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Purpose: The possibility of interaction between physical and mental fatigues was investigated in this study. Should any interaction between the physical and psychological fatigue takes place, it must accompany the changes in the brain. Therefore, the level of central activation ratio (central fatigue) has been measured as a function of monetary reward to elicit the extrinsic motivation. Methods: Twenty four healthy young male subjects performed quadriceps isotonic extensions until they experience the muscular fatigue. Then, the notification of the monetary reward depending on the level of extension force for the next 3 attempts were given to the experimental group, while no such information was given to the control group. During these post-fatigue isometric maximum voluntary contraction trials, the transcranial magnetic stimulation was delivered on the motor cortex to measure the central activation ratio. Two-way repeated ANOVA were performed. Results: Pre- vs. Post-fatigue comparisons confirmed that the subjects regardless of the group experienced the peripheral fatigue although the level of peripheral fatigue was less pronounced in the group with extrinsic motivation. On the other hand, the central activation ratio of the extrinsic motivation group did not displayed any decrease as the control group did. Conclusion: The results from this study provided an evidence showing the effects of motivation on the muscular fatigue. What’s intriguing is, however, the level of fatigue at the brain level showed no significant sign of fatigue when the monetary reward was suggested. It is presumable to suggest that the high motivation made our subjects prone to the central fatigue, and such effects might have decrease the peripheral muscle fatigue in turn.

[Purpose] Perception plays an important role in understanding the environment or related objects in order for humans to perform physical movements more effectively. Sometimes they create different movements with different perceptions. Especially, visual perception errors that occur in sports situations can have a considerable effect on performance. Accurate knowledge of the environment in this process of perception is important in performing movements or actions. The purpose of this study was to investigate the effect of learning formation on perception using Muller-Liar illusion diagrams. To measure this, we compared the feedback group that induced knowledge learning and the control group that did not provide knowledge To see if there is a difference. Therefore, in this study, we have provided a visual feedback that can establish the cognitive awareness of the actual stimuli length to subjects, and investigated the changes in their matching action responses. [Methods] A total of 32 young and healthy subjects were randomly divided into two groups (Feedback and Non-Feedback groups). Subjects were asked to match the stimulus size with their index fingers and thumbs. Initially (pre-test), three different visual stimuli (inward, outward, and no arrows) were randomly presented 60 times (20 times each) and the grip sizes were recorded using the Liberty Motion Analysis System (Polhemus Co., America). Then, video clips of two lines merging each other were presented as feedbacks. Post-test protocol was identical to the pre-test protocol. The data were analyzed using the 3-way ANOVA with one RM factor (2 x 3 x 2). [Results] Results showed a significant 2-way interaction effect. Post-hoc results showed significant interaction between stimulus shape and pre/post-tests only in the experimental group. There was a significant decrease in the grip size after feedback in the OUT condition of experimental group. However, in the control group, there was no interaction between stimulus shape and pre/post-tests. [Conclusion] Overall, current results indicates that, while visual illusion can affect the action, the provision of visual feedback can establish the awareness of actual stimulus size and suppress the influence of illusion on action.

Purpose The present study was to investigate to extent that effects of sensory information distortion by muscle vibration on continuous limb movement in aging and accuracy constraint Methods Young adult group (n=11) and older adult group (n=11) were divided. All participant were instructed to perform repetitive aiming movement to specified targets under three-accuracy constraints (i.e., low, high, and mixed accuracy constraints) in the vibration and no-vibration conditions. Kinematic data was collected by movement time and movement error frequence Results The results showed that compared with young adult, older adult increased movement time when accuracy constraint was high under vibration condition. Older adult also was a high degree of movement errors than young adults when accuracy constraint was high under vibration condition Conclusion The muscle vibration stimulation may influence considerably on the continuous limb movement probably due to degeneration in sensory information processing by aging.

[Purpose] While primary motor cortex activation has been implicated as a key factor in the arthrogenic muscle inhibition after knee joint injury, no viable rehabilitation protocol has been developed to accommodate this factor. In this study, transcranial magnetic stimulation was applied as a means of dissipating arthrogenic muscle inhibition by introducing temporary motor cortex excitation prior to the rehabilitation. [Subjects and Methods] Twenty-four subjects who have underwent the surgery due to knee injury were recruited, and randomly assigned to the control or the simulation groups. The levels of electromyography signals during the maximum voluntary contraction of the quadriceps muscle before, during, and after training designed for the quadriceps strength rehabilitation were measured. [Results] When compared to controls, subjects who received the transcranial magnetic stimulations showed significantly increased levels of voluntary muscle contraction after the training. Moreover, the beneficial effect of the stimulation increased as the rehabilitation progressed. [Conclusion] Transcranial magnetic stimulation itself does not directly improve the symptoms related to knee injuries. However, the use of this technique can provide a time window for effective intervention by dissipating the unwanted effect of the arthrogenic muscle inhibition during rehabilitation.

A multitude of events bombard our sensory systems at every moment of our lives. Thus, it is important for the sensory and motor cortices to gate unimportant events. Tactile suppression is a well-known phenomenon defined as a reduced ability to detect tactile events on the skin before and during movement. Previous experiments (Buckingham et al. in Exp Brain Res 201(3):411-419, 2010; Colino et al. in Physiol Rep 2(3):e00267, 2014) found detection rates decrease just prior to and during finger abduction and decrease according to the proximity of the moving effector. However, what effect does vision have on tactile gating? There is ample evidence (see Serino and Haggard in Neurosci Biobehav Rev 34:224-236, 2010) observing increased tactile acuity when participants see their limbs. The present study examined how tactile detection changes in response to visual condition (vision/no vision). Ten human participants used their right hand to reach and grasp a cylinder. Tactors were attached to the index finger and the forearm of both the right and left arm and vibrated at various epochs relative to a "go" tone. Results replicate previous findings from our laboratory (Colino et al. in Physiol Rep 2(3):e00267, 2014). Also, tactile acuity decreased when participants did not have vision. These results indicate that the vision affects the somatosensation via inputs from parietal areas (Konen and Haggard in Cereb Cortex 24(2):501-507, 2014) but does so in a reach-to-grasp context.

This study analyzed the health risk behavior of Korean college students by comparing them based on the college location (Seoul vs. non-Seoul). Converging analyses of health risk behaviors (drinking behavior, sex, suicidality) and health risk factors (mental health, stress) were attempted. The results showed the 23% of students were at risk of serious drinking problem, and the 52.6% of students consumed alcohol once in every other week or more often. In case of the sexual behavior, 40.6% had sexual experience. Importantly, the 25.4% and the 20.3% of college students in Seoul and non-Seoul area, respectively, had two or more sexual partners. Also, students in non-Seoul area had a tendency of the higher level of suicidality, and the lower level of mental health. Overall, the self-respect score was the only statistically significant factor showing the Seoul/non-Seoul difference. These results may be able to intervene the health risk behaviors of college students. Key Words : College Student, Health Risk Behavior, Health Risk Factor, Suicidality, Convergence

Although the behavioral characteristics and the neural correlates of prism adaptation processes have been studied extensively, the underlying mechanism is yet to be investigated. Recently, somatosensory suppression was heralded as a mechanism for the sensory re-alignment process accompanying the adaptation. Somatosensory suppression should facilitate the re-alignment process in the proprioceptive system. The shift in the proprioceptive system takes place mostly during a concurrent visual feedback (CVF) condition; during a terminal visual feedback (TVF) condition, the visual system experiences significant adaptation (visual shift), so somatosensory suppression should have minimal functional consequences under TVF. To test this hypothesis, a repetitive transcranial magnetic stimulation (rTMS) was applied to the primary somatosensory cortex as an artificial somatosensory suppression right after the reaching initiation in CVF and TVF conditions, and changes in adaptation were observed. Because somatosensory suppression is already in effect during CVF, rTMS would cause no significant changes. During TVF with rTMS, however, significantly different patterns of adaptation could be expected when compared to a sham rTMS condition. Young adults ( N = 12) participated in 4 sessions (CVF/TVF, real/sham rTMS); visual, proprioceptive, and total shifts were measured. Movement time and curvature of the reaching movement were measured during the adaptation phase. Results showed that while the total shift was unchanged, the proprioceptive shift increased and the visual shift decreased in the TVF condition when rTMS was delivered. However, the total, proprioceptive, and visual shifts were not influenced by rTMS in the CVF condition. Suppression of proprioception induced by the rTMS could be one of the requisites for successful proprioceptive shift during prism adaptation.

The authors characterized how motor planning influences temporal order judgment (TOJ) tasks. They examined this by applying vibrotactile stimulation during the planning stages of a bimanual arm movement that would bring the arms into a crossed configuration. The authors have previously shown that planning to cross the arms induces a subjective reversal of spatially defined temporal order judgments that evolves over the course of the planning period. It was unclear, however, whether this effect is modulated by the extent to which the arms would be crossed after movement. The authors examined this issue by having participants plan to move to 4 different targets that would leave the arms in crossed configurations of varying extents. The results demonstrate that even though cutaneous stimuli were applied before the movements, if participants were planning to move into a more crossed configuration, performance on the TOJ task worsened depending on where they were in the planning process. This data suggest the brain uses planning signals to predict sensations from impending movements in a context-dependent manner.

The effect of repetitive transcranial magnetic stimulation on kinesthetic perception, when applied to the somatosensory cortex, was examined. Further, the facilitatory and inhibitory effects of repetitive transcranial magnetic stimulation using different stimulation frequencies were tested. Six female ( M age = 32.0 years, SD = 6.7) and nine male ( M age = 32.9 years, SD = 6.6) participants were asked to perceive the tendon vibration illusion of the left wrist joint and to replicate the illusion with their right hand. When comparing changes in the corresponding movement amplitude and velocity after three different repetitive transcranial magnetic stimulation protocols (sham, 1 Hz inhibitory, and 5 Hz facilitatory repetitive transcranial magnetic stimulation), the movement amplitude was found to decrease with the inhibitory repetitive transcranial magnetic stimulation, while the movement velocity respectively increased and decreased with the facilitatory and inhibitory repetitive transcranial magnetic stimulation. These results confirmed the modulating effects of repetitive transcranial magnetic stimulation on kinesthetic perception in a single experimental paradigm.

When performing visually guided actions under conditions of perturbed visual feedback, e.g., in a mirror or a video camera, there is a spatial conflict between visual and proprioceptive information. Recent studies have shown that subjects without proprioception avoid this conflict and show a performance benefit. In this study, we tested whether deafferentation induced by repetitive transcranial magnetic stimulation (rTMS) can improve mirror tracing skills in normal subjects. Hand trajectory error during novel mirror drawing was compared across two groups of subjects that received either 1 Hz rTMS over the somatosensory cortex contralateral to the hand or sham stimulation. Mirror tracing was more accurate after rTMS than after sham stimulation. Using a position-matching task, we confirmed that rTMS reduced proprioceptive acuity and that this reduction was largest when the coil was placed at an anterior parietal site. It is thus possible, with rTMS, to enhance motor performance in tasks involving a visuoproprioceptive conflict, presumably by reducing the excitability of somatosensory cortical areas that contribute to the sense of hand position.

Objective. To determine bilateral lower extremity joint accommodations during gait in anterior cruciate ligament deficient subjects and uninjured controls. Design. Gait testing of 10 chronic anterior cruciate ligament deficient subjects prior to and 3 months following reconstructive surgery, and 10 uninjured controls. Background. It is possible that bilateral joint accommodations could occur as a result of anterior cruciate ligament injury and in response to surgical repair. Few studies have investigated bilateral joint accommodations to anterior cruciate ligament injury and there is little consistency in the reported results. Methods. Bilateral lower extremity kinematic and kinetic data were collected from 12 walking trials and inverse dynamics calculations were made to estimate bilateral knee and hip joint angle, moment, and power patterns during the stance phase of gait. Results. Control subjects exhibited asymmetrical hip but symmetrical knee joint moment and power patterns. In contrast, the anterior cruciate ligament deficient subjects exhibited symmetrical hip and asymmetrical knee joint moment and power patterns prior to and following reconstructive surgery. Conclusions. Gait asymmetry in healthy subjects should not be considered pathological. In addition, chronic anterior cruciate ligament injury results in joint specific, bilateral lower extremity accommodations in gait mechanics. These accommodations persist 3 months following surgical repair. Relevance

Objective. To determine how chronic anterior cruciate ligament deficient and surgically repaired subjects react to unexpected forward perturbations during gait as compared to healthy controls. Design. Gait testing of 10 chronic anterior cruciate ligament deficient subjects prior to and three months following reconstructive surgery, and 10 uninjured controls. Background. The ability of an anterior cruciate ligament injured individual to react and maintain equilibrium during gait perturbations is critical for the prevention of reinjury. No studies have investigated how these individuals respond to unexpected perturbations during normal gait. Methods. An unexpected forward perturbation was induced upon heel strike using a force plate capable of translational movement. Results. Prior to surgery, the anterior cruciate ligament subjects exhibited a greater knee extensor moment in response to the perturbation compared to healthy controls. Following surgery, the anterior cruciate ligament injured subjects exhibited a static knee position and a sustained knee extensor moment throughout stance in response to the perturbation as compared to controls. Conclusions. These data suggest that chronic anterior cruciate ligament deficient subjects rely heavily on knee extensor musculature to prevent collapse in response to an unexpected perturbation. This same reactive response was more pronounced 3 months following surgery. Relevance The results suggest that, prior to and following surgery, chronic anterior cruciate ligament injured subjects respond differently than healthy controls to an unexpected perturbation during gait. Anterior cruciate ligament injured or repaired subjects do not reduce or avoid vigorous contraction of the quadriceps muscles when responding to gait perturbations. 2003 Elsevier Science Ltd. All rights reserved.

To determine how normal gait patterns may change as a result of chronic anterior cruciate ligament deficiency and subsequent reconstructive surgery.Gait testing of 10 chronic anterior cruciate ligament deficient subjects prior to and 3 months following reconstructive surgery, and 10 uninjured controls.There is controversy whether persons with chronic anterior cruciate ligament deficiency develop a "quadriceps avoidance" pattern and how anterior cruciate ligament reconstructive surgery influences gait mechanics in these same individuals.Gait analysis was employed to determine kinematic, kinetic, and muscle Electromyographic data.Prior to surgery, no anterior cruciate ligament deficient subject exhibited a quadriceps avoidance pattern. Following surgery, the subjects exhibited a significantly greater knee extensor moment during early stance as compared to the control group. Prior to and following surgery, anterior cruciate ligament deficient subjects demonstrated a significantly greater hip extensor moment possibly to reduce anterior tibial translation. CONCLUSIONS; These data suggest that (1) development of a quadriceps avoidance pattern is less common than previously reported, (2) anterior cruciate ligament deficient subjects accommodate through alterations of hip joint mechanics, (3) surgical repair significantly alters lower extremity gait patterns, and (4) re-establishment of pre-injury gait patterns takes longer than 3 months to occur.The results suggest that chronic anterior cruciate ligament deficient subjects do not exhibit a quadriceps avoidance gait pattern. Surgical intervention significantly alters lower extremity gait mechanics in a population that has accommodated to anterior cruciate ligament deficiency.

Recent neurophysiological studies have started to shed some light on the cortical areas that contribute to eye-hand coordination. In the present study we investigated the role of the posterior parietal cortex (PPC) in this process in normal, healthy subjects. This was accomplished by delivering single pulses of transcranial magnetic stimulation (TMS) over the PPC to transiently disrupt the putative contribution of this area to the processing of information related to eye-hand coordination. Subjects made open-loop pointing movements accompanied by saccades of the same required amplitude or by saccades that were substantially larger. Without TMS the hand movement amplitude was influenced by the amplitude of the corresponding saccade; hand movements accompanied by larger saccades were larger than those accompanied by smaller saccades. When TMS was applied over the left PPC just prior to the onset of the saccade, a marked reduction in the saccadic influence on manual motor output was observed. TMS delivered at earlier or later periods during the response had no effect. Taken together, these data suggest that the PPC integrates signals related to saccade amplitude with limb movement information just prior to the onset of the saccade.

A number of different sites in the human brain have been shown to play a role in sensorimotor adaptation. However, the specific role played by each of these structures in the learning process is poorly understood. In the present study, the contribution of the dorsal aspect of the premotor cortex was examined by disrupting activity at this site using transcranial magnetic stimulation (TMS) while subjects wearing prism goggles pointed at visual targets. This manipulation slowed down the rate of adaptation when vision of the hand was available throughout the movement and reduced the presence of on-line trajectory corrections. This was accompanied by a reduced shift in the felt position of the arm. In contrast, TMS did not cause any alteration in the performance of this task when vision of the hand was available only at the end of the movement. Thus, we infer from this pattern of results that the human dorsal premotor cortex contributes to the generation of the visually based on-line error corrections that are responsible for the remapping of arm position sense underlying sensorimotor adaptation.

The purpose of this investigation was to determine the effect of unexpected forward perturbations (FP) during gait on lower extremity joint mechanics and muscle Electromyographic (EMG) patterns in healthy adults. The muscles surrounding the hip were found to be most important in maintaining control of the trunk and preventing collapse in response to the FP. Distinct lower extremity joint moment and power patterns were observed in response to the FP but an overall positive moment of support (Ms) was maintained. Therefore, reactive balance control was a synchronized effort of the lower extremity joints to prevent collapse during the FP. # 2002 Elsevier Science B.V. All rights reserved.

In order to successfully look at and reach for a visual target the central nervous system must perform a complex sensorimotor transformation. How this transformation is mapped onto relevant brain structures has become the subject of much recent investigation. In the present paper we examined the contribution of the human premotor cortex (PMC) to this transformation process during a task requiring coordinated eye and hand movements. For this purpose, we made use of single-pulse transcranial magnetic stimulation (TMS) to temporarily disrupt the processing occurring in the PMC during task performance. Subjects made open-loop pointing movements accompanied by saccades of the same size or two or three times larger. Under normal circumstances without TMS, the pointing movement amplitude increased with saccade amplitude. When TMS was applied over the PMC 100-200 ms after target presentation, the influence of saccade amplitude on the pointing movement amplitude was increased. This is the opposite effect to that observed in a previous study [Journal of Neurophysiology 84 (200) 1677-1680] when TMS was applied over the posterior parietal cortex (PPC) during the same task. We suggest that this pattern of results is consistent with the coding of the reach plan in eye-centered coordinates in the PPC and limb-centered coordinates in the PMC.

To reach for an object the brain must transform visual input from the eye into motor output of the arm. Recent neurophysiological experiments have shown that this transformation maps onto a network of brain areas including the posterior parietal (PPC) and premotor (PMC) cortices. In this chapter, we review evidence from our own experiments which demonstrate that this network can only partially complete the transformation when the eye and limb movement amplitudes are dissociated. We also discuss the effects of disrupting either the PPC or PMC using transcranial magnetic stimulation (TMS) on the ability to carry out the transformation successfully.