Somatosensory & motor research最新文献

Aims: Application of muscle-tendon vibration within the frequency range of 70-120Hz has been studied as a tool to stimulate somatosensory afferents with both the goal of studying human sensorimotor control and of improving post-stroke motor performance. Specific to applications for rehabilitation, current evidence is mixed as to whether dual muscle-tendon vibration is detrimental to the performance of goal-directed upper-limb movements. The current study aimed to determine the effects of muscle-tendon vibration over the wrist flexors and extensors (dual vibration) on performance of a computer goal-directed aiming task.

Methods: Twenty healthy participants were assigned to the vibration or control group. An aiming task that involved acquiring targets by moving an unseen cursor on a screen was performed. Vision of the cursor and hand were unavailable throughout the four blocks of movement execution. Only the vibration group received dual vibration throughout four blocks. Task performance was assessed using measures of endpoint accuracy and timing. Perceived hand location was assessed using a set of questions and a computerised conscious perception task.

Results: The vibration group had significantly shorter reaction times, without any change in endpoint accuracy, indicating more efficient and effective movement planning. The vibration group did report illusory movement sensation, which was reduced by block 4.

Conclusions: Dual vibration did not adversely affect aiming accuracy and showed some improvement in reaction time. The present findings support the potential for using dual vibration to stimulate the somatosensory system as participants improved their performance of a novel goal-directed movement. Notably, improvements were maintained when the vibration was removed.

Background: This study aimed to expand our existing information on changes in the regulation of motor movement and behaviour by investigating the effects of unilateral and bilateral lesions on the claustrum (CL).

Material and methods: 36 Wistar Albino adult male rats were randomly divided into six groups. An electrical lesion was created with a constant current source in the unilateral and bilateral anterior clastrum using a stereotaxic frame in rats. The lesioned groups and the control group underwent an automatic behaviour recording device such as mobilisation, freezing, eating, drinking behaviour, grooming, turning, etc. behaviour was recorded and analysed. Simultaneously, ultrasonic sounds in rats were examined with ultrasonic sound recording program. Anxiety was then reassessed with the elevated plus maze test. Data were compared with the control group. Rats were eventually sacrificed and the brain tissue was post-fixed. Histochemical examination was done and lesions' existence was confirmed.

Results: In this study, lesions of ventral of CL can cause increase in spontaneous behaviours such as freezing and rearing. And, it has been shown to cause a statistically significant change. In addition to the behavioural changes, right CL lesions have caused a significant increase in drinking behaviour associated with increased anxiety. All operated groups showed a significant decrease in clockwise and counterclockwise rotation movements.

Conclusion: Experimental results show that CL lesions influence spontaneous behaviour which indicate the need for new studies to understand the role of CL in anxiety-depression.

Purpose: Previous studies demonstrated that providing light finger touch to a stationary object leads to reduced body sway. The focus of the current exploratory study was on the investigation of postural sway during one-leg stance when light touch is provided by the contralateral foot.

Methods: Eleven healthy young adults participated in the study. They stood on the top of the force platform with eyes open and on their dominant leg with no touch and with a touch from the contralateral foot applied to the stance leg. Medial arch, heel, and big toe of the contralateral foot were used to touch the medial malleolus or mid shank of the stance leg. The excursion, velocity, and sway area of the centre of pressure were obtained and analysed.

Results: Standing with light touch from the contralateral foot to the medial malleolus resulted in significantly smaller postural sway as compared to standing with no touch (p < 0.05). There was no difference in the study outcomes between conditions of standing with a touch applied by the medial arch, heel, or big toe to the stance leg.

Conclusions: The results of the study suggest that the application of light touch provided by a contralateral foot could be an effective strategy for enhancing body stability when no external support is available. The study outcome provides a foundation for future studies exploring ways to enhance balance control during one-leg stance.

Purpose: This study aimed to identify the contribution of the common synaptic drives to motor units during obstacle avoidance, using coherence analysis between a-pair electromyography (EMG) signals (EMG-EMG coherence).

Materials and methods: Fourteen healthy volunteers walked on a treadmill with and without obstacle avoidance. During obstacle gait, subjects were instructed to step over an obstacle with their right leg while walking that would randomly and unpredictably appear. Surface EMG signals were recorded from the following muscles of the right leg: the proximal and distal ends of tibialis anterior (TAp and TAd), biceps femoris (BF), semitendinosus (ST), lateral gastrocnemius (LG), and medial gastrocnemius (MG). Beta-band (13-30 Hz) EMG-EMG coherence was analysed.

Results: Beta-band EMG-EMG coherence of TAp-TAd during swing phase and BF-ST during pre and initial swing phase when stepping over an obstacle were significantly higher compared to normal gait (both p < 0.05). Beta-band EMG-EMG coherence of TAp-TAd, BF-ST, and LG-MG during stance phase were not significantly different between the two gait conditions (all p > 0.05).

Conclusions: The present findings suggest increased common synaptic drives to motor units in ankle dorsiflexor and knee flexor muscles during obstacle avoidance. It also may reflect an increased cortical contribution to modify the gait patterns to avoid an obstacle.

Aim: This study aimed to compare the acute effects of different methods on ankle joint range of motion (ROM) in older adults.

Materials and methods: Seventy-eight older adults were randomly divided into three groups. After the warming-up, static stretching, proprioceptive neuromuscular facilitation (PNF) contract-relax, and roller massage were applied, at the same period. Before application, immediately after, 10 and 20 min after application, ankle joint dorsiflexion ROM was measured in the weight-bearing position.

Results: No statistically significant difference between the groups in demographic characteristics and baseline ankle ROM (p = 0.413). In all groups, post-application measurements revealed increased ankle joint motion (p < 0.0125). Groups were compared, and a statistically significant difference between the three groups was found (p < 0.05). There was no significant difference in the change of ROM between the Static Stretching and PNF Stretching Groups in the change of ROM group comparisons (p = 0.089). There was a statistically significant difference in ROM changes Roller Massage Group and both Static Stretching and the PNF Stretching Group (p = 0.001).

Conclusion: The acute effects of roller massage, on ankle ROM, were superior to static and PNF stretching. The application of roller massage, which was shown to be an effective method for increasing ROM, can be safely applied in physiotherapy programs for older adults.

Aim of the study: Brain-computer interfaces (BCIs) may help patients with severe neurological deficits communicate with the external world. Based on microelectrocorticography (µECoG) data recorded from the primary somatosensory cortex (S1) of unrestrained behaving rats, this study attempts to decode lever presses in a psychophysical detection task by using machine learning algorithms.

Materials and methods: 16-channel Pt-Ir microelectrode arrays were implanted on the S1 of two rats, and µECoG was recorded during a vibrotactile yes/no detection task. For this task, the rats were trained to press the right lever when they detected the vibrotactile stimulus and the left lever when they did not. The multichannel µECoG data was analysed offline by time-frequency methods and its features were used for binary classification of the lever press at each trial. Several machine learning algorithms were tested as such.

Results: The psychophysical sensitivities (A') were similar and low for both rats (0.58). Rat 2 (B'': -0.11) had higher bias for the right lever than Rat 1 (B'': - 0.01). The lever presses could be predicted with accuracies over 66% with all the tested algorithms, and the highest average accuracy (78%) was with the support vector machine.

Conclusion: According to the recent studies, sensory feedback increases the benefit of the BCIs. The current proof-of-concept study shows that lever presses can be decoded from the S1; therefore, this area may be utilised for a bidirectional BCI in the future.

Aim of the study: Sensory gating is a human higher cognitive function that serves to suppress excessive sensory information and prevent brain overactivity. To elucidate this function, a paired-pulse stimulation paradigm has been used while recording electroencephalography (EEG), and evaluated as an amplitude ratio of responses to a second stimulus (S2) over responses to the first stimulus (S1). The present study investigated the effects of the inter-stimulus interval (ISI) and inter-trial interval (ITI) on somatosensory gating using somatosensory-evoked potentials (SEPs).

Methods: In Experiment 1, ISI was set at five conditions: 200, 400, 600, 800, and 1000 ms. In Experiment 2, ITI was set at four conditions: 1, 2, 4, and 8 s.

Results: ISI affected the S2/S1 amplitude ratios of P22 and N27 at C3' and N30 at Fz, and these S2/S1 amplitude ratios decreased the most under the 200 and 400-ms conditions. ITI affected the S2/S1 amplitude ratios of P22, N27, and N60 at C3', and especially, the somatosensory gating did not work under the 1-s condition. These results suggest that not all SEP components are modulated in the same manner with changing ISI and ITI. The effects of ISI and ITI independently affected the somatosensory gating.

Conclusions: Based on our findings, preferable parameters are 200-400 ms for ISI and 4 s or longer for ITI to evaluate the functional mechanisms on somatosensory gating in SEPs.

This study examined whether tactile gating induced by the descending motor command to one finger spreads out to the other fingers to which the command is not delivered and whether this gating is dependent on the target finger to which the command is delivered. The change in perceptual threshold to the digital nerve stimulation of one finger induced by tonic contraction of the first dorsal interosseous or abductor digiti minimi muscle was examined. The perceptual threshold to the digital nerve stimulation of the thumb or little finger was increased by tonic contraction of the abductor digiti minimi muscle. This finding indicates that the descending motor command to the prime mover of the little finger abduction induces tactile gating not only in the finger to which the command is delivered but also in the other finger to which the command is not delivered. Tonic contraction of the first dorsal interosseous muscle did not change the perceptual threshold to the digital nerve stimulation in any finger. This finding means that tactile gating occurs particularly when the descending motor command is delivered to the dependent finger. Spreading out of tactile gating of one finger, to which the descending motor command is not delivered, is likely mediated by surround inhibition.

Aim of the study: The application of a noxious stimulus reduces the perception and responsiveness to other pain stimuli. This inhibition can be experimentally assessed with a method called 'counterirritation'. The question arises if counterirritation acts also on the perception and responsiveness to aversive but non-nociceptive stimuli (e.g., loud tones). Since aversive stimulation is often associated with state anxiety or state fear, we investigated in addition the modulatory effects of these emotions on counterirritation.

Material and methods: 51 subjects participated in our study. We presented tones with aversive loudness (105 dB), first alone then during counterirritation (immersion of the hand in a hot water bath of 46 °C) to assess inhibition of loudness perception and responsiveness. Influences of state anxiety and state fear on counterirritation were investigated by using the Neutral-Predictable(fear)- Unpredictable(anxiety) Paradigm (NPU), which is based on classical conditioning. Loudness ratings (perception of the aversive tones) and startle reflex (defensive reaction to aversive tones) were assessed.

Results: Counterirritation reduced startle reflex amplitudes, but not the loudness ratings. Although state anxiety and state fear were successfully induced, counterirritation remained unaffected.

Conclusions: Our study showed that pain inhibits the responsiveness to aversive stimuli (loud tones). Thus, the postulate that 'pain inhibits pain' might be better changed to 'pain inhibits aversiveness'. Consequently, our findings may also question the assumption of a clear pain specificity in inhibitory action as assumed by theoretical approaches like 'conditioned pain modulation' (CPM). Furthermore, counterirritation appeared one more time resistant to the influence of negative emotions.