Yu-Cheng Pei

Sagittal plane loading response during gait in different age groups and in people with knee osteoarthritis.

Chen CPC, Chen MJL, Pei YC, Lew HL, Wong PY, Tang SFT: Sagittal plane loading response during gait in different age groups and in people with knee osteoarthritis. Am J Phys Med Rehabil 2003;82:307–312. Objective To investigate the gait patterns and the sagittal ground reaction forces in different age groups and in people with knee osteoarthritis. Design Motion analysis and force platform data were collected for a total of 55 female subjects capable of independent ambulation. Subjects were divided into three groups consisting of the control group, the elderly group, and the osteoarthritis knee group. Gait parameters of walking velocity, cadence, step length, stride time, single- and double-support time, and sagittal ground reaction forces were obtained during comfortable walking speed. Gait analysis was performed in a tertiary hospital’s gait laboratory. Variables were analyzed using a univariate repeated-measures analysis of variance. Statistical significance was set at a value of P < 0.05. Results The osteoarthritis knee group had slower walking velocity, lower cadence, and longer stride time as compared with the elderly and young control groups (P < 0.05). In ground reaction force studies, the first peak time, expressed in percentage of gait cycle, was significantly longer in the osteoarthritis knee group (20.8 ± 3.2) as compared with the elderly (17.8 ± 2.0) and young control groups (17.1 ± 1.8, P < 0.01). The force during time of minimal midstance was larger in the osteoarthritis knee group (90.9 ± 5.3) as compared with the elderly and young control groups (P < 0.05). The second peak force was significantly smaller in the osteoarthritis knee group as compared with the young control group (P < 0.01). The force change in the midfoot region in the osteoarthritis knee and elderly groups revealed more loading force onto the midfoot region during midstance as compared with the young control group (P < 0.01). Conclusion Gait parameters in the elderly and osteoarthritis knee patients were characterized by slower walking velocity, lower cadence, shorter step length, longer stride time, and longer double-support time. Less heel contact and push-off forces were noticed in these two groups, with more loading force onto the midfoot during midstance.

Influence of heel height and shoe insert on comfort perception and biomechanical performance of young female adults during walking

Background: The possible negative effects of high-heeled shoes on subjective comfort perception and objective biomechanical assessment have been noted. Although shoe inserts have been widely applied in footwear to increase comfort and to reduce the frequency of movement-related injury, no study has attempted to identify insert effectiveness in high heels. The purpose of this study was to determine the effects of heel height and shoe inserts on comfort and biomechanics as represented by plantar pressure and ground reaction force (GRF). Methods: Twenty young female adults performed the test conditions formed by the cross-matching of shoe inserts (shoe without insert and shoe with total contact insert [TCI]) and heel height (a flat, a low heel [3.8 cm] and a high heel [7.6 cm]). Two-way analyses of variance for repeated measures design were used to test condition effects on comfort rating, plantar pressure, and GRF during gait. To determine the biomechanical variables that can predict comfort, a multiple linear regression with stepwise method was done. Results: The results showed that discomfort increased with heel height. In high heels, the plantar pressure in the heel and midfoot shifted to the medial forefoot, and the vertical and anteroposterior GRF increased. Use of the TCI reduced the peak pressure in the medial forefoot. Interestingly, the effectiveness of the TCI was greater in the higher heels than in the lower heels and in flat heels. The peak pressure in the medial forefoot, impact force, and the first peak vertical GRF could explain 75.6% of the variance of comfort in high-heeled gait. Conclusions: These findings suggest that higher heels result in decreased comfort, which can be reflected by both the subjective rating scale and biomechanical variables. Use of a TCI altered the biomechanics and therefore improved the comfort in high-heeled shoes.

Shape Invariant Coding of Motion Direction in Somatosensory Cortex

A subpopulation of neurons in primate somatosensory cortex signal the direction in which objects move across the skin of the fingertips.

Convergence of submodality-specific input onto neurons in primary somatosensory cortex.

At the somatosensory periphery, slowly adapting type 1 (SA1) and rapidly adapting (RA) afferents respond very differently to step indentations: SA1 afferents respond throughout the entire stimulus interval (sustained response), whereas RA afferents respond only at stimulus onset (on response) and offset (off response). We recorded the responses of cortical neurons to step indentations and found many neurons in areas 3b and 1 to exhibit properties that are intermediate between these two extremes: These neurons responded during the sustained portion of the stimulus and also at the offset of the stimulus. Several lines of evidence indicate that these neurons, which exist in large proportions even at these early stages of somatosensory cortical processing, receive input from both populations of afferents. First, we show that many cortical neurons have both a significant sustained response and a significant off response. Second, the strength of the off response is uncorrelated with that of the sustained response, which is to be expected if sustained and off responses stem from different populations of afferent fibers. Third, the bulk of the variance in cortical responses to step indentations can be accounted for using a linear combination of both SA1 and RA responses. Finally, we show that the off response in cortical neurons does not reflect rebound from inhibition. We conclude that the convergence of modality specific input onto individual neurons is common in primary somatosensory cortex and discuss how this conclusion might be reconciled with previous findings.

Neural Mechanisms of Tactile Motion Integration in Somatosensory Cortex

How are local motion signals integrated to form a global motion percept? We investigate the neural mechanisms of tactile motion integration by presenting tactile gratings and plaids to the fingertips of monkeys, using the tactile analogue of a visual monitor and recording the responses evoked in somatosensory cortical neurons. The perceived directions of the gratings and plaids are measured in parallel psychophysical experiments. We identify a population of somatosensory neurons that exhibit integration properties comparable to those induced by analogous visual stimuli in area MT and find that these neural responses account for the perceived direction of the stimuli across all stimulus conditions tested. The preferred direction of the neurons and the perceived direction of the stimuli can be predicted from the weighted average of the directions of the individual stimulus features, highlighting that the somatosensory system implements a vector average mechanism to compute tactile motion direction that bears striking similarities to its visual counterpart.

The tactile integration of local motion cues is analogous to its visual counterpart

The visual and somatosensory systems have been shown to process spatial information similarly. Here we investigate tactile motion processing using stimuli whose perceptual properties have been well established in vision research, namely superimposed gratings (plaids), barber poles, and bar fields. In both modalities, information about stimulus motion (speed and direction) conveyed by neurons at low levels of sensory processing is ambiguous, a conundrum known as the aperture problem. Our results suggest that the tactile perception of motion, analogous to its visual counterpart, operates in multiple stages: first, the perceived direction of motion is determined by a majority vote from local motion detectors, which are subject to the aperture problem. As in vision, the conflict between the cues from terminators and other local motion cues is gradually resolved over time so that the perceived direction approaches the veridical direction of motion.

Eye-hand Coordination of Elderly People Who Practice Tai Chi Chuan

BACKGROUND/PURPOSE The objective of this study was to evaluate the effect of motor control from Tai Chi Chuan (TCC) on eye-hand coordination in the elderly. METHODS Forty-two elderly people were recruited into this study. People in the TCC group (n = 22) had been practicing TCC regularly for more than 3 years. The control group (n = 20) comprised healthy and active elderly people. Subjects were asked to stroke target sensors in a test device with computer recording. There were three different target sensor sizes (1 cm, 1.5 cm and 2 cm in diameter) for different tests. For each target stroking, the following were recorded and calculated: start and end positions, duration of movement, pause time, peak velocity, and the time to reach peak velocity. RESULTS The TCC group showed significantly better results in decrease of displacement (p = 0.003), movement time (p = 0.002), pause time (p < 0.001), number of submovements (p = 0.001), and better skewness coefficients (p < 0.001) than the control group. However, the difference in the peak velocity of the TCC and control groups did not reach statistical significance (p = 0.026). CONCLUSION The elderly TCC group had better results on the eye-hand coordination test than the control elderly group.

Validity, Responsiveness, and Clinically Important Difference of the ABILHAND Questionnaire in Patients With Stroke

OBJECTIVE To investigate the criterion-related validity, responsiveness, and clinically important differences of the ABILHAND questionnaire in patients with stroke. DESIGN Validation and clinimetric study. SETTING Three medical centers. PARTICIPANTS Patients with stroke (N=51). INTERVENTIONS A total of 51 patients with stroke received 1 of 3 upper extremity rehabilitation programs for 4 weeks. MAIN OUTCOME MEASURES The ABILHAND and the criterion measures, including the Stroke Impact Scale (SIS), FIM, Nottingham Extended Activities of Daily Living (NEADL), and accelerometers, were administered at pretreatment and posttreatment. The score of the ABILHAND, given in logits, was based on the conversion of the ordinal score into a linear measure of ability. RESULTS Correlation coefficients (Pearson r) were moderate to large between the ABILHAND and SIS physical domains (.54-.66), fair to moderate between the ABILHAND and FIM-motor and NEADL (.28-.48), and moderate between the ABILHAND and accelerometer data (.45-.54). The responsiveness of the ABILHAND was large (standardized response mean=1.27). The minimal clinically important difference range for the ABILHAND was .26 to .35, and 51.0% of the patients showed a positive change that exceeded the lower bound of a clinically important difference after intervention. CONCLUSIONS The results support that the ABILHAND is an appropriate outcome measure for assessing upper extremity performance in daily activities in patients with stroke and is sensitive to detect change after rehabilitative interventions. The change score of a patient with stroke on the ABILHAND should reach .26 to .35 logits points to be regarded as a clinically important change.

Botulinum Toxin Type A on Oral Health in Treating Sialorrhea in Children With Cerebral Palsy: A Randomized, Double-Blind, Placebo-Controlled Study:

Intrasalivary gland injection of botulinum toxin type A is known to treat sialorrhea effectively in children with cerebral palsy. However, oral health may be compromised with escalating dose. In this randomized, double-blind, and placebo-controlled pilot trial, the authors aim to determine the therapeutic effect of low-dose, ultrasonography-controlled botulinum toxin type A injection to bilateral parotid and submandibular glands on oral health in the management of sialorrhea. Twenty children diagnosed with cerebral palsy were randomly assigned to 2 groups. The treatment group received botulinum toxin type A injections, whereas the control received normal saline in the same locations. The authors evaluated subjective drooling scales, salivary flow rate, and oral health (salivary compositions and cariogenic bacterial counts). A significant decrease was found in salivary flow rate at the 1- and 3-month follow-up in the botulinum toxin—treated group. The authors suggest that current protocol can effectively manage sialorrhea while maintaining oral health.

Neuromodulation accompanying focused ultrasound-induced blood-brain barrier opening

Burst-mode focused ultrasound (FUS) induces microbubble cavitation in the vasculature and temporarily disrupts the blood-brain barrier (BBB) to enable therapeutic agent delivery. However, it remains unclear whether FUS-induced BBB opening is accompanied by neuromodulation. Here we characterized the functional effects of FUS-induced BBB opening by measuring changes in somatosensory evoked potentials (SSEPs) and blood-oxygen-level dependent (BOLD) responses. Rats underwent burst-mode FUS (mechanical index (MI) of 0.3, 0.55 or 0.8) to the forelimb region in the left primary somatosensory cortex to induce BBB opening. Longitudinal measurements were followed for up to 1 week to characterize the temporal dynamics of neuromodulation. We observed that 0.8-MI FUS profoundly suppressed SSEP amplitude and prolonged latency, and this effect lasted 7 days. 0.55-MI FUS resulted in minimal and short-term suppression of SSEP for less than 60 minutes and didn’t affect latency. BOLD responses were also suppressed in an MI-dependent manner, mirroring the effect on SSEPs. Furthermore, repetitive delivery of 0.55-MI FUS every 3 days elicited no accumulative effects on SSEPs or tissue integrity. This is the first evidence that FUS-induced BBB opening is accompanied by reversible changes in neuron responses, and may provide valuable insight toward the development of FUS-induced BBB opening for clinical applications.