Somatosensory & motor research最新文献

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.

Purpose: We investigated the connectivity of neural signals from movement-related cortical areas to the primary motor area (M1) in the hemisphere contralateral to the movement side during the period of movement-related magnetic fields before movement.

Materials and methods: Participants were 13 healthy adults, and nerual signals were recorded using magnetoencephalography. Spontaneous extension of the right wrist was performed at the participant's own pace and following a visual cue in internal (IC) and external (EC) cue tasks. The connectivity of neural signals to M1 from each movement-related motor area was assessed by Granger causality analysis (GCA). The GCA was performed on the neural activity elicited in a frequency band between 7.8 and 46.9 Hz during the pre-movement periods, which occurred durng the readiness field (RF) and the negative slope prime (NSp). F-values, as connectivity values obtained by GCA, were compared between the EC and IC cue tasks.

Results: For NSp periods, the connectivity of neural signals from the left superior frontal area (SF-L) to M1 was dominant in the IC task, whereas that from the left superior parietal area (SP-L) to M1 was dominant in the EC task. The F value in the GCA from SP-L to M1 was greater in the EC task during RF than in the IC task during equivalent periods.

Conslusions: In the present study, there were differences in the connectivity of neural signals to M1 between IC and EC tasks. The present results suggested that the pattern of pre-movement neural activity that resulted in a movement was not uniform but differed between movement tasks just before the movement.

Background: Transcranial direct current stimulation (tDCS) is widely used in motor recovery. Nevertheless, whether tDCS improves motor learning in healthy older adults is still controversial. This review aims to investigate the effectiveness of tDCS on motor learning in healthy elderly individuals.

Methods: The PubMed, Cochrane Library, Web of Science and Embase databases were initially searched from inception to December 5, 2022. The standard mean difference (SMD) with the corresponding 95% confidence intervals (CIs) were analysed via random-effect models.

Results: Compared with the sham group, no significant effects were found regarding improvement in motor learning based on the speed or accuracy of the task and reaction time for the tDCS intervention group. After subgroup analysis, a significant effect was found for improved motor learning based on reaction time in the primary motor cortex (M1)-cerebellar group.

Conclusions: This review revealed that tDCS had no significant effect on improving the speed or accuracy of motor learning in healthy elderly adults. However, it has a significant effect on improving the motor learning ability based on the reaction time of the task (mainly referring to the tDCS stimulation position of M1 and cerebellar), although the results have obvious heterogeneity and uncertainty.

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.

Purpose/Aim. Autistic individuals may show either hyper- or hypo- responsiveness to touch compared to non-autistic individuals. These behavioural responses depend on perceptual and evaluative mechanisms, which unfold sequentially and thus can be distinguished by exploring the timing of neural responses. In this study, we examined neural response timing to pleasant, unpleasant, and affectively neutral textures, to determine whether these perceptual versus evaluative subprocesses differ in autism and how each subprocess contributes to behavioural responses.Materials and Methods. Our sample included n = 13 autistic and n = 14 non-autistic adults who completed functional magnetic resonance imaging. We analysed early, intermediate, and late phases of the tactile response, derived from studies of noxious tactile stimulation, to three different textures.Results. The autistic group showed distinct differences from the non-autistic group to each of the textures, showing earlier, somatosensory differences in response to the pleasantly and unpleasantly rated textures and later, frontomotor differences in response to the neutrally rated texture. Further, reduced early phase response to the pleasant texture correlated with increased sensory seeking behaviour.Conclusions. While preliminary, these results suggest distinct patterns between autistic and non-autistic individuals in how the neural response to touch unfolds and its correspondence with the perceived pleasantness of tactile experience. The findings suggest perceptual differences in response to affectively charged textures and evaluative differences in response to neutral, ambiguous textures. These temporal properties may inform future studies of tactile processing in autism, lending a better understanding of how individuals differ in their sensory experiences across contexts.