related to DLB pathology within the ventral visual stream and frontal brain areas. The effects of anti-dementia drugs on both cognitive and non-cognitive symptoms may reflect modulation of these areas.
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