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At least 433 records · Page 24Linked to original sources
PubMed2000

Stepping performance during obstacle clearance in women: age differences and the association with lower extremity strength in older women.

OBJECTIVE: To compare stepping performance during obstacle clearance in younger and older women, and to examine the relationship between lower extremity strength and stepping performance during obstacle clearance in older women. DESIGN: Correlational study. SETTING: A small community. PARTICIPANTS: Twenty-four older women (mean age = 74.4), and 16 younger women (mean age = 20.7). The older participants lived independently in the community and were able to walk unaided. MEASUREMENTS: Lower extremity muscle strength, measures of stepping performance including reaction time, movement time, extent of obstacle clearance, time to clear obstacle, among others. MAIN RESULTS: The older women were far slower in stepping than the younger women. Toe trajectories differed between older and younger women during the initial portion of the step. The younger women tended to lift the toe straight up, whereas the older women tended to move the toe backward, away from the obstacle, passing farther from the obstacle when the toe cleared the obstacle height. There was little, if any, association between relative lower extremity strength and stepping performance during obstacle clearance in older women. CONCLUSIONS: Dramatic differences in the speed of volitional stepping performance were found between younger and older women. Among the older women, lower extremity strength was not related to volitional stepping performance.

Adult↗
PubMed1984

Ability to judge lung volumes at different CO2-drives for ventilation and the possible influence of such a judgment on the ventilatory CO2-responsiveness.

Possible influences of changes in the CO2-respiratory drive on the ability to judge lung volumes and the possible effects of such judgments on the ventilatory CO2-responsiveness were studied in healthy subjects. The psychophysical relationships between objective and subjective magnitudes of lung volumes were determined at normocapnia, at three different levels of hypercapnia (breathing 1-3% CO2 in air) and at hypocapnia (after volitional hyperventilation). The relationships, expressed by a power function with the mean exponent 1.5 (SD +/- 0.3), were analyzed with respect to slope, intercept and correlation coefficient of the regression lines. None of these parameters was affected by variations in end-tidal PCO2 or by the concomitant changes in ventilation. In the 'attentive' pre-judgment breathing (APJB) the ventilatory response to CO2 was lower than during non-attentive breathing in three or four subjects. It is speculated that in these subjects the CO2-responsiveness was depressed by the increased attention during APJB. The question whether volitional hyperventilation gave rise to any specific post-hyperventilatory breathing pattern was analyzed. The results showed that the majority of post-hyperventilatory breathing pattern was apnoeic or hypopnoeic in character.

Adolescent↗
PubMed2002

Sustained contractions produced by plateau-like behaviour in human motoneurones.

Electrical stimulation over human muscle can generate force directly by activation of motor axons and indirectly by 'reflex' recruitment of spinal motoneurones. These experiments were designed to define the properties of the centrally generated 'reflex' force, including the optimal stimulus conditions for producing it in tibialis anterior (TA) and triceps surae (TS), and its interaction with volition. Subjects (n = 21) were seated with their foot strapped to an isometric myograph. Surface EMG was recorded from TS and TA. High-frequency electrical stimulation (100 Hz) of TS and TA with wide pulse widths (1 ms) was most effective to evoke the sustained centrally generated forces. The maximal force evoked by this mechanism during stimulation of TA for 40 s was approximately 42 % of that produced by a maximal voluntary contraction. For both muscle groups, ramp increases and decreases in stimulus frequency (from approximately 4 to 100 Hz and back to 4 Hz over 6 s) resulted in marked hysteresis in the force-frequency plot. After a single 'burst' of 100 Hz stimulation during prolonged stimulation at 25 Hz, force remained elevated. Repeated bursts often generated progressively larger force increments. These behaviours were abolished by an anaesthetic nerve block proximal to the stimulation site, confirming the central origin for the 'extra' force. After a brief voluntary contraction was performed during 25 Hz stimulation, force remained elevated, and this showed some gradation with voluntary contraction amplitude. Sometimes voluntary contractions alone initiated the sustained central motor output. Involuntary contractions often persisted for many seconds after electrical stimulation ceased. These were not terminated by brief inhibitory inputs to the active motoneurones but could be stopped by the voluntary command to 'relax completely'. Overall, these centrally generated contractions are consistent with activation of plateau potentials in motoneurones innervating the ankle dorsiflexors and plantarflexors. Large forces can be produced through this mechanism. The interaction with volitional drives suggests that plateau behaviour may contribute significantly to the normal output of human motoneurones.

Adult↗
PubMed2005

Selective recruitment of single motor units in human flexor digitorum superficialis muscle during flexion of individual fingers.

Flexor digitorum superficialis (FDS) is an extrinsic multi-tendoned muscle which flexes the proximal interphalangeal joints of the four fingers. It comprises four digital components, each with a tendon that inserts onto its corresponding finger. To determine the degree to which these digital components can be selectively recruited by volition, we recorded the activity of a single motor unit in one component via an intramuscular electrode while the subject isometrically flexed each of the remaining fingers, one at a time. The finger on which the unit principally acted was defined as the 'test finger' and that which flexed isometrically was the 'active' finger. Activity in 79 units was recorded. Isometric finger flexion forces of 50% maximum voluntary contraction (MVC) activated less than 50% of single units in components of FDS acting on fingers that were not voluntarily flexed. With two exceptions, the median recruitment threshold for all active-test finger combinations involving the index, middle, ring and little finger test units was between 49 and 60% MVC (60% MVC being the value assigned to those not recruited). The exceptions were flexion of the little finger while recording from ring finger units (median: 40% MVC), and vice versa (median: 2% MVC). For all active-test finger combinations, only 35/181 units were activated when the active finger flexed at less than 20% MVC, and the fingers were adjacent for 28 of these. Functionally, to recruit FDS units during grasping and lifting, relatively heavy objects were required, although systematic variation occurred with the width of the object. In conclusion, FDS components can be selectively activated by volition and this may be especially important for grasping at high forces with one or more fingers.

Adult↗
PubMed2001

Effectiveness of glycerol as a rehydrating agent.

On two occasions, 8 male subjects completed a dehydration protocol, immediately followed by a 180-min rehydration protocol, then a subsequent exercise bout. During each dehydration session, subjects lost 3.1 +/- 0.4% body weight (BW) following discontinuous exercise in the heat (40 degreesC, 33% rh). During the first 30 min of rehydration, subjects ingested either 1.0-g glycerol x kg body weight(-1) + 30% of the total rehydration water volume (GLY), or 30% of the total rehydration water volume without glycerol (CON). The five remaining ingestions (every 30 min) were equal to 14% of the remaining fluid volume and were identical in nature. Fluid volume ingested equaled fluid volume lost during dehydration. Following the 180 min rehydration period, subjects cycled (appoximately 50% VO2 peak) in the heat (40 degrees C, 33% rh) until volitional exhaustion. Three observations were made: (a) Following glycerol-induced rehydration, time to volitional exhaustion was greater during the subsequent exercise bout in the heat (CON: 38.0 +/- 2.0, GLY 42.8 +/- 1.0 min, p <.05); (b) glycerol-induced rehydration significantly increased plasma volume restoration within 60 min and at the end of the 180-min rehydration period; and (c) total urine volume was lower and percent rehydration was greater following GLY, but neither was significantly different.

Adult↗
PubMed2004

A simple multistage field test for the prediction of anaerobic capacity in female games players.

OBJECTIVE: To establish the validity of a 15 m multistage shuttle run test (MSRT) as a predictor of anaerobic capacity (expressed as mean power output (MPO) from the 30 second Wingate anaerobic test (WAnT)) in female university standard games players. METHODS: Data came from three phases using a total of 72 players (mean (SD) age 20.3 (1.5) years, body mass 64.9 (8.8) kg, and stature 1.67 (0.04) m). The repeatability of the MSRT was assessed in phase 1 by applying 95% limits of agreement (LoA) to the test and retest results from a random sample of 20 players. In phase 2, linear relations between MPO and performance on the MSRT were investigated in a random sample of 36 players. As a result, a calibration model (Y = a + bX) was developed and cross validated in phase 3, in which the remaining 36 players performed both the WAnT and the MSRT. Time (seconds) to volitional exhaustion/disqualification from the MSRT was substituted into the calibration model from which MPO was predicted. The agreement between MPO predicted and MPO measured from the WAnT was quantified using LoA. RESULTS: Insignificant bias between repeat applications of the MSRT (mean(diff) (SD(diff)) = 1.0 (3.5) seconds (4 (14) m), t = 1.23, p = 0.230) was found from phase 1. Data were homoscedastic (r = 0.061, p = 0.799) with LoA +/- 6.9 seconds (+/- 27 m). In phase 2 the strongest correlation was between MPO (W/kg(0.67)) and time to volitional exhaustion/disqualification on the MSRT; r = 0.715 (r(2) = 51.1%, p = 0.0005). As a result, the calibration model developed was: MPO (W/kg(0.67)) = 12.5 + (0.2 x time (seconds)) with a standard error of prediction of 2.1 W/kg(0.67). The cross validation in phase 3 showed insignificant bias between measured and predicted MPO (mean(diff) (SD(diff)) = 0.3 (2.8) W/kg(0.67), t = 0.75, p = 0.460). Data were homoscedastic (r = 0.05, p = 0.774) with LoA +/- 5.5 W/kg(0.67). CONCLUSIONS: The MSRT requires minimal equipment and training of assessors, and it is easy to perform. In the population studied, it provides scores that are repeatable, and anaerobic capacity (MPO) can be successfully predicted from its performance. It would seem therefore to be a useful field based test for use by female games players, their coaches, and support scientists.

Adult↗
PubMed2005

Abnormal vibration induced illusion of movement in essential tremor: evidence for abnormal muscle spindle afferent function.

OBJECTIVES: Vibration induced illusion of movement (VIIM) is abnormal in patients with idiopathic focal dystonia, an abnormality which corrects with fatigue of the vibrated muscle. Since dystonia and essential tremor sometimes coexist in families, we investigated the perception of VIIM and the effect of fatigue on VIIM in patients with essential tremor. METHODS: VIIM in 18 patients with essential tremor was compared with VIIM in 18 healthy control participants before and after volitional fatigue of the vibrated muscles. RESULTS: Vibration of the immobilised biceps produced a subnormal VIIM in patients with essential tremor (12.81 degrees (SEM 2.15)) compared with healthy control subjects (28.55 degrees (1.66)). The perception increased following volitional fatigue of the vibrated arm in patients with essential tremor (16.23 degrees (2.50)) but not in healthy controls (27.55 degrees (1.66)). No difference was observed in patients with alcohol or non-alcohol responsive tremor. CONCLUSIONS: The VIIM decreased with increasing age in healthy control subjects. Abnormal VIIM implies abnormal sensorimotor processing in patients with essential tremor, similar to that found in idiopathic focal dystonia, and the change of the perception with age could explain the age related onset of the disorder.

Afferent Pathways↗
PubMed1998

Respiratory insufficiency due to high anterior cervical cord infarction.

OBJECTS AND METHODS: Respiratory dysfunction may occur as a result of lesions in the upper cervical spinal cord disturbing the descending pathways subserving automatic and volitional ventilatory control. Four patients are described who presented with acute respiratory insufficiency caused by infarction of the anterior portion of the upper cervical cord due to presumed anterior spinal artery occlusion. RESULTS: Two patients presented after respiratory arrests; they were ventilated and there was no automatic or volitional respiratory effort. Both had signs of an extensive anterior spinal cord lesion at the C2 level and this was confirmed by MRI. One patient presented with a C4 infarction and required ventilation for three months. Ventilatory recovery was characterised by the development of an automatic respiratory pattern. The fourth patient required ventilation for two months after infarction at the C3 level. On attempted weaning he had prolonged periods of hypoventilation and apnoea during inattention and sleep indicating impairment of automatic respiratory control. CONCLUSION: Infarction of the spinal cord at high cervical levels may be due to fibrocartilaginous embolism and involvement of the descending respiratory pathways may occur. Extensive lesions at C1/2 cause complete interruption of descending respiratory control leading to apnoea. Partial lesions at C3/4 cause selective interruption of automatic or voluntary pathways and give rise to characteristic respiratory patterns. The prognosis depends on the level and extent of the lesion.

Adult↗
PubMed2000

Coughing and choking in motor neuron disease.

OBJECTIVES: To assess the frequency and severity of coughing and choking episodes, possible related factors, and their association with chest infections in patients with motor neuron disease (MND). METHODS: Thirty seven patients with MND and 23 healthy volunteers were studied. Cough was assessed using a questionnaire and a 3 day diary, and volitional cough quantified by peak cough flow and sound intensity. Other clinical symptoms, smoking habit, affective state, oral secretions, bulbar signs, and quantitative assessments of swallowing and respiratory function were documented. RESULTS: Patients with MND coughed and choked significantly more often and to a greater degree than the healthy volunteers (26 of 37 patients with MND and 2 of 23 volunteers, p<0.001). Female sex, older age, abnormal speech, reduced swallowing capacity, and low forced vital capacity (FVC)% predicted were each significantly associated with excessive coughing and choking episodes in patients with MND. Smokers had significantly more severe and prolonged episodes of coughing and choking than non-smokers (p<0.05). Patients with upper motor neuron bulbar signs had a greater tendency to severe and prolonged episodes of coughing and choking than those without (p<0. 05). Chest infections were reported only rarely among the patients who coughed and choked. CONCLUSIONS: Coughing and choking episodes are common in patients with MND but infrequently associated with overt chest infection. Upper motor neuron bulbar signs may both promote factors (for instance, dysphagia) which trigger cough and reduce volitional capacity to suppress it.

Aged↗
PubMed2006

Verification phase as a useful tool in the determination of the maximal oxygen uptake of distance runners.

This study investigated the utility of a verification phase for increasing confidence that a "true" maximal oxygen uptake had been elicited in 16 male distance runners (mean age (+/-SD), 38.7 (+/- 7.5 y)) during an incremental treadmill running test continued to volitional exhaustion. After the incremental test subjects performed a 10 min recovery walk and a verification phase performed to volitional exhaustion at a running speed 0.5 km.h(-1) higher than that attained during the last completed stage of the incremental phase. Verification criteria were a verification phase peak oxygen uptake or= 3%) lower than the peak values attained in the incremental phase. Further research is required to improve the verification procedure before its utility can be confirmed.

Adult↗
PubMed2001

Swallow-related cerebral cortical activity maps are not specific to deglutition.

Cortical representation of swallow-related motor tasks has not been systematically investigated. In this study, we elucidated and compared these cortical representations to those of volitional swallow using block-trial and single-trial methods. Fourteen volunteers were studied by functional magnetic resonance imaging. Cortical activation during both swallowing and swallow-related motor tasks that can be performed independent of swallowing, such as jaw clenching, lip pursing, and tongue rolling, was found in four general areas: the anterior cingulate, motor/premotor cortex, insula, and occipital/parietal region corresponding to Brodmann's areas 7, 19, and 31. Regions of activity, volume of activated voxels, and increases in signal intensity were found to be similar between volitional swallow and swallow-related motor tasks. These findings, using both block-trial and single-trial techniques, suggest that cerebral cortical regions activated during swallowing may not be specific to deglutitive function.

Adult↗
PubMed1979

Effects of oxone inhalation on work performance and VO2 max.

Ozone (O3) at near ambient smog alert levels has previously been shown to cause alterations in pulmonary function and exercise response in humans. The present study was designed to investigate the effects of O3 administered during graded bicycle exercise to volitional fatigue on work performance and maximal oxygen uptake (VO2max). Nine subjects performed three tests each while breathing either 0.00, 0.15, or 0.30 ppm O3. Forced vital capacity, residual volume, maximal midexpiratory flow rate, and forced expiratory volume in 1 s were assessed before, immediately after, and 4 h after exercise. O3 exposure resulted in no significant effect on maximal work rate, anaerobic threshold, or any pulmonary function parameter. However, maximal expired minute ventilation was decreased (P less than 0.05) in a dose dependent fashion. Thus, exercise ventilation during maximal work was a more sensitive indicator of the effects of O2 exposure than were standard pulmonary function tests. Although subjective symptoms of discomfort were reported more frequently with increased O2 level, it was concluded that exposure of healthy young men to as much as 0.30 ppm O2 for no more than 30 min of progressively incremented exercise to volitional fatigue, is insufficient to cause a significant decrease in work capacity or V02 max.

Adult↗
PubMed1983

Influence of body CO2 stores on ventilatory dynamics during exercise.

Pulmonary CO2 flow (the product of cardiac output and mixed venous CO2 content) is purported to be an important determinant of ventilatory dynamics in moderate exercise. Depletion of body CO2 stores prior to exercise should thus slow these dynamics. We investigated, therefore, the effects of reducing the CO2 stores by controlled volitional hyperventilation on cardiorespiratory and gas exchange response dynamics to 100 W cycling in six healthy adults. The control responses of ventilation (VE), CO2 output (VCO2), O2 uptake (VO2), and heart rate were comprised of an abrupt increase at exercise onset, followed by a slower rise to the new steady state (t1/2 = 48, 43, 31, and 33 s, respectively). Following volitional hyperventilation (9 min, PETCO2 = 25 Torr), the steady-state exercise responses were unchanged. However, VE and VCO2 dynamics were slowed considerably (t1/2 = 76, 71 s) as PETCO2 rose to achieve the control exercise value. VO2 dynamics were slowed only slightly (t1/2 = 39 s), and heart rate dynamics were unaffected. We conclude that pulmonary CO2 flow provides a significant stimulus to the dynamics of the exercise hyperpnea in man.

Carbon Dioxide↗
PubMed1995

Instantaneous heart rate increase with dynamic exercise: central command and muscle-heart reflex contributions.

R-R interval (RRI) changes were recorded from 15 healthy volunteers in response to volitional unloaded cycling and passively induced cycling (PC). PC was also combined with electrical stimulation (n = 5) to increase muscle mechanoreceptor activation. The electrocardiogram and leg electromyographic activity were continuously sampled by computer at 1,000 Hz, and an electronic trigger was used to designate the instant of pedal movement within an RRI. Changes in RRI were expressed as the difference of the interval in which the trigger was activated (onset RRI) and the average of resting intervals (4-8 intervals). Volitional unloaded cycling produced the greatest decrease in the onset RRI [907 +/- 11 (SE) to 855 +/- 10 ms; -5.4 +/- 0.4%; P < 0.01] when movement was initiated within the first one-third of the interval. A shortening of the onset RRI was also detected when trigger activation occurred in the last one-third of the interval (906 +/- 12 to 875 +/- 11 ms; -3.1 +/- 0.4%; P < 0.01). There were no significant effects of PC alone on the onset RRI. However, PC+electrical stimulation shortened the onset RRI (906 +/- 12 to 883 +/- 11 ms; -2.5 +/- 0.2%; P < 0.05) but only when the movement was initiated within the first one-third of the interval.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Changes in muscle proton transverse relaxation times and acidosis during exercise and recovery.

We studied changes in muscle proton (1H) transverse relaxation times (T2) by magnetic resonance imaging during exercise and compared these changes with alterations in muscle metabolism measured by phosphorus-31 magnetic resonance spectroscopy (31P-MRS). Eleven subjects completed two trials of intermittent incremental forearm wrist flexion exercise requiring 30 contractions/min for 5 min, 7 min of recovery between stages, and 5-N load increments/stage. Between stages of the first trial, T2 images of muscle 1H were obtained. Muscle T2 increased from 27.3 +/- 1.1 (SD) ms at rest to 35.8 +/- 3.6 ms after volitional fatigue (P < 0.05), whereas less active wrist extensor muscle T2 remained unchanged (26.8 +/- 0.9 to 28.8 +/- 1.6 ms; P > 0.05). After localizing the predominant muscle recruited from the T2 images, subjects completed an identical trial at least 1 wk later but involving surface coil 31P-MRS of the T2-enhanced muscle to measure the H+ concentration ([H+]). Intramuscular [H+] of T2-enhancing muscle increased from 1.1 +/- 0.1 x 10(-7) M at rest to 4.1 +/- 2.0 x 10(-7) M after volitional fatigue. Both muscle T2 and intramuscular [H+] increased in a bimodal manner, with T2 increasing before muscle [H+] (P < 0.05). The correlation coefficient between the percent change in T2 and muscle [H+] during exercise was +0.74 (range 0.48-0.98; P < 0.05) and +0.47 during recovery. After 12 min of recovery, muscle [H+] decreased to 1.4 +/- 0.3 x 10(-7) M (P < 0.05), and T2 remained close to postexercise values (32.2 +/- 3.1 ms, P > 0.05). The data indicate that 1) the T2 increases during increases in exercise intensity are nonlinear, 2) the T2 increases during exercise are significantly correlated with increases in [H+], and 3) the slow recovery of T2 compared with [H+] indicates that [H+] has a minor contribution to the recovery in T2.

Acidosis↗
PubMed2005

Cardiac structure and function in monozygotic twin pairs discordant for physical fitness.

Cross-sectional studies in athletes and untrained subjects suggest that exercise training induces adaptations in cardiac structure and function. However, the role of genetic variation on the results has largely been ignored in these studies. The purpose of this study was to investigate the effects of long-term volitionally increased physical activity on electrocardiographic and echocardiographic parameters in male monozygotic twin pairs discordant for physical activity and fitness. On the basis of the mailed questionnaires, a telephone interview, and the inclusion criteria, 12 pairs of young adult male monozygotic twins were recruited from a Finnish twin cohort. All subjects completed a maximal oxygen uptake (.VO2 (max)) test and electrocardiography and echocardiography studies. Nine pairs had at least 9% difference in .VO2(max) and were selected for further analysis and for a second echocardiography study. Twins were divided into the more (MAG) and less active group (LAG), according to their VO2(max). On average, MAG had 18% higher VO2(max) compared with LAG. In electrocardiography, MAG had 29% (P = 0.02) higher Cornell voltage and 37% (P = 0.01) higher right-side hypertrophy index. In echocardiography, no significant differences were observed between the groups, and left ventricular mass index was only 7% (P = 0.16) higher in MAG. These results show that the volitionally increased physical activity that has led to an 18% increase in cardiorespiratory fitness induces greater changes in electro- than echocardiographic parameters. Electrocardiographic changes were suggestive of left ventricular hypertrophy, and echocardiography showed a similar but statistically nonsignificant trend.

Adult↗
PubMed2005

Determinants of skin sympathetic nerve responses to isometric exercise.

Exercise-induced increases in skin sympathetic nerve activity (SSNA) are similar between isometric handgrip (IHG) and leg extension (IKE) performed at 30% of maximal voluntary contraction (MVC). However, the precise effect of exercise intensity and level of fatigue on this relationship is unclear. This study tested the following hypotheses: 1) exercise intensity and fatigue level would not affect the magnitude of exercise-induced increase in SSNA between IHG and IKE, and 2) altering IHG muscle mass would also not affect the magnitude of exercise-induced increase in SSNA. In protocol 1, SSNA (peroneal microneurography) was measured during baseline and during the initial and last 30 s of isometric exercise to volitional fatigue in 12 subjects who randomly performed IHG and IKE bouts at 15, 30, and 45% MVC. In protocol 2, SSNA was measured in eight subjects who performed one-arm IHG at 30% MVC with the addition of IHG of the contralateral arm in 10-s intervals for 1 min. Exercise intensity significantly increased SSNA responses during the first 30 s of IHG (34+/-13, 70+/-11, and 92+/-13% change from baseline) and IKE (30+/-17, 69+/-12, and 76+/-13% change from baseline) for 15, 30, and 45% MVC. During the last 30 s of exercise to volitional fatigue, there were no significant differences in SSNA between exercise intensities or limb. SSNA did not significantly change between one-arm and two-arm IHG. Combined, these data indicate that exercise-induced increases in SSNA are intensity dependent in the initial portion of isometric exercise, but these differences are eliminated with the development of fatigue. Moreover, the magnitude of exercise-induced increase in SSNA responses is not dependent on either muscle mass involved or exercising limb.

Adult↗
PubMed2005

Effects of short-term training on sensory and motor function in severed nerves of long-term human amputees.

Much has been studied and written about plastic changes in the CNS of humans triggered by events such as limb amputation. However, little is known about the extent to which the original pathways retain residual function after peripheral amputation. Our earlier, acute study on long-term amputees indicated that central pathways associated with amputated peripheral nerves retain at least some sensory and motor function. The purpose of the present study was to determine if these functional connections would be strengthened or improved with experience and training over several days time. To do this, electrodes were implanted within fascicles of severed nerves of long-term human amputees to evaluate the changes in electrically evoked sensations and volitional motor neuron activity associated with attempted phantom limb movements. Nerve stimulation consistently resulted in discrete, unitary, graded sensations of touch/pressure and joint-position sense. There was no significant change in the values of stimulation parameters required to produce these sensations over time. Similarly, while the amputees were able to improve volitional control of motor neuron activity, the rate and pattern of change was similar to that seen with practice in normal individuals on motor tasks. We conclude that the central plasticity seen after amputation is most likely primarily due to unmasking, rather than replacement, of existing synaptic connections. These results also have implications for neural control of prosthetic limbs.

Adult↗