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Biomedical subjects

P B Vrtunski

Publications and source records attributed to P B Vrtunski.

17 recordsLinked to original sources
PubMed1998

Clozapine effects on force control in schizophrenic patients.

We previously reported significant differences in force control (FC) function between schizophrenics treated with typical antipsychotic drugs (APD) and those treated with clozapine. Clozapine treatment was associated with an attenuation of the capacity for fine motor control. We now report that a test-retest study with 41 treatment-refractory patients confirms our earlier finding; the FC deficit is due primarily to clozapine treatment. An additional comparison was made with 10 patients who were administered the FC test repeatedly through the initial clozapine titration interval of 6-8 weeks. The results suggest that two distinct clozapine effects can be distinguished, an initial transient stage characterized by 'drowsiness' and a subsequent stage with dose-dependent emerging myoclonic features.

Adult↗
PubMed1996

Effect of clozapine on motor function in schizophrenic patients.

It is well established that clozapine is less likely than typical antipsychotic drugs to cause clinically discernible extrapyramidal side-effects. There is a paucity of data, however, on clozapine's motor effects. In this report we compare normal controls to groups of chronic schizophrenic patients treated with either typical antipsychotic drugs or with clozapine. Motor function was measured with a target-matching task, a test relying on submaximal sustained force control. Results indicated that patients on clozapine performed with significantly lower accuracy (greater variability) of force control. Even though the clozapine patients were treatment resistant to typical antipsychotic drugs, and many had a history of tardive dyskinesia, we postulate that the observed deficit is likely due to clozapine treatment rather than to earlier treatments or other factors. The observed force control deficit may be the result of an increase in myoclonus and a generally lower level of overall motor activity.

Adult↗
PubMed1994

Motor mechanisms in schizophrenic patients with tardive dyskinesia.

A specific aspect of the motor output of patients with tardive dyskinesia was investigated with an experimental procedure referenced in force control function (i.e., the maintenance of sustained force output). We hypothesized that response output (button press) at a given level would be significantly altered when preceded by an output of a higher force than when preceded by an output of a lower force. The difference could be interpreted as a behavioral measure of fatigability and/or threshold change, and its quantitative aspects could serve as a marker of motor impairment. Three groups of subjects participated in the study: schizophrenic patients with tardive dyskinesia (TD), schizophrenic patients without tardive dyskinesia, and normal control subjects. The test used was a target-matching task with force output ranging from 5 to 560 cN. Three dependent measures were used: output force, steadiness of force maintenance, and latency of target capture. Results indicated that precedent output at the previous trial significantly altered force, but even better group separation was attained with the measure of steadiness. The TD schizophrenic group's performance was least efficient, the control group's was most efficient, and the non-TD schizophrenic group's performance was intermediate. The principal conclusions reached were that the target-matching response reflects mechanisms related to both fatigability and recruitment of motor units involved in output control.

Adult↗
PubMed1991

Isometric force control in schizophrenic patients with tardive dyskinesia.

Force control (FC) function, considered to be a constituent component of motor output, was investigated in psychiatric patients with dyskinetic impairments. Twenty-one patients with mild-to-moderate tardive dyskinesia were compared to 25 nondyskinetic patients on an FC test for both hands and oromandibular region. Results indicate that FC impairment is readily observed in dyskinetic subjects. The FC steadiness (i.e., the ability to maintain a sustained force output) in dyskinetic and control subjects was found to be inversely proportional to the amount of force generated. This method provides an objective, simple, and precise quantification of motor impairment along a force-defined continuum. It may be useful in studying tardive dyskinesia and the effects of neuroleptic medication on motor output control.

Adult↗
PubMed1989

Voluntary movement dysfunction in schizophrenics.

Several aspects of fine motor control were compared in schizophrenics and two control populations. The motor behavior analyzed was a button-press response in a forced choice paradigm. Three areas of abnormality were seen in schizophrenics: first, the interval preceding the motor response was characterized by reduced motor steadiness prior to the button-press response; second, the motor response was made with excessive force (hyperdynamia); and third, the agonist-antagonist synchrony (motor reversal) was impaired. Schizophrenics on and off neuroleptics did not differ on any measure of motor control, but schizophrenics with clinically observed tardive dyskinesia were found to have significantly less steadiness prior to the motor response than other schizophrenics.

Adult↗
PubMed1986

Abnormalities of fine motor control in schizophrenia.

Response time and fine motor control during a classification task were examined in schizophrenics and nonschizophrenics. The task involved decisions about either the sensory characteristics of auditory and visual stimuli or the referential meanings of spoken words and viewed pictures. Nonschizophrenics responded more quickly and exhibited a smoother and faster motor response on all tasks. Response time and motor control were influenced by stimulus modality and the complexity of the classification task in both groups. In the analysis of motor control, the schizophrenics differed from the nonschizophrenics in exhibiting a pattern suggestive of a specific difficulty with decisions involving referential meaning. The observed motor control dysfunction in schizophrenics is a psychomotor deficit similar to previously reported abnormalities in smooth pursuit eye movement. Further, the interaction of group and task variables in the motor response suggests that decisions about the abstract referential meaning of words and pictures produce greater cognitive loads in schizophrenics than in nonschizophrenics.

Adult↗
PubMed1985

Psychomotor decline can be described by discontinuities in response trajectories.

Force exerted in the isometric button-press response in a choice reaction time experiment was measured in order to study discontinuities in the response trajectory. Groups of young and elderly subjects were compared on performance with four choice reaction time tasks of varying difficulty. An additional comparison (with one task only) was made with a group of brain-damaged subjects. Velocity changes within the response trajectory were used to locate its discontinuities. The principal finding was that response discontinuities were least frequent in young subjects, intermediate in elderly, and most frequent in brain-damaged. Also, in the comparison of young and elderly across four stimulus conditions, the number of discontinuities was greater with more difficult than with easier tasks. Psychomotor decline was interpreted as an increase in the number of response discontinuities.

Adult↗
PubMed1984

Factor analysis of choice reaction time in young and elderly subjects.

To increase the utility of reaction time in applied research, we investigated the dynamic characteristics of the button-press response in four two-choice reaction-time tasks. 11 dependent variables were derived from the performance of two groups of normal young and elderly subjects. Factor analysis yielded five factors: baseline, premotor, motor, force, and release. The factors derived from each single stimulus condition were differentially sensitive in separating the two groups. Young and elderly subjects were most consistently differentiated by a release factor in each of the four stimulus conditions. This factor was interpreted as being relatively free of cognitive components and presumed to incorporate high psychomotor organization. The least efficient in differentiation was the baseline factor; it separated the young and elderly subjects in only one stimulus condition. Four factors from the test with visual-verbal stimuli separated the two age groups statistically, while only two factors did so in the test with auditory-verbal stimuli. The differences between stimulus conditions were interpreted as evidence of microbehavioral adjustments in response-performance dynamics and varying strategies used in handling the task demands.

Adult↗
PubMed1983

Microbehavioural analysis of the choice reaction time response in senile dementia.

Microbehavioural analysis of the human button-press response in a choice reaction time task enabled us to observe the traditional components of reaction time performance and also several additional indicators of psychomotor organization. The principal finding reported here is that in normal subjects stimulus conditions of varying difficulty differentially affect segments of the button-press response not ordinarily associated with cognitive demands of the task. This observation suggested the presence of a certain interaction between cognitive demands of the task and the subsequent motor output control. In a comparison of normal elderly and demented subjects, we demonstrated that the slower reaction times of the demented represent a virtual psychomotor disintegration. The apparent disintegration is interpreted as an inability of demented subjects properly to prepare, organize, and execute the response. The degree of disintegration is most evident during the motor time, which represents a transition between resting state and actual response completion.

Aged↗
PubMed1979

Evaluation of delayed auditory feedback (DAF) effect: comparison between subjective judgments and objective measures.

The effect of Delayed Auditory Feedback (DAF) on speech duration was evaluated subjectively and measured objectively in 30 subjects (10 normals, 10 nonfluent aphasics and 10 fluent aphasia). The average correlation coefficient between the subjective and objective data was .52 for 180 msec. delay and .46 for 360 msec. delay. Analysis of variance of data derived from the two methods showed the same highly significant differences among groups, delay and tasks. We conclude from these results that both objective and subjective procedures are equally useful in evaluating DAF effect on speech duration, and that both may also be valuable in assessing other types of behavior.

Aphasia↗
PubMed1978

Delayed auditory feedback and aphasia.

The effect of Delayed Auditory Feedback (DAF) was evaluated in three groups of subjects: 10 normal controls, 10 non-fluent aphasics, and 10 fluent aphasics. Speec production tasks consisted of (1) repeating sound and words; (2) naming objects; (3) producing sentences from given stimulus words; (4) answering questions; (5) reciting nursery rhymes; and (6) reading. Two delays were used, 180 and 360 msec. Two independent judges rated patients' responses for changes in intensity, duration, and quality of speech. Inter-judge reliability was considered satisfactory. Contrary to some previous reports, all subjects, including all the fluent aphasics, showed some DAF effect. Fluent aphasics, however, showed a significantly smaller DAF effect than non-fluent aphasics. Patient with conduction aphasia appeared to be the least impaired. Overall DAF effect was greater with 180 msec. than with 360 msec. The largest DAF effect occurred during answering question, followed by repeating, reading, nursery rhymes, sentence production, and naming, in that order. Repetition of a complex word produced a greater DAF effect than repetition of a simple sound. Finally, we found a differential effect of DAF on the three measures used in the study. We hypothesize that DAF effects result from changes in two separate monitoring systems. One systems is related to changes in the intensity of speech and does not appear to be affected by aphasia. The other is responsible for duration and qualitative changes in speech and is differentially affected in relation to pathology producing aphasia.

Adult↗
PubMed1977

Neuropsychological correlates of hypertension.

Twenty newly diagnosed, untreated hypertensive men (diastolic blood pressure greater than 105 mm Hg) and 20 normotensive controls were given a neuropsychological battery, including tests of generalized, more global functions (eg, reaction time and full-scale IQ) and of specific functions (eg, language and visual-spatial abilities) sensitive to focal damage. Tests of specific abilities yielded no differences between the two groups. In contrast, tests of general neuropsychological functioning revealed a deficit among hypertensives, who were significantly slower on the reaction time test and had a shorter span for digits in forward order. Results suggest that arterial hypertension is associated with impairment of vigilance and attention span. Future research will determine whether this impairment is associated with the diffuse pathological changes seen in the brain of hypertensive subjects, or with a more "functional" change (eg, reduced cerebral blood flow).

Attention↗
PubMed1976

Response to delayed auditory feedback in patients with hemispheric lesions.

The effect of delayed auditory feedback (DAF) on the performance of verbal and nonverbal tasks at two levels of difficulty by patients with left or right hemispheric lesions and non brain-damaged controls was compared. All subjects showed DAF effects, as measured by increases in response duration and intensity. While controls showed an increase in DAF effects as a function of increased task difficulty, the brain-damaged patients failed to show such an increase on tasks on which they were presumably impaired (verbal tasks for lefts, nonverbal for rights). Findings suggest a clear dissociation between DAF effects in unilateraly lesioned patients due to the nature of the stimulus material and its difficulty level.

Aphasia↗
PubMedDate not supplied

Information overload disrupts digit recall performance in schizophrenics.

The effect of auditory information overload on schizophrenics was examined by using a modified forward digit recall task. When memory capacity was exceeded, schizophrenics, but not controls, showed severe disruptions in performance on individual trials. Theories to account for the disruptions are discussed. A combination of factors, rather than simply limited information handling capacity, appears best able to account for the phenomenon. It is emphasized that further understanding of active cognitive process requires examination of trial by trial individual subject data.

Adult↗