Altered nigrostriatal and nigrocortical functional connectivity in rapid eye movement sleep behavior disorder.

Study Objectives: Rapid eye movement sleep behavior disorder (RBD) is a condition closely associated with Parkinson disease (PD). RBD is a sleep disturbance that frequently manifests early in the development of PD, likely reflecting disruption in normal functioning of anatomical areas affected by neurodegenerative processes. Although specific neuropathological aspects shared by RBD and PD have yet to be fully documented, further characterization is critical to discovering reliable biomarkers that predict PD onset.

Reflexive and volitional saccades: biomarkers of Huntington disease severity and progression.

Background: Huntington disease (HD) is a genetic, neurodegenerative disorder characterized by chorea, behavioral co-morbidities, cognitive deficits, and eye movement abnormalities. We sought to evaluate whether reflexive and voluntary orienting prove useful as biomarkers of disease severity in HD.

Methods: Eleven HD subjects were evaluated with the motor subscale of the Unified Huntington Disease Rating Scale (UHDRS) and the Montreal Cognitive Assessment.

Effects of haloperidol on cognition in schizophrenia patients depend on baseline performance: a saccadic eye movement study.

Schizophrenic patients are heterogeneous with respect to voluntary eye movement performance, with some showing impairment (e.g., high antisaccade error rates) and others having intact performance.

Reduced volume of the putamen in REM sleep behavior disorder patients.

Objective: The purpose of this study was to quantify volumes of specific subcortical gray matter nuclei implicated in Parkinson's disease (PD) as a preliminary step for identifying a non-invasive clinical biomarker for PD. We hypothesized that REM sleep behavior disorder (RBD) patients, at risk for developing PD, will demonstrate a pattern of neuronal degeneration reflected in reduced striatal volumes on T1-weighted MRI.

Methods: We compared measures of RBD patients confirmed by polysomnography (PSG) with groups of age/gender-matched Control subjects and early PD (EPD) patients (Hoehn & Yahr < 2).

Comparison of 50- and 100-g L -tryptophan depletion and loading formulations for altering 5-HT synthesis: pharmacokinetics, side effects, and mood states.

Rationale: Differences in 5-hydroxytryptamine (5-HT) function have been the subject of extensive research in psychiatric studies. Many studies have manipulated L -tryptophan (Trp) levels to temporarily decrease (depletion) or increase (loading) 5-HT synthesis. While most researchers have used a 100-g formulation, there has been ongoing interest in using smaller-sized formulations.

Levodopa slows prosaccades and improves antisaccades: an eye movement study in Parkinson's disease.

Background: The integrity of frontal systems responsible for voluntary control and their interaction with subcortical regions involved in reflexive responses were studied in patients with Parkinson's disease (PD). Previous studies have shown that patients with PD have impaired executive function, including deficits in attention, motor planning and decision making.

Methods: Executive function was measured through eye movements: reflexive (stimulus driven) prosaccades and voluntary (internally guided) antisaccades.

Dissociating cognitive deficits involved in voluntary eye movement dysfunctions in Parkinson's disease patients.

In an attempt to distinguish and define the altered cognitive processes associated with Parkinson's disease (PD), we examine and try to dissociate the components of an effective voluntary saccade: (1) the planning and execution of a voluntary saccade; (2) the suppression of reflexive eye movements; and (3) the working memory processes required. We tested 14 PD patients (off their medications) and 11 control subjects on antisaccade (AS), delayed antisaccade (DAS), and remembered antisaccade (RAS) paradigms. The three tasks required identical responses, each task only differing in a single manipulation for direct comparison--a delay period was added in the DAS, and the target was removed during the delay period of the RAS--allowing us to study the specific cognitive processes involved in the execution of a voluntary saccade.