Effects of Perturbation Velocity, Direction, Background Muscle Activation, and Task Instruction on Long-Latency Responses Measured From Forearm Muscles.

The central nervous system uses feedback processes that occur at multiple time scales to control interactions with the environment. The long-latency response (LLR) is the fastest process that directly involves cortical areas, with a motoneuron response measurable 50 ms following an imposed limb displacement. Several behavioral factors concerning perturbation mechanics and the active role of muscles prior or during the perturbation can modulate the long-latency response amplitude (LLRa) in the upper limbs, but the interactions among many of these factors had not been systematically studied before. We conducted a behavioral study on thirteen healthy individuals to determine the effect and interaction of four behavioral factors - background muscle torque, perturbation direction, perturbation velocity, and task instruction - on the LLRa evoked from the flexor carpi radialis (FCR) and extensor carpi ulnaris (ECU) muscles after velocity-controlled wrist displacements. The effects of the four factors were quantified using both a 0D statistical analysis on the average perturbation-evoked EMG signal in the period corresponding to an LLR, and using a timeseries analysis of EMG signals. All factors significantly modulated LLRa, and their combination nonlinearly contributed to modulating the LLRa. Specifically, all the three-way interaction terms that could be computed without including the interaction between instruction and velocity significantly modulated the LLR. Analysis of the three-way interaction terms of the 0D model indicated that for the ECU muscle, the LLRa evoked when subjects are asked to maintain their muscle activation in response to the perturbations was greater than the one observed when subjects yielded to the perturbations (p < 0.001), but this effect was not measured for muscles undergoing shortening or in absence of background muscle activation. Moreover, higher perturbation velocity increased the LLRa evoked from the stretched muscle in presence of a background torque (p < 0.001), but no effects of velocity were measured in absence of background torque. Also, our analysis identified significant modulations of LLRa in muscles shortened by the perturbation, including an interaction between torque and velocity, and an effect of both torque and velocity. The time-series analysis indicated the significance of additional transient effects in the LLR region for muscles undergoing shortening.

Effects of treadmill training on the balance, functional capacity and quality of life in Parkinson's disease: A randomized clinical trial.

Background There is growing evidence that exercise modalities have considerable effects on Parkinson's disease (PD). This trial aimed to provide a more detailed viewpoint of short-term and long-term treadmill training (TT) effects on some motor and non-motor features of PD. Methods In this prospective, randomized, single-blind clinical trial, 20 mild to moderate PD patients, admitted in Rasoul-e-Akram hospital in Tehran, Iran, were randomly allocated in case (11) and control (9) groups. Treadmill intervention was performed at moderate intensity with 60% of heart rate reserved (HRR) in two 30-min sessions/week for a duration of 10 weeks. Both the groups were evaluated for three times; at the baseline, 2 months later and then 2 months after the second evaluation. We assigned the Timed Up and Go test (TUG), 6-min walk test (6MW), and the SF-8 healthy questionnaire, for assessment of balance, functional capacity, and Quality of life (QoL), respectively. Results Balance and functional capacity were significantly improved in the case group after the intervention (TUG p-value: 0.003, 6MW p-value: 0.003). Moreover, the long-term analysis revealed significant results as well (TUG p-value: 0.001, 6MW p-value: 0.004). Mental condition's scores of SF-8 in cases were not statistically different in short-term follow-up (F/U). However, analysis illustrated p-value: 0.016 for long-term assessment. The intervention induced significant changes in physical condition's scores in both of the F/Us (PC p-value: 0.013). Conclusions This study provides evidence that a TT of mild to moderate intensity has significant and persistent benefits for the balance, functional capacity, and QoL in PD.

The Effect of Luteinizing Hormone Reducing Agent on Anxiety and Novel Object Recognition Memory in Gonadectomized Rats.

INTRODUCTION: Mood disorders such as anxiety and depression are common following menopause and andropause. Lack of sex steroid hormones is suggested as the primary cause of these disturbances. The level of luteinizing hormone (LH) would also rise 3-4 times than normal in these people. The potential effects of LH on mood and cognitive symptoms following menopause and andropause are still unknown. This study aimed to investigate the effect of increased LH on novel object discrimination (NOD) memory and anxiety like behavior in gonadectomized rats. METHODS: Four-month-old male and female Wistar rats were randomly assigned into 4 groups (in each sex): control rats (Cont), gonadectomized without treatment (GnX), gonadectomized treated with triptorelin, a GnRH agonist which reduces LH release eventually, (GnX+Tr), gonadectomized treated with triptorelin plus sex steroid hormone, estradiol in female and testosterone in male rats (GnX+Tr+S/T). After 4 weeks treatment, anxiety score (elevated plus maze) and NOD were measured. Data were analyzed using One-way ANOVA, and P-values less than 0.05 were considered as significant. RESULTS: Gonadectomy increased anxiety like behaviors (decrease of presence time in the open arms) in female rats (P=0.012), but not in male ones (P=0.662). Additionally, triptorelin alone reduced the increased anxiety score in gonadectomized female rats, compared to group treated with both triptorelin and estradiol. Furthermore, it was shown that gonadectomy and or treatment with triptorelin and sex steroids had no significant effect on novel object recognition memory in both female (P=0.472) and male rats (P=0.798). CONCLUSION: Findings of this study revealed that increased level of LH following menopause or andropause should be considered as a possible cause for increased anxiety. Also, this study showed that LH reducing agents would reduce anxiety like behavior in gonadectomized female rats. The effect of increased LH on cognitive functions such as novel object recognition memory was not evident in this study and needs further studies.