Reaching movements are automatically redirected to nearby options during target split.

Motor behavior often occurs in environments with multiple goal options that can vary during the ongoing action. We explored this situation by requiring subjects to select between different target options during an ongoing reach. During split trials the original target was replaced with a left and a right flanking target, and participants had to select between them.

Stability of bimanual finger tapping coordination is constrained by salient phases.

In bimanual cyclical continuous movements, the relative timing of the most salient movement phase in each movement is a predominant constraint. This is the case for coordination when both movements have a single most salient phase (the relative-salience hypothesis). We tested whether the relative-salience hypothesis could explain results obtained for repetitive discrete movements, utilizing finger tapping.

Spinal Circuits Mediate a Stretch Reflex Between the Upper Limbs in Humans.

Inter-limb reflexes play an important role in coordinating behaviors involving different limbs. Previous studies have demonstrated that human elbow muscles express an inter-limb stretch reflex at long-latency (50-100 ms), a timing consistent with a trans-cortical linkage. Here we probe for inter-limb stretch reflexes in the shoulder muscles of human participants.

Performance evaluation of lysimeter experiments for simulating pesticide dissipation in paddy fields. Part 2: Nursery-box application and foliar application.

Comparative experiments investigating the dissipation of four nursery-box-applied pesticides and three foliar-applied pesticides were conducted using lysimeters and in actual paddy fields. In the lysimeter experiments, there were test plots for submerged application for both application types. Analytical concentrations of the pesticides in paddy water were evaluated using appropriate kinetic models.

Performance evaluation of lysimeter experiments for simulating pesticide dissipation in paddy fields. Part 1: Submerged application of granular pesticides.

Three-year comprehensive experiments were conducted to compare the dissipation patterns of a total of 16 pesticides, including 3 metabolites, as granular formulations applied in lysimeters and paddy fields with two soil types. Analytical concentrations of the target pesticides in paddy water were analyzed using a granular kinetic model consisting of the following parameters: release rate, decrease rate, and dissolved concentration. Results of parameter grouping analyses of the kinetic models showed that 56% of data reproducibility (entire grouping) was obtained between replicates for the lysimeters.

Effect of salient points in movements on the constraints in bimanual coordination.

The relative-salience hypothesis has been proposed as a possible explanation for the stability of bimanual coordination. This explanation proceeds from a psychological viewpoint and is based on the following tenets: (1) cyclic joint motions involving two movements are conceived of as a unified event, (2) if a "single" point in each movement is seen as the most salient, the salient points of the two movements prefer to go together, and (3) in other cases, a unified event will be constrained by movement direction. In this investigation, we examined whether the relative-salience hypothesis could predict the type of constraint (i.

Muscle Relaxation of the Foot Reduces Corticospinal Excitability of Hand Muscles and Enhances Intracortical Inhibition.

The object of this study was to clarify the effects of foot muscle relaxation on activity in the primary motor cortex (M1) of the hand area. Subjects were asked to volitionally relax the right foot from sustained contraction of either the dorsiflexor (tibialis anterior; TA relaxation) or plantarflexor (soleus; SOL relaxation) in response to an auditory stimulus. Single- and paired-pulse transcranial magnetic stimulation (TMS) was delivered to the hand area of the left M1 at different time intervals before and after the onset of TA or SOL relaxation.

Corticospinal excitability modulation in resting digit muscles during cyclical movement of the digits of the ipsilateral limb.

We investigated how corticospinal excitability of the resting digit muscles was modulated by the digit movement in the ipsilateral limb. Subjects performed cyclical extension-flexion movements of either the right toes or fingers. To determine whether corticospinal excitability of the resting digit muscles was modulated on the basis of movement direction or action coupling between ipsilateral digits, the right forearm was maintained in either the pronated or supinated position.

Potential explanation of limb combination performance differences for two-limb coordination tasks.

Rhythmic two-limb coordinated movements in the sagittal plane are variable and inaccurate when the movements are in the opposite direction as compared with those in the same direction (directional constraint). The magnitude of directional constraint depends on the particular limb combination. It is prominent in ipsilateral hand-foot coordination, but minimal in bimanual hand coordination.

Motor imagery of voluntary muscle relaxation induces temporal reduction of corticospinal excitability.

Voluntary muscle relaxation is an "active process" requiring cortical activation. However, cortical activation during motor imagery of muscle relaxation has not been well understood. The purpose of this study was to clarify time-dependent changes in corticospinal excitability during the imagery of muscle relaxation.

Factors that determine directional constraint in ipsilateral hand-foot coordinated movements.

In performing simultaneous rhythmic movements of the ipsilateral hand and foot, there are differences in the level of stability between same directional (stable) and opposite directional (unstable) movements. This is the directional constraint. In this study, we investigated three factors ("interaction in efferent process," "interaction of afferent signals," and "error correction") proposed to underlie for the directional constraint.

Interaction between simultaneous contraction and relaxation in different limbs.

We investigated the interaction between relaxation and contraction for remote, ipsilateral muscles of the hand and foot (wrist extensor/ankle dorsiflexor). Subjects sat in an armchair and were able to freely move their right hand and foot. They performed eight tasks: (1) wrist extension from a flexed (relaxed) position, (2) ankle dorsiflexion from a plantarflexed (relaxed) position, (3) wrist relaxation from an extended position, (4) ankle relaxation from a moderately dorsiflexed position.

Brain activity during motor imagery of an action with an object: a functional magnetic resonance imaging study.

We utilized functional magnetic resonance imaging to investigate the brain regions activated during motor imagery of an action with an object both with and without passively holding the object. Participants performed the following tasks: (1) 'Imagery with Ball' condition: subjects imagined squeezing a foam ball (7cm diameter) while holding the ball, (2) 'Imagery' condition: subjects imagined squeezing a ball without holding the ball, and (3) 'Ball' condition: subjects held the ball without motor imagery. Regions activated by the 'Imagery with Ball' condition were located in the left dorsolateral prefrontal cortex (DLPFC), supplemental motor areas (SMA), inferior parietal lobule (IPL), superior parietal lobule (SPL), insula, cerebellum and basal ganglia.

Ipsilateral wrist-ankle movements in the sagittal plane encoded in extrinsic reference frame.

When performing oscillatory movements of two joints in the sagittal plane, there is a directional constraint for performing such movements. Previous studies could not distinguish whether the directional constraint reflected movement direction encoded in the extrinsic (outside the body) reference frame or in the intrinsic (the participants' torso/head) reference frame since participants performed coordinated movements in a sitting position where the torso/head was stationary relative to the external world. In order to discern the reference frame in the present study, participants performed paced oscillatory movements of the ipsilateral wrist and ankle in the sagittal plane in a standing position so that the torso/head moved relative to the external world.

Modulation of corticospinal excitability during acquisition of action sequences by observation.

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.

Influence of somatosensory input on corticospinal excitability during motor imagery.

Our previous studies showed that corticospinal excitability during imagery of squeezing a foam ball was enhanced by somatosensory input generated by passively holding the ball. In the present study, using the same experimental model, we investigated whether corticospinal excitability was influenced by holding the object with the hand opposite to the imagined hand. Corticospinal excitability was assessed by monitoring motor evoked potentials (MEPs) in the first dorsal interosseous muscle following transcranial magnetic stimulation over the motor cortex during motor imagery.

The modulation of corticospinal excitability during motor imagery of actions with objects.

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.

Determinant of leg stiffness during hopping is frequency-dependent.

Identifying the major determinant of leg stiffness during hopping would be helpful in the development of more effective training methods. Despite the fact that overall leg stiffness depends on a combination of the joint stiffness, it is unclear how the major determinants of leg stiffness are influenced by hopping frequency. The purpose of this study was to identify the major determinant of leg stiffness over a wide range of hopping frequencies.

Leg stiffness adjustment for a range of hopping frequencies in humans.

The purpose of the present study was to determine how humans adjust leg stiffness over a range of hopping frequencies. Ten male subjects performed in place hopping on two legs, at three frequencies (1.5, 2.

Passive knee movement-induced modulation of the soleus H-reflex and alteration in the fascicle length of the medial gastrocnemius muscle in humans.

In humans, an inhibitory via Ia afferent pathway from the medial gastrocnemius (MG) to the soleus (SOL) motoneuron pool has been suggested. Herein, we examined the relation between MG fascicle length changes and the SOL H-reflex modulation during passive knee movement. Twelve subjects performed static and passive (5 degrees s(-1)) knee movement tasks with the ankle immobilized using an isokinetic dynamometer in sitting posture.

Execution-dependent modulation of corticospinal excitability during action observation.

Excitability of the corticospinal pathway increased during observation of an action. The present study investigated whether corticospinal excitability during an action observation is modulated by physical movement executed by the observers themselves. Participants alternately repeated the observation of a pinching action with the thumb and index finger and execution (30 times) of the same action.

Influence of touching an object on corticospinal excitability during motor imagery.

We investigated whether corticospinal excitability during the imagery of an action involving an external object was influenced by actually touching the object. Corticospinal excitability was assessed by monitoring motor evoked potentials (MEPs) in the first dorsal interosseous muscle following transcranial magnetic stimulation over the motor cortex during imagery of squeezing a ball-with or without passively holding the ball. The MEPs amplitude during imagery when the ball was held was larger than that when the ball was not held.

Knee stiffness is a major determinant of leg stiffness during maximal hopping.

Understanding stiffness of the lower extremities during human movement may provide important information for developing more effective training methods during sports activities. It has been reported that leg stiffness during submaximal hopping depends primarily on ankle stiffness, but the way stiffness is regulated in maximal hopping is unknown. The goal of this study was to examine the hypothesis that knee stiffness is a major determinant of leg stiffness during the maximal hopping.

Combining observation and imagery of an action enhances human corticospinal excitability.

The present study investigated whether combining observation and imagery of an action increased corticospinal excitability over the effects of either manipulation performed alone. Corticospinal excitability was assessed by motor-evoked potentials in the biceps brachii muscle following transcranial magnetic stimulation over the motor cortex during observation, imagery or both. The action utilized was repetitive elbow flexion/extension.