Determining the optimal challenge point for motor skill learning in adults with moderately severe Parkinson's disease.

Objective: To test the predictions of the Challenge Point Framework (CPF) for motor learning in individuals with Parkinson's disease (PD) by manipulating nominal task difficulty and conditions of practice.

Methods: Twenty adults with PD and 20 nondisabled controls practiced 3 variations of a laboratory-based goal-directed arm movement over 2 days. A between-group (PD, nondisabled) 2-factor design compared 2 levels of nominal task difficulty (low, high) and 2 levels of practice condition (low, high demand).

Role of the basal ganglia in category learning: how do patients with Parkinson's disease learn?

The purpose of the present study was to gain a deeper understanding of the role of the basal ganglia in learning and memory by examining learning strategies among patients with basal ganglia dysfunction. Using a probabilistic category learning task (the "weather prediction" task) previously shown to be sensitive to basal ganglia function, the authors examined patterns of performance during learning and used mathematical models to capture different learning strategies. Results showed that patients with Parkinson's disease exhibit different patterns of strategy use.

Dissociating medial temporal and basal ganglia memory systems with a latent learning task.

The medial temporal (MT) lobes and basal ganglia have both been implicated as brain substrates of associative learning. Here, we show a dissociation between medial temporal and basal ganglia damage using a latent learning task, in which prior exposure to cues, uncorrelated with each other, slows subsequent learning of an association between them. Consistent with prior work, we found a robust exposure effect in healthy controls, with exposed controls learning more slowly than non-exposed controls.

Function of the 'direct' and 'indirect' pathways of the basal ganglia motor loop: evidence from reciprocal aiming movements in Parkinson's disease.

The purpose of this study was to test the validity of a neural-network model of the basal ganglia developed by Bischoff and colleagues (A. Bischoff, Modeling the basal ganglia in the control of arm movements (Doctoral dissertation, University of Southern California, 1998). Dissertation Abstr.

Sensory-motor control in the ipsilesional upper extremity after stroke.

There is substantial evidence to indicate that sensory-motor control of the ipsilesional upper extremity (UE) in adults after unilateral stroke is abnormal. Some of the sensory-motor deficits differ as a function of the side of the cerebral lesion. Rapid movements of the ipsilesional UE that require precise timing and sequencing are more affected in individuals with lesions in the left hemisphere.