Biomedical subjects

P S Pohl

Publications and source records attributed to P S Pohl.

11 recordsLinked to original sources

PubMed2006

Implicit learning of a motor skill after mild and moderate stroke.

OBJECTIVE: To determine if adults in the subacute phase post moderate or mild stroke could learn a motor task under implicit practice conditions. DESIGN: Non-randomized, between-group design. SETTING: Subjects' homes. SUBJECTS: Sample of convenience of 15 adults with moderate stroke, 22 adults with mild stroke, and 32 age-matched controls. Stroke severity was determined using the Orpington Prognostic Scale. INTERVENTION: Practice of movements to target switches in two conditions, a repeated series and a random series. Practice was organized into a single session of six blocks of 80 trials such that blocks 1 and 2 were the random series, blocks 3 and 4 the repeated series, block 5 the random series, and block 6 the repeated series. Explicit knowledge of the two conditions was not provided. MAIN MEASURES: The mean response time and the coefficient of variation were calculated for each block for each group. RESULTS: Regardless of group, participants had a slower response time when practice was unexpectedly switched from the repeated to random condition. The response time and coefficient of variation for those with moderate stroke were persistently greater than those with mild stroke and controls, who were not different from each other. CONCLUSIONS: Implicit motor learning is preserved in adults with moderate stroke and may be a viable strategy for teaching motor skills in rehabilitation. The clinician should be aware that subjects with moderate stroke, even when performing with the less affected upper extremity, have significantly slower and more variable movements than those with mild stroke and controls.

Aged↗

PubMed2001

Implicit learning of a perceptual-motor skill after stroke.

BACKGROUND AND PURPOSE: A motor skill can be learned implicitly, without awareness of what is being learned. The purpose of this study was to examine the ability of adults who had unilateral stroke to learn implicitly a perceptual-motor task. SUBJECTS: Subjects were 47 people who were poststroke and 36 control subjects. METHODS: Participants performed sequences of hand movements in response to target lights in 2 conditions: a patterned sequence and a random sequence. Participants were not given explicit knowledge of the presence of the 2 conditions. Those who had stroke performed with the upper-extremity ipsilateral to the lesion. RESULTS: Subjects who had stroke performed more slowly than control subjects. For both groups, times decreased with practice of the patterned sequence, increased with introduction of the random sequence, and decreased again with reintroduction of the patterned sequence. Group differences persisted in a retention test given the next day of the patterned sequence, and both groups showed decreased times over the course of the retention test. DISCUSSION AND CONCLUSION: People with stroke are able to learn a perceptual-motor task even without explicit instructions regarding the patterned sequence embedded in the task.

Analysis of Variance↗

PubMed2000

Impaired direction and extent specification of aimed arm movements in humans with stroke-related brain damage.

The role of sensorimotor (S-M) areas in the specification of kinematic parameters for aiming movements was studied by comparing the performance of six subjects with unilateral stroke to that of matched control subjects. Rapid arm movements were made to one of four targets by rotating the forearm in a short (20 degrees) or long (45 degrees) arc of motion. Thus, the four targets represented two directions (flexion or extension) and two extents (short or long). Subjects with stroke used the arm ipsilateral to the side of the lesion. A timed-response paradigm was used to dissociate response initiation and specification. Subjects initiated movements in concert with the last of four regularly timed tones. A visual cue of the designated target was presented during the preparation interval (400-0 ms) before the last tone. Targets were presented in a fixed sequence (predictable condition) or a random sequence (unpredictable condition). No significant differences in performance were found between stroke and control groups in the predictable condition. In the unpredictable condition, subjects with stroke produced more direction errors and were less accurate in extent than the control subjects. As specification time increased to 400 ms, the frequency of direction errors attenuated less for stroke than for control groups, but the reduction in magnitude of extent errors was similar for the two groups. When specification was minimal (i.e., <100 ms), default responses were distributed equally between directions and clustered around the short extent. Further, wrong direction responses did not converge on the designated extent as specification time increased. This pattern of findings is consistent with a view of parameterization of planning and executing movements, in which direction and extent can be specified in parallel. Our results suggest that ipsilateral S-M areas contribute to the specification of an optimal motor program, particularly when imperative programming of unimanual goal-directed aiming movements is required.

Acoustic Stimulation↗

PubMed2000

Upper extremity control in adults post stroke with mild residual impairment.

Motor control deficits in the upper extremity (UE) ipsilateral to the side of brain damage persist after stroke, but it is not known if the presence of these deficits is related to impairment of the contralateral UE. The purpose of this study was to investigate whether motor deficits are present in the ipsilateral UE when contralateral UE impairment is mild in adults with chronic stroke. Right-handed adults (10 controls, 10 right stroke, 10 left stroke) performed rapid continuous aiming movements to small and large targets. Using kinematic analysis, temporal measures of the movement were defined, including movement time (MT) and the three components of MT: acceleration, deceleration, and dwell time (i.e., time on target). Participants with right stroke had prolonged MT only with the left UE, primarily due to longer dwell times. Participants with left stroke had prolonged MT with both UEs as a result of longer dwell times. The results indicate that control deficits of the ipsilateral UE are evident in individuals with left but not right brain damage who have minimal impairment of the contralateral UE. These findings are consistent with the role of the left hemisphere in the control of both UEs.

Aged↗

PubMed2000

Reliability of lower extremity isokinetic strength testing in adults with stroke.

OBJECTIVE: To evaluate the reliability of isokinetic strength testing of knee flexion and extension at 60 degrees per second, and ankle plantar flexion and dorsiflexion at 30 degrees per second in adults with stroke. DESIGN: Test-retest using intraclass correlation coefficients (ICC). SETTING: Human performance laboratory. SUBJECTS: Ten adults post stroke with a mean age of 64 years (five males) and 10 adults without neurological injury with a mean age of 69 years (three males) who served as controls. MAIN OUTCOME MEASURES: Peak torque and average torque. RESULTS: The reliability of strength of the less-affected lower extremity was high with values ranging from 0.75 to 0.97. Knee extension, ankle plantar flexion and the peak torque of dorsiflexion were reliable for the affected limb, ranging from 0.80 to 0.90. In contrast, affected knee flexion was not reliable with values of 0.48 and 0.44 for peak torque and average peak torque respectively. CONCLUSIONS: Isokinetic knee and ankle strength of the less-affected limb are reliable. Isokinetic strength of the affected lower extremity is also reliable with the noted exception of knee flexion.

Aged↗

PubMed1999

Practice effects on the less-affected upper extremity after stroke.

OBJECTIVE: To test the hypotheses that (1) adults who have had a stroke, using the less affected upper extremity (UE), improve performance of an aiming task with practice, and (2) compared with control subjects, stroke patients show less improvement in a complex condition. DESIGN: Movement time (MT) and kinematic data were collected over practice. Comparisons were made between the less-affected UE of stroke patients and the same hand of controls. SETTING: A human performance laboratory. PARTICIPANTS: A matched sample of right-handed adults, 10 with unilateral stroke and 10 nondisabled controls. INTERVENTION: Practice of an aiming task in an easy and complex condition as defined by target width and distance between two targets. MAIN OUTCOME MEASURES: MT, peak velocity, and temporal phases of the trajectory. RESULTS: Adults who had experienced a stroke had persistently longer MTs than control subjects; however, all participants achieved faster MTs with practice in both conditions. The absolute amount of time in each temporal phase decreased without a change in the relative times. Peak velocity increased only in the easy condition. CONCLUSIONS: Adults with stroke damage can improve motor performance of the less-affected UE with practice. Further study is needed to see if practice effects are permanent and generalizable.

Cerebrovascular Disorders↗

PubMed1997

Motor task difficulty and brain activity: investigation of goal-directed reciprocal aiming using positron emission tomography.

Differences in the kinematics and pattern of relative regional cerebral blood flow (rCBF) during goal-directed arm aiming were investigated with the use of a Fitts continuous aiming paradigm with three difficulty conditions (index of difficulty, ID) and two aiming types (transport vs. targeting) in six healthy right-handed young participants with the use of video-based movement trajectory analysis and positron emission tomography. Movement time and kinematic characteristics were analyzed together with the magnitude of cerebral blood flow to identify areas of brain activity proportionate to task and movement variables. Significant differences in rCBF between task conditions were determined by analysis of variance with planned comparisons of means with the use of group mean weighted linear contrasts. Data were first analyzed for the group. Then individual subject differences for the movement versus no movement and task difficulty comparisons were related to each individual subjects' anatomy by magnetic resonance imaging. Significant differences in rCBF during reciprocal aiming compared with no-movement conditions were found in a mosaic of well-known cortical and subcortical areas associated with the planning and execution of goal-directed movements. These included cortical areas in the left sensorimotor, dorsal premotor, and ventral premotor cortices, caudal supplementary motor area (SMA) proper, and parietal cortex, and subcortical areas in the left putamen, globus pallidus, red nucleus, thalamus, and anterior cerebellum. As aiming task difficulty (ID) increased, rCBF increased in areas associated with the planning of more complex movements requiring greater visuomotor processing. These included bilateral occipital, left inferior parietal, and left dorsal cingulate cortices--caudal SMA proper and right dorsal premotor area. These same areas showed significant increases or decreases, respectively, when contrast means were compared with the use of movement time or relative acceleration time, respectively, as the weighting factor. Analysis of individual subject differences revealed a correspondence between the spatial extent of rCBF changes as a function of task ID and the individuals' movement times. As task ID decreased, significant increases in rCBF were evident in the right anterior cerebellum, left middle occipital gyrus, and right ventral premotor area. Functionally, these areas are associated with aiming conditions in which the motor execution demands are high (i.e., coordination of rapid reversals) and precise trajectory planning is minimal. These same areas showed significant increases or decreases, respectively, when contrast means were compared with the use of movement time or relative acceleration time, respectively, as the weighting factor. A functional dissociation resulted from the weighted linear contrasts between larger (limb transport) or smaller (endpoint targeting) type amplitude/target width aiming conditions. Areas with significantly greater rCBF for targeting were the left motor cortex, left intraparietal sulcus, and left caudate. In contrast, those areas with greater rCBF associated with limb transport included bilateral occipital lingual gyri and the right anterior cerebellum. Various theoretical explanations for the speed/accuracy tradeoffs of rapid aiming movements have been proposed since the original information theory hypothesis of Fitts. This is the first report to relate the predictable variations in motor control under changing task constraints with the functional anatomy of these rapid goal-directed aiming movements. Differences in unimanual aiming task difficulty lead to dissociable activation of cortical-subcortical networks. Further, these data suggest that when more precise targeting is required, independent of task difficulty, a cortical-subcortical loop composed of the contralateral motor cortex, intraparietal sulcus, and caudate is activated. This is consistent with the role of motor cortex

Adult↗

PubMed1996

The locus of age-related movement slowing: sensory processing in continuous goal-directed aiming.

Prolonged movement times in elderly persons have been well documented; however, the locus of this slowing is uncertain. Kinematic analysis of discrete aiming has revealed deficits primarily in the target approach phase, suggesting inefficient feedback processing. This study investigated age-related movement slowing in a continuous aiming task, for which movements are mediated by feedforward and on-line sensory processes. Two-dimensional video-recordings were made of young and elderly adults performing reciprocal tapping using the right and left hands under three different accuracy conditions. The elderly subjects exhibited more discrete adjustments in the trajectories coupled with longer times in this period. Further, the elderly spent more time reversing direction between target hits, especially in the high accuracy condition. Longer time on target was seen in the left-hand performance of the elderly. Results suggest that the locus of age-related slowing in the performance of continuous aiming may reflect a greater dependence on slower feedback processes instead of rapid, on-line, and feedforward sensory processes. Age-related differences in hand performance may provide further insight into central processing deficits.

Adult↗

PubMed1996

Learning a partial-weight-bearing skill: effectiveness of two forms of feedback.

BACKGROUND AND PURPOSE: Partial weight bearing (PWB) is a skill commonly taught by physical therapists. This study compared the effects of practice with either augmented feedback provided during the task (concurrent feedback) or augmented feedback provided after the task (postresponse feedback) for the learning of PWB with crutches. SUBJECTS: Sixty young adults without known impairment of the neuromusculoskeletal system volunteered for the study. METHODS: Subjects practiced supporting 30% of body weight while stepping onto a floor scale. Augmented feedback was provided during each trial for the concurrent feedback group and either following each trial or after every five trials for the postresponse feedback groups. Subjects returned 2 days later for a no-feedback retention test. RESULTS: During practice, the concurrent feedback group was more accurate and consistent than either of the postresponse feedback groups. During retention, however, the postresponse feedback groups were the most accurate; all groups were equally consistent during retention. CONCLUSION AND DISCUSSION: These results suggest that practice with concurrent feedback is beneficial for the immediate performance but not for the learning of this sensorimotor skill.

Adult↗

PubMed1995

Effects of unilateral brain damage on the control of goal-directed hand movements.

Insight into the functional neural substrates associated with the control of goal-directed purposive movements can be obtained through the study of the performance of individuals with brain damage. The control of rapid reciprocal aiming was investigated by comparing ipsilateral limb performance of subjects with unilateral brain damage to that of controls performing with the same limb. Thirty right-hand-dominant individuals, ten with right hemisphere stroke, ten with left hemisphere stroke, and ten age-matched controls performed unconstrained alternating tapping movements under three conditions of task complexity. The path of the stylus was recorded by video using two-dimensional kinematic techniques. Key kinematic features of the vertical and horizontal components of the trajectories were analyzed using both quantitative and qualitative methods. All subjects with brain damage showed prolonged movement times; however, the locus of the slowing depended on lesion side. Specifically, subjects with left stroke showed deficits in the open-loop component of the movement across all three conditions of task complexity, and a prolonged reversal phase surrounding target impact, particularly in the most complex condition. In contrast, subjects with right stroke showed deficits in the closed-loop phase of the movement prior to target impact, particularly in the most complex condition when visual information was necessary for accuracy. Together, these results suggest that for the control of rapid goal-directed aiming movements, the left hemisphere is dominant for task-relevant aspects of processing associated with the ballistic component and the timing or triggering of sequential movements. In contrast, the right hemisphere is dominant for processing associated with rapid, on-line visual information even when target location is known and direction is certain.

Aged↗

PubMed1994

Effects of physical guidance and knowledge of results on motor learning: support for the guidance hypothesis.

The guidance hypothesis (Schmidt, 1991) predicts that the guiding properties of augmented feedback are beneficial for motor learning when used to reduce error, but detrimental when relied upon. Therefore, a heavily guiding form of feedback might be detrimental for learning. In addition, the guidance hypothesis predicts that practice with a high relative frequency of augmented feedback would be detrimental for learning. An experiment is described that crossed two forms of feedback with two levels of relative frequency. Subjects practiced movements to a target with either physical guidance or knowledge of results, and with either a high or faded relative frequency. The high frequency physical guidance condition resulted in the poorest retention, and both high frequency feedback conditions resulted in the least accuracy in transfer. These results provide support for the guidance hypothesis and suggest consideration of the combined effects on learning of the type and relative frequency of augmented feedback and acquisition-test conditions.

Adult↗