Biomedical subjects
Publications and source records attributed to Wouter Hulstijn.
The oral administration of a single dose of levodopa (L-dopa) in 10 healthy human male subjects induced cognitive, not motor, changes during figure-copying tasks that were unrelated to the neuroendocrine and behavioural effects of levodopa. Results point to a decrease in alertness induced by levodopa.
RATIONALE: Action monitoring has been studied extensively by means of measuring the error-related negativity (ERN). The ERN is an event-related potential (ERP) elicited immediately after an erroneous response and is thought to originate in the anterior cingulate cortex (ACC). Although the ACC has a central role in the brain, only a few studies have been performed to investigate directly the effects of drugs on action monitoring. A recent theory argues that the mesencephalic dopamine system carries an error signal to the ACC, where it generates the ERN. METHODS: ERPs and behavioral measurements were obtained from 12 healthy volunteers performing an Eriksen Flankers task. On each of the 4 test days, the stimulant D-amphetamine, the sedative lorazepam, the antidepressant mirtazapine, or a placebo was orally administered in a double-blind, four-way crossover design. RESULTS: The indirect dopamine agonist amphetamine led to a strong enlargement of ERN amplitudes without affecting reaction times. Lorazepam and mirtazapine both showed slowing of responses, but only lorazepam led to reduced ERN amplitudes. CONCLUSIONS: Administration of amphetamine leads to stimulated action monitoring, reflected in increased ERN amplitudes. This result provides evidence for dopaminergic involvement in action monitoring and is in line with differences in ERN amplitude found in neuropsychiatric disorders also suggesting dopaminergic involvement. The different effects for lorazepam and mirtazapine are probably caused by the neurobiological characteristics of these two types of sedation. Action monitoring is suppressed after administration of lorazepam, because the GABAergic pathways directly inhibit ACC functioning, whereas the histaminergic pathways of mirtazapine do not innervate the ACC directly.
UNLABELLED: This study was designed to investigate if persons who stutter differ from persons who do not stutter in the coproduction of different types of consonant clusters, as measured in the number of dysfluencies and incorrect speech productions, in speech reaction times and in word durations. Based on the Gestural Phonology Model of Browman and Goldstein, two types of consonant clusters were formed: homorganic and heterorganic clusters, both intra-syllabic (CVCC) and inter-syllabic (CVC#CVC). Overall, the results indicated that homorganic clusters elicited more incorrect speech productions and longer reaction times than the heterorganic clusters, but there was no difference between the homorganic and the heterorganic clusters in the word duration data. Persons who stutter showed a higher percentage dysfluencies and a higher percentage incorrect speech productions than PWNS but there were no main group effects in reaction times and word durations. However, there was a significant three-way interaction effect between group, cluster type and cluster place: homorganic clusters elicited longer reaction times than heterorganic clusters, but only in the inter-syllabic condition and only for persons who stutter. These results suggest that the production of two consonants with the same place of articulation across a syllable boundary puts higher demands on motor planning and/or initiation than producing the same cluster at the end of a syllable, in particular for PWS. The findings are discussed in light of current theories on speech motor control in stuttering. EDUCATIONAL OBJECTIVES: The reader will be able to describe: (1) the effect of gestural overlap between consonant clusters on speech reaction time and word duration of people who do and do not stutter and be able to (2) identify the literature in the field of gestural overlap between consonant clusters.
Action monitoring has been studied in many tasks by means of measuring the error-related negativity (Ne/ERN), but never in a motor control task requiring precise force production. Errors in discrete choice reaction tasks are the result of incorrect selections, but errors in force production can also arise from incorrect executions. ERPs were obtained while participants produced low or high isometric forces with their left or right hand. As expected, incorrect choices of hand elicited an Ne/ERN. Interestingly, Ne/ERNs were also present in the less discrete selection error of an incorrect choice of force, but only when erroneously a low instead of a high force was chosen. In both force ranges, no Ne/ERNs were found after errors in execution. These errors showed a large positivity in feedback ERPs and, similar to correct responses, a prolonged negativity in response ERPs. We propose that, compared to selection errors, the time uncertainty aspects of execution errors and the resulting changing response representations prohibit error detection by the internal monitoring system responsible for generating the Ne/ERN.
The present study focuses on the ability of participants with spastic hemiparesis caused by cerebral palsy to adjust an ongoing movement. Typical symptoms associated with the disorder would lead one to expect that people with spastic hemiparesis would be unable to adjust their movements quickly and proportionally to a sudden change in the environment with their spastic arm. The results of the present experiment, however, prove otherwise. Eight hemiparetic adolescents with cerebral palsy and eight healthy control participants were asked to quickly hit a target projected onto a fronto-parallel screen. The target either remained stationary or started to move immediately after hand movement onset. Participants needed to adapt the ongoing movement to hit moving targets. The task was performed with the spastic and non-spastic arm by the hemiparetic participants and with the dominant arm by the healthy participants. Kinematic analyses showed that although the spastic arm of the hemiparetic participants displayed a significant increase in spatial variability which led to more errors, they were capable of successfully adapting their movement in a qualitative manner. The latency of the response to the change in target position was longer for the hemiparetic participants compared to the healthy control participants, but only 25 ms. Surprisingly, no between arm latency difference was found in the hemiparetic participants. Given the commonly observed movement deficits of the spastic arm, these results show that participants with spastic hemiparesis displayed a remarkable ability in adjusting movements quickly.
To explore whether underweight anorexia nervosa patients show psychomotor differences relative to normal controls, 32 female hospitalised patients, aged between 14 and 25 years, were compared with 32 healthy, normal weight controls, matched for sex, age and educational level. Using computerised analysis of writing and drawing behaviour, reaction times and movement times and their different components were analysed, while cognitive and motor demands were manipulated in five drawing and copying tasks. Anorexia nervosa patients were, compared to normal weight controls, significantly faster in a drawing task and showed shorter reaction times in copying tasks. Movement times did not differ significantly between the two groups. In the most complex copying task, a significant group x complexity interaction for reaction time (patients shorter) and reinspection time (patients longer) was found. Patients also made more errors than controls. The finding of a consistent pattern of shorter reaction times in underweight anorexia nervosa patients seems to run contrary to previous findings of disturbed cognitive functioning (i.e. impaired attention) in these patients. The differences seem to be related to cognitive factors more than to motor (executive) components.