Academic journal article Cognitive, Affective and Behavioral Neuroscience

Executive Function in Parkinson's Disease: Contributions of the Dorsal Frontostriatal Pathways to Action and Motivation

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Executive Function in Parkinson's Disease: Contributions of the Dorsal Frontostriatal Pathways to Action and Motivation

Article excerpt

Abstract Disruption of the dorsal frontostriatal pathways in Parkinson's disease (PD) is associated with impairments in motivation, as well as in executive function. The goal of this study was to investigate whether these impairments are related and, if so, whether the disruption of frontostriatal pathways compromises the ability to process the motivational aspects of feedback in such tasks. In Experiment 1, informative feedback improved the performance of young, healthy participants in a task-switching paradigm. This task-switching paradigm was then used in Experiment 2 to test whether feedback would improve the performance of 17 PD patients and age-matched controls. The PD group benefitted from feedback to the same degree as control participants; however, depression scores on the Beck Depression Inventory were significantly related to feedback usage, especially when response selection demands were high. Regardless of feedback, PD patients were more impaired when response demands were high than in an equally difficult condition with low action demands. These results suggest that response selection is a core impairment of insufficient dopamine to the dorsal frontal striatal pathways.

Keywords Depression . Task switching . Basal ganglia

Cognitive impairments are consistently observed as a result of insufficient dopamine to frontostriatal pathways in Parkinson's disease (PD). Although less visible than the motor and postural symptoms, cognitive impairments are not a trivial consequence of this disorder (Goldman, Baty, Buckles, Sahrmann, & Morris, 1998; Lees & Smith, 1983). Cognitive impairments are primarily in the realm of executive function and learning and are thought to arise because of deficient dopaminergic input from the basal ganglia to the prefrontal cortex (A. E. Taylor, Saint-Cyr, & Lang, 1986). As research into the cognitive sequelae of PD has progressed, another line of research has arisen that emphasizes an apparently different aspect of cognitive impairment. These studies have focused on motivational impairments in PD and, specifically, on abnormal responses to rewards (Czernecki, Pillon, Houeto, Pochon, Levy, & Dubois, 2002; Goerendt, Lawrence, & Brooks, 2004; Kunig, Leenders, Martin-Solch, Missimer, Magyar, & Schultz, 2000; Mazzoni, Hristova, & Krakauer, 2007). The goal of these experiments is to reconcile these seemingly disparate views of cognitive disorders in PD in order to understand the contribution of frontostriatal pathways to cognition.

Impairments of executive function have been well documented in PD over the last few decades. PD patients do poorly on executive function tests that require nonautomatic responding (A. E. Taylor et al., 1986), including tasks that require filtering the contents of working memory (Lee et al., 2010) and tests such as the Stroop task that require overcoming a prepotent response (Witt et al., 2006). In addition, those with PD are reliably impaired when required to switch quickly between multiple tasks (A. R. Cools, van den Bercken, Horstink, van Spaendonck, & Berger, 1984). Indeed, task switching has been a primary focus for investigations of executive function and PD. Task switching is a control process that produces a change in responding from one stimulus set, task, or rule to another (Monsell, 2003). Many studies have demonstrated that PD patients are slower at shifting than healthy controls. Greater shift costs were observed for patients, as compared with controls, when a switch was required between (1) responding to target stimuli in different modalities (Ravizza & Ivry, 2001), (2) responding to different stimulus features (i.e., shapes, letters) of a target (Hayes, Davidson, Keele, & Rafal, 1998; Pollux, 2004), (3) the type of information retrieved (i.e., make an odd/even judgment or a consonant/vowel judgment) (R. Cools, Barker, Sahakian, & Robbins, 2001a, Cools, Barker, Sahakian, & Robbins, 2001b; Rogers et al. …

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