Reduced task-related functional connectivity during a set-shifting task in unmedicated early-stage Parkinson's disease patients.

Background: Patients with Parkinson's disease (PD) often suffer from cognitive impairments, including set-shifting deficits, in addition to the characteristic motor symptoms. It is hypothesized that the striatal dopamine depletion leads to a sub-optimal functional connectivity between task-related brain areas and consequently results in impaired task-performance. In this study, we aimed to examine this hypothesis by investigating the task-related functional connectivity of brain areas that are believed to be involved in set-shifting, such as the dorsolateral prefrontal cortex (DLPFC), posterior parietal cortex (PPC) and the superior frontal gyrus (SFG), during a set-shifting task.

Cortical Thickness, Surface Area and Subcortical Volume Differentially Contribute to Cognitive Heterogeneity in Parkinson's Disease.

Parkinson's disease (PD) is often associated with cognitive deficits, although their severity varies considerably between patients. Recently, we used voxel-based morphometry (VBM) to show that individual differences in gray matter (GM) volume relate to cognitive heterogeneity in PD. VBM does, however, not differentiate between cortical thickness (CTh) and surface area (SA), which might be independently affected in PD.

Decreased neural activity and neural connectivity while performing a set-shifting task after inhibiting repetitive transcranial magnetic stimulation on the left dorsal prefrontal cortex.

Background: Sub-optimal functioning of the dorsal prefrontal cortex (PFC) is associated with executive dysfunction, such as set-shifting deficits, in neurological and psychiatric disorders. We tested this hypothesis by investigating the effect of low-frequency 'inhibiting' off-line repetitive transcranial magnetic stimulation (rTMS) on the left dorsal prefrontal cortex on behavioural performance, neural activity, and network connectivity during the performance of a set-shifting paradigm in healthy elderly (mean age 50+).

Results: Behaviorally, we found a group-by-session interaction for errors on set-shift trials, although post hoc tests did not yield significant findings.

Impaired planning in Parkinson's disease is reflected by reduced brain activation and connectivity.

Objective: Parkinson's disease (PD) often entails impairments of executive functions, such as planning. Although widely held that these impairments arise from dopaminergic denervation of the striatum, not all executive functions are affected early on, and the underlying neural dynamics are not fully understood. In a combined longitudinal and cross-sectional study, we investigated how planning deficits progress over time in the early stages of PD compared to matched healthy controls.

Reduced neural connectivity but increased task-related activity during working memory in de novo Parkinson patients.

Objective: Patients with Parkinson's disease (PD) often suffer from impairments in executive functions, such as working memory deficits. It is widely held that dopamine depletion in the striatum contributes to these impairments through decreased activity and connectivity between task-related brain networks. We investigated this hypothesis by studying task-related network activity and connectivity within a sample of de novo patients with PD, versus healthy controls, during a visuospatial working memory task.

Compensatory fronto-parietal hyperactivation during set-shifting in unmedicated patients with Parkinson's disease.

Patients with Parkinson's disease (PD) often suffer from impairments in executive functions, such as mental rigidity, which can be measured as impaired set-shifting. Previous studies have shown that set-shifting deficits in patients with PD result from hypo-excitation of the caudate nucleus and lateral prefrontal cortices. The results of these studies may have been influenced by the inclusion of patients on dopaminergic medication, and by choosing set-shifting paradigms in which performance also depends on other cognitive mechanisms, such as matching-to-sample.

Failure of stop and go in de novo Parkinson's disease--a functional magnetic resonance imaging study.

Behavioral impairments in response inhibition and initiation are common in Parkinson's disease (PD) and are associated with reduced impulse control. No prior study, however, has investigated the functional correlates of response inhibition in de novo PD. Twenty-one de novo PD patients and 37 matched healthy controls performed a stop-signal task during functional magnetic resonance imaging.

The learning-oddball paradigm: data of 24 separate individuals illustrate its potential usefulness as a new clinical tool.

Objective: In a previous article reporting group data, we presented event-related potentials (ERPs), which were evoked by randomly presented target stimuli in a 'learning-oddball' task. These ERPs contained a large N2-P3 complex that decreased and a Contingent Negative Variation (CNV) that increased when the targets were presented in a regular fashion. Using the learning-oddball paradigm, the aim of the present paper was to determine ERP effects of introducing regularity in individual participants.

Event related potentials to digit learning: tracking neurophysiologic changes accompanying recall performance.

The aim of this study was to track recall performance and event-related potentials (ERPs) across multiple trials in a digit-learning task. When a sequence is practiced by repetition, the number of errors typically decreases and a learning curve emerges. Until now, almost all ERP learning and memory research has focused on effects after a single presentation and, therefore, fails to capture the dynamic changes that characterize a learning process.