High‐speed memory scanning in Parkmson's disease: Adverse effects of levodopa

Abstract

High-speed memory scanning as assessed by the Sternberg paradigm was studied in 12 nondemented patients with fluctuating Parkinson's disease and 13 age-matched healthy controls. Patients were first assessed before taking their morning dose of levodopa ("off") and again after that dose had produced full clinical effect ("on") after that dose had produced full clinical effect ("on"). Although motor components of the measured choice reaction time were slower in patients when off than in control subjects, memory scanning speed was not different. After levodopa (on), patients' motor time normalized, but cognitive processing speed became significantly slower when compared with previous performance in the off condition and with controls. Contrary to previous concepts of bradyphrenia in patients with Parkinson's disease, these results indicate that dopaminergic stimulation can reduce cognitive processing speed.

Individual capacity differences predict working memory performance and prefrontal activity following dopamine receptor stimulation

“…In the present study, we propose that low-span subjects improved on our working memory task when suboptimal PFC dopamine levels were augmented, whereas their higher span counterparts overdosed from dopaminergic augmentation, which led to performance deterioration. Our behavioral finding is also consistent with the Poewe et al (1991) study of PD patients, which showed that dopaminergic medication improved patients' motor speeds but decreased their memory retrieval rates during a verbal delayed-recognition task. Thus, as has been found in animal studies that examined the effects of various dosages of dopaminergic agonist and antagonist treatments (Arnsten & Goldman-Rakic, 1998;Sawaguchi & GoldmanRakic, 1994;Williams & Goldman-Rakic, 1995;Zahrt et al, 1997), each individual has an optimal dopamine concentration for optimal cognitive processing.…”

“…Insight regarding how dopaminergic stimulation may influence this verbal recognition task derives from a behavioral study of Parkinson's disease (PD) patients who were tested on and off their dopaminergic replacement medications (Poewe, Berger, Benke, & Schelosky, 1991). Patients showed facilitated motor speed (decreased RT intercept) and impaired cognitive efficiency (increased RT slope) when they were on their medication in comparison with when they were off their medication.…”

Levodopa and executive performance in Parkinson's disease: A randomized study

“…Furthermore, our research indicates that CR-LD is not associated with this observed impairment (Shohamy et al, 2006) but with improved performance with respect to pre-LD. These findings are consistent with the hypothesis that LD-related impairment on specific highly demanding executive function tasks (Cools et al, 2002;Frank et al, 2004;Kulisevsky et al, 1996;Mattay et al, 2002;Poewe et al, 1991;Swainson et al, 2000) depends, at least in part, on the rapid rise of LD plasma levels. Thus, a less abrupt pattern of variation of dopamine concentration in the parkinsonian brain, such as that associated with a slower rise of LD plasma levels, might alleviate performance deficiencies associated to high LD plasma levels (Kulisevsky, 2000).…”

Comparative cognitive effects of bilateral subthalamic stimulation and subcutaneous continuous infusion of apomorphine in Parkinson's disease

“…32,33 Worsening has also been found in cognitive processing speed 34 and frontal functions. 33 In STN-DBS-treated patients, worsening in phonetic verbal fluency and speed of naming has been observed previously by us and other authors.…”