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M W Horstink

Publications and source records attributed to M W Horstink.

At least 19 recordsLinked to original sources
PubMed1998

Genetic and environmental risk factors in Parkinson's disease.

Parkinson's disease (PD) is a multifactorial disorder, caused by a combination of age, genetics and environmental factors. Nigral cells are susceptible to multiple causes of derangement of normal cell function, all of which may contribute to the same Parkinson phenotype. Autosomal dominant alpha-synuclein-gene PD represents one of the pure genetic forms, whereas cases of sporadic PD probably depend more on age and environmental factors, MPTP-Parkinsonism being the purest example of an environmentally caused Parkinson phenotype. This review suggests that pesticides-herbicides, smoking and head trauma probably represent the most eligible candidates for environmental factors involved in provoking PD or influencing its natural course.

Aging↗
PubMed1998

Reliance on external cues for movement initiation in Parkinson's disease. Evidence from movement-related potentials.

The aim of this study was to investigate the neurophysiological mechanisms underlying Parkinson's disease patients' increased reliance on external cues for the initiation of movement. Lateralized movement-related cortical potentials were recorded in a noise-compatibility task with seven patients and seven age-matched control subjects. In this two-choice task, visual stimuli containing incompatible target and distractor elements, which simultaneously instructed for responses from both hands, initially caused activation of the motor cortex controlling the wrong response hand. The incorrect response activation was of higher amplitude in patients than in control subjects, causing a longer response delay relative to response times when target and distractors instructed the same hand. In addition, hand-specific motor cortex activation started earlier in patients than in control subjects. These results indicate that visual stimuli exerted an earlier and stronger influence on movement initiation in patients than in control subjects. We hypothesize that information from sensory stimuli relevant for the generation of a response can have rapid access to motor structures in Parkinson's disease patients, thereby facilitating the initiation of movement. The findings may reflect a compensatory mechanism, but could also be related to excitability changes in the motor cortex intrinsic to the pathophysiology of Parkinson's disease.

Aged↗
PubMed1998

EEG findings in patients with vascular parkinsonism.

OBJECTIVES: To investigate whether the conventional and quantitative EEGs of patients with vascular parkinsonism (VP) differ from those of idiopathic Parkinson's disease (PD) patients. MATERIAL AND METHODS: The EEGs of 13 patients with vascular parkinsonism and 14 patients with idiopathic Parkinson's disease were scored on a simple scale regarding aspects of conventional EEG variables. Alpha band power asymmetry and EEG slowing (increased delta and theta power) were calculated by the neurometrics method of quantitative EEG data evaluation. RESULTS: Analysis of both conventional and quantitative EEG data shows that VP patients had significantly less EEG slowing than PD patients. CONCLUSION: This study shows that the EEG in a group of patients with vascular parkinsonism differ from a patient group with idiopathic Parkinson's disease. Our results indicate that VP patients are not PD patients with subcortical vascular lesions, because then they would have had at least as much EEG slowing as PD patients.

Aged↗
PubMed1998

Cognitive deficits following stroke in the basal ganglia.

OBJECTIVE: To examine the effect of a stroke in the basal ganglia on cognitive functioning. DESIGN: As part of a larger prospective study on the neuropsychological and psychosocial consequences of stroke, 12 patients with a stroke confined to the basal ganglia were examined. SETTING: The patients were assessed in one of the three participating hospitals. SUBJECTS: The results of 12 patients with a stroke in the basal ganglia (mean age 55 years), were compared to 24 controls (mean age 54.3 years). MAIN OUTCOME MEASURES: Different aspects of memory, attention and concentration, visuospatial and visuoconstructive functions, language and arithmetic were assessed using neuropsychological tests. RESULTS: The data show a significant abnormality in cognitive functioning on all cognitive domains. CONCLUSIONS: The results stress the notion that subcortical damage may lead to substantial neuropsychological disorders and have clear implications for neurological rehabilitation.

Basal Ganglia↗
PubMed1998

[Cognitive deficits in Parkinson's disease].

In neuropsychological studies of Parkinson's disease, cognitive deficits are frequently reported, but the nature of these deficits is not clear. As far as cognitive deficits are manifest in parkinsonian patients at an early stage of the disease, many studies tend to describe them as fitting a frontal syndrome. As a consequence of dysfunction of the striatum, the (pre)frontal cortex receives deficient input from the striatum, which might explain the similarity of the cognitive deficits of parkinsonian patients with those of patients with frontal dysfunction. The present studies provide evidence that the cognitive deficits of parkinsonian patients display a certain similarity with those of patients with frontal dysfunction at the level of the ultimate performance, but that the underlying processes have a distinct character. Parkinsonian patients exhibit a decrease in self-generated problem-solving. This deficit is manifest at a level of cognitive function, which goes beyond task or domain. Among all disease variables, only severity of the disease and especially rigidity proved to be related consistently to this decrease in self-generated problem-solving.

Adult↗
PubMed1997

Symptoms and duration of the prodromal phase in Parkinson's disease.

To investigate the duration of a prodromal phase before the onset of the classic symptoms of idiopathic Parkinson's disease, the authors conducted a retrospective case-control study of 60 patients with Parkinson's disease and 58 age- and sex-matched control subjects, covering the decade preceding the onset of classic Parkinson's disease. The symptoms were derived from files of the patients' general practitioners. Compared with control subjects, patients pre-Parkinson's disease had more central nervous system, psychologic, musculoskeletal, and cardiovascular (i.e., autonomic) symptoms. Patients pre-Parkinson's disease also made more visits to general practitioners and medical specialists. The results indicate that the onset of classic parkinsonism is frequently preceded by a prodromal phase lasting from 4-6 years.

Adult↗
PubMed1997

Q10 therapy in patients with idiopathic Parkinson's disease.

A 3-month open-label trial was performed to evaluate the efficacy of 200 mg Q10 daily in 10 patients with Parkinson's disease. Motor performance was assessed with UPDRS and motor tests. There was no significant effect on the clinical ratings.

Aged↗
PubMed1996

Movement-related potential measures of different modes of movement selection in Parkinson's disease.

Movement-related potentials were recorded preceding self-paced voluntary movements in patients with Parkinson's disease and in healthy subjects of the same age group. We compared the Readiness Potential preceding joystick movements in a fixed direction and preceding joystick movements in freely selected directions. In normal subjects the Readiness Potential amplitude was higher preceding freely selected movements than preceding movements in a fixed direction. The Readiness Potential in Parkinson patients failed to be modified by the different modes of movement selection. The modulation of the Readiness Potential by different ways of preparing for movement might be due to the supplementary motor area (SMA) being more strongly engaged by tasks requiring internal control of movements than by tasks that are externally structured. The results suggest that this task-dependent variation of SMA activity is reduced in Parkinson's disease. A failing capacity to adapt SMA activity to different task demands has previously been suggested by evidence from positron emission tomography studies using similar tasks.

Adult↗
PubMed1996

[Functional MRI: imaging of motor cortex function].

OBJECTIVE: To image the motor cortex with functional MRI (fMRI), and locate the activated area with the proportional grid of Talairach. DESIGN: Descriptive. SETTING: St. Radboud Academic Hospital Nijmegen. METHODS: In ten volunteers functional images of the motor cortex were made during execution of a motor task (finger movements). From the functional images the positions of activated areas were calculated using the 3D Talairach grid system. RESULTS: fMRI of the motor cortex was possible using a 1.5 T MRI scanner. Task activation of the motor cortex gave a signal increase in Brodmann's area 4, the precentral gyrus. CONCLUSION: Imaging of the active motor cortex with fMRI is feasible. The use of the 3D Talairach proportional grid system for the calculation of the position of an activated area in the motor cortex is possible with adequate accuracy.

Adult↗
PubMed1996

Quantitative gait analysis in patients with vascular parkinsonism.

Until now the clinical criteria for the diagnosis of vascular parkinsonism (VP) have been disputed. The purpose of the present study is to investigate whether quantitative gait analysis can differentiate between the gait pattern of patients with VP and the gait pattern of patients with idiopathic Parkinson's disease (PD). Twelve patients with VP, 12 patients with PD, and 10 neurologically nondiseased controls were examined by quantitative gait analysis. Patients with VP, having a similar gait velocity and stride length, showed relatively preserved arm swing with markedly more anteflexion in the shoulder on the forward sway of the arm swing than patients with PD. Patients with VP also showed less flexion dystonic posture of the elbow, hip, knee, and trunk than did patients with PD. There was no significant difference in the excursions and coordination of arm swing in the patients with VP compared with the control group. Both patient groups showed reduced leg movements, reduced hip extension, and reduced knee flexion and extension as compared with the controls.

Aged↗
PubMed1996

Dipole source analysis suggests selective modulation of the supplementary motor area contribution to the readiness potential.

The readiness potential preceding voluntary movement is modulated by the mode of movement selection, i.e. it has a higher amplitude preceding freely selected than before prescribed movements (Praamstra, P., Stegeman, D.F., Horstink, M.W.I.M., Brunia, C.H.M. and Cools, A.R. Movement-related potentials preceding voluntary movement are modulated by the mode of movement selection. Exp. Brain Res., 1995, 103: 429-439). One cortical area that is likely to be involved in this modulation is the supplementary motor area (SMA). Recent attempts to elucidate the neural generators of the readiness potential using spatiotemporal dipole source analysis, however, failed to establish a significant SMA contribution to the readiness potential. This might be explained by a failure of the proposed analyses to discriminate between SMA and motor cortex contributions to the readiness potential. We applied a dipole source analysis approach that better separates these overlapping source activities. The resulting source model includes an SMA source generating pre-movement activity consistent with evidence from intracranial recordings in humans. The SMA source accounts almost completely for the modulation of the readiness potential by different modes of movement selection. On the basis of these results, the relation between scalp-recorded movement-related activity, intracranially recorded potentials, and findings from functional imaging studies of voluntary movement, appears more transparent than suggested by previous dipole source analyses of premovement potentials.

Adult↗
PubMed1996

Executive functions and disease characteristics in Parkinson's disease.

In the present study, we investigated the association of two executive functions with disease characteristics in Parkinson's disease (PD), especially with severity of motor symptoms. We operationalized two executive functions, viz. fluency and cognitive shifting, each in a number of tests with heterogeneous materials, but with an identical format. We calculated the correlations between test performance and disease characteristics, including the factor scores of the Unified Parkinson's Disease Rating Scale (UPDRS). The results of this study show that only cognitive shifting was consistently associated with the severity of motor symptoms in PD, in particular with rigidity. None of the fluency tests had a significant association with severity of motor symptoms. The present study indicates that PD, as reflected by the severity of motor symptoms, is not associated with a general decrease in executive function. In spite of the fact that both are executive functions and both require generation of items, fluency and cognitive shifting are differentially related to PD.

Aging↗
PubMed1996

Memory performance under varying cueing conditions in patients with Parkinson's disease.

The present study is a continuation of a previous study in memory performance which showed that Parkinson's disease (PD) patients increasingly relied on explicit cues which prompt the external strategy of serial clustering, in comparison to control subjects (CS), who profited increasingly from implicit cues which prompt the internal and more effective strategy of semantic clustering. In this study, we investigated whether the recall of PD patients can be affected by adding or removing explicit cues. We manipulated the California Verbal Learning Test in two ways. First, we told the subjects under study in advance from which categories the items to be recalled were derived, thus making the implicit cue to cluster semantically explicit (explicit condition). Next, we permuted the sequence of the items in each trial, thus preventing the subjects from adhering to the serial order, i.e. to explicit cues (permuted condition). We included the data of our previous study (mixed condition) in the analysis of memory and learning performance in the three conditions. Learning of PD patients, as reflected in the semantic ratio, proved to be more affected by the cueing conditions than that of CS. Total performance and the serial ratios did not show a significant interaction between group and cueing condition. The results are discussed in terms of external and internal generation of problem-solving strategies.

Adult↗
PubMed1996

Movement preparation in Parkinson's disease. Time course and distribution of movement-related potentials in a movement precueing task.

Investigations of the effects of advance information on movement preparation in Parkinson's disease using reaction time (RT) measures have yielded contradictory results. In order to obtain direct information regarding the time course of movement preparation, we combined RT measurements in a movement precueing task with multi-channel recordings of movement-related potentials in the present study. Movements of the index and middle fingers of the left and right hand were either precued or not by advance information regarding the side (left or right hand) of the required response. Reaction times were slower for patients than for control subjects. Both groups benefited equally from informative precues, indicating that patients utilized the advance information as effectively as control subjects. Lateralization of the movement-preceding cerebral activity [i.e. the lateralized readiness potential (LRP)] confirmed that patients used the available partial information to prepare their responses and started this process no later than controls. In conjunction with EMG onset times, the LRP onset measures allowed for a fractionation of the RTs, which provided clues to the stages where the slowness of Parkinson's disease patients might arise. No definite abnormalities of temporal parameters were found, but differences in the distribution of the lateralized movement-preceding activity between patients and controls suggested differences in the cortical organization of movement preparation. Differences in amplitude of the contingent negative variation (CNV) and differences in the way in which the CNV was modulated by the information given by the precue pointed in the same direction. A difference in amplitude of the P300 between patients and controls suggested that preprogramming a response required more effort from patients than from control subjects.

Adult↗