Movement In Healthy Individuals Research Articles

Effect of Transcranial Direct Current Stimulation on Movement Variability in Repetitive - Simple Tapping Task

Purpose: Accuracy and variability of movement in daily life require synchronization of muscular activities through a specific chronological order of motor performance, which is controlled by higher neural substrates and/or lower motor centers. We attempted to investigate whether transcranial direct current stimulation (tDCS) over primary sensorimotor areas (SM1) could influence movement variability in healthy subjects, using a tapping task. Methods: Twenty six right-handed healthy subjects with no neurological or psychiatric disorders participated in this study. They were randomly and equally assigned to the real tDCS group or sham control group. Direct current with intensity of 1 mA was delivered over their right SM1 for 15 minutes. For estimation of movement variability before and after tDCS, tapping task was measured, and variability was calculated as standard deviation of the inter-tap interval (SD-ITI). Results: At the baseline test, there was no significant difference in SD-ITI between the two groups. In two-way ANOVA with repeated measurement no significant differences were found in a large main effect of group and interaction effect between two main factors (i.e., group factor and time factor (pre-post test)). However, significant findings were observed in a large main effect of the pre-post test. Conclusion: Our findings showed that the anodal tDCS over SM1 for 15 minutes with intensity of 1 mA could enhance consistency of motor execution in a repetitive-simple tapping task. We suggest that tDCS has potential as an adjuvant brain facilitator for improving rhythm and consistency of movement in healthy individuals.

Quantifying forearm and wrist joint power during unconstrained movements in healthy individuals.

BackgroundWrist movement-related injuries account for a large number of repetitive motion injuries. Remarkably little, if any, empirical data exist to quantify the impact of neuromuscular disorders affecting the wrist or to validate the effectiveness of rehabilitation training programs on wrist functions. The aim of this project was to develop a biomechanical model for quantifying wrist and forearm kinetics during unconstrained movements, to assess its reliability and to determine its sensitivity.MethodsTwenty healthy subjects with no history of upper arm and wrist pain volunteered for the experiment. To evaluate the reliability of the data, we quantified their forearm and wrist kinetics on two different days (minimum and maximum number of days between experimental sessions were 1 and 4 days respectively). To measure forearm and wrist kinetics, an apparatus was built to offer rotational inertia during forearm and wrist movements. An inertial measurement unit was located near the top of the device measuring its angular position along the frontal and sagittal planes. We used a mathematical model to infer forearm and wrist torque. Thereafter, we calculated the product of torque and angular velocity to determine forearm and wrist power.ResultsResults revealed that for 75% of the power and torque measurements the ICC was greater than 0.75 (range: 0.77 – 0.83). Torque and power measurements for adduction movements, however, were less reliable (i.e., ICC of 0.60 and 0.47, respectively) across testing sessions. The biomechanical model was robust to small measurement errors, and the power peaks between the first and second testing session were not different indicating that there was no systematic bias (i.e., motor performance improvement) between testing sessions.ConclusionsThe biomechanical model can be used to assess the effectiveness of rehabilitation programs, document the progression of athletes or conduct research-oriented testing of maximum forearm and wrist kinetic capacities. Nonetheless, caution should be taken when assessing forearm and wrist power adduction movements. Future studies should aim at defining a set of normative values, for various age groups, for forearm and wrist joint torque and power in healthy individuals.Electronic supplementary materialThe online version of this article (doi:10.1186/1743-0003-11-157) contains supplementary material, which is available to authorized users.

Perceptual and videofluoroscopic analyses of relation between backed articulation and velopharyngeal closure following cleft palate repair

PurposePerceptual and videofluoroscopic (VF) analyses were performed to analyze velopharyngeal (VP) closure motions and tongue backing movement in subjects with postalveolar, palatal, and velar backed articulation (BA). Materials and methodsFor perceptual analysis, the timing of the appearance of BA and the VP closure level of 22 children with BA following palatal repair were compared to those of 17 subjects with normal articulation, 17 subjects with lateral articulation, and 11 subjects with glottal stop. For VF analysis, 16 subjects with BA and two healthy adult males as references were enrolled. On VF images, the proportions of the time required to complete VP closure and the duration of articulation (VPC/DA) were recorded and then analyzed based on the various degrees of tongue backing movement. ResultsThe appearance of BA was recognized just after the acquisition of VP closure, and it was later than that of glottal stop and earlier than lateral articulation. On VF images, VP closure was achieved before tongue movement in healthy individuals, but after tongue movement in BA subjects. VPC/DA on articulation of both /ta/ and /sa/ were significantly smaller for healthy individuals than for BA subjects (P<0.05). The timing of the complete VP closure approached that of articulation when the site of articulation shifted posteriorly (P<0.01). ConclusionsBA may result from precedent tongue backing movement before the completion of VP closure, as a process that may assist the VP closure motion for articulation.

Expression of the nociceptin/orphanin FQ receptor in the intestinal mucosa of IBS patients

Nociceptin/orphanin FQ (N/OFQ) and the N/OFQ peptide (NOP) receptor play important roles in regulating gastrointestinal function. To assess whether the NOP receptor is implicated in the etiopathogenesis of irritable bowel syndrome (IBS), we measured the levels of NOP receptor mRNA and protein in the jejunal and colonic tissues of healthy subjects and patients with diarrhea-predominant IBS (D-IBS) and constipation-predominant IBS (C-IBS). Mucosal biopsies were obtained from the jejunum and colon of patients diagnosed with D-IBS and C-IBS by the Rome III criteria and from healthy control subjects. The expression of NOP receptor mRNA was measured quantitatively using quantitative PCR (qPCR) and NOP protein expression was assayed immunohistochemically using a rabbit monoclonal antibody to OFQ. NOP receptor mRNA was detected in the jejunum and colon of healthy subjects and was more highly expressed in the jejunum than in the colon. Expression was lower in the jejunum and colon of patients with D-IBS; however, it was similar in patients with C-IBS and healthy subjects. The numbers of OFQ-positive cells in the jejunum and colon were similar among the three groups. The NOP receptor may be involved in the regulation of intestinal movement in healthy individuals. Its involvement in the pathophysiology of IBS may depend on whether the IBS is constipation- or diarrhea-predominant.

Incorporating Feedback from Multiple Sensory Modalities Enhances Brain–Machine Interface Control

The brain typically uses a rich supply of feedback from multiple sensory modalities to control movement in healthy individuals. In many individuals, these afferent pathways, as well as their efferent counterparts, are compromised by disease or injury resulting in significant impairments and reduced quality of life. Brain-machine interfaces (BMIs) offer the promise of recovered functionality to these individuals by allowing them to control a device using their thoughts. Most current BMI implementations use visual feedback for closed-loop control; however, it has been suggested that the inclusion of additional feedback modalities may lead to improvements in control. We demonstrate for the first time that kinesthetic feedback can be used together with vision to significantly improve control of a cursor driven by neural activity of the primary motor cortex (MI). Using an exoskeletal robot, the monkey's arm was moved to passively follow a cortically controlled visual cursor, thereby providing the monkey with kinesthetic information about the motion of the cursor. When visual and proprioceptive feedback were congruent, both the time to successfully reach a target decreased and the cursor paths became straighter, compared with incongruent feedback conditions. This enhanced performance was accompanied by a significant increase in the amount of movement-related information contained in the spiking activity of neurons in MI. These findings suggest that BMI control can be significantly improved in paralyzed patients with residual kinesthetic sense and provide the groundwork for augmenting cortically controlled BMIs with multiple forms of natural or surrogate sensory feedback.

Spinal interneuron circuits reduce approximately 10-Hz movement discontinuities by phase cancellation

Tremor imposes an important limit to the accuracy of fine movements in healthy individuals and can be a disabling feature of neurological disease. Voluntary slow finger movements are not smooth but are characterized by large discontinuities (i.e., steps) in the tremor frequency range (approximately 10 Hz). Previous studies have shown that these discontinuities are coherent with activity in the primary motor cortex (M1), but that other brain areas are probably also involved. We investigated the contribution of three important subcortical areas in two macaque monkeys trained to perform slow finger movements. Local field potential and single-unit activity were recorded from the deep cerebellar nuclei (DCN), medial pontomedullary reticular formation, and the intermediate zone of the spinal cord (SC). Coherence between LFP and acceleration was significant at 6 to 13 Hz for all areas, confirming the highly distributed nature of the central network responsible for this activity. The coherence phase at 6 to 13 Hz for DCN and pontomedullary reticular formation was similar to our previous results in M1. By contrast, for SC the phase differed from M1 by approximately pi rad. Examination of single-unit discharge confirmed that this was a genuine difference in neural spiking and could not be explained by different properties of the local field potential. Convergence of antiphase oscillations from the SC with cortical and subcortical descending inputs will lead to cancellation of approximately 10 Hz oscillations at the motoneuronal level. This could appreciably limit drive to muscle at this frequency, thereby reducing tremor and improving movement precision.

One- or Two-Legged Standing

To highlight the capacity of one- and two-legged standing protocols when assessing postural behavior induced by a rigid ankle orthosis, 14 healthy individuals stood upright barefoot and wore either an elastic stocking on the preferred leg or a rigid orthosis with or without additional taping in one- or two-legged (TL) conditions. Traditional center-of-pressure (CP) measures were evaluated for the total two-feet resultant CP and under the feet (plantar CP). Focusing on the plantar CP displacements under the leg fitted with the various orthoses demonstrated particular postural behaviors for traditional parameters with main effects along the mediolateral axis. Only the TL protocol showed the limiting effects of the rigid shells on the inversion-eversion movements in healthy individuals.

Coordination between upper- and lower-limb movements is different during overground and treadmill walking

Locomotion studies employ either treadmill (TW) or overground walking (OW), considering that differences between them are negligible. The present study tests this notion by comparing coordination between upper- and lower-limb movements in healthy individuals during OW and TW at matched speeds. Results indicated that TW induced a higher cadence, which highly influenced interlimb coordination, in terms of frequency coupling and relative phase between arm and thigh motion. At low speed, the 2:1 pattern (double arm swing per stride) displayed lower incidence in TW compared to OW, and this was correlated with a lower sagittal acceleration at the shoulders, at twice the stride frequency, in the former condition. The low occurrence of the 2:1 coupling in TW, moreover, was correlated to a preferential adoption of a cadence exceeding 80% of the arm's resonant frequency, whereas higher incidence of this pattern in OW involved a preferential cadence below the 80% threshold. Results indicated also that the relative phase between arm and ipsilateral thigh swinging was smaller in TW, in relation to an earlier occurrence of maximum thigh extension, shortened stance phase, and increased cadence. These findings suggest that arm-leg coordination is different in OW and TW, and that difference can be mainly ascribed to condition-specific setting of central mechanisms for scaling stride frequency, for controlling dynamic axial posture (sagittal shoulder acceleration), and, possibly, for maintaining inter-limb synchrony. Awareness of a different "motor set" in TW and OW is critical if data from the two paradigms are used in physiological and patho-physiological studies.

Pharmacological treatment effects on eye movement control

The increasing use of eye movement paradigms to assess the functional integrity of brain systems involved in sensorimotor and cognitive processing in clinical disorders requires greater attention to effects of pharmacological treatments on these systems. This is needed to better differentiate disease and medication effects in clinical samples, to learn about neurochemical systems relevant for identified disturbances, and to facilitate identification of oculomotor biomarkers of pharmacological effects. In this review, studies of pharmacologic treatment effects on eye movements in healthy individuals are summarized and the sensitivity of eye movements to a variety of pharmacological manipulations is established. Primary findings from these studies of healthy individuals involving mainly acute effects indicate that: (i) the most consistent finding across several classes of drugs, including benzodiazepines, first- and second- generation antipsychotics, anticholinergic agents, and anticonvulsant/mood stabilizing medications is a decrease in saccade and smooth pursuit velocity (or increase in saccades during pursuit); (ii) these oculomotor effects largely reflect the general sedating effects of these medications on central nervous system functioning and are often dose-dependent; (iii) in many cases changes in oculomotor functioning are more sensitive indicators of pharmacological effects than other measures; and (iv) other agents, including the antidepressant class of serotonergic reuptake inhibitors, direct serotonergic agonists, and stimulants including amphetamine and nicotine, do not appear to adversely impact oculomotor functions in healthy individuals and may well enhance aspects of saccade and pursuit performance. Pharmacological treatment effects on eye movements across several clinical disorders including schizophrenia, affective disorders, attention deficit hyperactivity disorder, Parkinson’s disease, and Huntington’s disease are also reviewed. While greater recognition and investigation into pharmacological treatment effects in these disorders is needed, both beneficial and adverse drug effects are identified. This raises the important caveat for oculomotor studies of neuropsychiatric disorders that performance differences from healthy individuals cannot be attributed to illness effects alone. In final sections of this review, studies are presented that illustrate the utility of eye movements for use as potential biomarkers in pharmacodynamic and pharmacogenetic studies. While more systematic studies are needed, we conclude that eye movement measurements hold significant promise as tools to investigate treatment effects on cognitive and sensorimotor processes in clinical populations and that their use may be helpful in speeding the drug development pathway for drugs targeting specific neural systems and in individualizing pharmacological treatments.

Differences in symmetry of lumbar region passive tissue characteristics between people with and people without low back pain

Background Several investigators have suggested that passive tissue characteristics of the lumbar region may be altered in people with low back pain. Passive stiffness of the lumbar region has been examined during physiological movements in healthy individuals and intersegmental spine mobility and stiffness have been examined in people with and people without low back pain. However, no investigators have examined differences in passive tissue characteristics of the lumbar region during a physiological movement between people with and people without low back pain. Methods Subjects were moved passively through a trunk lateral bending motion on a passive movement device. Lumbar region kinematics were measured with a motion capture system and force required to move the subject was measured with a force transducer. Lumbar region extensibility was defined as the maximum excursion of the lumbar region. Passive elastic energy was defined as the area under the torque-lumbar region angle curve. Differences in lumbar region extensibility and passive elastic energy between sides were examined in people with and people without low back pain ( n = 41). Findings People in the Rotation with Extension low back pain subgroup demonstrated greater asymmetry of passive elastic energy than people without low back pain ( P = 0.04). There were no differences between groups in symmetry of lumbar region extensibility ( P = 0.37). Interpretation Asymmetry in passive elastic energy of the lumbar region may be related to the low back pain problem in the Rotation with Extension subgroup. The asymmetry in passive elastic energy may be associated with asymmetry of loading on the spine, which has been reported to be a risk factor for low back pain. Thus, it may be important to consider the asymmetry when planning an intervention strategy for people in the Rotation with Extension subgroup.

Failure to Use Movement in Postural Strategies Leads to Increased Spinal Displacement in Low Back Pain

Lumbar and hip movements, before and in response to rapid bilateral arm flexion, were evaluated in 10 people with recurrent low back pain (LBP) and 10 matched control subjects when standing on a flat surface or short base. To evaluate the preparatory movement and resultant displacement of the lumbopelvic region associated with internal perturbation in people with or without LBP. Strategies to control the trunk involve movement. Small spinal movements (preparatory movement), opposite to the direction of reactive moments, precede voluntary arm movements in healthy individuals. However, people with LBP often use less spinal movement. We hypothesized that the tendency to reduce spinal motion in LBP may be associated with decreased preparatory motion, and this may counter intuitively lead to increased displacement of the trunk in response to arm movements. Movements at the lumbopelvic region before and in response to rapid bilateral arm flexion were examined using electromagnetic motion sensors when subjects were standing on a flat surface or short base. In control subjects, preparatory extension of the lumbar spine preceded a resultant flexion of the region in 88% of trials on the flat surface. People with LBP used preparatory extension less frequently (69%, P = 0.027). Consequently, the spinal displacement (resultant flexion) induced by shoulder flexion was significantly greater in the LBP group (3.2 degrees +/- 1.8 degrees) than controls (1.8 degrees +/- 1.6 degrees, P = 0.004). There was a significant correlation (r = 0.47) between preparatory and resultant movement of the lumbar spine in the LBP group, which indicates that subjects with reduced preparatory extension were more likely to have a greater resultant displacement. These data suggest that spinal movement is different in people with LBP, and reduced spinal movement in advance of predictable perturbation may be associated with compromised quality of trunk control.

Cortical adaptations and motor performance improvements associated with short-term bimanual training

Bimanual movement can increase activity within the stroke-affected hemisphere and may contribute to recovery in some patients. To understand how bimanual learning may aid recovery post-stroke, the present study used EEG to investigate cortical adaptations associated with short-term bimanual training and the behavioral modulations that transfer to unimanual movement in healthy individuals. Movement-related potentials (MRP) and reaction times (RT) were recorded from 10 healthy subjects during blocks of unimanual visuomotor trials before and after a bimanual training task. We hypothesized that short-term bimanual practice would induce adaptive cortical changes evident in the MRPs to movements involving a single hand. Post-training results showed that: (1) the late MRP amplitude did not change, (2) RT significantly decreased, and (3) there was a trend for the early MRP amplitude to increase. There was a strong relationship between modulation of early MRP amplitude and RT in the unimanual movement blocks before and after training. Specifically, a subgroup showed a significant decrease in RT in conjunction with a significant increase in the early MRP amplitude. Lastly, comparing later to earlier trials within the bimanual training block, task accuracy and early MRP amplitude significantly increased and (2) a positive re-afferent potential significantly decreased. Results suggest that short-term bimanual training is associated with possible transfer effects to a unimanual task reflected in changes of MRP components and RT. Furthermore, results from the bimanual training trial itself indicate that short-term bimanual training can change the level of motor preparation and sensory feedback in all subjects.