Integration of proprioceptive and visual feedback during online control of reaching

Visual and proprioceptive feedback both contribute to perceptual decisions, but it remains unknown how these feedback signals are integrated together or consider factors such as delays and variance during online control. We investigated this question by having participants reach to a target with randomly applied mechanical and/or visual disturbances. We observed that the presence of visual feedback during a mechanical disturbance did not increase the size of the muscle response significantly but did decrease variance, consistent with a dynamic Bayesian integration model. In a control experiment we verified that vision had a potent influence when mechanical and visual disturbances were both present but opposite in sign. These results highlight a complex process for multi-sensory integration, where visual feedback has a relatively modest influence when the limb is mechanically disturbed, but a substantial influence when visual feedback becomes misaligned with the limb.

The Influence of Neuroticism on the Muscle Response in the Trapezius and Frontalis Muscles to Anticipatory Stress

Objective quantification of mental stress in the workplace would be beneficial for designing work tasks to avoid the negative consequences of mental stress. Methods such as surface electromyography have proven to be sensitive to mental demands. However, there is little knowledge about the muscle response and moderating factors during anticipatory stress paradigms. This study examined whether the personality dimension neuroticism moderates the muscle response to the expectation of an unpredictable electrical shock. Forty-seven subjects underwent three expectation phases, in which they could expect a pleasant audio signal (NoShock) or an electric shock in two conditions (anticipation of the first: Shock1, and second electric shock: Shock2) at an unpredictable moment. The frontalis muscle activity and the upper and upper/middle parts of the trapezius muscle were recorded using surface electromyography. Neuroticism was surveyed using the Big Five Inventory to assign the subjects to a group with lower or higher neuroticism. Shock1 only induced higher trapezius muscle activity in the higher neuroticism group, which vanished during Shock2, while the frontalis muscle showed no significant effects. The results suggest that neuroticism should be considered a moderating factor in assessing anticipatory stress using surface electromyography at the trapezius muscle.

Dynamic analysis of lower leg muscles response to whole body vibration stimulation at different frequencies and postures: implications for training

PurposeTo characterise the mechanical and neuromuscular response of lower limb muscles in subjects undergoing Whole Body Vibration (WBV) at different frequencies while holding two static postures.MethodsTwenty-five participants underwent WBV at 15, 20, 25 and 30 Hz while holding a static ‘hack squat’ and on ‘fore feet’ posture. Surface electromyography (sEMG) and soft tissue accelerations were collected from Gastrocnemius Lateralis (GL), Soleus (SOL) and Tibialis Anterior (TA) muscles.ResultsOnly specific WBV settings led to a significant increase in muscle contraction. Specifically, the WBV-induced activation of SOL and GL was maximal in fore-feet and in response to higher frequencies. Estimated displacement at muscle bellies revealed a resonant pattern never highlighted before. After stimulation starts, muscle oscillation reaches a peak followed by a drop and a further stabilisation (few seconds after the peak) that suggests the occurrence of a neuromuscular activation to reduce the vibration-induced oscillation.ConclusionLower leg muscles need a response time to tune to a vibratory stimulation, which discourages the use of dynamic exercises on vibrating platforms. To maximize calf muscle response to WBVs, a stimulation frequency in the range of 25-30 Hz and an ‘on fore feet’ posture are recommended.

RESULTS OF STUDY OF THE HYPOGLOSSAL NERVE FUNCTIONS IN PATIENTS AFTER HYPOGLOSSAL-FACIAL ANASTOMOSIS

Hypoglossal-facial anastomosis is a common method of restoring and/or replacing lost facial nerve function. At the same time, there are works that compare functional disorders of the XII pair of cranial nerves that arise in patients with various types of hypoglossal-facial anastomosis, which, in turn, indicates the rather great importance of this problem, as well as the need for further research. There are several modifications of the hypoglossal-facial anastomosis, which differ significantly, including the effect on the function of the tongue muscles. An important instrumental method for studying the function of the hypoglossal nerve is electromyography, namely, the determination of the total evoked potentials of the tongue muscles. In order to study complications in the form of dysfunction of the tongue muscles due to hypoglossal-facial anastomosis, a comparative analysis of the data of the tongue electromyography in patients after performing these interventions was carried out. Materials and methods. The study included 55 patients with chronic suppurative otitis media, with tumors of the cerebello-pontine angle (acoustic and vestibular schwannomas, tumors of the jugular glomus) complicated by a lesion of the facial nerve. In the main group of patients (20 patients), the original technique of the modified hypoglossal-facial anastomosis was used to restore the facial nerve function. Patients (n=35) in the control group underwent a classic hypoglossal-facial anastomosis. Results. As can be seen from the above data, when comparing the tongue muscles contraction amplitude 3, 6 and 12 months after the formation of the hypoglossal-facial anastomosis, a statistically significant decrease in this indicator is observed on the side of performing the hypoglossal-facial anastomosis in comparison with the intact side at all stages of the study (p <0.05) (p <0.05) (p <0.01), respectively. When comparing the indicators of the total muscle response in patients after using the modified and classical methods of XII-VII anastomosis, there was a statistically significant increase in the compound muscle response of the tongue in the main group - by an average of 10.94% (p <0.05). Conclusion. Performing hypoglossal-facial anastomosis leads to gross dysfunction of the hypoglossal nerve on the side of the intervention, manifested in the form of a significant decrease in the amplitude of muscle contraction according to electromyography of the tongue. The use of the modified technique of XII-VII anastomosis provided the restoration of the total muscle potential of the tongue by 8.82% after 3 months, by 8.7% – after 6 months. and by 15.38% – after 12 months after surgery in comparison with the group where the classic hypoglossal-facial anastomosis was performed.