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). Method. 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.