Does 20 Hz Transcranial Alternating Current Stimulation over the Human Primary Motor Cortex Modulate Beta Rebound Following Voluntary Movement?

Beta frequency oscillations originating from the primary motor cortex increase in amplitude following the initiation of voluntary movement, a process termed beta rebound. The strength of beta rebound has been reported to predict the recovery of motor function following stroke, suggesting therapeutic applications of beta rebound modulation. The present study examined the effect of 20 Hz transcranial alternating current stimulation (tACS) on the beta rebound induced by self-paced voluntary movement. Electroencephalograms (EEGs) and electromyograms (EMGs) were recorded from 16 healthy adults during voluntary movements performed before and after active or sham tACS. There was no significant change in average beta rebound after active tACS. However, the beta rebound amplitude was significantly enhanced in a subset of participants, and the magnitude of the increase across all participants was negatively correlated with the difference between individual peak beta frequency and tACS frequency. Thus, matching the stimulus frequency of tACS with individual beta frequency may facilitate therapeutic enhancement for motor rehabilitation.

Movement of the stimulated finger in a Go/NoGo task enhances attention directed to that finger as evidenced by P300 amplitude modulation.

Somatosensory cues and the optimal allocation of attentional resources are critical for motor performance, but it is uncertain how movement of a body part modulates directed attention and the processing of somatosensory signals originating from that same body part. The current study measured motor reaction time (RT) and the P300 event-related potential during a required movement response to stimulation of the same body part in a Go/NoGo task under multiple response. In the Movement Condition, participants were instructed to extend their right index finger in response to mild electrical stimulation of the same finger (Go signal) or remain still when receiving electrical stimulation to the fifth right finger (NoGo signal). Movement RTs and P300 amplitudes and latencies were measured under varying Go signal 50% probabilities. In other trial blocks, participants were required to count Go signals but not respond with movement or to ignore all signals while engaged in an unrelated task. Mean RT in the Movement Condition was 234.5 ms. P300 response amplitudes at midline electrodes (Fz, Cz, Pz) were the largest in the Movement Condition. The P300 amplitude at parietal electrode site Pz was significantly greater during Movement Condition trials than during Count Condition trials. The increase in P300 amplitude during trials requiring movement of the same body part receiving somatosensory stimulation suggests that movement itself modulates the attentional resources allocated to that body part.

Case report: Self-restraint in a patient with alien hand syndrome following cerebral infarction involving the anterior cerebral artery territory.

Frontal alien hand syndrome (AHS) presents as impulsive grasping and groping and compulsive manipulation of environmental objects that can affect the dominant or nondominant hand. A few reports have shown improvements in neuropsychological scores over time when self-restraint of the right hand AHS was enforced. A 72-year-old woman presented with right-handed involuntary instinctive grasping reactions and compulsive manipulation of tools after an infarction of the frontal lobe and corpus callosum (CC). She was diagnosed with cerebral infarction involving the anterior cerebral artery territory and a frontal variant of AHS. At AHS onset, the patient was unaware that her right hand was moving against her will; she was only aware that her right hand was moving when the therapist pointed it out to her. Later, she began to recognize that her right hand was involuntarily moving, and she could restrain the movement of her right hand with her left hand. Approximately 5 months following AHS onset, the patient could voluntarily restrain her AHS symptoms by telling her right hand not to move against her will in her head. Most neuropsychological scores improved by 5 months following AHS onset. However, the patient showed disruptions in the genu and midbody of the left cingulate cortex, as shown via diffusion tensor imaging (DTI), and the sensation of the "right hand moving by itself" remained even 5 months after AHS onset. Although damage to the CC fibers was evident on DTI at 5 months following onset, the patient exhibited no sensory deficits and demonstrated good hand ownership as well as early improvement in attention and cognitive dysfunction. Therefore, the patient recognized her AHS symptoms, which included her hand moving against her will, and was able to consciously restrain her hand movement.

Effects of repetitive practice of motor tasks on somatosensory gating.

Introduction: During voluntary muscle contraction, the amplitude of the somatosensory evoked potential (SEP) is reduced by inhibiting sensory information from a peripheral nerve supplying the contracted muscle. This phenomenon is called "gating." We reported that participants with good motor skills indicated strong suppression of somatosensory information. The present study investigated the effects of motor performance improvement following repetitive practice on the SEP amplitude. Methods: The ball rotation task (BR task) was practiced by 15 healthy participants repetitively. SEPs were recorded before (pre) and after (post) repetitive practice. Results: The BR task performance was significantly improved and the required muscle activation to perform the task was significantly reduced after the repetitive practice. The degree of gating was not significant between pre and post- for the SEP amplitude. A significant correlation was found between changes in SEP amplitude from pre to post and performance improvement. Discussion: After repetitive practice, the degree of gating did not change, but the performance of the BR task improved, and the muscle activity required for the BR task decreased. These results suggest that repetitive practice does not change the degree of gating but changes the mechanism of gating. Furthermore, they indicate that suppression of the somatosensory area may play a role in improving task performance.

Transcranial direct current stimulation to the left dorsolateral prefrontal cortex enhances early dexterity skills with the left non-dominant hand: a randomized controlled trial.

BACKGROUND: The left dorsolateral prefrontal cortex (DLPFC) is involved in early-phase manual dexterity skill acquisition when cognitive control processes, such as integration and complexity demands, are required. However, the effectiveness of left DLPFC transcranial direct current stimulation (tDCS) on early-phase motor learning and whether its effectiveness depends on the cognitive demand of the target task are unclear. This study aimed to investigate whether tDCS over the left DLPFC improves non-dominant hand dexterity performance and determine if its efficacy depends on the cognitive demand of the target task. METHODS: In this randomized, double-blind, sham-controlled trial, 70 healthy, right-handed, young adult participants were recruited. They were randomly allocated to the active tDCS (2 mA for 20 min) or sham groups and repeatedly performed the Purdue Pegboard Test (PPT) left-handed peg task and left-handed assembly task three times: pre-tDCS, during tDCS, and post tDCS. RESULTS: The final sample comprised 66 healthy young adults (mean age, 22.73 ± 1.57 years). There were significant interactions between group and time in both PPT tasks, indicating significantly higher performance of those in the active tDCS group than those in the sham group post tDCS (p < 0.001). Moreover, a greater benefit was observed in the left-handed assembly task performance than in the peg task performance (p < 0.001). No significant correlation between baseline performance and benefits from tDCS was observed in either task. CONCLUSIONS: These results demonstrated that prefrontal tDCS significantly improved early-phase manual dexterity skill acquisition, and its benefits were greater for the task with high cognitive demands. These findings contribute to a deeper understanding of the underlying neurophysiological mechanisms of the left DLPFC in the modulation of early-phase dexterity skill acquisition. TRIAL REGISTRATION: This study was registered in the University Hospital Medical Information Network Clinical Trial Registry in Japan (UMIN000046868), Registered February 8, 2022 https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000053467.

Event-Related Brain Potentials N140 and P300 during Somatosensory Go/NoGo Tasks Are Modulated by Movement Preparation.

The Go/NoGo task requires attention and sensory processing to distinguish a motor action cue or 'Go stimulus' from a 'NoGo stimulus' requiring no action, as well as motor preparation for a rapid Go stimulus response. The neural activity mediating these response phases can be examined non-invasively by measuring specific event-related brain potentials (ERPs) using electroencephalography. However, it is critical to determine how different task conditions, such as the relationship between attention site and movement site, influence ERPs and task performance. In this study, we compared attention-associated ERP components N140 and P300, the performance metrics reaction time (RT) and accuracy (%Error) and movement-related cortical potentials (MRCPs) between Go/NoGo task trials in which attention target and movement site were the same (right index finger movement in response to right index finger stimulation) or different (right index finger movement in response to fifth finger stimulation). In other Count trials, participants kept a running count of target stimuli presented but did not initiate a motor response. The N140 amplitudes at electrode site Cz were significantly larger in Movement trials than in Count trials regardless of the stimulation site-movement site condition. In contrast, the P300 amplitude at Cz was significantly smaller in Movement trials than in Count trials. The temporal windows of N140 and P300 overlapped with the MRCP. This superposition may influence N140 and P300 through summation, possibly independent of changes in attentional allocation.

The impact of visual cross-modal conflict with semantic and nonsemantic distractors on working memory task: A functional near-infrared spectroscopy study.

Cross-modal conflicts arise when information from multisensory modalities is incongruent. Most previous studies investigating audiovisual cross-modal conflicts have focused on visual targets with auditory distractors, and only a few studies have focused on auditory targets with visual distractors. Moreover, no study has investigated the differences in the impact of visual cross-modal conflict with semantic and nonsemantic competition and its neural basis. This cross-sectional study aimed to characterize the impact of 2 types of visual cross-modal conflicts with semantic and nonsemantic distractors through a working memory task and associated brain activities. The participants were 33 healthy, right-handed, young male adults. The paced auditory serial addition test was performed under 3 conditions: no-distractor and 2 types of visual distractor conditions (nonsemantic and semantic distractor conditions). Symbols and numbers were used as nonsemantic and semantic distractors, respectively. The oxygenated hemoglobin (Oxy-Hb) concentration in the frontoparietal regions, bilateral ventrolateral prefrontal cortex (VLPFC), dorsolateral prefrontal cortex, and inferior parietal cortex (IPC) were measured during the task under each condition. The results showed significantly lower paced auditory serial addition test performances in both distractor conditions than in the no-distractor condition, but no significant difference between the 2 distractor conditions. For brain activity, a significantly increased Oxy-Hb concentration in the right VLPFC was only observed in the nonsemantic distractor condition (corrected P = .015; Cohen d = .46). The changes in Oxy-Hb in the bilateral IPC were positively correlated with changes in task performance for both types of visual cross-modal distractor conditions. Visual cross-modal conflict significantly impairs auditory working memory task performance, regardless of the presence of semantic or nonsemantic distractors. The right VLPFC may be a crucial region to inhibit visual nonsemantic information in cross-modal conflict situations, and bilateral IPC may be closely linked with the inhibition of visual cross-modal distractor, regardless of the presence of semantic or nonsemantic distractors.

The relationships between motor behavior and sensory gating in the ball rotation task.

During voluntary muscle contraction, sensory information induced by electrostimulation of the nerves supplying the contracting muscle is inhibited and the amplitude of the corresponding somatosensory evoked potential (SEP) decreases. This phenomenon is called "gating." The reduction of the SEP amplitude is reportedly significantly larger when task performance is high. However, the relationship between dexterous movement skills and gating remains unclear. In this study, we investigated through a ball rotation (BR) task how dexterous movement skills affect the SEP amplitudes. Thirty healthy subjects performed the BR task comprising the rotation of two wooden balls as quickly as possible. We estimated the median number of ball rotations for each participant and classified the participants into two (fast and slow) groups based on the results. Moreover, we recorded SEPs, while the subjects performed BR tasks or rested. SEP amplitude reduction (P45) was significantly larger in the fast than in the slow group. We also observed that the P45 amplitude during the BR task was attenuated even more so in the case of the participants with better dexterous movement skills. Our results suggest that the participants with better dexterous movement skills might display stronger somatosensory information suppression because of increasing the motor cortex activity and the afferent input during the BR task.

The Effect of Pedaling at Different Cadence on Attentional Resources.

We investigated the relationship between attentional resources and pedaling cadence using electroencephalography (EEG) to measure P300 amplitudes and latencies. Twenty-five healthy volunteers performed the oddball task while pedaling on a stationary bike or relaxing (i.e., no pedaling). We set them four conditions, namely, (1) performing only the oddball task (i.e., control), (2) performing the oddball task while pedaling at optimal cadence (i.e., optimal), (3) performing the oddball task while pedaling faster than optimal cadence (i.e., fast), and (4) performing the oddball task while pedaling slower than optimal cadence (i.e., slow). P300 amplitudes at Cz and Pz electrodes under optimal, fast, and slow conditions were significantly lower than those under control conditions. P300 amplitudes at Pz under fast and slow conditions were significantly lower than those under the optimal condition. No significant changes in P300 latency at any electrode were observed under any condition. Our findings revealed that pedaling at non-optimal cadence results in less attention being paid to external stimuli compared with pedaling at optimal cadence.

Validation of Potential Reference Measure for Indoor Walking Distance to Evaluate Wearable Sensing Devices.

The walking distance estimated from the coordinate position information of the center of mass obtained via Xsens MTw Awinda were validated from 5 adult volunteers and the accuracy was shown significantly high. (Average absolute error of -1.22% with a standard deviation of 2.26%).

Accuracy of Posture Estimation by ActiGraph and Development of Posture Prediction Model from Raw Acceleration Data.

Full body motion tracking system was used to obtain accurate posture information under free-living condition and the accuracy of posture prediction by ActiGraph was verified. ActiGraph tends to detect people as standing when they are actually sitting. By combining a prediction model that detects posture change, lying posture, and walking from raw acceleration data obtained by ActiGraph, we were able to predict posture information with higher accuracy.Clinical Relevance- By combining model for predicting posture changes, lying posture, and walking from raw acceleration data obtained by ActiGraph, it is possible to obtain more accurate posture information.

Impact of the Pressure-Free Yutori Education Program on Myopia in Japan.

This study aimed to investigate the influence of educational pressure on myopia. A less-intense school curriculum was introduced nationally in Japan beginning in 2012 based on a pressure-free education policy. In this retrospective observational study, a total of 1025 Japanese medical students of Asahikawa Medical University underwent measurements of the cycloplegic refractive error and axial length (AL), from 2011 to 2020. The spherical equivalent (SE) and AL were correlated significantly with the fiscal year of births (p = 0.004 and p = 0.034, respectively) only during enforcement of the system of high-pressure education. The SE and AL regression rates during the two educational approaches differed significantly (p = 0.004 and p = 0.037, respectively). The prevalence of high myopia was correlated significantly (p < 0.001) only during the system of high-pressure education. The regression of the prevalence rate of high myopia during the two education approaches differed significantly (p = 0.010). The progression rates of myopia and increased prevalence of high myopia were observed only during high-pressure education, suggesting that not only ophthalmologists but also educators and the government should work on together to control the progression of myopia.

Altered somatosensory evoked potentials associated with improved reaction time in a simple sensorimotor response task following repetitive practice.

INTRODUCTION: Repetitive practice of sensorimotor tasks is widely used for neurorehabilitation; however, it is unknown how practice alters sensory processing (e.g., recognition, discrimination, and attentional allocation) and associated cognitive processing, such as decision-making. The purpose of this study was to investigate whether long-latency somatosensory evoked potentials (SEPs) reflecting sensory processing, attention, and decision-making are altered by sensorimotor learning. METHODS: Fifteen participants performed a simple sensorimotor response task (thumb opposition in response to surface electrical stimulation), with experimental recording sessions before and after three days of practice. We then compared multiple SEP waveforms and reaction times (RTs) between pre- and postpractice trials. RESULTS: The RT was reduced after practice of three days, and we found a significant positive correlation between ΔRT and ΔN140lat at F3, Cz, and C3', ΔRT and ΔN250lat at F3, and there was a significant negative correlation between ΔRT and ΔP300amp at C3'. CONCLUSION: The present study suggests that motor learning improves somatosensory processing and attentional allocation via neuroplasticity and that these alterations are reflected by specific SEP changes.

Comparison of the sacral table angles by progression stage of lumbar spondylolysis.

STUDY DESIGN: Retrospective study. OBJECTIVES: The purpose of this study was to investigate sacral table angle (STA) values in early-stage spondylolysis. Several studies suggested that the STA of patients with L5 spondylolysis or spondylolisthesis was significantly lower than that of healthy controls. Separation of the pars interarticularis creates shear stress between the upper sacral end plate and L5 vertebra. This was considered the cause of low STA in patients with spondylolysis or spondylolisthesis. However, if a low STA value is obtained in the early stage of L5 spondylolysis, it suggests that low STA does not result in the remodeling of the sacral end plate. METHODS: Patients with L5 spondylolysis and those with low back pain without pars defect were retrospectively identified from a hospital database in 2014-2016. Pars defect of the spondylolysis was classified into three categories based on CT and MRI results: early, progressive, or terminal stage. The STA difference between groups was calculated using one-way analysis of variance and Scheffe F test, which were used for post hoc testing. RESULTS: A total of 84 cases of L5 spondylolysis and 70 cases of low back pain were identified. No significant difference was found between the STAs of the early- or progressive-stage spondylolysis and the terminal-stage L5 spondylolysis and low back pain patients. The STA of the terminal-stage L5 spondylolysis was significantly lower than that of low back pain patients. CONCLUSIONS: In conclusion, patients with early- or progressive-stage spondylolysis do not have low STA. Low STA is seen only in patients with terminal-stage spondylolysis, suggesting that low STA is associated with remodeling changes in response to shear force after onset of spondylolysis. STA value might not important as a prognostic parameter about development of the spondylolysis. LEVEL OF EVIDENCE: Level IV.

Corticospinal excitability related to reciprocal muscles during the motor preparation period: effect of movement repetition.

OBJECTIVES: Voluntary movements require a preparatory phase before action initiation to elaborate optimal motor commands. This study investigated the time course of change in corticospinal excitability related to each agonist or antagonist muscle during the motor preparation period and the influence of movement repetition on time course change in corticospinal excitability. METHODS: The participants were instructed to perform wrist flexion as quickly as possible in response to the appearance of a red circle. One hundred fifty milliseconds after the presentation of the red circle cue, we delivered transcranial magnetic stimulation at the primary motor cortex related to the agonist flexor and the antagonist extensor carpi radialis muscles. RESULTS: The motor evoked potential amplitudes for both the flexor and extensor carpi radialis during the motor preparation period which were regressed on the logarithm of time, and there were no significant differences in the slope of the logarithmic curves in the early half trials of movement repetition. However, the slope of the logarithmic curve of the flexor carpi radialis was steeper than that of the extensor carpi radialis in the late half trials of movement repetition. CONCLUSION: These results implied that corticospinal excitability for agonist muscles during the motor preparation period is consistently modulated by movement repetition, whereas that for antagonist muscles is weakened by movement repetition.

Change-Driven M100 Component in the Bilateral Secondary Somatosensory Cortex: A Magnetoencephalographic Study.

Our previous demonstration that the M100 somatosensory evoked magnetic field (SEF) has a similar temporal profile, dipole orientation and source location whether induced by activation (ON-M100) or deactivation (OFF-M100) of electrical stimulation suggests a common cortical system to detect sensory change. While we have not recorded such change-driven components earlier than M100 using electrical stimulation, clear M50 responses were reported using both ON and OFF mechanical stimulation (Onishi et al. in Clin Neurophysiol 121:588-593, 2010). To examine the significance of M50 and M100 in reflecting the detection of somatosensory changes, we recorded these waveforms in 12 healthy subjects (9 males and 3 females) by magnetoencephalography in response to mechanical stimulation from a piezoelectric actuator. Onset and offset (ON and OFF) stimuli were randomly presented with three preceding steady state (PSS) durations (0.5, 1.5 and 3 s) in one consecutive session. Results revealed that (i) onset and offset somatosensory events elicited clear M50 and M100 components; (ii) M50 and M100 components had distinct origins, with M50 localised to the contralateral primary somatosensory cortex (cS1) and M100 to the bilateral secondary somatosensory cortex (iS2, cS2); and (iii) the amplitude of M50 in cS1 was independent of the PSS durations, whereas that of M100 in S2 was dependent on the PSS durations for both ON and OFF events. These findings suggest that the M50 amplitude in cS1 reflects the number of activated mechanoreceptors during Onset and Offset, whereas the M100 amplitude in S2 reflects change detection based on sensory memory for Onset and Offset stimuli at least in part. We demonstrated that the M50 in cS1 and M100 in S2 plays different roles in the change detection system in somatosensory modality.

Segmental Lordosis of the Spondylolytic Vertebrae in Adolescent Lumbar Spondylolysis: Differences between Bilateral L5 and L4 Spondylolysis.

STUDY DESIGN: Retrospective study. PURPOSE: This study aimed to investigate whether segmental lumbar hyperlordosis of the affected vertebra in patients with spondylolysis occurs only at L5 or also occurs at L4. OVERVIEW OF LITERATURE: To the best of our knowledge, increase in segmental lordosis of the spondylolytic vertebrae has only been investigated in bilateral L5 spondylolysis; it has not been examined at different levels of bilateral spondylolysis. According to the characteristics of segmental lordosis in bilateral L5 spondylolysis, patients with bilateral L4 spondylolysis may also have increased segmental lordosis of the L4 vertebra. METHODS: Patients with bilateral spondylolysis of the L5 or L4 vertebra in 2013-2015 were retrospectively identified from the hospital database. Standing lateral lumbar radiographs were assessed for the angle of segmental lordosis of the L5 and L4 vertebra, sacral slope, and lumbar lordosis. The differences in segmental lordosis of the L5 and L4 vertebra, sacral slope, and lumbar lordosis were determined using non-paired Student t-test. RESULTS: Overall, 15 cases of bilateral L4 spondylolysis and 41 cases of bilateral L5 spondylolysis satisfied the inclusion and exclusion criteria. Lordosis of the L4 vertebra was significantly greater in the bilateral L4 spondylolysis group (24.2°±7.0°) than that in the L5 spondylolysis group (20.3°±6.1°, p=0.047). Lordosis of the L5 vertebra was significantly lower in the L4 spondylolysis group (27.7°±8.2°) than that in the L5 spondylolysis group (32.5°±7.3°, p=0.040). The sacral slope and lumbar lordosis did not significantly differ between the groups. CONCLUSIONS: Adolescent patients with bilateral spondylolysis have segmental hyperlordosis of the affected vertebra not only at the L5 level but also at the L4 level.

Cortical Oxyhemoglobin Elevation Persists After Moderate-Intensity Cycling Exercise: A Near-Infrared Spectroscopy Study.

Near-infrared spectroscopy (NIRS) can measure cortical activity during gross motor tasks based on the cerebral hemodynamic response. Although some reports suggest that cycling exercise improves cortical oxygenation, its after-effects are unknown. We examined the after-effects of low- and moderate-intensity cycling exercise on cortical oxygenation. Ten healthy volunteers (mean age 21.3 ± 0.7 years; 4 women) underwent cycle ergometer exercise at 30% or 50% of VO2peak for 20 min, followed by an 8-min post-exercise rest (PER). O2Hb levels of the supplementary motor area (SMA) and sensorimotor cortex (SMC) were recorded using a near-infrared spectroscopy system. Skin blood flow (SBF) and mean arterial pressure (MAP) were continuously measured. The peak values of O2Hb between exercise and PER were compared. The O2Hb, SBF, and MAP increased in the exercise phase. SBF degraded over time, and MAP decreased immediately after exercise. The O2Hb decreased immediately and increased again in the PER. There were no significant differences between exercise and PER in the SMC in the 30% VO2peak experiment or in the SMA and SMC in the 50% VO2peak experiment. The O2Hb in the motor-related area was elevated during both exercise and PER especially in the 50% VO2peak experiment.

Electrical Stimulation of Denervated Rat Skeletal Muscle Ameliorates Bone Fragility and Muscle Loss in Early-Stage Disuse Musculoskeletal Atrophy.

We tested whether daily muscle electrical stimulation (ES) can ameliorate the decrease in cortical bone strength as well as muscle and bone geometric and material properties in the early stages of disuse musculoskeletal atrophy. 7-week-old male F344 rats were randomly divided into three groups: age-matched control group (Cont); a sciatic denervation group (DN); and a DN + direct electrical stimulation group (DN + ES). Denervated tibialis anterior (TA) muscle in the DN + ES group received ES with 16 mA at 10 Hz for 30 min/day, 6 days/week. Micro CT, the three-point bending test, and immunohistochemistry were used to characterize cortical bone mechanical, structural, and material properties of tibiae. TA muscle in the DN + ES group showed significant improvement in muscle mass and myofiber cross-sectional area relative to the DN group. Maximal load and stiffness of tibiae, bone mineral density estimated by micro CT, and immunoreactivity of DMP1 in the cortical bone tissue were also significantly greater in the DN + ES group than in the DN group. These results suggest that daily ES-induced muscle contraction treatment reduced the decrease in muscle mass and cortical bone strength in early-stage disuse musculoskeletal atrophy and is associated with a beneficial effect on material properties such as mineralization of cortical bone tissue.

The Variation in the Lumbar Facet Joint Orientation in an Adult Asian Population and Its Relationship with the Cross-Sectional Area of the Multifidus and Erector Spinae.

STUDY DESIGN: Cross-sectional study of healthy volunteers. PURPOSE: We aimed to investigate the variation in the lumbar facet joint orientation in an adult Asian population. The relationship between the facet joint orientation and muscle cross-sectional area (CSA) of multifidus and erector spinae was also clarified. OVERVIEW OF LITERATURE: Several studies have reported that lumbar pathologies, such as lumbar spondylolysis and degenerative spondylolisthesis, were related to the horizontally shaped lumbar facet joint orientation at the lower lumbar level. However, data regarding variations in the facet joint orientation in asymptomatic subjects have not been well documented. METHODS: In 31 healthy male adult Asian volunteers, the facet joint orientation and CSA of multifidus and erector spinae were measured using magnetic resonance imaging at the L4-5 and L5-S1 levels. Variation in the facet joint orientation was examined using coefficients of variation (CV). Pearson's product-moment coefficient was used to investigate the relationship between the facet joint orientation and CSA of multifidus and erector spinae. RESULTS: Lumbar facet joint orientation had a wider range of variation at L5-S1 (CV=0.30) than at L4-5 (CV=0.18). The L4-5 facet joint orientation had a weak but significant correlation with the CSA of erector spinae (r=0.40; p=0.031). The CSA of the multifidus had no relationship with the facet joint orientation at the L4-5 (r=0.19; p=0.314) and the L5-S1 level (r=0.19; p=0.312). CONCLUSIONS: The lumbar facet joint orientation was found to have a wide variation, particularly at the L5-S1 in the Asian adult population, and the facet joint orientation had a relationship with the CSA of the erector spinae at the L4-5.