In addition to fluctuating cognition, LBD patients display deficits in attention, executive function and visuo-perceptual processing. Specifically, neuropsychological studies in DLB have noted deficits in attentional function ranging from simple processing speed through to complex attentional tasks requiring significant executive input. Selective attention and the maintenance of vigilance are both impaired. Both fluctuating cognition and attentional deficits have major impact on activities of daily living and evidence suggests they are likely to have a significant role in the formation of the distressing visual hallucinations that frequently accompany LBD.