Absolute basophil count is associated with time to recurrence in patients with high-grade T1 bladder cancer receiving bacillus Calmette-Guérin after transurethral resection of the bladder tumor

BACKGROUND

Basophils, eosinophils and monocytes may be involved in BCG-induced immune responses and be associated with outcomes of bladder cancer patients receiving intravesical BCG. Our objective was to explore the association of baseline counts of basophils, eosinophils and monocytes with outcomes of patients with high-grade T1 bladder cancer receiving a standard course of intravesical BCG.

METHODS

We retrospectively reviewed medical records of patients with primary T1 HG/G3 bladder cancer. After re-TURBT, patients were treated with a 6-week course of intravesical BCG induction followed by intravesical BCG every week for 3 weeks given at 3, 6, 12, 18, 24, 30 and 36 months from initiation of therapy The analysis of potential risk factors for recurrence, muscle invasion and cancer-specific and overall survival was performed using univariable Cox regression models. Those factors that presented, at univariate analysis, an association with the event at a liberal p < 0.1, have been selected for the development of a multivariable model.

RESULTS

A total of 1045 patients with primary T1 HG/G3 were included. A total of 678 (64.9%) recurrences, 303 (29.0%) progressions and 150 (14.3%) deaths were observed during follow-up. Multivariate analysis showed that logarithmic transformation of basophils count was associated with a 30% increment in the hazard of recurrence per unit increase of logarithmic basophils count (HR 1.30; 95% confidence interval 1.09-1.54; p = 0.0026). Basophil count modeled by quartiles was also significantly associated with time to recurrence [second vs. lower quartile HR 1.42 (1.12-1.79); p = 0.003, third vs. lower quartile HR 1.26 (1.01-1.57); p = 0.041; upper vs. lower quartile HR 1.36 (1.1-1.68); p = 0.005]. The limitations of a retrospective study are applicable.

CONCLUSION

Baseline basophil count may predict recurrence in BCG-treated HG/G3 T1 bladder cancer patients. External validation is warranted.

Impairment of toll-like receptors 2 and 4 leads to compensatory mechanisms after sciatic nerve axotomy

Background

Peripheral nerve injury results in retrograde cell body-related changes in the spinal motoneurons that will contribute to the regenerative response of their axons. Successful functional recovery also depends on molecular events mediated by innate immune response during Wallerian degeneration in the nerve microenvironment. A previous study in our lab demonstrated that TLR 2 and 4 develop opposite effects on synaptic stability in the spinal cord after peripheral nerve injury. Therefore, we suggested that the better preservation of spinal cord microenvironment would positively influence distal axonal regrowth. In this context, the present work aimed to investigate the influence of TLR2 and TLR4 on regeneration and functional recovery after peripheral nerve injury.

Methods

Eighty-eight mice were anesthetized and subjected to unilateral sciatic nerve crush (C3H/HeJ, n = 22, C3H/HePas, n = 22; C57Bl6/J, n = 22 and TLR2^−/−, n = 22). After the appropriate survival times (3, 7, 14 days, and 5 weeks), all mice were killed and the sciatic nerves and tibialis cranialis muscles were processed for immunohistochemistry and transmission electron microscopy (TEM). Gait analysis, after sciatic nerve crushing, was performed in another set of mice (minimum of n = 8 per group), by using the walking track test (CatWalk system).

Results

TLR4 mutant mice presented greater functional recovery as well as an enhanced p75^NTR and neurofilament protein expression as compared to the wild-type strain. Moreover, the better functional recovery in mutant mice was correlated to a greater number of nerve terminal sprouts. Knockout mice for TLR2 exhibited 30 % greater number of degenerated axons in the distal stump of the sciatic nerve and a decreased p75^NTR and neurofilament protein expression compared to the wild type. However, the absence of TLR2 receptor did not influence the overall functional recovery. End-point equivalent functional recovery in transgenic mice may be a result of enhanced axonal diameter found at 2 weeks after lesion.

Conclusions

Altogether, the present results indicate that the lack of TLR2 or the absence of functional TLR4 does affect the nerve regeneration process; however, such changes are minimized through different compensatory mechanisms, resulting in similar motor function recovery, as compared to wild-type mice. These findings contribute to the concept that innate immune-related molecules influence peripheral nerve regeneration by concurrently participating in processes taking place both at the CNS and PNS.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0579-6) contains supplementary material, which is available to authorized users.

Does PSA reduction after antibiotic therapy permits postpone prostate biopsy in asymptomatic men with PSA levels between 4 and 10 ng/mL?

Purpose

We investigated the effect of antibiotics on PSA in asymptomatic patients with mild PSA elevation.

Materials and Methods

We prospectively evaluated, in a non-randomized design, 106 asymptomatic patients with PSA of 4-10ng/mL, with a negative digital rectal examination and with no urinary tract infection evidence for 2 years. Patients were divided into two groups: those treated with antibiotics for 3 weeks (G1) and those who were not treated (G2). PSA was taken six weeks after and prostate biopsy was performed in all patients.

Results

PCa was diagnosed in 25 of 106 patients (23.6%): 16 (25.0%) in G1 and 9 (21.4%) in G2 (p>0.05). PSA normalization was experienced in 24.5%. In G1, PSA returned to <4ng/mL in 15 (23.4%) patients compared to 11 (26%) patients in G2. In the patients with a positive biopsy, no significant variation was noted in PSA, fPSA, %fPSA and DPSA after antibiotic treatment. A significantly lower cancer detection rate was noted with decreased PSA, fPSA, and DPSA after antibiotic use. A PSA reduction rate of ≥10% occurred in 58.5%, and this was similar in both G1 and G2 groups. The sensibility, specificity and accuracy of PSA reduction of ≥10% were 31%, 23% and 25%, respectively.

Conclusion

Empirical antibiotic therapy in asymptomatic male patients is not related to PSA reduction. The greater than 10% PSA reduction after antibiotic in this population cannot postpone prostate biopsy.

Electromechanical delay: An experimental artifact

The time delay between the onset of muscle activation and the onset of force or motion is commonly referred to as electromechanical delay, motor time, or motor execution time. This time has been used in the study of reaction time, of physiological properties of muscle, and of population differences. In this study, we show that electromechanical delay is comprised of two components. The first is transport time (t(t)) which is very brief (perhaps 10 ms). The second is the time to generate detectable changes in force (t(f)). The absolute duration of electromechanical delay is usually dominated by the second component which is influenced by four separate factors that are related in the following way: [Formula: see text] That is, t(f) is a function (g) of the product of two ratios. One is between the threshold T of the measuring device and the rate R at which muscle force rises. The other is the ratio of the mechanical impedances of the measuring device (Z(d)) and the muscle (Z(m)). We conclude that the measured absolute value of electromechanical delay has no physiological or psychological meaning and that task and performance induced changes need great care in their interpretation.

The effect of galvanic vestibular stimulation on postural response of Down syndrome individuals on the seesaw

In order to better understand the role of the vestibular system in postural adjustments on unstable surfaces, we analyzed the effects of galvanic vestibular stimulation (GVS) on the pattern of muscle activity and joint displacements (ankle knee and hip) of eight intellectually normal participants (control group--CG) and eight control group individuals with Down syndrome (DS) while balancing on seesaws of different heights. The CG individuals adopted a pattern of muscle activation characterized by alternation between ankle agonist and antagonist muscles. The individuals with DS adopted a pattern of muscle co-contraction. The GVS affected neither the ability of CG individuals to maintain balance nor their pattern of muscle contraction. On the other hand, the individuals with DS showed greater sensitivity to GVS while balancing on a seesaw and were not able to select the appropriate motor strategy to efficiently balance and compensate the effects of GVS. These increased vestibular sensitivities observed in individuals with DS can reflect deficits in the proprioceptive system.

[Transumbilical single-incision laparoscopic ureterolithotomy]

INTRODUCTION

laparoendoscopic single-site surgery (LESS) using transumbilical access and conventional laparoscopic instruments is a very attractive alternative to perform ureterolithotomy for ureteral stone with failed endourological management.

MATERIAL AND METHOD

a 29-year-old woman presented with chronic right lumbar pain and a 1.2 cm impacted calculus localized at transition of abdominal to pelvic ureter. Semi-rigid ureteroscopy had failed to fragment the stone and shockwave lithotripsy was not available. Double-J ureteral catheter had been inserted preoperatively. We performed a transumbilical single-incision laparoscopic ureterolithotomy. Three conventional trocars were inserted in a single semi-circular umbilical incision. Right colon was detached and the ureter was identified. Calculus was extracted and the ureteral incision was closed with intracorporal sutures.

RESULTS

ureterolithotomy was successfully completed, with all the operative steps performed transumbically. Operative time was 180 minutes. No single-port device or articulating and bent instruments were utilized. Estimated blood loss was less than 50 mL. No intraoperative, access-related and postoperative complications took place. The duration of hospitalization was 24 hours and scarless appearance was observed on postoperative day 15.

CONCLUSION

transumbilical single-incision laparoscopic ureterolithotomy is feasible and safe. This approach offers an inherent cosmetic advantage and few postoperative discomfort. Additional experience and continued investigation are warranted.

Assessment of postural adjustments in persons with intellectual disability during balance on the seesaw

BACKGROUND

The purpose of this study was to investigate the kinematic and electromyography strategy used by individuals with intellectual disability to keep equilibrium during anterior-posterior balance on seesaws with different degrees of instability.

METHOD

Six individuals with Down syndrome (DS) and six control group individuals (CG) balanced on three seesaws. The movement of the hip, knee and ankle joints and electromyography activities of selected leg and trunk muscles were recorded.

RESULTS

Both groups maintained their balance mainly at the ankle joint. Contrary to the CG, the individuals with DS adopted a pattern of co-contraction and were not able to modulate the magnitude of postural response with the seesaw's degree of instability.

CONCLUSIONS

These unusual strategies used by individuals with DS, such as their inability to discriminate different levels of mechanical demands in terms of the seesaw's instability, can reflect deficits in the proprioceptive system. The integration at cerebellum level could be a good candidate.

Coupling between muscle activities and muscle torques during horizontal-planar arm movements with direction reversal

In this study we investigated the hypothesis that the simple set of rules used to explain the modulation of muscle activities during single-joint movements could also be applied for reversal movements of the shoulder and elbow joints. The muscle torques of both joints were characterized by a triphasic impulse. The first impulse of each joint accelerated the limb to the target and was generated by an initial burst of the muscles activated first (primary mover). The second impulse decelerated the limb to the target, reversed movement direction and accelerated the limb back to the initial position, and was generated by an initial burst of the muscles activated second (secondary movers). A third impulse, in each joint, decelerated the limb to the initial position due to the generation of a second burst of the primary movers. The first burst of the primary mover decreased abruptly, and the latency between the activation of the primary and secondary movers varied in proportion with target distances for the elbow, but not for the shoulder muscles. All impulses and bursts increased with target distances and were well coupled. Therefore, as predicted, the bursts of muscle activities were modulated to generate the appropriate level of muscle torque.

Postural strategy to keep balance on the seesaw

This work investigates the kinematic and electromyography (EMG) strategy used by the central nervous system (CNS) to keep equilibrium during anterior-posterior balance on seesaws with different degrees of instability. The movement of hip, knee, and ankle were reconstructed using a 3D motion-analysis system and the EMG activities of selected ankle, knee, and hip muscles were recorded. Balance was kept mainly at the ankle joint. The EMG patterns of the gastrocnemius and anterior tibialis alternated between agonist and antagonist bursts. The agonist burst started before the end of the lengthening phase and was prolonged until the end of the shortening phase. The EMG activities of the muscles crossing the knee and hip joints were characterized by a pattern of generalized co-activation. The movements at these two joints were very small, suggesting a neural or biomechanical constraint underlying the operations of the equilibrium control. Our results also indicate that the strategy to keep balance on the seesaw is qualitatively the same for the different levels of mechanical demands in terms of the seesaw's instability.

Effect of age and gender in the control of elbow flexion movements

In previous studies of rapid elbow movements in young healthy men, characteristic task-dependent changes in the patterns of muscle activation when movement speed or distance was varied have been reported. In the present study, the authors investigated whether age or gender is associated with changes in the patterns of muscle activity previously reported in young men. Arm movements of 10 healthy older and 10 healthy younger participants (5 men and 5 women in each group) were studied. Surface electromyograms (EMGs) from agonist (biceps) and antagonist (triceps) muscles, kinematic and kinetic parameters, as well as anthropometric and strength measures were recorded. All 4 groups of participants showed similar task- (distance or speed) dependent changes in biphasic EMG activity. Similar modulation of the initial rate of rise of the EMG, integrated agonist and antagonist EMG activity, as well as their relative timing were observed in all 4 groups. Those results suggest that older individuals of both genders retain the control strategies for elbow movements used by young individuals. Despite the qualitative similarities in the patterns of muscle activation, the men moved more quickly than the women, and younger participants moved more quickly than older participants. Those performance differences could not be explained in terms of differences in body size and strength alone.

Horizontal-plane arm movements with direction reversals performed by normal individuals and individuals with down syndrome

We examined the systematic variation in shoulder and elbow torque, as well as movement kinematics, for horizontal-plane arm movements with direction reversals performed by normal individuals and individuals with Down syndrome. Eight neurologically normal individuals and eight individuals with Down syndrome performed horizontal, planar reversal movements to four different target locations. The four locations of the targets were chosen such that there is a systematic increase in elbow interaction torque for each of the four different target locations. This systematic increase in interaction torque has previously been shown to lead to progressively larger movement reversal errors, and trajectories that do not show a sharp reversal of direction, for movements to and from the target in patients who have proprioceptive abnormalities. We computed joint torques at the elbow and shoulder and found a high correlation between elbow and shoulder torque for the neurologically normal subjects. The ratio of joint torques varied systematically with target location. These findings extend previously reported findings of a linear synergy between shoulder and elbow joints for a variety of point-to-point movements. There was also a correlation between elbow and shoulder torque in individuals with Down syndrome, but the magnitude of the correlation was less. The ratio of joint torques changed systematically with target direction in individuals with Down syndrome but was slightly different from the ratio observed for neurologically normal individuals. The difference in the ratio was caused by the generation of proportionately more elbow torque than shoulder torque. The fingertip path of individuals with Down syndrome showed a sharp reversal in moving toward and then away from the target. In this respect, they were similar to neurologically normal individuals but dissimilar to individuals with proprioceptive deficits. Finally, we observed that individuals with Down syndrome spend proportionately more time in the vicinity of the target than normal individuals. Collectively these results show that there is a systematic relationship between joint torques at the elbow and shoulder. This relationship is present for reversal movements and is also present in individuals with Down syndrome.

Effects of direction and curvature on variable error pattern of reaching movements

A number of studies have analyzed various indices of the final position variability in order to provide insight into different levels of neuromotor processing during reaching movements. Yet the possible effects of movement kinematics on variability have often been neglected. The present study was designed to test the effects of movement direction and curvature on the pattern of movement variable errors. Subjects performed series of reaching movements over the same distance and into the same target. However, due either to changes in starting position or to applied obstacles, the movements were performed in different directions or along the trajectories of different curvatures. The pattern of movement variable errors was assessed by means of the principal component analysis applied on the 2-D scatter of movement final positions. The orientation of these ellipses demonstrated changes associated with changes in both movement direction and curvature. However, neither movement direction nor movement curvature affected movement variable errors assessed by area of the ellipses. Therefore it was concluded that the end-point variability depends partly, but not exclusively, on movement kinematics.

Directional control of planar human arm movement

We examined the patterns of joint kinematics and torques in two kinds of sagittal plane reaching movements. One consisted of movements from a fixed initial position with the arm partially outstretched, to different targets, equidistant from the initial position and located according to the hours of a clock. The other series added movements from different initial positions and directions and >40-80 cm distances. Dynamic muscle torque was calculated by inverse dynamic equations with the gravitational components removed. In making movements in almost every direction, the dynamic components of the muscle torques at both the elbow and shoulder were related almost linearly to each other. Both were similarly shaped, biphasic, almost synchronous and symmetrical pulses. These findings are consistent with our previously reported observations, which we termed a linear synergy. The relative scaling of the two joint torques changes continuously and regularly with movement direction. This was confirmed by calculating a vector defined by the dynamic components of the shoulder and elbow torques. The vector rotates smoothly about an ellipse in intrinsic, joint torque space as the direction of hand motion rotates about a circle in extrinsic Cartesian space. This confirms a second implication of linear synergy that the scaling constant between the linearly related joint torques is directionally dependent. Multiple linear regression showed that the torque at each joint scales as a simple linear function of the angular displacement at both joints, in spite of the complex nonlinear dynamics of multijoint movement. The coefficients of this function are independent of the initial arm position and movement distance and are the same for all subjects. This is an unanticipated finding. We discuss these observations in terms of the hypothesis that voluntary, multiple degrees of freedom, rapid reaching movements may use rule-based, feed-forward control of dynamic joint torque. Rule-based control of joint torque with separate dynamic and static controllers is an alternative to models such as those based on the equilibrium point hypotheses that rely on a positionally based controller to produce both dynamic and static torque components. It is also an alternative to feed-forward models that directly solve the problems of inverse dynamics. Our experimental findings are not necessarily incompatible with any of the alternative models, but they describe new, additional findings for which we need to account. The rules are chosen by the nervous system according to features of the kinematic task to couple muscle contraction at the shoulder and elbow in a linear synergy. Speed and load control preserves the relative magnitudes of the dynamic torques while directional control is accomplished by modulating them in a differential manner. This control system operates in parallel with a positional control system that solves the problems of postural stability.

Multidimensional assessment of motor function in a child with cerebral palsy following intrathecal administration of baclofen

This case report describes an 11-year-old boy with spastic diplegia whose reflex status, range of motion (ROM), strength, and motor performance were measured before and after implantation of an indwelling system for delivery of intrathecally administered baclofen. Before baclofen use, the subject experienced clonus that interfered with walking, needed assistance with transfers, and was unable to independently put on underwear and socks. Measures of spasticity, kinematics and electromyographic activity during voluntary movements, ROM, Gross Motor Function Measure (GMFM) scores, and self-reports of change were obtained at baseline, before and after bolus baclofen injection, during a double-blind placebo-controlled clinical trial of baclofen administration via an indwelling pump, and after 1 and 2 years of baclofen therapy. Spasticity, Babinski reflexes, clonus, strength, and coactivation of antagonist muscles during voluntary movement were decreased shortly after baclofen administration began. Hip and ankle ROM increased, upper-extremity movement speed increased, independence in dressing and transfers improved, and orthoses were discarded. After 1 and 2 years, GMFM scores were 7.8% and 6.4% above baseline, respectively; the subject won a fitness award. After 2 years, ROM was worse than at baseline and concerns regarding hip subluxation arose. Single-joint movement control and independence improved and spasticity decreased during baclofen administration.

Organization of a simple two-joint synergy in individuals with Down syndrome

Subjects with Down syndrome and age- and gender-matched control subjects performed discrete elbow or wrist, flexion or extension movements in a sagittal plane, moving one of the joints as fast as possible. The hand was either pronated or supinated. In control subjects, alternating bursts of activity were seen in the agonist-antagonist muscle pair controlling the nonfocal joint. Subjects with Down syndrome, in most series, demonstrated simultaneous bursts of activity in the flexor and extensor muscles controlling both joints. This group difference was particularly pronounced for the muscles controlling the nonfocal joint. We assume that the central nervous system may use two strategies to avoid flapping of a postural joint. The more universal co-contraction strategy in Down syndrome may be viewed as an adaptive feature reflecting a general tendency of these persons to trade efficacy for safety.

Coordinating movement at two joints: a principle of linear covariance

1. Six subjects performed fast, "single-joint" flexions at either the elbow or shoulder over three angular distances in a sagittal plane. Movement endpoints were located to require flexion of only a single, "focal" joint, without any external, mechanical constraint on the other, "nonfocal" joint. Three subjects performed another series of movements between two targets while moving along different paths and in which both joints were flexed. 2. We compared the torque patterns that were produced at the two joints. For single-joint movements, they were both biphasic pulses that accelerated and then decelerated the limb. 3. The torque at the nonfocal joint of a single joint movement was very close to linearly proportional to that at the focal joint throughout the movement. Elbow and shoulder torques differed by a linear scaling constant and went through extrema and zero crossings almost simultaneously. 4. In contrast, during movements in which subjects were explicitly instructed to use a hand path they would not naturally, use the linear interjoint torque scaling rule did not apply. This demonstrated that when we wish to move along a path between two targets that is not produced by linear torque covariation, we are able to modify that rule at will. 5. We speculate that linear, dynamic covariation of the torque patterns across two joints may be an important principle for reducing the number of degrees of freedom that the nervous system must independently control in performing unconstrained limb movements over naturally chosen paths.

Paradoxical effects of practice of fast single-joint movements

We studied the effects of extensive practice of fast, unidirectional, single-joint elbow flexions against a small extending torque bias upon the kinematic and electromyographic (EMG) characteristics of the movements as well as upon the reconstructed hypothetical control patterns (equilibrium trajectories). The subjects were tested at different distances, both with and without the bias torque prior to and after the practice sessions. The basic finding was paradoxical: The subjects did not improve their performance at the practiced task (against the bias) and at other distances in the same condition; however, they showed an increase in movement speed and a decrease in movement time at all distances in unpracticed conditions (without the bias). Changes in the EMG patterns were similar in both conditions. We hypothesize that the principle of learning the dynamics of interaction with the experimental setup in combination with a very steep learning curve form the basis for the observed paradoxical effects of practice. The equilibrium-point hypothesis of movement control provides the least controversial description of these effects as compared to the force-control and EMG-control approaches.

Organizing principles for voluntary movement: extending single-joint rules

1. Four subjects performed fast flexions of the elbow or shoulder over three different distances. Elbow flexions were performed both in a horizontal, single-degree-of-freedom manipulandum and in a sagittal plane with the limb unconstrained. Shoulder flexions were only performed in the sagittal plane by the unconstrained limb. We simultaneously recorded kinematic and electromyographic (EMG) patterns at the "focal" joint, that which the subject intentionally flexed, and at the other, "nonfocal" joint that the subject had been instructed to not flex. 2. Comparisons of the elbow EMG patterns across tasks show that agonist and antagonist muscles were similar in pattern but not size, reflecting the net muscle torque patterns. Comparisons at the shoulder also revealed similar EMG patterns across tasks that reflected net muscle torques. 3. Comparisons of EMG patterns across joints show that elbow and shoulder flexors behaved similarly. This was not true of the extensors. The triceps EMG burst was delayed for longer distances but the posterior deltoid had an early, distance-invariant onset. 4. Similarities in EMG reflect torque demands required at the focal joint to produce flexion and at the nonfocal joint to reduce extension induced by dynamic interactions with the focal, flexing joint. These similarities appear despite very different kinematic intentions and outcomes. This argues against a strong role for length-sensitive reflexes in their generation. 5. These results support the hypothesis that movements are controlled by muscle activation patterns that are planned for the expected torque requirements of the task. This general rule is true whether we are performing single-joint or multiple-joint movements, with or without external constraints. The similarities between single-joint and multijoint movement control may be a consequence of ontogenetic development of multijoint movement strategies that prove useful and are therefore also expressed under the constrained conditions of specialized tasks such as those performed in single-joint manipulanda.

The effects of intrathecally administered baclofen on function in patients with spasticity

The purpose of this article is to review the literature on the effects of intrathecally administered baclofen on impairment in spasticity and muscle activation patterns, on functional limitations in mobility and self-care, and on disability in daily life roles. We found plentiful evidence of improvement in spasticity, spasms, and bladder function and some reports of improved patterns of muscle activation and kinematics of single-joint movement. Improved ability to accomplish transfers, self-care, and locomotion is less consistently studied but has also been reported in about 60% to 70% of patients. Evidence of improved quality of life is primarily anecdotal but may be found in 10% to 30% of patients. We conclude that research protocols should be developed to clarify effects on control of voluntary movement, functional limitations, and quality of life.

Practice and transfer effects during fast single-joint elbow movements in individuals with Down syndrome

BACKGROUND AND PURPOSE

The purpose of this study was to investigate the effects of prolonged practice of a simple motor task (a fast, unidirectional single-joint movement) on different indexes of motor performance in individuals with Down syndrome.

SUBJECTS

Eight individuals with Down syndrome were tested before and after practice involving 1,100 movements.

METHODS

The test consisted of three series of elbow flexion movements. In the first series, the subjects were asked to move "as fast as possible" over four distances. In the second series, the subjects moved over one distance at a "comfortable speed." The initial position of the elbow joint for these two series of movements was 55 degrees into flexion (full elbow extension equals 0 degrees). In the third series, the subjects were also asked to move "as fast as possible" over two distances, but from another initial elbow position (73 degrees into flexion).

RESULTS

After training over a 2-week period, all subjects improved their performance on all tasks as reflected by both kinematic and electromyographic data. In particular, they increased the quantity of the agonist activity, decreased the antagonist onset latency, and doubled their peak velocity. They were able to transfer the improvement in their performance to the nontrained distances and to the different starting position. Subjects decreased their movement time by proportionally decreasing both the acceleration and deceleration times.

CONCLUSION AND DISCUSSION

This study supports the idea that subjects with Down syndrome can use patterns of muscle activation that are qualitatively indistinguishable from those used by individuals who are neurologically normal. With appropriate training, individuals with Down syndrome achieved similar levels of motor performance to that described in the literature for individuals who are neurologically normal.

Preprogrammed reactions in individuals with Down syndrome: the effects of instruction and predictability of the perturbation

Preprogrammed reactions to unexpected loadings and unloadings of an elbow joint resisting an extending bias load were studied in subjects with Down syndrome. The subjects were instructed to either "let go" or "return back as fast as possible." Both predictable and unpredictable perturbation directions were used. Integrated electromyograms of the two elbow flexors and two elbow extensors were used to characterize the preprogrammed reactions. All the subjects were able to modulate their preprogrammed reactions in response to a change in the instruction. They were also able to grade the preprogrammed responses corresponding to the magnitude of the perturbation. Two basic patterns of modulation were observed, "reciprocal" and "coactivation." There were no effects of the predictability of the perturbation direction. Reconstructed joint compliant characteristics suggested an unchanged gain in the arc of the tonic stretch reflex. We propose that there are no abnormalities in the preprogrammed reactions of some individuals with Down syndrome. The apparent "clumsiness" of individuals with Down syndrome in a changing environment is assumed to reflect an adaptation to their impaired decision-making ability. The high variability of motor performance in subjects with Down syndrome may result from mixing different strategies for solving motor tasks.

Kinematic description of variability of fast movements: analytical and experimental approaches

Analysis of variability of fast aimed movements predicts the properties of trajectory variance. The analysis is based on a kinematic model with nonlinear changes in "internal time". The purpose of the work was to identify different sources of variability and their influence on the trajectory variance. An analytical expression for the speed-accuracy trade-off is introduced. Experiments were performed with subjects making single-joint elbow flexion movements over different distances as fast as possible with their eyes closed to memorized targets. Standard deviation of movement trajectory increased during the first part of the movement and subsequently decreased. The variance peaked after the time of peak velocity, close to the time of peak deceleration. A dependence of the trajectory variance on movement distance (speed-accuracy trade-off) was seen during the movement (at times of peak velocity and peak deceleration) but not after the movement termination. We conclude that the previously reported drop in the variability of movement trajectory during the deceleration phase does not necessarily mean a compensation by the control system but may result from purely kinematic properties of the movement. The importance of the time of measurement for analysis of the speed-accuracy trade-offs is emphasized.