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Biomedical subjects

S Hocherman

Publications and source records attributed to S Hocherman.

At least 19 recordsLinked to original sources
PubMed2006

Effect of ropinirole on visuo-motor test in newly diagnosed Parkinson's disease patients.

OBJECTIVES: The aim of this study was to assess the sensitivity of the visuo-motor test (VMT) compared with the Unified Parkinson's Disease Rating Scale (UPDRS) in newly diagnosed Parkinson's disease (PD) patients. METHODS: VMT and UPDRS were carried out in 20 patients before treatment onset, 2 weeks after treatment with ropinirole 1.5 mg/day and 2 weeks following increasing the dose of ropinirole to 3.0 mg/day. RESULTS: Improvement in clinical status was seen in all patients, with a mean UPDRS reduction of 16.6% following treatment with ropinirole 1.5 mg/day, and 38.9% reduction in UPDRS observed with ropinirole 3.0 mg/day. Initial improvement was not correlated with severity of PD, although further improvement with ropinirole 3.0 mg/day correlated linearly with patient's baseline UPDRS. Improvement in the ability to control the direction of the moving hand during tracing is expressed by the reduction of VMT variables following treatment. Mean VMT variables were 36.2% at baseline, 34.0% with ropinirole 1.5 mg/day and 31.7% with ropinirole 3.0 mg/day. Although changes in VMT variables were less uniform across patients, on average, it did correlate with patients UPDRS. CONCLUSIONS: We suggest that VMT can be useful in the assessment of treatment effect on high-level motor planning and cognitive capabilities in newly diagnosed PD patients, added to the UPDRS which does not appropriately comply with those skills.

Adult↗
PubMed2001

Accuracy of reproducing hand position when using active compared with passive movement.

BACKGROUND AND PURPOSE: Evaluating proprioception is relevant to physical rehabilitation because of its significance in motor control. One method of proprioceptive testing involves having subjects either imitate or point at a joint position or movement which was presented via a passive movement. However, as the muscle spindles are subject to central fusimotor control, the proprioceptive system may be better-tuned to movements created by active muscular contraction than to passive movements. The objective of the present study was to determine whether accuracy of reproducing hand position is dependent on whether proprioceptive input is obtained via an active or a passive movement. METHOD: Thirty-nine healthy volunteers (mean age (+/- SD) 24.6 (+/- 3.6) years) participated in the study. Subjects' right hands, which were obscured from view, were acoustically guided to five targets on a digitizer tablet with either an active or passive upper extremity movement. Subjects were then asked to reproduce the targets' location by either reaching to them with the unseen hand or by use of a laser beam. Distance from target and angular deviations were calculated in both absolute and relative terms. Repeated measures analysis of variance (ANOVA) was performed for each variable followed by predetermined contrasts. RESULTS: Comparison between the active and passive conditions when reconstruction of target location was guided kinaesthetically indicates significant differences in absolute distance, range and angular deviation. The comparison when reconstruction of target location was guided visually indicates significant differences in absolute distance, absolute angle and angular deviation. CONCLUSIONS: The ability to reproduce hand position accurately is enhanced when position is encoded by active upper extremity movement compared with passive movement. The results have implications for the design of strategies for evaluating as well as treating patients with impaired proprioception and limited movement.

Adult↗
PubMed2000

Improvement in cognition associated with novel antipsychotic drugs: a direct drug effect or reduction of EPS?

BACKGROUND: Administration of novel, versus classic, antipsychotic agents to patients suffering from psychosis is associated both with moderately better scores on cognitive tests, and with fewer extrapyramidal symptoms (EPS). Because improved motor functioning may enable better performance on some components of cognitive test batteries, and because the advantages of the novel antipsychotics on cognitive performance are not very large, it is sometimes difficult to discern if improvement in a given cognitive task is due to a direct effect of the novel antipsychotic drug, or is secondary to the novel drug's decreased propensity to induce EPS. In an attempt to distinguish between these two possibilities, the present study examined the ability of patients suffering from schizophrenia receiving classic, versus novel antipsychotics, to perform a computerized visuo-motor test (VMT). VMT assesses planning capabilities, attention and executive functions known to be impaired in schizophrenia, which are suggested to be affected by novel antipsychotics. METHODS: Seventy-six patients suffering from schizophrenia or schizophreniform disorder, receiving haloperidol (23 patients, mean dose 10.01+/-6.1mg/day), olanzapine (26 patients, mean dose 10.56 +/- 4.9 mg/day) or risperidone (27 patients, mean dose 4.35 +/- 1.7 mg/day) were assessed for EPS using the parkinsonian subscale of the Extrapyramidal Symptom Rating Subscale (ESRS), and with the VMT. RESULTS: Cognitive functioning as measured by the VMT was better for patients receiving risperidone or olanzapine, compared with those receiving haloperidol (F=6.636, df=2,67, P=0. 002), while the patients receiving haloperidol or risperidone suffered from more severe EPS compared with the patients receiving olanzapine (F=3.996, df=2,71, P=0.023). DISCUSSION: Although the patients receiving risperidone suffered from EPS similar in severity to the EPS of the patients receiving haloperidol, their performance on a task involving visuo-motor and attentional skills was similar to that of the patients receiving olanzapine. This finding implies that there is a dissociation between the antipsychotic drug's ability to affect cognitive functioning, and EPS. This dissociation indirectly suggests that the advantages offered by novel antipsychotics on cognitive performance are a direct effect, rather than being entirely mediated by improved movement abilities.

Adolescent↗
PubMed2000

The role of feedback in manual tracking of visual targets.

The role of visual feedback in manual tracking was investigated in 24 subjects who tracked 5-, 10-, and 40-mm/diameter targets, moving on a screen at 18 to 25 mm/sec., along various paths, by moving an unseen handle over a digitizing tablet. A cursor indicating instantaneous handle position was visible at all times on half the trials and hidden within a circle coaxial with the target but double its diameter in the other half. The handle had to be within the instantaneous target's digitizer-defined boundaries for the latter to keep moving. All tracking movements were segmented into small movement steps. A tendency to outrun the target was seen, indicating predictive control. Absence of visual feedback had negligible effect on movement velocity. Movement direction appeared to involve open-loop programming but improved significantly when subjects could see the cursor. Occasional corrective movements occurred only when visual feedback was given. Otherwise, a large positional error accumulates despite reasonable ability to control tracking direction.

Adult↗
PubMed1999

Visuomotor performance in patients with essential tremor.

Essential tremor (ET) is the most prevalent extrapyramidal disorder, yet its diagnosis is still controversial. This article introduces new findings that pertain to this diagnostic problem. Twenty-three patients with ET were studied. Patients with parkinsonism, cerebellar signs, severe head injury, or those under neuroleptic medication were excluded. Twenty-five normal subjects served as control subjects. Visuomotor tests involving tracking and tracing along three different paths with both the right and left hands, were used. Performance was assessed by measuring test duration, directional error, the proportion of the cumulative test time during which directional error exceeded half the maximal possible level (PT50%), the mean distance from the model path, the velocity of the hand movement, and the number of tracking interruptions. In 15 of 23 patients performance was the same as in the control subjects. These patients were defined as having a "simple condition" of ET (ETs). Considerable visuomotor impairment was found in eight patients who were regarded as having a "complex condition" of ET (ETc). Patients with ETc had significantly lower tracking speed, more tracking interruptions, longer test duration, greater directional error, greater PT50%, and greater distance from path than patients with ETs or control subjects. Most patients with ET appear to have normal visuomotor capabilities (ETs) but some display significant visuomotor disturbances (ETc). Considering the presence of similar impairments in patients with early Parkinson's disease and the increased prevalence of parkinsonism in patients with ET, it is possible that preclinical parkinsonism exists in patients with ETc. Further follow up of patients with ETc is necessary to verify this possibility.

Disease Progression↗
PubMed1998

Deprenyl monotherapy improves visuo-motor control in early parkinsonism.

Deprenyl is a potent MAO-B inhibitor which is commonly prescribed for treatment of parkinsonism. Despite prevalent use its effects on the symptoms and course of Parkinson's disease (PD) are still debated. The present study was therefore undertaken in order to measure quantitatively changes in visuo-motor control (VMC), consequent to deprenyl monotherapy in early PD. Previous work from our laboratory has shown typical VMC deterioration in PD patients, that correlates with disease severity. Thus, measurements of such changes provides a sensitive tool with which the symptomatic effects of drug treatment can be assessed quantitatively. Fourteen newly diagnosed, PD patients with light symptoms were studied. The VMC of all patients was tested after the first neurological examination, before drug treatment commenced. A second test was done after 30 days of treatment with deprenyl at a dose of 2.5 mg/day. Following this test, dosage was increased to 10 mg/day and a third VMC test was given after 30 more days of treatment. Our results show significant improvement in VMC functions following 30 days of 2.5 mg/day treatment and a continuing improvement after the next 30 days of 10 mg/day treatment. This improvement pertains mainly to directional control of self initiated movements and is smaller for movements that are guided externally. We conclude that deprenyl monotherapy has a clear symptomatic beneficial effect for patients with early PD.

Antiparkinson Agents↗
PubMed1998

Visuomotor control abnormalities in patients with unilateral parkinsonism.

Visuomotor performance is known to be disturbed in patients who have advanced Parkinson's disease (PD). The degree of impairment in the early stages of PD was investigated in both the symptomatic and asymptomatic hand of patients with unilateral disease. We examined the visuomotor performance of 10 early unilateral parkinsonian patients and 15 control subjects by using several tracing and tracking tasks that were performed with unseen hands, in which feedback was given through a screen cursor. Significant impairment in control of movement direction was found in tracing of screen paths but not in tracking. Significant slowing of movement was found in target tracking, whereas tracing velocity was normal. Although all patients were judged by standard clinical criteria to be unilaterally affected, visuomotor functions were found to be impaired equally in both hands. Visuomotor control of movement direction and movement velocity is performed independently. Performance along both control dimensions is impaired in the mild stages of parkinsonism, even before the appearance of motor symptoms.

Aged↗
PubMed1998

Visual and kinesthetic control of goal-directed movements to visually and kinesthetically presented targets.

The study investigated the contribution of kinesthetic and visual input to the performance of reaching movements and identified rules governing the transformation of information between these two sensory modalities. The study examined the accuracy by which 39 subjects reproduced locations of five targets in a horizontal plane. Mode of target presentation and feedback during reproduction of a target's location was either visual, kinesthetic or a combination of both modalities. Thus, it was possible to examine performance when target presentation and reproduction involved feedback from the same sensory modality (intramodal) as well as from different sensory modalities (intermodal). Errors in target reproduction were calculated in terms of distance and systematic biases in movement extent. The major findings of the study are (1) Intramodal reproduction of a target's location on the basis of kinesthetic feedback is somewhat less accurate than intramodal reproduction on the basis of visual feedback (2) Intermodal performance is significantly less accurate than intramodal performance. (3) Accuracy of performance does not depend on the direction of information transfer between sensory modalities. (4) Intermodal performance is characterized by systematic biases in extent of movement which are dependent on the direction of information transfer between modalities. (5) When presentation of the target's location is bimodal, reproduction is adversely affected by the conflicting input. The results suggest that transformation rules, used to combine input from various sensory modalities, depend on environmental conditions and attention.

Adult↗
PubMed1994

Two-dimensional tracing and tracking in patients with Parkinson's disease.

We investigated the execution of two-dimensional, visually guided hand movements in patients with Parkinson's disease (PD) and in control subjects. Testing involved moving an unseen handle along a straight line or a sinusoidal path over a horizontally placed digitizing tablet. The path was displayed on a computer screen together with a pointer that represented the handle's location. The size of all video displays corresponded, with a 1:1 ratio, to the actual movements. We used the following tests. (1) Tracing, in which each subject was asked to move the pointer over the entire path, from left to right, with no speed requirements. (2) Tracking along a displayed path: a small circle moved along the path at a speed of 4, 7, or 10 mm/sec. The subject was asked to maintain the pointer inside the circle throughout its movement. When missed, the circle stopped moving until the pointer was again brought inside it. (3) Tracking along an unseen path: same as (2), except that the path was not displayed. Analysis of movement accuracy and of movement kinematics revealed that the patient's ability to control the direction of hand movement was impaired and that this impairment was evident in tracing as well as in tracking, was greater for sinusoidal than for straight-movement paths, and was independent of movement speed.

Aged↗
PubMed1993

Proprioceptive guidance and motor planning of reaching movements to unseen targets.

The ability to make accurate reaching movements toward proprioceptively defined target locations was studied in seven normal subjects who were trained to reach to five different targets in a horizontal plane, with no vision of hand or target. The task consisted of moving a handle from a fixed origin to each target location, fast and accurately. Target locations were learned in training sessions that utilized acoustic cuing. Most movements were rapid, with a bell-shaped velocity profile. The error in target reproduction, which constituted the difference between the position consciously identified as the correct target location and the real target location, was calculated in each trial. This was compared with the error in preprogrammed reaching, which constituted the difference between the point in space where the initial fast movement toward the target ended and the target location. The absence of significant differences between these two error types indicated that the transformation from an internal representation of target location into a motor program for reaching to it did not introduce an additional reaching error. Learning of target locations was done only with the right hand, yet, reaching of both hands was tested. This allowed a comparison between the subjects' ability to utilize a transformed spatial code (reaching with the untrained hand) and their ability to use a direct sensory-motor code (reaching with the trained hand). While transformation of the spatial code was found to reduce it's accuracy, utilization of this code in motor programming again did not appear to introduce an additional error.

Adult↗
PubMed1993

Reaction and movement times in patients with hemiparesis for unilateral and bilateral elbow flexion.

BACKGROUND AND PURPOSE: This work was designed to study the effects of bilateral elbow flexion on the reaction and movement times of the impaired upper extremity of patients with hemiparesis. SUBJECTS: The subjects consisted of an experimental group of patients with hemiparesis (n = 25) and a control group of age-matched healthy volunteers (n = 26). METHODS: Each subject performed three sets of 16 elbow flexion trials. Two of these sets required unilateral movements, one for each upper extremity. The third set of movements required simultaneous elbow flexions of both upper extremities. In each trial, subjects were instructed to flex their elbows in response to an auditory signal from a supported initial position of 150 degrees through a goal orientation of 120 degrees. "Reaction time" was defined as the time between the auditory signal and movement initiation. "Movement time" was defined as the time between movement initiation and the completion of 30 degrees of elbow flexion. RESULTS: When subjects were asked to bilaterally flex their elbows, the reaction and movement times increased in both extremities. CONCLUSION AND DISCUSSION: It was speculated that in patients with hemiparesis, movement time of the nonparetic extremity in the bilateral task is limited by the rate of performance of the paretic extremity. The decrease in speed of these performance-determining variables in the bilateral task warrants consideration during physical therapy intervention for patients with hemiparesis.

Aged↗
PubMed1991

Effects of hand movement path on motor cortical activity in awake, behaving rhesus monkeys.

Neuronal activity was studied in the primary (M1), supplementary (M2), dorsal premotor (PMd), and ventral premotor (PMv) cortex of awake, behaving rhesus monkeys. The animals performed forelimb movements to three targets, each approached by three different types of trajectories. With one trajectory type, the monkey moved its hand straight to the target, with another, the path curved in a clockwise direction, and with a third, the path curved in a counter-clockwise direction. We examined whether neuronal activity in these areas exclusively reflects a hand movement's net distance and direction or, alternatively, whether other factors also influence cortical activity. It was found that neuronal activity during all phases of a trial reflects aspects of movement in addition to target location. Among these aspects may be selection of an integrated motor act from memory, perhaps specifying the entirety of a path by which the hand moves to a target.

Animals↗
PubMed1990

Neuronal activity in the medial geniculate nucleus and in the auditory cortex of the rhesus monkey reflects signal anticipation.

A Rhesus monkey was trained to discriminate between 2 acoustic signals, preceded by visual cues, that instructed which of 2 movements to make. In 75% of the trials the visual cue correctly indicated which of the 2 acoustic signals would follow. In 25% of the trials the visual cue was misleading, readying for the wrong acoustic signal. Based on the visual cue the monkey could anticipate which acoustic signal would be presented, a possibility confirmed by behavioural analysis. Movements conforming with the acoustic instruction signals were reinforced. The activity of 65 medial geniculate nucleus (MGN) and 107 primary auditory cortex (ACx) neurons was recorded during task performance. Significant response differences to anticipated vs unanticipated acoustic signals were found in 32% of the MGN and 27% of the ACx neurons. In both structures some of the affected neurons responded more vigorously to the correctly anticipated acoustic signals while others responded more vigorously to the unanticipated ones. An index of relative response intensity (RRI) was derived for each neuron by comparing its response to the sound signal in reinforced trials with that obtained in trials with no visual cues and no reinforcement (a 'blank' condition). For both MGN and ACx the analysis of RRIs revealed two anticipation-related effects. One consisted of response facilitation to anticipated sound signals together with suppression of responses to unanticipated sound signals. The other consisted of facilitation of responses to unanticipated sound signals, combined with base-line responsiveness to anticipated sounds. These effects can be interpreted to reflect a context-relevant trial by trial selection of neuronal channels which conduct information along the thalamocortical segment of the auditory system. The similarity between the effects of anticipation at the thalamic and the cortical levels suggests that the changes in excitability which underlay trial by trial neuronal selectivity occur subcortically.

Acoustic Stimulation↗
PubMed1989

Responses of ankle musculature of healthy subjects and hemiplegic patients to sinusoidal anterior-posterior movements of the base of support.

The responses of the medical gastrocnemius and tibialis anterior muscles to continuous sinusoidal perturbation of the base of support were studied in two groups of subjects, forty-two volunteers aged 20 to 84 years and 17 hemiplegic patients aged 52 to 81 years. EMGs were recorded while subjects stood on a platform oscillating in the anterior-posterior direction. Movement amplitude was adjusted to the maximum the subject could sustain without assisted support within the limits of the instrument. In healthy subjects, two basic activation modes were indicated: (a) a reciprocal contraction pattern in which activity of the medial gastrocnemius and tibialis anterior muscles was concentrated in the anterior and posterior half of the oscillation, respectively. This pattern prevailed in the younger subjects whose maximal movement amplitude reached the highest limit of the instrument; (b) a less discrete pattern, characterized by tonic contraction and periods of coactivation of the two muscles, was seen in older subjects who had difficulties in maintaining stance on the moving platform. The disruption of the discrete reciprocal response mode in this group of patients was related to decline in function of postural mechanisms with aging and demanded additional stiffening of the ankle join, presumably a manifestation of reduced automatism in favor of closer CNS modulation. The typical response mode in the sound leg of the hemiplegic patients was variable coactivation of the two muscles. In the afflicted leg, the establishment of a motor set was impaired: Low tone was associated with negligible muscular activity, although with more elevated tone, low level uniform cocontraction was evident.

Journal Article↗
PubMed1989

Electromyographic responses of distal ankle musculature of standing hemiplegic patients to continuous anterior-posterior perturbations during imposed weight transfer over the affected leg.

This study was undertaken to evaluate the influence of weight shift over the affected leg of standing hemiplegic patients on the electromyographic responses of the medial gastrocnemius and tibialis anterior muscles during continuous anterior-posterior movements of the base of support. Recordings were taken from 10 hemiplegic subjects and from 9 healthy subjects of comparable age. Each subject was first tested standing with both feet on a level surface and then with either leg (in healthy subjects) or the unaffected leg (in hemiplegic subjects) raised on a step. The second testing position caused unloading of the elevated leg and weight shift, that is, loading of the other leg. The measured variables were modulation of muscular activity, determined by a modulation index formulated for that purpose, and the relative amount of integrated electromyographic activity in each muscle. Changes in both variables in the uneven stance position as compared with even stance, occurred primarily in the unaffected (unloaded) leg in the hemiplegic subjects. These changes were comparable to changes in the unloaded leg of the healthy subjects. Thus, imposed loading on the affected leg of the hemiplegic subjects did not significantly improve either the reduced modulation or the relatively low IEMG activity of the investigated muscles. Further studies are required to evaluate the contribution of weight shift to recovery of postural responses in the affected leg of hemiplegic patients.

Ankle Joint↗
PubMed1988

Perception of the immediate extrapersonal space through proprioceptive inputs.

In the present work we sought to examine the idea that an internalized representation of space can be formed and used in the absence of visual information. To this end human subjects were trained to locate 5 points within a horizontal plane at shoulder level, under guidance of an acoustic signal. Next, reaching accuracy was determined for both the trained and the untrained hands without external cues. This allowed comparison of hand positioning that could be based upon a memory trace or proprioceptive inputs (trained hand) to hand positioning that must be based upon a more abstract internal representation than proprioceptive memory (untrained hand). The effect of training on reach accuracy of the two hands and the effect of prolongation the time interval between guided and recall (unguided) trials were studied. Finally, subjects were asked to interpolate between already learned target positions, a procedure which tested their ability to utilize an abstract construct of space. The relative contribution of the elbow and shoulder joints to reaching errors was determined. This analysis served to evaluate whether representation of spatial locations was based on joint angle coordinates, or on a more abstract extracorporeal reference system. Our results indicate that a memorized sensory image of the limb, which corresponds to the hand being at the target position, is used whenever possible. An abstract representation of position is used whenever comparison of the actual sensory input to a memorized sensory trace is made impossible, costing an approximately 25% reduction in accuracy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Postural responses of normal geriatric and hemiplegic patients to a continuing perturbation.

The electromyographic (EMG) activity of the gastrocnemius and tibialis anterior muscles was recorded from normal geriatric subjects and from hemiplegic patients subjected to a continuous back-and-forth movement of the platform on which they stood. The platform oscillated at a fixed frequency of 0.5 Hz. Movement amplitude was the largest each patient could withstand without support of the hands. Standing on the moving platform continued for 5 min. EMG recordings continued for 60 s, commencing 2 min after movement onset. Analysis of the EMG, in normal subjects revealed a typical pattern of reciprocal activity in the tibialis anterior and gastrocnemius, in synchrony with the back-and-forth movements of the platform. The cyclic activation of each muscle started before movement of the platform could cause its stretch. The normal movement-induced pattern of leg muscle activation was greatly disturbed or totally absent in hemiplegic patients. In such patients, various patterns of tonic activation of one or both muscles were observed in the sound as well as the afflicted leg. Occasional periodic activation of one muscle or the other was observed. However, such activation was not well synchronized with movement of the platform and did not last long. Based on the above observations, we concluded that the ability to adapt to a rhythmic platform movement by production of anticipatory phasic muscular contractions is severely disrupted in hemiplegics.

Aged↗