A failure of 'pop-out' in visual search tasks in dementia with Lewy Bodies as compared to Alzheimer's and Parkinson's disease.

OBJECTIVES: The pattern of neural damage in dementia with Lewy Bodies (DLB) led us to hypothesize that patients with DLB would be particularly impaired on parallel ('pop-out') search tasks, relative to serial search tasks, and that this would serve to distinguish DLB from other forms of neurodegenerative disease, particularly Alzheimer's disease (AD). METHODS: To explore this possibility we tested four groups of observers (DLB, Alzheimer's Disease, Parkinson's Disease and age-matched controls) on parallel and serial search tasks, and a choice reaction time task. RESULTS: The DLB participants performed in a quantitatively and qualitatively different manner to the other groups. As predicted, they were particularly impaired on the parallel search task relative to the other observer groups. CONCLUSIONS: This pattern of deficit may reflect damage in the occipital areas leading to deficits in figure-ground segregation, and can assist differential diagnosis of DLB from other patients groups such as AD.