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Abstract Evaluating reciprocal inhibition of the thigh muscles is important to investigate the neural circuits of locomotor behaviors. However, measurements of reciprocal inhibition of thigh muscles using spinal reflex, such as H‐reflex, have never been systematically established owing to methodological limitations. The present study aimed to clarify the existence of reciprocal inhibition in the thigh muscles using transcutaneous spinal cord stimulation (tSCS). Twenty able‐bodied male individuals were enrolled. We evoked spinal reflex from the biceps femoris muscle (BF) by tSCS on the lumber posterior root. We examined whether the tSCS‐evoked BF reflex was reciprocally inhibited by the following conditionings: (1) single‐pulse electrical stimulation on the femoral nerve innervating the rectus femoris muscle (RF) at various inter‐stimulus intervals in the resting condition; (2) voluntary contraction of the RF; and (3) vibration stimulus on the RF. The BF reflex was significantly inhibited when the conditioning electrical stimulation was delivered at 10 and 20 ms prior to tSCS, during voluntary contraction of the RF, and during vibration on the RF. These data suggested a piece of evidence of the existence of reciprocal inhibition from the RF to the BF muscle in humans and highlighted the utility of methods for evaluating reciprocal inhibition of the thigh muscles using tSCS.

Interlimb coordination involving cyclical movements of hand and foot in the sagittal plane is more difficult when the limbs move in opposite directions compared with the same direction (directional constraint). Here we first investigated whether the directional constraint on hand-foot coordination exists in motor imagery (imagined motion). Participants performed 10 cyclic coordinated movements of right wrist flexion-extension and right ankle dorsiflexion-plantarflexion as quickly and precisely as possible, in the following three conditions; (1) actual movements of the two limbs, (2) imaginary movements of the two limbs, and (3) actual movement of one limb combined with imaginary movement of the other limb. Each condition was performed under two directions; the same and the opposite direction. Task execution duration was measured as the time between the first and second press of a button by the participants. The opposite directional movement took a significantly longer time than did the same directional movement, irrespective of the condition type. This suggests that directional constraint of hand-foot coordination occurs even in motor imagery without actual motor commands or kinesthetic signals. We secondarily examined whether the corticospinal excitability of wrist muscles is modulated in synchronization with an imaginary foot movement to estimate the neural basis of directional constraint on imaginary hand-foot coordination. The corticospinal excitability of the forearm extensor in resting position increased during dorsiflexion and decreased during plantarflexion similarly in both actual and imaginary foot movements. This corticospinal modulation depending on imaginary movement phase likely produces the directional constraint on the imaginary hand-foot coordination.

Abstract When we have rehearsed a movement using an object, we can reproduce the movement without holding the object. However, the reproduced movement sometimes differs from the movement holding a real object, likely because movement recognition is inaccurate. In the present study, we tested whether the recognition capability was dissociated from the acquisition of motor skill memory. Twelve novices were asked to rotate two balls with their right hand as quickly as possible; they practiced the task for 29 days. To evaluate recognition capability, we calculated the difference in coordination pattern of all five digits between the ball-rotation movement and the reproduced movement without holding balls. The recognition capability did not change within the first day, but improved after one week of practice. On the other hand, performance of the ball rotation significantly improved within the first day. Since improvement of performance is likely associated with acquisition of motor skill memory, we suggest that recognition capability, which reflects the capability to cognitively access motor skill memory, was dissociated from the acquisition of motor skill memory. Therefore, recognition of one’s own skilled movement would rely on a hierarchical structure of acquisition of motor skill memory and cognitive access to that memory.

Transvertebral magnetic stimulation (TVMS) of the human lumbar spinal cord can evoke bilateral rhythmic leg movements, as in walking, supposedly through the activation of spinal locomotor neural circuitry. However, an appropriate stimulus intensity that can effectively drive the human spinal locomotor circuitry to evoke walking-like movements has not been determined. To address this issue, TVMS was delivered over an intervertebral space of the lumbar cord (L1–L3) at different stimulus intensities (10–70% of maximum stimulator output) in healthy human adults. In a stimulus intensity-dependent manner, TVMS evoked two major patterns of rhythmic leg movements in which the left-right movement cycles were coordinated with different phase relationships: hopping-like movements, in which both legs moved in the same direction in phase, and walking-like movements, in which both legs moved alternatively in anti-phase; uncategorized movements were also observed which could not be categorized as either movement type. Even at the same stimulation site, the stimulus-evoked rhythmic movements changed from hopping-like movements to walking-like movements as stimulus intensity was increased. Different leg muscle activation patterns were engaged in the induction of the hopping- and walking-like movements. The magnitude of the evoked hopping- and walking-like movements was positively correlated with stimulus intensity. The human spinal neural circuitry required a higher intensity of magnetic stimulation to produce walking-like leg movements than to produce hopping-like movements. These results suggest that TVMS activates distinct neural modules in the human spinal cord to generate hopping- and walking-like movements.

Purpose. This study investigated the relationship between subjective effort (SE) and kinematics/kinetics throughout an entire 50 m sprint. Methods. Fifteen male sprinters performed the 50 m sprint at 3 different levels of SE (100 %SE; maximal-effort, 90 %SE and 80 %SE, sub-maximal efforts). Kinematic and kinetic data were obtained with a digital high speed camera and 50 ground reaction force (GRF) plates placed every 1 m in the running lane. Variables recorded were sprint time, running speed, step frequency, step length, aerial time, contact time, GRF, and ground reaction impulse (GRI). Results & Discussion. Sprint times decreased with increases in SE. However, some subjects ran their fastest 50m at a sub-maximal SE. Thus, the optimal combination of step length & frequency necessary for obtaining maximum speed does not necessarily occur at maximal SE. Indeed, while step frequency significantly increased with an increase in SE, step length was usually the longest at a sub-maximal SE. The vertical GRI in the first half of the ground contact period was significantly greater at sub-maximal SEs. Vertical GRIs and horizontal GRIs in the second half of the ground contact period did not significantly differ among different SEs. Our results suggest that those runners who increase SF too much at maximal SE do so at the cost of decreasing step length (SL). Thus, applying a large force against the ground in the first half of the ground contact period would be effective for improving step length.

This research investigated the difference in aspects of gaze control between esports experts (Expert) and players with lower skills (Low Skill) while playing the real-time strategy game called StarCraft. Three versions of this game at different difficulty levels were made with the StarCraft Editor, and the gaze movements of seven Expert and nine Low Skill players were analyzed while they played the games. The gaze of Expert players covered a significantly larger area in the horizontal direction than the gaze of Low Skill players. Furthermore, the magnitude and number of saccadic eye movements were greater, and saccade velocity was faster in the Expert than in the Low Skill players. In conclusion, StarCraft experts have a specific gaze control ability that enables them to quickly and widely take visual information from all over the monitor. This could be one of the factors enabling StarCraft experts to perform better than players with lower skills when playing games that require task-switching ability.

Abstract Rhythmic movements occur in many aspects of daily life. Examples include clapping the hands and walking. The production of two independent rhythms with multiple limbs is considered to be extremely difficult. In the present study we evaluated whether two different, independent rhythms that involved finger tapping and walking could be produced. In Experiment I, twenty subjects that had no experience of musical instrument training performed rhythmic finger tapping with the right index finger and one of four different lower limb movements; (1) self-paced walking, (2) given-paced walking, (3) alternative bilateral heel tapping from a sitting position, and (4) unilateral heel tapping with the leg ipsilateral to the tapping finger from a sitting position. The target intervals of finger tapping and heel strikes for walking step/heel tapping were set at 375 ms and 600 ms, respectively. The even distribution of relative phases between instantaneous finger tapping and heel strike was taken as the criteria of independency for the two rhythms. In the self-paced walking and given-paced walking tasks, 16 out of 20 subjects successfully performed finger tapping and walking with independent rhythms without any special practice. On the other hand, in the bipedal heels striking and unipedal heel striking tasks 19 subjects failed to perform the two movements independently, falling into interrelated rhythms with the ratio mostly being 2:1. In Experiment II, a similar independency of finger tapping and walking at a given pace was observed for heel strike intervals of 400, 600, and 800 ms, as well as at the constant 375 ms for finger tapping. These results suggest that finger tapping and walking are controlled by separate neural control mechanisms, presumably with a supra-spinal locus for finger tapping, and a spinal location for walking.

Short-term motor practice leads to plasticity in the primary motor cortex (M1). The purpose of this study is to investigate the factors that determine the increase in corticospinal tract (CST) excitability after motor practice, with special focus on two factors; “the level of muscle activity” and “the presence/absence of a goal of keeping the activity level constant.” Fifteen healthy subjects performed four types of rapid thumb adduction in separate sessions. In the “comfortable task” (C) and “forceful task” (F), the subjects adducted their thumb using comfortable and strong forces. In the “comfortable with a goal task” (CG) and “forceful with a goal task” (FG), subjects controlled the muscle activity at the same level as in the C and F, respectively, by adjusting the peak electromyographic amplitude within the target ranges. Paired associative stimulation (PAS), which combines peripheral nerve (median nerve) stimulation and transcranial magnetic stimulation (TMS), with an inter-stimulus interval of 25 ms (PAS25) was also done. Before and after the motor tasks and PAS25, TMS was applied to the M1. None of the four tasks showed any temporary changes in behavior, meaning no learning occurred. Motor-evoked potential (MEP) amplitude increased only after the FG and it exhibited a positive correlation with the MEP increase after PAS25, suggesting that FG and PAS25 share at least similar plasticity mechanisms in the M1. Resting motor threshold (RMT) decreased only after FG, suggesting that FG would also be associated with the membrane depolarization of M1 neurons. These results suggest task-dependent plasticity from the synergistic effect of forceful muscle activity and of setting a goal of keeping the activity level constant.

The effect of the different training regimes and histories on the spatiotemporal characteristics of human running was evaluated in four groups of subjects who had different histories of engagement in running-specific training; sprinters, distance runners, active athletes, and sedentary individuals. Subjects ran at a variety of velocities, ranging from slowest to fastest, over 30 trials in a random order. Group averages of maximal running velocities, ranked from fastest to slowest, were: sprinters, distance runners, active athletes, and sedentary individuals. The velocity-cadence-step length (V-C-S) relationship, made by plotting step length against cadence at each velocity tested, was analyzed with the segmented regression method, utilizing two regression lines. In all subject groups, there was a critical velocity, defined as the inflection point, in the relationship. In the velocity ranges below and above the inflection point (slower and faster velocity ranges), velocity was modulated primarily by altering step length and by altering cadence, respectively. This pattern was commonly observed in all four groups, not only in sprinters and distance runners, as has already been reported, but also in active athletes and sedentary individuals. This pattern may reflect an energy saving strategy. When the data from all groups were combined, there were significant correlations between maximal running velocity and both running velocity and step length at the inflection point. In spite of the wide variety of athletic experience of the subjects, as well as their maximum running velocities, the inflection point appeared at a similar cadence (3.0 ± 0.2 steps/s) and at a similar relative velocity (65–70%Vmax). These results imply that the influence of running-specific training on the inflection point is minimal.

Among tennis coaches and players, the standard volley and drop volley are considered basically similar, but muscles need to be relaxed (deactivation) just at the moment of impact when hitting the drop volley. However, this is not evidence-based. The aim of this study was to clarify racket head trajectory and muscle activity during the drop volley and to compare them with those of the standard volley. We hypothesized that 1) the racket head would move less forward for the drop volley than for the standard volley and 2) the wrist and elbow muscles be relaxed for the drop volley at the time of ball impact. Eleven male college students with sufficient tennis experience volunteered to participate in this study. Wireless EMG sensors recorded activation of the four arm muscles. Each subject performed the standard volley or the drop volley with both a forehand and a backhand from a position near the net. Four high speed video cameras (300 Hz) were set up on the court to measure ball speed and racket head trajectory. Returned ball speed of the drop volley was significantly lower than that of the standard volley (p < 0.05). The racket head moved less forward than in the standard volley, supporting the first hypothesis. Muscle activity of the drop volley, just before and after ball impact for both the forehand and backhand, was lower than that of the standard volley. However, the activity was in the form of a gradual increase as impact time approached, rather than a sudden deactivation (relaxation), which did not support the second hypothesis. For the drop volley, lower muscle activity in the forearm enabled a softer grip and thus allowed a "flip" movement of the racket to diminish the speed of the returned ball.

Fine motor control of not only muscle contraction but also muscle relaxation is required for appropriate movements in both daily life and sports. Movement disorders such as Parkinson’s disease and dystonia are often characterized by deficits of muscle relaxation. Neuroimaging and neurophysiological studies suggest that muscle relaxation is an active process requiring cortical activation, and not just the cessation of contraction. In this article, we review the neural mechanisms of muscle relaxation, primarily utilizing research involving transcranial magnetic stimulation (TMS). Several studies utilizing single-pulse TMS have demonstrated that, during the relaxation phase of a muscle, the excitability of the corticospinal tract controlling that particular muscle is more suppressed than in the resting condition. Other studies, utilizing paired-pulse TMS, have shown that the intracortical inhibition is activated just before muscle relaxation. Moreover, muscle relaxation of one body part suppresses cortical activities controlling other body parts in different limbs. Therefore, the cortical activity might not only be a trigger for muscle relaxation of the target muscles but could also bring about an inhibitory effect on other muscles. This spread of inhibition can hinder the appropriate contraction of muscles involved in multi-limb movements such as those used in sports and the play of musical instruments. This may also be the reason why muscle relaxation is so difficult for beginners, infants, elderly, and the cognitively impaired.

During coordination of the movement of two limbs, the movements often interfere with each other, i.e., interlimb coordination is constrained. Many movement-related parameters such as movement direction, movement frequency, the coupling of limbs, neural network among limbs, and muscle homology are considered constraints of interlimb coordination, and they are roughly consolidated into two constraints, a neuromuscular constraint, and a perceptual-cognitive constraint. Interlimb coordination is considered to be governed by a coalition of neuromuscular and perceptual-cognitive constraints. On the other hand, spontaneous interlimb coordination is considered purely perceptual in nature. In this review, we focused on an influential study on interlimb coordination published in Nature by Mechsner et al. (2001), which supported the latter psychological approach. Thorough verification of the paper with reference to related studies revealed that no studies have yet proposed decisive contrary evidence against the psychological approach. Rather, investigation of interlimb coordination with perceptual-cognitive perspective has uncovered new findings. As a next psychological approach, the proposal of a unified and predictive explanation for movements is required. In addition, neural mechanisms that connect perceptual-cognitive representation to an appropriate motor command, if any, should be addressed.

The present study employed functional magnetic resonance imaging (fMRI) to examine the characteristics of negative blood oxygen level-dependent (Negative BOLD) signals during motor execution. Subjects repeated extension and flexion of one of the following: the right hand, left hand, right ankle, or left ankle. Negative BOLD responses during hand movements were observed in the ipsilateral hemisphere of the hand primary sensorimotor area (SMI), medial frontal gyrus (MeFG), middle frontal gyrus (MFG), and superior frontal gyrus (SFG). Negative BOLD responses during foot movements were also noted in the bilateral hand SMI, MeFG, MFG, SFG, inferior frontal gyrus, middle temporal gyrus, parahippocampal gyrus, anterior cingulate cortex, cingulate gyrus (CG), fusiform gyrus, and precuneus. A conjunction analysis showed that portions of the MeFG and CG involving similar regions to those of the default mode network were commonly deactivated during voluntary movements of the right/left hand or foot. The present results suggest that three mechanisms are involved in the Negative BOLD responses observed during voluntary movements: (1) transcallosal inhibition from the contralateral to ipsilateral hemisphere in the SMI, (2) the deactivated neural network with several brain regions, and (3) the default mode network in the MeFG and CG.

It has been demonstrated that expertise in sport influences standing balance ability. However, little is known concerning how physical contact in sport affects balance ability. The aim of this study was to examine whether differences between contact and limited-contact sport experiences results in differences in postural control. Twenty male collegiate athletes (10 soccer/contact, 10 baseball/limited contact) and ten male untrained students stood quietly on a force plate under various bipedal and unipedal conditions, with and without vision. Significant differences for sway area and COP speed were found between the soccer players and the other two groups for unipedal stances without vision. Soccer players were found to have superior postural control compared with participants involved in limited contact sport or no sport at all. Contact sports may lead to increased postural control through enhanced use of proprioceptive and vestibular information.

Functional plasticity of the sensorimotor cortex occurs following motor practice, as well as after limb amputation. However, the joint effect of limb amputation and intensive, long-term motor practice on cortical plasticity remains unclear. Here, we recorded brain activity during unilateral contraction of the hip, knee, and ankle joint muscles from a long jump Paralympic gold medalist with a unilateral below-knee amputation (Amputee Long Jumper, ALJ). He used the amputated leg with a prosthesis for take-off. Under similar conditions to the ALJ, we also recorded brain activity from healthy long jumpers (HLJ) and non-athletes with a below-knee amputation. During a rhythmic isometric contraction of knee extensor muscles with the take-off/prosthetic leg, the ALJ activated not only the contralateral primary sensorimotor cortex (M1/S1), but also the ipsilateral M1/S1. In addition, this ipsilateral M1/S1 activation was significantly greater than that seen in the HLJ. However, we did not find any significant differences between the ALJ and HLJ in M1/S1 activation during knee muscle contraction in the non-take-off/intact leg, nor during hip muscle contraction on either side. Region of interest analysis revealed that the ALJ exhibited a greater difference in M1/S1 activity and activated areas ipsilateral to the movement side between the take-off/prosthetic and non-take-off/intact legs during knee muscle contraction compared with the other two groups. However, difference in activity in M1/S1 contralateral to the movement side did not differ across groups. These results suggest that a combination of below-knee amputation and intensive, prolonged long jump training using a prosthesis (i.e. fine knee joint control) induced an expansion of the functional representation of the take-off/prosthetic leg in the ipsilateral M1/S1 in a muscle-specific manner. These results provide novel insights into the potential for substantial cortical plasticity with an extensive motor rehabilitation program. Keywords: Athlete, Amputee, Motor learning, Rehabilitation, Plasticity, Prosthesis

We investigated the weight transferring aspect of gait pattern during treadmill walking and muscle strength of the knee extensors and flexors following unilateral anterior cruciate ligament (ACL) reconstruction surgery. At 6 and 12 postoperative months, 11 patients (six men, five women) walked on a split-belt treadmill with two embedded force plates at their preferred speeds, 20% slower and 20% faster. Seventeen healthy control subjects (nine men, eight women) were also evaluated. Peak values of three components of ground reaction force (vertical, anteroposterior, and mediolateral) were measured bilaterally, and their variabilities were analyzed by coefficients of variation (CVs). The CVs for the anteroposterior forces differed between the reconstructed and contralateral limbs at 6 postoperative months, and this difference disappeared at 12 months. This was not matched by the time course change of quadriceps strength since quadriceps weakness in the reconstructed limb persisted up to 12 months postoperative. These findings suggest that gait alteration in anteroposterior forces may not be caused by quadriceps weakness alone, and the reconstructed and contralateral limbs may compensate for gait execution over the first year following ACL reconstruction surgery.

Successful baseball hitting involves a combination of highly trained perceptual skills and forceful bat swing motions. The purpose of the present study was to quantify the horizontal movement of the head and eyes while baseball batters hit a fastball to clarify a visual strategy for this highly trained interceptive task. Six collegiate baseball players hit a fastball that was launched from a pitching machine. The ball speed was 31.9 m·s-1 for the Slow Ball Task and 40.3 m·s-1 for the Fast Ball Task. Horizontal head movements were analysed using images that were captured by two high-speed video cameras. The Horizontal eye movement was recorded with electrooculography. The angular speed of the horizontal head and eye movements during hitting were divided into four time periods (I-40 = 21-40% of total ball-flight, I-60 = 41-60% of total ball-flight, I-80 = 61-80% of total ball-flight, I-100 = 81-100% of total ball-flight) and analysed using analysis of variance and a Tukey post-hoc multiple-comparison. In the Slow Ball Task, the horizontal angular velocity of the head during I-80 was significantly faster than that during I-40 (p < 0.05). In the Fast Ball Task, the horizontal angular velocity of the head during I-80 was significantly faster than that during I-40 and I-60 (p < 0.05). These results indicated that the tracking motion of the head became faster as the launched ball came close to the batters, but there was no change in the angular tracking motion of the eyes. Therefore, rapid eye movement may not be suitable to accurately estimate the ball's future location during fastball hitting based on the eye-centered coordinates. Our findings suggest that conventional vision training with a wide range of saccadic or smooth-pursuit eye movements does not reflect the characteristics of tracking strategies during baseball hitting.

Background: A better understanding of the neural mechanisms that underlie the development of fear of falling (FoF) in seniors may help to detect potential treatable factors and reduce future falls. We therefore investigate the neural correlates of FoF in older adults using 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET).Methods: This cohort study included 117 community-dwelling older adults. At baseline, participants were assessed for FoF, psychiatric symptoms, walking speed, global cognition and cerebral glucose metabolism with FDG-PET. The incidence of FoF in the participants who did not report FoF (N-FoF) at baseline was again ascertained 2 years later. FDG uptake was compared between the FoF and non-FoF groups. Logistic regression analyses to examine the predictors of newly developed FoF (D-FoF) using normalized regional FDG uptake were then performed.Results: At baseline, 50.4% (n = 59) of participants had FoF. The FoF group had significantly decreased glucose metabolism in the left superior frontal gyrus (supplementary motor area, SMA; BA6) compared to the non-FoF group. After 2 years, 19 out of the 58 participants in the non-FoF group developed FoF. Logistic regression analysis revealed that decreased cerebral glucose metabolism in the left SMA at the baseline was a significant predictor of the future development of FoF, independently of psychiatric symptoms and walking speed.Conclusion: In healthy older adults, hypometabolism in the left SMA, which is involved in motor planning and motor coordination, contributes to the development of FoF. Our result might help elucidate underlying mechanism of the association between deficits in motor control and FoF.

The object of this study was to clarify whether corticospinal excitability controlling hand muscles changes concurrently with increases in the imagined contraction level of foot dorsiflexion. Twelve participants performed actual and imagined dorsiflexion of their right foot at three different EMG levels (10, 40 or 80% of the maximum voluntary contraction). During isometric actual- or imagined- dorsiflexion, transcranial magnetic stimulation (TMS) was delivered to the right hand area of the left primary motor cortex. Motor evoked potentials (MEPs) were recorded from the right extensor carpi radialis (ECR) and flexor carpi radialis (FCR). During actual contraction, MEP amplitudes of ECR and FCR increased with an increased EMG level of dorsiflexion. Similarly, during imagery contraction, MEP amplitudes of ECR and FCR increased with the intensity of imagery contraction. Furthermore, a correlation between MEP amplitude during actual contraction and imagery contraction was observed for both ECR and FCR. Motor imagery of foot contraction induced an enhancement of corticospinal excitability for hand muscles that was dependent on the imagined contraction levels, just as what was observed when there was an actual contraction.

In the present review, we include a series of recent experiments in order to update and summarize the characteristics of ball spin in baseball pitching. The motion of a ball thrown by a pitcher is influenced by three forces: gravity, the drag force due to air resistance, and the lift force which deflects a ball vertically or laterally due to the Magnus effect (Magnus force). The forces acting on a baseball are influenced by the ball's translational speed and spin rate as well as the orientation of the spin axis. The lift force acting on the ball becomes greater with increases in the “spin parameter” (proportion of the spin rate and the movement speed) when the spin axis of the ball is orthogonal to the direction of movement. On the other hand, when the spin axis is located in line with the direction of the movement (so-called “gyro ball”), the drag force becomes smaller and the lift force decreases to nearly zero regardless of the spin parameter. The orientation of the spin axis also affects the direction of the lift force on the ball; that is, the lift force acts perpendicular to the cross product of the spin axis and the direction of motion. There are great variations in the spin of fastballs; both spin rate and orientation of the spin axis vary widely across individual pitchers. When the spin rate is extremely low, such as with a knuckle ball, the amount and direction of lift force changes irregularly during flight. This is caused by seams on the ball surface, which cause an unpredictable “fluttering” trajectory. The reason for the success of pitchers that can produce abnormal or unique ball spins is discussed.

Periodic interlimb coordination shows lower performance when the ipsilateral hand and foot (e.g. right hand and right foot) are simultaneously moved than when the contralateral hand and foot (e.g. right hand and left foot) are simultaneously moved. The present study aimed to investigate how brain activity that is related to the dependence of hand-foot coordination on limb combination, using functional magnetic imaging (fMRI). Twenty-one right-handed subjects performed periodic coordinated movements of the ipsilateral or contralateral hand and foot in the same or opposite direction in the sagittal plane. Kinematic data showed that performance was lower for the ipsilateral hand-foot coordination than for the contralateral one. A comparison of brain activity between the same and opposite directions showed that there was a greater activation of supplemental motor area (SMA) for ipsilateral hand-foot coordination as compared to that seen during contralateral hand-foot coordination. We speculate that this might reflect a difference in the degree of inhibition of the neural circuit that disrupts opposite directional movements between ipsilateral and contralateral hand-foot coordinated movements.

The contribution of visual information about a pitched ball to the accuracy of baseball-bat contact may vary depending on the part of trajectory seen. The purpose of the present study was to examine the relationship between hitting accuracy and the segment of the trajectory of the flying ball that can be seen by the batter. Ten college baseball field players participated in the study. The systematic error and standardized variability of ball-bat contact on the bat coordinate system and pitcher-to-catcher direction when hitting a ball launched from a pitching machine were measured with or without visual occlusion and analyzed using analysis of variance. The visual occlusion timing included occlusion from 150 milliseconds (ms) after the ball release (R+150), occlusion from 150 ms before the expected arrival of the launched ball at the home plate (A-150), and a condition with no occlusion (NO). Twelve trials in each condition were performed using two ball speeds (31.9 m·s-1 and 40.3 m·s-1). Visual occlusion did not affect the mean location of ball-bat contact in the bat's long axis, short axis, and pitcher-to-catcher directions. Although the magnitude of standardized variability was significantly smaller in the bat's short axis direction than in the bat's long axis and pitcher-to-catcher directions (p < 0.001), additional visible time from the R+150 condition to the A-150 and NO conditions resulted in a further decrease in standardized variability only in the bat's short axis direction (p < 0.05). The results suggested that there is directional specificity in the magnitude of standardized variability with different visible time. The present study also confirmed the limitation to visual information is the later part of the ball trajectory for improving hitting accuracy, which is likely due to visuo-motor delay.

In the present review, how to measure motor imagery ability, brain activity during motor imagery, the benefits of motor imagery practice, and the influence of sensory inputs on motor imagery, are summarized. First, the classification of motor imagery is explained. Many methods have been utilized to evaluate motor imagery ability. For example, questionnaires, mental chronometry, and mental rotation tasks have been used in the psychological approach. Brain activity has been measured utilizing transcranial magnetic stimulation (TMS), functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and electroencephalography (EEG). Some brain regions are activated motor execution in both and motor imagery, including the supplementary motor area (SMA), the premotor cortex (PM) and the parietal cortex. Although motor imagery is done without movement or muscle contraction, sensory input from the periphery interacts with motor imagery. Brain activation during imagery of an action, as assessed by TMS, is stronger when sensory inputs resemble those present during the actual execution of the action. Many studies have provided evidence of the effects of motor imagery practice on basic motor skills and sport performance. Most elite athletes (70-90%) report that they use motor imagery to improve performance, and professional players, as compared to amateurs, utilize imagery practice more often. Many studies have confirmed that motor imagery practice can also be useful not only in sports, but also for improving performance in patient rehabilitation programs.

The aim of the present study was to elucidate the adaptive and de-adaptive nature of human running on a split-belt treadmill. The degree of adaptation and de-adaptation was compared with those in walking by calculating the antero-posterior component of the ground reaction force (GRF). Adaptation to walking and running on a split-belt resulted in a prominent asymmetry in the movement pattern upon return to the normal belt condition, while the two components of the GRF showed different behaviors depending on the gaits. The anterior braking component showed prominent adaptive and de-adaptive behaviors in both gaits. The posterior propulsive component, on the other hand, exhibited such behavior only in running, while that in walking showed only short-term aftereffect (lasting less than 10 seconds) accompanied by largely reactive responses. These results demonstrate a possible difference in motor strategies (that is, the use of reactive feedback and adaptive feedforward control) by the central nervous system (CNS) for split-belt locomotor adaptation between walking and running. The present results provide basic knowledge on neural control of human walking and running as well as possible strategies for gait training in athletic and rehabilitation scenes.

Systemic inflammatory response syndrome is associated with either fever or hypothermia, but the mechanisms responsible for switching from one to the other are unknown. In experimental animals, systemic inflammation is often induced by bacterial lipopolysaccharide (LPS). To identify the diencephalic and brainstem structures involved in the fever-hypothermia switch, we studied the expression of c-Fos protein, a marker of neuronal activation, in rats treated with the same high dose of LPS (0.5 mg/kg, intravenously) either in a thermoneutral (30 °C) or cool (24 °C) environment. At 30 °C, LPS caused fever; at 24 °C, the same dose caused profound hypothermia. Both fever and hypothermia were associated with the induction of c-Fos in many brain areas, including several structures of the anterior preoptic, paraventricular, lateral, and dorsal hypothalamus, the bed nucleus of the stria terminalis, the posterior pretectal nucleus, ventrolateral periaqueductal gray, lateral parabrachial nucleus, area postrema, and nucleus of the solitary tract. Every brain area studied showed a comparable response to LPS at the two different ambient temperatures used, with the exception of two areas: the dorsomedial hypothalamic nucleus (DMH), which we studied together with the adjacent dorsal hypothalamic area (DA), and the paraventricular hypothalamic nucleus (PVH). Both structures had much stronger c-Fos expression during LPS hypothermia than during fever. We propose that PVH and DMH/DA neurons are involved in a circuit, which - depending on the ambient temperature - determines whether the thermoregulatory response to bacterial LPS will be fever or hypothermia.

Excitability of the corticospinal pathway increases during observation of an action. However, how corticospinal excitability changes during observation of sequential actions in the course of acquiring novel skills (observational learning) remains unexplored. To investigate this, we used a previously unpracticed sequence of ten hand postures. Participants were asked to repeat observation and replication of the sequence. This block of observation and replication was repeated 5 times. During observation of a given hand posture (OK sign), motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation were recorded from hand muscles. In experiment 1, the OK sign appeared in the 9th position of the sequence. Almost all participants could replicate the OK sign only at the 5th block of the experiment. MEP amplitude was greater than that in the control, and decreased with the stages. This suggested that during observational learning of sequential hand postures MEP changed with the progress of the learning. To evaluate this idea, we performed two additional experiments. In experiment 2, the OK sign appeared in the 2nd position. Almost all participants replicated the OK sign even in the 1st block. The MEP amplitude did not change across stages. In experiment 3, the OK sign appeared in the 9th position, but the order of other signs was randomized in every stage. Many participants were not able to replicate the OK sign even during the 5th block of the experiment. The MEP amplitude did not change across stages. These results suggest that: (1) During observational learning modulation of corticospinal excitability is associated with the learning process. (2) Corticospinal excitability decreases as learning progresses.

We investigated whether corticospinal excitability during motor imagery of actions (the power or the pincer grip) with objects was influenced by actually touching objects (tactile input) and by the congruency of posture with the imagined action (proprioceptive input). Corticospinal excitability was assessed by monitoring motor evoked potentials (MEPs) in the first dorsal interosseous following transcranial magnetic stimulation over the motor cortex. MEPs were recorded during imagery of the power grip of a larger-sized ball (7 cm) or the pincer grip of a smaller-sized ball (3 cm)--with or without passively holding the larger-sized ball with the holding posture or the smaller-sized ball with the pinching posture. During imagery of the power grip, MEPs amplitude was increased only while the actual posture was the same as the imagined action (the holding posture). On the other hand, during imagery of the pincer grip while touching the ball, MEPs amplitude was enhanced in both postures. To examine the pure effect of touching (tactile input), we recorded MEPs during imagery of the power and pincer grip while touching various areas of an open palm with a flat foam pad. The MEPs amplitude was not affected by the palmer touching. These findings suggest that corticospinal excitability during imagery with an object is modulated by actually touching an object through the combination of tactile and proprioceptive inputs.

Context: Deficits in knee position sense following reconstruction of the anterior cruciate ligament (ACL) can delay an athlete's return to sport participation and increase the risk of reinjury. Deficits in position sense postreconstruction have been evaluated using either a position-reproducing or position-matching task. Objective: The aim of our study was to combine both to determine which assessment would be more effective to identify deficits in knee position sense. Design: Longitudinal laboratory-based study. Participants: Eleven athletes (6 men and 5 women; mean age, 20.5 [1.2] y), who had undergone ACL reconstruction with an ipsilateral hamstring autograft, and 12 age-matched controls. Interventions: Position sense was evaluated at 6 and 12 months postreconstruction and once for the control group. In addition, peak isokinetic knee extension and flexion strength, at 60°/s and 180°/s, was assessed for the ACL reconstruction group to evaluate possible influences of muscle strength on knee joint position sense. Main Outcome Measures: The variables include the angular differences between the reference limb and indicator limb, and peak torque values of isokinetic knee extension and flexion. Results: Significant matching differences were identified at 6 months postsurgery on the position-matching task, but not at 12 months postsurgery. No significant between-group and within-subject differences were identified on the position-reproducing task. No significant matching errors were identified for the control group. There was no correlation between errors in position sense and maximum isokinetic strength. Conclusion: The position-matching task is more sensitive than the position-reproducing task to identify deficits in knee position sense over the first year following ACL reconstruction surgery. [ABSTRACT FROM AUTHOR]