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Studies of neuropsychological patients and experimental animals have demonstrated that the striatum plays a role in implicit habit learning. Here, we examined the performance of patients with Parkinson's disease (PD) on a concurrent discrimination task that can be learned implicitly by neurologically intact individuals. Participants viewed a pair of shapes on each trial and, under a timed deadline, guessed which one concealed a smiling face. About half the control participants exhibited minimal awareness of the cue-reward relationships as assessed by a post-test evaluation. Nevertheless, these participants were able to perform the discrimination task; there was no correlation between awareness and performance on the task. In contrast, minimally aware patients with PD showed no learning, whereas those who were more aware of the relationships performed as well as control participants on the task. There was a significant correlation between awareness and performance in patients with PD. These data support the idea that the basal ganglia play a role in implicit habit learning and underscore the importance of using tests of awareness to assess the content and process of learning in humans.

Parkinson's disease has been associated with executive dysfunction, especially task-switching deficits. One factor contributing to task-switching costs is backward inhibition, as measured by less efficient performance when switching back to a task from which one has recently switched away. This alternating-switch cost is considered to be due to persisting inhibition of elements of the previous task set after a switch. In this study, patients with mild to moderate Parkinson's disease and controls performed three tasks (A-C) in an intermixed fashion. Patients with mild to moderate Parkinson's disease and controls showed equivalent response times. However, the patients made significantly more errors during an alternating switch (i.e., ABA) than did control participants. In contrast, there was no group difference in accuracy in the comparable condition of two consecutive switches between different tasks (i.e., CBA). In addition, accuracy for the two groups was similar for trials in which the task was repeated. These data suggest that Parkinson's disease is associated with either increased backward inhibition, or a reduced ability to overcome this inhibition when reactivating a recently abandoned task set.

Wilson's disease (WD) is an autosomal recessive disease that causes increased copper deposition in the liver and basal ganglia with resultant hepatic and neurologic sequelae. In the past few years, dramatic new discoveries have changed our understanding of the pathophysiology of WD. Although there are potentially life-saving therapies for WD, there is much controversy surrounding the optimal treatments of patients in the various stages of the disease. Specifically, the relative roles of penicillamine, trientene, and tetrathiomolybdate in the initial treatment of the symptomatic patient with WD remain to be defined. Zinc monotherapy for maintenance treatment and in the treatment of asymptomatic patients with WD is still controversial. It is also unclear whether neurologic status alone is an indication for liver transplantation in WD. This paper reviews the pathogenesis, genetics, clinical presentation, and diagnosis, with a special emphasis on the treatment controversies that arise in the care of the WD patient.

Although a referral bias may have resulted in a higher proportion of atypical cases and consequently an overestimation of dystonia, asymmetric limb dystonia particularly affecting one arm initially was observed in 92% of all our CBD cases. Predominant leg dystonia is uncommon, and head, neck, or axial dystonia is rare. Dystonia is often associated with myoclonus, rigidity, apraxia, alien hand phenomenon, and sensory cortical signs in the affected limb, and there are no significant differences between the occurrence of these or other features, between patients with or without dystonia. There is no effective treatment for this relentless disorder except for temporary relief of dystonia and pain with local botulinum toxin injections. Further clinicopathologic studies are needed to elucidate the anatomical and physiologic substrates of dystonia in this disorder.