Higher cortical deficits influence attentional processing in dementia with Lewy bodies, relative to patients with dementia of the Alzheimer's type and controls

Abstract

Background: Attentional dysfunction is believed to be a prominent and distinguishing neuropsychological feature of dementia with Lewy bodies (DLB); yet, the specific nature of the attentional deficit and factors that can potentially influence attentional processing in DLB have not been fully defined. Aims: To clarify the nature of the attentional deficit in early-stage DLB relative to patients with early-stage dementia of the Alzheimer's type (DAT) and elderly controls, and examine the effect of task complexity and type of cognitive load on attentional processing in DLB. Methods: Attentional impairment and fluctuating attention were investigated in three groups of subjectspatients with clinical features of early probable DLB (n = 20), a group with early probable DAT (n = 19) and healthy elderly controls (n = 20)-using an experimental computerised reaction time paradigm. Results: Patients with DLB showed greater attentional impairment and fluctuations in attention relative to patients with DAT and elderly controls. The attentional deficit was generalised in nature but increased in magnitude as greater demands were placed on attentional selectivity. Attentional deficits in DLB were most pronounced under task conditions that required more active recruitment of executive control and visuospatial cognitive processes. Conclusions: Attentional deficits in DLB are widespread and encompass all aspects of attentional function. Deficits in higher cortical function influence the degree of attentional impairment and fluctuating attention, suggesting that attentional processing in DLB is mediated by interacting cortical and subcortical mechanisms. These findings serve to clarify the nature of the attentional deficit in DLB and have potentially important ramifications for our understanding of the neurocognitive underpinnings of fluctuations.

Cerebral Substrates Related to Impaired Performance in the Clock-Drawing Test in Dementia with Lewy Bodies

“…DLB patients show impaired reflexive and intentional saccade performance [32] . Furthermore, relatively greater impairments of visuospatial and attentional functions are consistently documented in DLB patients compared to control subjects or AD patients [2,33] . Bradshaw et al [33] demon- Vox.…”

“…Furthermore, relatively greater impairments of visuospatial and attentional functions are consistently documented in DLB patients compared to control subjects or AD patients [2,33] . Bradshaw et al [33] demon- Vox. = Number of voxels in each detected region; x, y, z = stereotactic coordinates in the Montreal Neurological Institute space; Z score = SPM{Z} score.…”

“…Therefore, the decreased thalamic activity found in the impaired CDT group might reflect a fundamental disturbance in the central regulation of arousal systems in these DLB patients. Prominent fluctuation in consciousness is a core feature of DLB [8,9] , and marked fluctuations in attention and alertness occur not only at a clinical level but also on a second-to-second basis, shown as high variability on electroencephalograms and in reaction time tasks [33,38] .…”

Effect of cognitive fluctuation on neuropsychological performance in aging and dementia

“…31 The loss of these projections has been described in DLB, but neuronal counts did not correlate with sleep disturbances or fluctuations. DLB is associated with greater attentional deficits compared with AD 32 ; however, loss of attentional control is also an early finding in AD. 33,34 EEG recordings of patients with AD and patients with DLB demonstrate differences in compressed spectral arrays favoring posterior alpha activity in patients with DLB with fluctuations.…”

Psychomotor Slowing in Mild Cognitive Impairment, Alzheimer’s Disease and Lewy Body Dementia: Mechanisms and Diagnostic Value

“…In mild cognitive impairment (MCI), slowing concerns CRT only [1,3] and has been observed 3 years before a formal diagnosis of dementia [4] . In Lewy body dementia (LBD), CRT slowing and variability have been reported [5][6][7] . Reaction time (RT) slowing is usually attributed to attention deficit, but its mechanism has not been specifically addressed.…”