Cognitive slowing in Parkinson's disease fails to respond to levodopa treatment

Abstract

To evaluate clinically the slowing of cognitive processing in Parkinson's disease, we used a visual discrimination task consisting of 15 superimposed images of objects. The time needed to identify 12 objects increased by 58% in 70 patients withdrawn from levodopa treatment compared with 20 controls matched for age and education. Perceptual, motor, and psycholinguistic factors, as well as mood, only partially accounted for the slowness of performance. The 15-objects test scores of the parkinsonian patients correlated significantly with both their intellectual impairment and the severity of their parkinsonian disability, but not with the duration of the disease. The scores did not correlate with depression. Levodopa had no effect on the score, although the parkinsonian motor disability score was improved by 54%. The results indicate a cognitive slowing in Parkinson's disease which is probably related to abnormalities of nondopaminergic neuronal systems in the brain.

Disentangling the Role of Cortico-Basal Ganglia Loops in Top–Down and Bottom–Up Visual Attention: An Investigation of Attention Deficits in Parkinson Disease

“…The enhancement of AC observed in our patients is consistent with the increased distractibility manifested by PD patients in the presence of irrelevant but salient stimuli, as shown in prior studies (Uc et al, 2007;Henik et al, 1993;Sharpe, 1990;Wright et al, 1990;Pillon et al, 1989). In a controlled study carried out on medicationwithdrawn PD patients performing a visuospatial memory task, behavioral and electroencephalographic measures indicated that patients were severely impaired at filtering out distractors .…”

“…Finally, they are more prone to interference in the presence of a distractor stimulus compared with normal controls, as measured on a dichotic listening task (Sharpe, 1992). Moreover, several behavioral studies indicate that parkinsonian patients with overall well-preserved cognitive functions may nevertheless be impaired at a variety of visual attention tasks (Filoteo et al, 1995;Wright, Burns, Geffen, & Geffen, 1990;Yamada, Izyuuinn, Schulzer, & Hirayama, 1990) and more specifically at tasks tapping selective attention mechanisms (Cools, Rogers, Barker, & Robbins, 2009;Henik, Singh, Beckley, & Rafal, 1993;Pillon et al, 1989).…”

Dopamine deficiency increases synchronized activity in the rat subthalamic nucleus

“…There is a nonlinear dose dependent effect of 6-OHDA on noradrenergic neurons, and more recent work has shown that desipramine is not needed at the lower doses of 6-OHDA used in current study (Jouve et al, 2010). Notice that even in case of minor noradrenergic degeneration following 6-OHDA injection, the animal model would be closer to human PD where same degeneration of catecholaminergic cells is likely to be associated to the pathological state (Delaville et al, 2011;Mavridis et al, 1991;Pillon et al, 1989). For control subjects (n = 8), an equal volume of vehicle (6 μl saline with 0.1% ascorbic acid) was injected.…”

Dopaminergic Modulation of Visual-Spatial Working Memory in Parkinson’s Disease

“…Unclear results emerged from previous studies exploring the effect of L-dopa administration on WM-related cognitive functioning in PD patients. Some investigators reported performance improvement of WM tasks after L-dopa treatment [27,43,44] while others did not find any effect [45] or found a slowing effect [46] of L-dopa on the cognitive processing speed of these patients. These contrasting results may be partially explained by the clinical heterogeneity of the different PD patient groups examined and by the different methodological procedures used.…”