Biology subjects

Ushiyama, J.

Publications and source records attributed to Ushiyama, J..

3 recordsLinked to original sources

bioRxiv2021

The presence of corticomuscular coherence during unipedal stance

Standing in unipedal stance requires higher effort to maintain posture balance within narrow base-of-support. Although changes in cortical activity are known to occur as standing task difficulty increased, it is unclear whether it indicates a change in cortical control of muscle activity. To elucidate this point, this study examined corticomuscular coherence (CMC) between the sensorimotor cortex and ankle joint muscles during three tasks such as bipedal stance, unipedal stance, and isometric contraction tasks. For twenty-one healthy participants, we measured the maximal peak of CMC (CMCmax) between electroencephalograms overlying the foot representation area and surface electromyograms from the tibialis anterior (TA), medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus (SOL), respectively, for each task. We also measured the center of pressure (COP) during both stance tasks. Although there was no significant CMC during bipedal stance in all participants, most participants (n = 14) showed significant CMC for all muscles during unipedal stance with larger COP fluctuation in most participants. Indeed, there was significant difference in CMCmax between unipedal and bipedal stance tasks. The greater CMC would indicate increased cortical control of muscle activity to compensate for postural instability during unipedal stance.

neuroscience↗

bioRxiv2021

Gymnasts' ability for general motor imagery evaluated by bioelectric sensorimotor rhythms

Previous psychological studies using questionnaires have consistently reported that athletes have superior motor imagery ability, both for sports-specific and sports non-specific movements. However, regarding motor imagery of sports non-specific movements, no physiological studies have demonstrated differences in neural activity between athletes and non-athletes. The purpose of the present study was to examine differences in bioelectric sensorimotor rhythms during kinesthetic motor imagery (KMI) of sports non-specific movements between gymnasts and non-gymnasts. We selected gymnasts as an example population because they are likely to have particularly superior motor imagery ability due to frequent usage of motor imagery including KMI as part of daily practice. Healthy young participants (16 gymnasts and 16 non-gymnasts) performed repeated motor execution and KMI of sports non-specific movements (wrist dorsiflexion and shoulder abduction of the dominant hand). Scalp electroencephalogram (EEG) was recorded over the contralateral sensorimotor cortex. During motor execution and KMI, sensorimotor EEG power is known to decrease in the - (8-15 Hz) and {beta}-bands (16-35 Hz), referred to as event-related desynchronization (ERD). We calculated the maximal peak of ERD both in the - (ERDmax) and {beta}-bands ({beta}ERDmax) as a measure of changes in corticospinal excitability. ERDmax was significantly greater in gymnasts, who subjectively evaluated their KMI as being more vivid, for both KMI tasks. On the other hand, {beta}ERDmax was greater in gymnasts only for shoulder abduction KMI. These findings suggest gymnasts signature of flexibly modulating sensorimotor rhythm with no movements, which may be the basis of their superior ability of KMI for sports non-specific movements. New & NoteworthyKinesthetic motor imagery of sports non-specific movements was compared between gymnasts and non-gymnasts (i.e., healthy controls) from both physiological and psychological approaches. The EEG sensorimotor rhythms during kinesthetic motor imagery were more desynchronized in gymnasts who subjectively imaged their own movements as being more vivid. The work reveals novel ability in gymnasts to flexibly control their sensorimotor rhythms with no actual movements, which would be the basis of their superior ability of motor imagery.

neuroscience↗

bioRxiv2021

Rhythmic Accessibility to Sequential Working Memory in a Theta Phase-Dependent Manner

Working memory is active short-term memory storage that is easily accessible for later utilization. There is emerging evidence that memorized items are represented rhythmically on the specific phase of the theta-band (4-7 Hz) neural oscillation. However, it is still unknown how this process impacts the accessibility to the active memory storage. Here we show that simply memorizing sequential information causes theta-band fluctuation in our behaviour (i.e., reaction time, RT). We measured RTs to a visual probe that appeared at sequentially memorized locations after a random interval. Consequently, RTs to the probes fluctuated in the theta range as a function of the random interval, and the behavioural rhythmicity supported the hypothesis of the phase-dependent coding of sequential working memory. The current results demonstrate that our behaviour fluctuates unconsciously in the theta-range when recalling sequential memory, suggesting that accessibility to sequential working memory is rhythmic rather than stable, possibly reflecting theta-phase dependent coding.

neuroscience↗