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Biomedical subjects

R Iansek

Publications and source records attributed to R Iansek.

At least 37 records · Page 2Linked to original sources
PubMed1998

Abnormalities in the stride length-cadence relation in parkinsonian gait.

The purpose of this investigation was to clarify abnormalities in the stride length-cadence relation in gait hypokinesia in Parkinson's disease (PD). A second aim was to investigate the effect of levodopa medication on the foot-step pattern. In the first experiment, 20 subjects with idiopathic PD and 20 age-, sex-, and height-matched controls performed a series of 10 m walking trials at cadence rates ranging from 40 steps/min to 180 steps/min. Cadence rates were set by an electronic metronome, and gait patterns were measured by using a footswitch stride-analyzer system. By instructing subjects to concentrate on walking in time to the metronome beat, the baseline stride length could be monitored for a range of velocities with the compensatory effects of cadence removed. Linear-regression analysis revealed that the mean slope for the regression of stride length against cadence was not different from normal in PD, although there was a statistically significant difference in mean intercept between the PD group (0.25) and the control group (0.59); [t (19) = -4.76; p = 0.0001]. The second experiment evaluated the effects of levodopa on stride-length regulation in 10 subjects with idiopathic PD on average 45 min before and after the first morning dose was administered. There was a statistically significant increase in stride length for all cadence rates from premedication to postmedication phases and the maximal stride length was achieved at higher cadence rates after medication. The slope of the regression of stride length against cadence did not alter according to medication status, although the mean intercept was significantly lower before levodopa (-0.06) compared with after levodopa (0.27); [t (9) = -3.83; p = 0.004]. These results suggest that defective scaling of stride length underlies gait disturbance in PD.

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PubMed1998

Sequence heterogeneity in Parkinsonian speech.

Parkinson's disease (PD) is a neurodegenerative movement disorder primarily due to basal ganglia dysfunction. While much research has been conducted on Parkinsonian deficits in the traditional arena of musculoskeletal limb movement, research in other functional motor tasks is lacking. The present study examined articulation in PD with increasingly complex sequences of articulatory movement. Of interest was whether dysfunction would affect articulation in the same manner as in limb-movement impairment. In particular, since very similar (homogeneous) articulatory sequences (the tongue twister effect) are more difficult for healthy individuals to achieve than dissimilar (heterogeneous) gestures, while the reverse may apply for skeletal movements in PD, we asked which factor would dominate when PD patients articulated various grades of artificial tongue twisters: the influence of disease or a possible difference between the two motor systems. Execution was especially impaired when articulation involved a sequence of motor program heterogeneous in terms of place of articulation. The results are suggestive of a hypokinesic tendency in complex sequential articulatory movement as in limb movement. It appears that PD patients do show abnormalities in articulatory movement which are similar to those of the musculoskeletal system. The present study suggests that an underlying disease effect modulates movement impairment across different functional motor systems.

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PubMed1998

Bimanual co-ordination in Parkinson's disease.

The basal ganglia may be involved in bimanual co-ordination. Parkinson's disease (which impairs basal ganglia output) is clinically reported to cause difficulties in the performance of co-ordinated bimanual movements. Nevertheless, any bimanual co-ordination difficulties may be task specific, as experimental observations are equivocal. To infer the role of the basal ganglia in co-ordinating the two arms, this study investigated the bimanual co-ordination of patients with Parkinson's disease. Sixteen Parkinson's disease patients and matched control subjects performed a bimanual cranking task, at different speeds (1 and 2 Hz) and phase relationships. All subjects performed the required bimanual in-phase movement on a pair of cranks, at fast (2 Hz) and slow (1 Hz) speeds. However, the Parkinson's disease patients were unable to perform the asymmetrical anti-phase movement, in which rotation of the cranks differed by 180 degrees, at either speed; but instead reverted to the in-phase symmetrical movement. For Parkinson's disease patients, performance of the in-phase movement was more accurate and stable when an external timing cue was used; however, for anti-phase movement, the external cue accentuated the tendency for patients to revert to more symmetrical, in-phase movements.

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PubMed1998

Performance on clinical tests of balance in Parkinson's disease.

BACKGROUND AND PURPOSE: Due to the high incidence of falls in people with idiopathic Parkinson's disease (PD), the assessment of standing balance is a key component of physical therapist evaluation. This study investigated performance on clinical tests of standing balance in subjects with and without PD. SUBJECTS: The subjects were 10 persons with PD who had a history of falls (age range = 60-80 years), 10 persons with PD who had no history of falls (age range = 63-79 years), and 10 persons with no known neurological impairment (age range = 60-78 years) who served as a comparison group. METHODS: Subjects were tested on their ability to maintain stability in 3 conditions: (1) steady standing (feet apart, feet together, tandem stance, step stance, and single-limb stance), (2) in response to perturbations generated by self-initiated movements (arm raise, functional reach, bend-reach, and step tests), and (3) in response to an external perturbation to upright stance (shoulder tug). Balance was measured at peak dosage in the levodopa medication cycle (in the morning) and 7 days later. RESULTS: The mean Hoehn and Yahr Disability Scale score was 3.0 for the fallers with PD and 2.5 for the nonfallers with PD. Performance on the tandem stance, single-limb stance, functional reach, and shoulder tug tests demonstrated differences between the subjects with PD and the comparison group and between the fallers and nonfallers with PD. The results of these tests were highly repeatable over 7 days (ICC = .61-.94). CONCLUSION AND DISCUSSION: Although there was a small sample size, performance was highly consistent across 7 days when testing occurred during peak dosage of levodopa. A small battery of tests were sensitive enough to discriminate between people with PD who fall and those with no history of falls.

Accidental Falls↗
PubMed1998

Provision of external cues and movement sequencing in Parkinson's disease.

The basal ganglia (BG) may play a part in motor sequencing. Individuals with Parkinson's disease (PD) may exhibit progressive slowing (sequence effect) during motor sequences such as writing (micrographia) and gait. In the present study, a serial two-way choice reaction time (CRT) task was employed, in which advance information about each next movement was not provided until the participant began moving, thereby assessing the participant's ability to utilize advance information. Participants were 13 individuals with idiopathic PD and 13 age-matched controls. Both PD subjects and controls showed a significant sequence effect in the absence of advance information, possibly reflecting difficulty in initiating and maintaining movement without external cues. PD subjects and controls both exhibited a sequence effect at moderate levels of advance information. At high levels of advance information, PD subjects showed the effect but controls did not, suggesting that controls, unlike PD subjects, were able to use the extra information to facilitate performance, perhaps reflecting more frontal aspects of impairment in PD.

Adult↗
PubMed1997

Movement-related potentials in Parkinson's disease. Motor imagery and movement preparation.

Movement-related potentials (MRPs) associated with voluntary movements reflect cortical activity associated with processes of movement preparation and movement execution. Early-stage pre-movement activity is reduced in amplitude in Parkinson's disease. However, it is unclear whether this neurophysiological deficit relates to preparatory or execution-related activity, since previous studies have not been able to separate different functional components of MRPs. Motor imagery is thought to involve mainly processes of movement preparation, with reduced involvement of end-stage movement execution-related processes. Therefore, MRP components relating to movement preparation and execution may be examined separately by comparing MRPs associated with imagined and actual movements. In this study, MRPs were recorded from 14 subjects with Parkinson's disease and 10 age-matched control subjects while they performed a sequential button-pressing task, and while they imagined performance of the same task. Early-stage pre-movement activity was present in both Parkinson's disease patients and control subjects when they imagined movement, but was reduced in amplitude compared with that for actual movement. Movement execution-related components, arising predominantly from the primary motor cortex, were relatively unaffected in Parkinson's disease subjects. However, motor preparatory processes, probably involving the supplementary motor area, were reduced in amplitude overall and abnormally prolonged, indicating impaired termination following the motor response. Further, this impaired termination of preparatory-phase activity was observed only in patients with more severe parkinsonian symptoms, and not in early-stage Parkinson's disease.

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PubMed1996

Movement-related potentials associated with movement preparation and motor imagery.

Movement-related potentials (MRPs), reflecting cortical activity associated with voluntary movement, typically show a slowly increasing negative potential beginning between 1 and 2 s prior to movement, which most likely reflects motor preparatory processes. Studies of regional cerebral blood flow implicate the supplementary motor area in such preparatory processes; however, the contribution of the supplementary motor area to premovement activity observed in MRPs is debated. It is possible to examine MRPs relating to movement preparation alone, in the absence of movement execution, by recording MRPs associated with imagined movements. In this study, MRPs were recorded from 11 healthy control subjects while performing a sequential button-pressing task in response to external cues, and while imaging performance of the same task in response to the same cues. The early component of MRPs was found not to differ in amplitude, onset time, or topography when performing compared with imagining movement, indicating that both movement execution and motor imagery involve similar pre-movement preparatory processes generated in the same cortical area-most likely the supplementary motor area. It is therefore concluded that the early component of the MRP reflects activity arising pre-dominantly from the supplementary motor area and is associated with pre-movement motor preparatory processes which occur relatively independently of actual movement execution.

Adult↗
PubMed1996

Bradykinesia and movement precision in Huntington's disease.

To determine whether bradykinesia in patients with Huntington's disease (HD) reflects impaired force production or an increased requirement for terminal visual guidance, 11 HD patients and matched controls performed drawing movements with varying precision requirements. Participants used an electronic pen upon a WACOM SD420 graphics tablet to join targets of either 10 or 20 mm diameter which were separated by a distance of 62.5 or 125 mm. While HD patients had slower movements, exhibiting more cycles of acceleration and deceleration, patients were not disproportionately affected by variations in target size or separation. Bradykinesia did not seem to be a product of impaired force production or increased reliance upon terminal visual guidance, since neither accelerative or decelerative phases were specifically affected by HD. However, movements of HD patients were of less consistent duration, implying variability associated with internal cues regulating movement.

Adult↗
PubMed1996

Simon effect and attention in Parkinson's disease: a comparison with Huntington's disease and Tourette's syndrome.

Patients with hyperkinetic basal-ganglia disorders (Huntington's disease, HD; and Tourette's syndrome, TS) have difficulty with spatially incongruent stimulus-response configurations, the Simon effect, and with inhibiting inappropriate responses in a conditionality paradigm. However Parkinson's disease (PD) patients with hypokinetic basal-ganglia disorder show normal (for their age) conditionality and congruency effects, probably because the task is extremely sensitive to aging and PD patients are typically older than HD and TS individuals. Overall, HD patients were by far the most affected, reflecting the likely greater involvement of the caudate (with its predominantly cognitive role) than the putamen; the latter structure, with a predominantly motor involvement, is the more affected in PD.

Aged↗
PubMed1996

Stride length regulation in Parkinson's disease. Normalization strategies and underlying mechanisms.

Results of our previous studies have shown that the slow, shuffling gait of Parkinson's disease patients is due to an inability to generate appropriate stride length and that cadence control is intact and is used as a compensatory mechanism. The reason for the reduced stride length is unclear, although deficient internal cue production or inadequate contribution to cortical motor set by the basal ganglia are two possible explanations. In this study we have examined the latter possibility by comparing the long-lasting effects of visual cues in improving stride length with that of attentional strategies. Computerized stride analysis was used to measure the spatial (distance) and temporal (timing) parameters of the walking pattern in a total of 54 subjects in three separate studies. In each study Parkinson's disease subjects were trained for 20 min by repeated 10 m walks set at control stride length (determined from control subjects matched for age, sex and height), using either visual floor markers or a mental picture of the appropriate stride size. Following training, the gait patterns were monitored (i) every 15 min for 2 h; (ii) whilst interspersing secondary tasks of increasing levels of complexity; (iii) covertly, when subjects were unaware that measurement was taking place. The results demonstrated that training with both visual cues and attentional strategies could maintain normal gait for the maximum recording time of 2 h. Secondary tasks reduced stride length towards baseline values as did covert monitoring. The findings confirm that the ability to generate a normal stepping pattern is not lost in Parkinson's disease and that gait hypokinesia reflects a difficulty in activating the motor control system. Normal stride length can be elicited in Parkinson's disease using attentional strategies and visual cues. Both strategies appear to share the same mechanism of focusing attention on the stride length. The effect of attention appears to require constant vigilance to prevent reverting to more automatic control mechanisms.

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PubMed1996

Effects of magnetic stimulation over supplementary motor area on movement in Parkinson's disease.

Movement execution can be delayed by transcranial magnetic stimulation delivered over primary motor cortical areas, resulting in transient inhibition of cortico-motor output. Inhibition or disruption of higher-order motor planning and preparatory processes, such as are thought to occur in the supplementary motor area (SMA), would allow an examination of processes at other stages of the motor control system. In this study, six subjects with Parkinson's disease and six healthy control subjects performed a non-cued sequential finger movement task. At various times relative to movement, high-intensity single-pulse magnetic stimulation was delivered over the region of the SMA, with minimal current spread to primary motor areas. When magnetic stimulation was given at early stages during the movement for parkinsonian subjects, movement times were significantly increased, indicating disrupted movements. Supplementary motor area stimulation had no effect when delivered during later stages of the movement or immediately prior to movement onset, and had no apparent effect on control subjects at any time. It is therefore suggested that the SMA is important in motor planning and preparatory processes, since SMA stimulation has no effect on movements in their later stages when planning may be complete, but may disrupt movements in their early stages, when preparation for later stages may still be in progress. Further, possible instability of motor planning/preparation processes in Parkinson's disease is suggested, since these processes appeared more susceptible to disruption by magnetic stimulation in parkinsonian subjects than controls.

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PubMed1996

Temporal stability of gait in Parkinson's disease.

BACKGROUND AND PURPOSE. Evaluation of physical therapy for gait disorders in patients with Parkinson's disease (PD) requires an under-standing of how the patients' medication cycle affects function. Four experiments were conducted to investigate stability of gait variables. METHODS AND RESULTS. In experiment 1, 15 subjects with idiopathic PD and 15 subjects without PD performed two sets of gait trials spaced 30 minutes apart, with the initial trial conducted with the subjects at a peak dose of medication. Strong correlations, as determined by intraclass correlation coefficients (ICC[2,1]), occurred between repeat measures of speed (ICC = .92), cadence (ICC = .92), stride length (ICC = .94), and time spent in double support (DS) (ICC = .93). In experiment 2, 16 subjects with PD were tested at the same time on two consecutive days. There was good repeatability for speed (ICC = .88), cadence (ICC = .85), stride length (ICC = .84), and DS (ICC = .80). When we assessed the repeatability of measurements taken at peak dose and at end of dose, there were low correlations for speed (ICC = -.54), cadence (ICC = -.07), stride length (ICC = -.35), and DS (ICC = -.38). In a final experiment on 16 subjects with PD, we used time-series analysis to examine the stability of measurements taken every 15 minutes for 2 1/2 hours. Slopes of regression models, standard deviations, and residual autocorrelations were negligible, indicating that the measurements were stable. CONCLUSION AND DISCUSSION. The parkinsonian gait pattern is reproducible across either brief time intervals or 24 hours when peak medication prevails. At the end of dose, however, marked changes in gait occur, apparently related to depletion of medication.

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PubMed1995

Impaired movement sequencing in patients with Huntington's disease: a kinematic analysis.

This experiment asked whether Huntington's disease, like Parkinson's disease, another disorder of the basal ganglia, causes a specific progressive deficit in the performance of sequential movement. Ten patients with Huntington's disease and their age-matched controls wrote the lower-case letter "l" four times in a linked cursive script, upon a graphics tablet which sampled pen position at 200 Hz. Kinematic features of sequential movement (stroke length, stroke duration, peak velocity, time to peak velocity and time from peak to zero velocity) were examined in a Group by Stroke Position (2 x 8) design, to identify which aspects of movement might show progressive disturbances. Unlike Agostino et al. [Brain 115, 1481-1495, 1992], this experiment did in fact find progressive changes in the performance of sequential movements. Kinematic analysis indicated a progressive increase in movement duration during sequential movement, that was associated with the accelerative phase of movement.

Adult↗
PubMed1995

Contingent and non-contingent auditory cueing in Parkinson's disease.

Parkinson's disease (PD) patients and their normal controls performed two experiments involving a sequential movement task, depressing a series of buttons at choice points along a response board. Visual or auditory cues were presented prior to each move according to various contingencies. PD, a disorder characterised by degeneration of the basal ganglia (BG), typically manifests with poor execution of motor sequences. We found that external cueing facilitated motor sequencing in PD patients. In particular, auditory cues which occurred late in the movement cycle maximally facilitated switching between subcomponents of a sequence. Based on physiological findings reported in the primate literature [Brotchie et al., Brain 114, 1685-1702, 1978; Schultz and Romo, Exp. Brain Res. 1, 363-384, 1992], it is suggested that external cues enhance performance by replacing defective, internally generated cues (discharges) of the BG. This has implications for the use of physical training strategies in the treatment of PD.

Acoustic Stimulation↗
PubMed1995

Movement-related potentials in Parkinson's disease. Presence and predictability of temporal and spatial cues.

Activity of the supplementary motor area may be inferred from movement-related potentials (MRPs) which are associated with the preparation and execution of voluntary, or internally determined movements. Supplementary motor area activity may be abnormal in Parkinson's disease since its major input from the basal ganglia is disrupted. Investigation of the abnormalities in supplementary motor area activity associated with movement deficits in Parkinson's disease may therefore reveal functions of the basal ganglia and the supplementary motor area. Movement-related potentials associated with sequential movements were investigated under various cueing conditions in Parkinson's disease subjects and age-matched controls. In controls, MRPs revealed involvement of the supplementary motor area in movements which can be internally determined (non-cued and externally cued, predictable movements, but not unpredictable movements). In Parkinson's disease, however, the supplementary motor area was only involved in movements which must be internally determined (non-cued movements, but not externally cued movements); therefore impaired internal control mechanisms, operating via the supplementary motor area, are bypassed when external cues are given. As a result, Parkinson's disease patients are more reliant on external cues and are unable to use predictive models to internally guide movement. Supplementary motor area involvement also relied on the predictability (in controls) or presence (in Parkinson's disease) of timing cues and not spatial cues, indicating a role of the supplementary motor area and basal ganglia in the temporal organizations of sequential movement rather than the programming of specific movements. For non-cued movements, abnormalities in MRPs for Parkinson's disease subjects consisted of delayed MRP onset and peak times, and prolonged cortical activity following movement. These observations led to a proposed model of the interaction between the basal ganglia and the supplementary motor area, involving the temporal organization of voluntary and internally determined sequential movements.

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