Eriko Shibata

The effects of kinesthetic illusory sensation induced by a visual stimulus on the corticomotor excitability of the leg muscles.

A novel method of visual stimulus, reported by Kaneko et al. [14], induced a vivid kinesthetic illusion and increased the corticomotor excitability of the finger muscles without any overt movement. To explore the effect of this method on the lower limbs, motor evoked potentials (MEP) were recorded from the left tibialis anterior (TA) and soleus muscles using transcranial magnetic stimulation (TMS). A computer screen that showed the moving image of an ankle movement was placed over the subjects leg, and its position was modulated to induce an illusory sensation that the subjects own ankle was moving (illusion condition). TMS was delivered at rest and at two different times during the illusion condition (ankle dorsiflexion phase: illusion-DF; ankle plantarflexion phase: illusion-PF). The MEP amplitude of the TA, which is the agonist muscle for ankle dorsiflexion, was significantly increased during the illusion-DF condition. This indicated that the visual stimulus showing the moving image of an ankle movement could induce a kinesthetic illusion and selectively increase the corticomotor excitability in an agonist muscle for an illusion, as was previously reported for an upper limb. The MEP amplitude of the soleus, which is the agonist muscle for ankle plantarflexion, increased during the illusion-PF condition, but not significantly. Because of the vividness of the illusory sensation was significantly greater during the illusion-DF condition than the illusion-PF condition, we concluded that the vividness of the illusory sensation had a crucial role in increasing corticomotor excitability.

The effect of fatigued internal rotator and external rotator muscles of the shoulder on the shoulder position sense

The purpose of this study was to investigate which muscle group, the agonist or antagonist, contributes most to the shoulder position sense (SPS). The SPS was tested under 2 conditions: fatigued shoulder internal rotator (IR) muscles (pectoralis major and latissimus dorsi) and fatigued external rotator (ER) muscles (infraspinatus). In each condition, the SPS was measured before and after a fatiguing task involving the IR or ER muscles by repeating shoulder joint rotation. SPS was measured using a method in which subjects reproduced a memorized shoulder joint rotation angle. The position error values in all conditions (fatigued IR and ER muscles) and measurement periods (before- and after-fatigue task) were compared using 2-way analysis of variance with repeated measures (IR/ER×before/after). Position error increased significantly after both fatigue tasks (before- vs. after-fatigue: IR muscle, 2.68° vs. 4.19°; ER muscle, 2.32° vs. 4.05°). In other words, SPS accuracy decreased when either the agonist or antagonist muscle was fatigued. This finding indicated that SPS may be affected by an integrated information of the afferent signals in the agonist and antagonist muscles.

Kinesthetic perception based on integration of motor imagery and afferent inputs from antagonistic muscles with tendon vibration.

The perceptual integration of afferent inputs from two antagonistic muscles, or the perceptual integration of afferent input and motor imagery are related to the generation of a kinesthetic sensation. However, it has not been clarified how, or indeed whether, a kinesthetic perception would be generated by motor imagery if afferent inputs from two antagonistic muscles were simultaneously induced by tendon vibration. The purpose of this study was to investigate how a kinesthetic perception would be generated by motor imagery during co-vibration of the two antagonistic muscles at the same frequency. Healthy subjects participated in this experiment. Illusory movement was evoked by tendon vibration. Next, the subjects imaged wrist flexion movement simultaneously with tendon vibration. Wrist flexor and extensor muscles were vibrated according to 4 patterns such that the difference between the two vibration frequencies was zero. After each trial, the perceived movement sensations were quantified on the basis of the velocity and direction of the ipsilateral hand-tracking movements. When the difference in frequency applied to the wrist flexor and the extensor was 0Hz, no subjects perceived movements without motor imagery. However, during motor imagery, the flexion velocity of the perceived movement was higher than the flexion velocity without motor imagery. This study clarified that the afferent inputs from the muscle spindle interact with motor imagery, to evoke a kinesthetic perception, even when the difference in frequency applied to the wrist flexor and extensor was 0Hz. Furthermore, the kinesthetic perception resulting from integrations of vibration and motor imagery increased depending on the vibration frequency to the two antagonistic muscles.

Acute Effect of Visually Induced Kinesthetic Illusion in Patients with Stroke: A Preliminary Report

A kinesthetic illusion induces a feeling as if an individual’s own body is moving during sensory input, even though the body is actually in a resting state. In a previous study, we reported that a visually induced kinesthetic illusion (KiNVIS) increases corticospinal tract excitability that is associated with activity of the motor-association regions. The present study explored the acute effect of KiNVIS on motor function in five patients who had experienced stroke, as a preliminary study. Five Japanese patients with stroke, who had been otherwise healthy, participated in the present trial. During KiNVIS, a display was set over the forearm so that the position of the display would give the illusion that the patient’s forearm was actually the same as that depicted in a movie. The movie showed a hand grasping and opening on the uninvolved side, and was repeatedly played for 15 min. Motor function was evaluated with the upper extremity section of the Fugl-Meyer Assessment (FMA-UE) as a primary outcome. Furthermore, we measured a performance of an appropriate motor task for each patient to detect change in motor function as a secondary outcome. In each patient, a positive effect on motor function was detected immediately after KiNVIS, and the appearance of reciprocal muscular control was observed in surface electromyography. There was no difference in the FMA-UE score between before and after the intervention; however, the score was slightly increased in two patients. Furthermore, upon comparison of the individual measurement results, each examination indicated positive changes in motor function. KiNVIS may have an acute positive effect in patients with stroke. The study provides, for the first time, evidence for the therapeutic potential of KiNVIS in stroke rehabilitation.

Effects of different movement directions on electromyography recorded from the shoulder muscles while passing the target positions

PURPOSE We compared electromyography (EMG) recorded from the shoulder joint muscles in the same position for different movement directions. METHODS Fifteen healthy subjects participated. They performed shoulder elevation from 0° to 120°, shoulder depression from 120° to 0°, shoulder horizontal adduction from -15° to 105°, and shoulder horizontal abduction from 105° to -15°. The target positions were 90° shoulder elevation in the 0°, 30°, 60°, and 90° planes (0°, 30°, 60°, and 90° positions). EMG signals were recorded from the supraspinatus (SSP) muscle by fine-wire electrodes. EMG signals from the infraspinatus (ISP), anterior deltoid, middle deltoid, and posterior deltoid muscles were recorded using active surface electrodes. RESULTS During elevation and horizontal abduction, the SSP showed significantly higher activity than that shown during depression and during horizontal adduction in the 0°, 30°, and 60° positions. During elevation, the ISP showed significantly higher activity than during depression and during horizontal adduction in the 90° position. During horizontal abduction, the ISP showed significantly higher activity than during depression in the 90° position. CONCLUSIONS When the movement tasks were performed in different movement directions at the same speed, each muscle showed characteristic activity.

Muscular responses appear to be associated with existence of kinesthetic perception during combination of tendon co-vibration and motor imagery

The afferent inputs from peripheral sensory receptors and efferent signals from the central nervous system that underlie intentional movement can contribute to kinesthetic perception. Previous studies have revealed that tendon vibration to wrist muscles elicits an excitatory response—known as the antagonist vibratory response—in muscles antagonistic to the vibrated muscles. Therefore, the present study aimed to further investigate the effect of tendon vibration combined with motor imagery on kinesthetic perception and muscular activation. Two vibrators were applied to the tendons of the left flexor carpi radialis and extensor carpi radialis. When the vibration frequency was the same between flexors and extensors, no participant perceived movement and no muscle activity was induced. When participants imagined flexing their wrists during tendon vibration, the velocity of perceptual flexion movement increased. Furthermore, muscle activity of the flexor increased only during motor imagery. These results demonstrate that kinesthetic perception can be induced during the combination of motor imagery and co-vibration, even with no experience of kinesthetic perception from an afferent input with co-vibration at the same frequency. Although motor responses were observed during combined co-vibration and motor imagery, no such motor responses were recorded during either co-vibration alone or motor imagery alone, suggesting that muscular responses during the combined condition are associated with kinesthetic perception. Thus, the present findings indicate that kinesthetic perception is influenced by the interaction between afferent input from muscle spindles and the efferent signals that underlie intentional movement. We propose that the physiological behavior resulting from kinesthetic perception affects the process of modifying agonist muscle activity, which will be investigated in a future study.

Working Memory Training Improves Dual-Task Performance on Motor Tasks

ABSTRACT The authors investigated whether working memory training improves motor-motor dual-task performance consisted of upper and lower limb tasks. The upper limb task was a simple reaction task and the lower limb task was an isometric knee extension task. 45 participants (age = 21.8 ± 1.6 years) were classified into a working memory training group (WM-TRG), dual-task training group, or control group. The training duration was 2 weeks (15 min, 4 times/week). Our results indicated that working memory capacity increased significantly only in the WM-TRG. Dual-task performance improved in the WM-TRG and dual-task training group. Our study provides the novel insight that working memory training improves dual-task performance without specific training on the target motor task.

The Long-Term Potentiation-Like Effect in the Corticomotor Area after Transcranial Direct Current Stimulation with Motor Imagery

The purpose of the present study was to clarify a long-term potentiation like effect in the corticomotor area after anodal transcranial direct current stimulation (tDCS), which had been done with motor imagery. Anodal tDCS was applied transcranially as an intervention to the left hand motor area in the right hemisphere for 15 min with the intensity of 1.0 mA during resting or motor imagery (MI) conditions. In the MI condition, subjects performed motor imagery of index finger abduction. Motor-evoked potentials (MEPs) were recorded from the first dorsal interossei (FDI) of the left hand before the intervention and at 0 min, 15 min, 30 min and 60 min after the intervention. The stimulus intensities of TMS were set at 1.05, 1.15, and 1.25 times the strength of the resting motor threshold (RMth). Increases of MEPs were detected with all intensities of TMS at 0 min and 15 min after tDCS with motor imagery. However, in the resting condition, MEP amplitudes were elevated only at 15 min after tDCS and at the highest TMS intensity of 1.25×RMth. The facilitatory effect induced by tDCS with motor imagery was significantly long-lasting and definite compared to that after tDCS without motor imagery.

P29-5 The effects of kinesthetic illusory feeling induced by a visual stimulus on corticomotor excitability of leg muscles

When a briefly presented target is surrounded by four dots that onset at the same time as the target but remain visible after the target terminates, the four dots reduce a person’s ability to identify the target. This phenomenon called object substitution masking (OSM). In the present study we investigated temporal aspects of OSM using a transcranial magnetic stimulation (TMS) to V1 and hV5/MT+ that might play an important role for OSM. Ten participants volunteered for the study. We employed the paradigm proposed by Di Lollo et al. (2000) which could induce OSM effects. Search items were circles with a gap, similar to Landolt-Cs. In the stimulus array, eight items were regularly spaced on an imaginary circle (3.6o in radius). The mask was composed of four dots (0.11o) presented on the vertices of an imaginary square (1.61o×1.61o) centered on one of eight items. Luminance of stimulus was chosen to produce greatest OSM effects in each subject. In a half number of trials, that were randomly chosen, the screen turned black after the target offset (simultaneous-offset trials). In the remaining trials, the sequence was the same, except that the mask remained after the target offset for 160 ms (delayed-offset trials). There were two TMS conditions with double-pulse TMS applied over V1 at 40 80 ms and hV5/MT+ at 80 120 ms from target stimulus offset. It was found that the amount of OSM (simultaneous-offset accuracy minus delayed-offset accuracy) decreased in both conditions at V1 and at hV5/MT+ for subjects who showed a large OSM amount without TMS. Our results showed that both regions in V1 and hV5/MT+ were significantly influenced by TMS, suggesting that OSM, at least in part, is mediated by these areas. We conclude that TMS of V1 at 40 80 ms and hV5/MT+ at 80 120 ms reduced OSM.

P3-16 Effects of sensory input by means of highly elastic adhesive tape on the gain modification of the spinal reflex

Objective: We reported previously that motor imagery executed with cutaneous input by cutaneous input tape (CIT) facilitated corticospinal tract excitability. However, the amount of influence induced by the cutaneous input has not been clarified. The purpose of the present study was to clarify the influence of the CIT on motor neuron pool excitability. Methods: Healthy subjects participated in this experiment. There were four test conditions, the rest condition: Rest, the cutaneous input-rest condition: CI-Rest, the motor imagery condition: MI, and the cutaneous input-motor imagery condition: CI-MI. H-reflex was recorded from the right soleus muscle for each condition. CIT was applied from the right sole to the gastrocnemius muscle. The motor imagery was executed, so that the ankle plantar flexion was imaged in the brain. H-reflex test stimulus intensity was defined as the level at which half amplitude of the maximum H-reflex amplitude could be evoked. Results: The mean value of H-reflex amplitude increased in the order of Rest, MI, CI-Rest, and CI-MI, and there was a significant main effect on the condition. A post hoc test revealed that the H-reflex amplitude increased more significantly in CI-MI than in Rest or MI. The increasing ratio of H-reflex amplitude during motor imagery was significantly larger than that recorded without CIT. Conclusions: The results of this study suggested that CIT affects the motor neuron pool excitability at the spinal level during motor imagery. One possible explanation is that two independent facilitatory effects of CIT and the motor imagery were finally detected after those independent interventions were combined. Another possible explanation is purposive utilization. A facilitatory effect of gain modification induced by taping was shown during motor imagery, but this effect did not occur during the rest condition, when no motor imagery was invoked.