How do plants read their own shapes?

Contents 333 I. 333 II. 334 III. 334 IV. 336 336 References 337 SUMMARY: Although the sensing of shape and deformation was historically involved in the control of animal locomotion, it is now increasingly being incorporated in developmental biology. Proprioception, the perception of the self, is particularly key to the question of the reproducibility of shapes: the many regulators of growth may lead to a large array of geometries, but shape sensing restricts these diverse outputs to a limited number of forms. Mechanistically, and in addition to geometrical feedback onto the diffusion and transport of molecular factors, we highlight the role of shape-derived mechanical stress and strain in this process. Through examples at the cell, tissue and organism scales, it appears that such mechanical feedback adds robustness to morphogenesis. Interestingly, synergies exist between shape sensing and response to external cues, such as wind and gravity. Understanding the molecular basis of proprioception is now within reach and opens up many avenues for an integrative view of development.

An evaluation of the posterior cruciate ligament function in total knee arthroplasty with regard to its morphology and clinical properties

The aim of the study was to determine the degree of posterior cruciate ligament (PCL) degeneration and the reduction in the number of its mechanoreceptors, in patients with advanced degenerative joint disease. PCLs taken from study group of 50 patients in the mean age of 70.7 (53-84) years with a diagnosis of advanced idiopathic osteoarthritis undergoing condylar total knee arthroplasty were compared to those taken form the control group of 10 knee joints of cadavers. Groups were matched with regard to sex and age. Histological examination of PCLs of the study group showed changes of an inflammatory process and no significant signs of osteoarthritis in the control group. A close correlation was found between the severity of degenerative changes on the X-ray images according to the Ahlbäck scale, and the increased mucoid degeneration (p < 0.0001), the severity of the degeneration of the collagen structure (p < 0.0001) and the presence of proprioceptors of PCLs (p < 0.0001). Conserving the PCL by the use of type cruciate retaining knee arthroplasty does not guarantee the preservation of correct proprioceptive sensation.

Peripheral nerve injury induces adult brain neurogenesis and remodelling

Unilateral peripheral nerve chronic constriction injury (CCI) has been widely used as a research model of human neuropathic pain. Recently, CCI has been shown to induce spinal cord adult neurogenesis, which may contribute to the chronic increase in nociceptive sensitivity. Here, we show that CCI also induces rapid and profound asymmetrical anatomical rearrangements in the adult rodent cerebellum and pons. This remodelling occurs throughout the hindbrain, and in addition to regions involved in pain processing, also affects other sensory modalities. We demonstrate that these anatomical changes, partially reversible in the long term, result from adult neurogenesis. Neurogenic markers Mash1, Ngn2, doublecortin and Notch3 are widely expressed in the rodent cerebellum and pons, both under normal and injured conditions. CCI-induced hindbrain structural plasticity is absent in Notch3 knockout mice, a strain with impaired neuronal differentiation, demonstrating its dependence on adult neurogenesis. Grey matter and white matter structural changes in human brain, as a result of pain, injury or learned behaviours have been previously detected using non-invasive neuroimaging techniques. Because neurogenesis-mediated structural plasticity is thought to be restricted to the hippocampus and the subventricular zone, such anatomical rearrangements in other parts of the brain have been thought to result from neuronal plasticity or glial hypertrophy. Our findings suggest the presence of extensive neurogenesis-based structural plasticity in the adult mammalian brain, which may maintain a memory of basal sensory levels, and act as an adaptive mechanism to changes in sensory inputs.

Muscle Activation During Landing Before and After Fatigue in Individuals With or Without Chronic Ankle Instability

CONTEXT

Ankle instability is a common condition in physically active individuals. It often occurs during a jump landing or lateral motion, particularly when participants are fatigued.

OBJECTIVE

To compare muscle activation during a lateral hop prefatigue and postfatigue in individuals with or without chronic ankle instability (CAI).

DESIGN

Cross-sectional study.

SETTING

Sports medicine research laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 32 physically active participants volunteered for the study. Sixteen participants with CAI (8 men, 8 women; age = 20.50 ± 2.00 years, height = 172.25 ± 10.87 cm, mass = 69.13 ± 13.31 kg) were matched with 16 control participants without CAI (8 men, 8 women; age = 22.00 ± 3.30 years, height = 170.50 ± 9.94 cm, mass = 69.63 ± 14.82 kg) by age, height, mass, sex, and affected side.

INTERVENTION(S)

Electromyography of the tibialis anterior, peroneus longus, gluteus medius, and gluteus maximus was measured before and after a functional fatigue protocol.

MAIN OUTCOME MEASURE(S)

Activation of 4 lower extremity muscles was measured 200 milliseconds before and after landing from a lateral hop.

RESULTS

We observed no interactions. The group main effects for the peroneus longus demonstrated higher muscle activation in the CAI group (52.89% ± 11.36%) than in the control group (41.12% ± 11.36%) just before landing the lateral hop (F_1,30 = 8.58, P = .01), with a strong effect size (d = 1.01). The gluteus maximus also demonstrated higher muscle activation in the CAI group (45.55% ± 12.08%) than in the control group (36.81% ± 12.08%) just before landing the lateral hop (F_1,30 = 4.19, P = .049), with a moderate effect size (d = 0.71). We observed a main effect for fatigue for the tibialis anterior, with postfatigue activation higher than prefatigue activation (F_1,30 = 7.45, P = .01). No differences were present between groups for the gluteus medius.

CONCLUSIONS

Our results support the presence of a centralized feed-forward neuromuscular alteration in patients with CAI, not only in the ankle-joint muscles but also in the proximal hip muscles. These results may have implications for rehabilitation programs in these patients.

Importance of Proprioceptive Information for Postural Control in Children with Strabismus before and after Strabismus Surgery

The objective of this study is to examine the role of proprioception in postural balance in children with strabismus before and after realignment of their visual axes by eye surgery. Postural recordings were made with the TechnoConcept® force platform in 23 children. Several conditions were studied, whether the subjects had both eyes open, or either the dominant or the non-dominant eye open, without and with foam pads of 4 mm underfoot. Recordings were performed before and after strabismus surgery. The surface area, the length and the mean speed of the center of pressure (CoP) were analyzed. Before strabismus surgery, all children showed better stability with both eyes open with respect to the condition with the non-dominant eye open; furthermore postural stability improved in the presence of foam pads. After surgery, the surface area of CoP decreased significantly, especially in the non-dominant eye viewing condition. We suggest that strabismic children use mainly proprioceptive information in order to control their posture, but also visual inputs, which are important for obtaining a good postural stability. The alignment of the visual axes after surgery provides enhanced postural stability, suggesting, again the major role of visual inputs in the control of posture. Proprioceptive plasticity after strabismus surgery may allow better visual rehabilitation.

Feeling force: physical and physiological principles enabling sensory mechanotransduction

Organisms as diverse as microbes, roundworms, insects, and mammals detect and respond to applied force. In animals, this ability depends on ionotropic force receptors, known as mechanoelectrical transduction (MeT) channels, that are expressed by specialized mechanoreceptor cells embedded in diverse tissues and distributed throughout the body. These cells mediate hearing, touch, and proprioception and play a crucial role in regulating organ function. Here, we attempt to integrate knowledge about the architecture of mechanoreceptor cells and their sensory organs with principles of cell mechanics, and we consider how engulfing tissues contribute to mechanical filtering. We address progress in the quest to identify the proteins that form MeT channels and to understand how these channels are gated. For clarity and convenience, we focus on sensory mechanobiology in nematodes, fruit flies, and mice. These themes are emphasized: asymmetric responses to applied forces, which may reflect anisotropy of the structure and mechanics of sensory mechanoreceptor cells, and proteins that function as MeT channels, which appear to have emerged many times through evolution.

Evidence that subclinical somatoform dissociation is not characterised by heightened awareness of proprioceptive signals

INTRODUCTION

It has been suggested that abnormal perceptual processing and somatosensory amplification may be contributory factors to somatoform symptom reporting. A key source of somatosensory information is proprioception, yet the perception and integration of this sense has not been sufficiently investigated in those prone to somatoform disorders.

METHODS

Subclinical groups of high- and low-scorers on the Somatoform Dissociation Questionnaire made judgements about the location of their unseen hand following congruent or incongruent visuo-proprioceptive feedback, which was manipulated using a MIRAGE-mediated reality system.

RESULTS

No differences were found between groups, with both groups displaying normal proprioceptive accuracy under congruent conditions and equivalent visuo-proprioceptive integration under incongruent conditions.

CONCLUSIONS

The results suggest that amplification of, or abnormal weighting for, proprioceptive signals is not a contributing factor to somatoform symptom reporting.

Reduced plantar sole sensitivity facilitates early adaptation to a visual rotation pointing task when standing upright

Humans are capable of pointing to a target with accuracy. However, when vision is distorted through a visual rotation or mirror-reversed vision, the performance is initially degraded and thereafter improves with practice. There are suggestions this gradual improvement results from a sensorimotor recalibration involving initial gating of the somatosensory information from the pointing hand. In the present experiment, we examined if this process interfered with balance control by asking participants to point to targets with a visual rotation from a standing posture. This duality in processing sensory information (i.e., gating sensory signals from the hand while processing those arising from the control of balance) could generate initial interference leading to a degraded pointing performance. We hypothesized that if this is the case, the attenuation of plantar sole somatosensory information through cooling could reduce the sensorimotor interference, and facilitate the early adaptation (i.e. improvement in the pointing task). Results supported this hypothesis. These observations suggest that processing sensory information for balance control interferes with the sensorimotor recalibration process imposed by a pointing task when vision is rotated.

Development of Proprioceptive Acuity in Typically Developing Children: Normative Data on Forearm Position Sense

This study mapped the development of proprioception in healthy, typically developing children by objectively measuring forearm position sense acuity. We assessed position sense acuity in a cross-sectional sample of 308 children (5–17 years old; M/F = 127/181) and a reference group of 26 healthy adults (18–25 years old; M/F = 12/14) using a body-scalable bimanual manipulandum that allowed forearm flexion/extension in the horizontal plane. The non-dominant forearm was passively displaced to one of three target positions. Then participants actively matched the target limb position with their dominant forearm. Each of three positions was matched five times. Position error (PE), calculated as the mean difference between the angular positions of the matching and reference arms, measured position sense bias or systematic error. The respective standard deviation of the differences between the match and reference arm angular positions (SDP_diff) indicated position sense precision or random error. The main results are as follows: First, systematic error, measured by PE, did not change significantly from early childhood to late adolescence (Median PE at 90° target: −2.85° in early childhood; −2.28° in adolescence; and 1.30° in adults). Second, response variability as measured by SDP_diff significantly decreased with age (Median SDP_diff at 90° target: 9.66° in early childhood; 5.30° in late adolescence; and 3.97° in adults). The data of this large cross-sectional sample of children document that proprioceptive development in typically developing children is characterized as an age-related improvement in precision, not as a development or change in bias. In other words, it is the reliability of the perceptual response that improves between early childhood and adulthood. This study provides normative data against which position sense acuity in pediatric patient populations can be compared. The underlying neurophysiological processes that could explain the observed proprioceptive development include changes in the tuning of muscle spindles at the spinal level, the maturation of supraspinal somatosensory pathways and the development of interhemispheric callosal connections responsible for the transfer of somatosensory information.

The influence of proprioception on reading performance

BACKGROUND

Visual ergonomics has an impact on visual performance in reading. Based on the assumption that reading from an LCD screen held in the hands provides more accurate information about the distance to the object than reading from a screen, which has no contact with our body, this study assessed the influence of the proprioceptive input on the speed of reading and on accommodative and pupillary responses and their micro-oscillations.

METHODS

Participants (n = 47; all emmetropic, non-amblyopic), were asked to read in their minds two-digit numerals presented on a 10-inch LCD screen at 40 cm distance. In one condition, the participants held the screen in their hands; in the other, the screen was placed on the holder and there was no body contact with the participant. The number of numerals read in 90 seconds was recorded. Accommodative and pupillary responses were measured with Power Refractor 3 at a 50 Hz measurement rate.

RESULTS

The number of numerals read was greater for the condition with proprioceptive input than in the condition without contact. The mean pupil size and the average accommodative response were similar in the two conditions. The rate of change in pupil size showed a steeper decline in the condition without the proprioceptive input compared to the condition with this input. The increase in the lag of accommodation with time was similar in both conditions, as well as pupillary and accommodative micro-oscillations.

CONCLUSIONS

When the screen was held in the hands, reading of numerals was faster and resulted in less pupil size change over the 90-second test interval. This indicates that proprioception might influence some aspects of visual performance.

Validity and Reliability of a Digital Inclinometer to Assess Knee Joint-Position Sense in a Closed Kinetic Chain

CONTEXT

Knee joint position sense (JPS) is a key parameter for optimum performance in many sports but is frequently negatively affected by injuries and/or fatigue during training sessions. Although evaluation of JPS may provide key information to reduce the risk of injury, it often requires expensive and/or complex tools that make monitoring proprioceptive deterioration difficult.

OBJECTIVE

To analyze the validity and reliability of a digital inclinometer to measure knee JPS in a closed kinetic chain (CKC).

DESIGN

The validity and intertester and intratester reliability of a digital inclinometer for measuring knee JPS were assessed.

SETTING

Biomechanics laboratory.

PARTICIPANTS

10 athletes (5 men and 5 women; 26.2 ± 1.3 y, 71.7 ± 12.4 kg; 1.75 ± 0.09 m; 23.5 ± 3.9 kg/m²).

INTERVENTION

Knee JPS was measured in a CKC.

MAIN OUTCOME MEASURES

Absolute angular error (AAE) of knee JPS in a CKC.

RESULTS

Intraclass correlation coefficient (ICC) and standard error of the mean (SEM) were calculated to determine the validity and reliability of the inclinometer. Data showed that the inclinometer had a high level of validity compared with an isokinetic dynamometer (ICC = 1.0, SEM = 1.39, p < 0.001), and there was very good intra- and inter-tester reliability for reading the inclinometer (ICC = 1.0, SEM = 0.85, p < 0.001). Compared with AutoCAD video analysis, inclinometer validity was very high (ICC = 0.980, SEM = 3.46, p < 0.001) for measuring AAE during knee JPS in a CKC. In addition, the intertester reliability of the inclinometer for obtaining AAE was very high (ICC = .994, SEM = 1.67, p < 0.001).

CONCLUSION

The inclinometer provides a valid and reliable method for assessing knee JPS in a CKC. Health and sports professionals could take advantage of this tool to monitor proprioceptive deterioration in athletes.

Integration of Visual and Proprioceptive Limb Position Information in Human Posterior Parietal, Premotor, and Extrastriate Cortex

The brain constructs a flexible representation of the body from multisensory information. Previous work on monkeys suggests that the posterior parietal cortex (PPC) and ventral premotor cortex (PMv) represent the position of the upper limbs based on visual and proprioceptive information. Human experiments on the rubber hand illusion implicate similar regions, but since such experiments rely on additional visuo-tactile interactions, they cannot isolate visuo-proprioceptive integration. Here, we independently manipulated the position (palm or back facing) of passive human participants' unseen arm and of a photorealistic virtual 3D arm. Functional magnetic resonance imaging (fMRI) revealed that matching visual and proprioceptive information about arm position engaged the PPC, PMv, and the body-selective extrastriate body area (EBA); activity in the PMv moreover reflected interindividual differences in congruent arm ownership. Further, the PPC, PMv, and EBA increased their coupling with the primary visual cortex during congruent visuo-proprioceptive position information. These results suggest that human PPC, PMv, and EBA evaluate visual and proprioceptive position information and, under sufficient cross-modal congruence, integrate it into a multisensory representation of the upper limb in space.

SIGNIFICANCE STATEMENT

The position of our limbs in space constantly changes, yet the brain manages to represent limb position accurately by combining information from vision and proprioception. Electrophysiological recordings in monkeys have revealed neurons in the posterior parietal and premotor cortices that seem to implement and update such a multisensory limb representation, but this has been difficult to demonstrate in humans. Our fMRI experiment shows that human posterior parietal, premotor, and body-selective visual brain areas respond preferentially to a virtual arm seen in a position corresponding to one's unseen hidden arm, while increasing their communication with regions conveying visual information. These brain areas thus likely integrate visual and proprioceptive information into a flexible multisensory body representation.

Dependence of auditory spatial updating on vestibular, proprioceptive, and efference copy signals

Humans localize sounds by comparing inputs across the two ears, resulting in a head-centered representation of sound-source position. When the head moves, information about head movement must be combined with the head-centered estimate to correctly update the world-centered sound-source position. Spatial updating has been extensively studied in the visual system, but less is known about how head movement signals interact with binaural information during auditory spatial updating. In the current experiments, listeners compared the world-centered azimuthal position of two sound sources presented before and after a head rotation that depended on condition. In the active condition, subjects rotated their head by ∼35° to the left or right, following a pretrained trajectory. In the passive condition, subjects were rotated along the same trajectory in a rotating chair. In the cancellation condition, subjects rotated their head as in the active condition, but the chair was counter-rotated on the basis of head-tracking data such that the head effectively remained fixed in space while the body rotated beneath it. Subjects updated most accurately in the passive condition but erred in the active and cancellation conditions. Performance is interpreted as reflecting the accuracy of perceived head rotation across conditions, which is modeled as a linear combination of proprioceptive/efference copy signals and vestibular signals. Resulting weights suggest that auditory updating is dominated by vestibular signals but with significant contributions from proprioception/efference copy. Overall, results shed light on the interplay of sensory and motor signals that determine the accuracy of auditory spatial updating.

The effect of proprioception exercises on functional status in patients with anterior cruciate ligament reconstruction

OBJECTIVE

To evaluate knee proprioception in patients with anterior cruciate ligament (ACL) injuries and to assess the effectiveness of an exercise program consisting mainly of proprioception exercises addressing pain, proprioception, and functional status following ACL reconstruction.

MATERIALS AND METHODS

Twenty male patients, diagnosed with unilateral ACL injury and scheduled for reconstruction, participated in the study along with 16 age- and sex-matched healthy volunteers. Arthroscopic reconstruction of the ACL using autologous hamstring tendon was performed in every case by the same surgeon. After the operation, a six-month rehabilitation program was initiated. Knee proprioception, pain, and functional status were evaluated before and six months after the reconstruction. An isokinetic dynamometer was used to evaluate proprioception and a visual analog scale (VAS) and the Tegner Lysholm Knee Scoring Scale were used to evaluate pain and functional status respectively.

RESULTS

Preoperative proprioception loss was detected on the patients' injured side when compared to the uninjured side and to healthy volunteers (p = 0.00). A significant improvement was found in pain severity, proprioception, and functional capacity after the postoperative six-month rehabilitation program (p = 0.00).

CONCLUSION

Preoperative proprioception loss was detected in ACL-injured patients. The rehabilitation program predominantly consisting of proprioception exercises provided considerable improvement on knee proprioception and functional status.

Mechanoreceptors of the ligaments and tendons around the knee

Proprioceptive inputs from the joints and limbs arise from mechanoreceptors in the muscles, ligaments and tendons. The knee joint has a wide range of movements, and proper neuroanatomical organization is critical for knee stability. Four ligaments (the anterior (ACL) and posterior (PCL) cruciate ligaments and the medial (MCL) and lateral (LCL) collateral ligaments) and four tendons (the semitendinosus (STT), gracilis (GT), popliteal (PoT), and patellar (PaT) tendons) from eight fresh frozen cadavers were harvested. Each harvested tissue was divided into its bone insertion side and its tendinous part for immunohistochemical examination using S100 staining. Freeman-Wyke's classification was used to identify the mechanoreceptors. The mechanoreceptors were usually located close to the bone insertion. Free nerve endings followed by Ruffini endings were the most common mechanoreceptors overall. No Pacini corpuscles were observed; free nerve endings and Golgi-like endings were most frequent in the PCL (PCL-PaT: P = 0.0.1, PCL-STT: P = 0.00), and Ruffini endings in the popliteal tendon (PoT-PaT: P = 0.00, Pot-STT: P = 0.00, PoT-LCL: P = 0.00, PoT-GT: P = 0.00, PoT-ACL: P = 0.09). The cruciate ligaments had more mechanoreceptors than the medial structures (MS) or the patellar tendon (CR-Pat: P = 0.000, CR-MS: P = 0.01). The differences in mechanoreceptor distributions between the ligaments and tendons could reflect the different roles of these structures in the dynamic coordination of knee motion. Clin. Anat. 29:789-795, 2016. © 2016 Wiley Periodicals, Inc.

Hand Positions Alter Bistable Visual Motion Perception

We found that a hand posture with the palms together located just below the stream/bounce display could increase the proportion of bouncing perception. This effect, called the hands-induced bounce (HIB) effect, did not occur in the hands-cross condition or in the one-hand condition. By using rubber hands or covering the participants’ hands with a cloth, we demonstrated that the visual information of the hand shapes was not a critical factor in producing the HIB effect, whereas proprioceptive information seemed to be important. We also found that the HIB effect did not occur when the participants’ hands were far from the coincidence point, suggesting that the HIB effect might be produced within a limited spatial area around the hands.

Vestibular nucleus neurons respond to hindlimb movement in the conscious cat

The limbs constitute the sole interface with the ground during most waking activities in mammalian species; it is therefore expected that somatosensory inputs from the limbs provide important information to the central nervous system for balance control. In the decerebrate cat model, the activity of a subset of neurons in the vestibular nuclei (VN) has been previously shown to be modulated by hindlimb movement. However, decerebration can profoundly alter the effects of sensory inputs on the activity of brain stem neurons, resulting in epiphenomenal responses. Thus, before this study, it was unclear whether and how somatosensory inputs from the limb affected the activity of VN neurons in conscious animals. We recorded brain stem neuronal activity in the conscious cat and characterized the responses of VN neurons to flexion and extension hindlimb movements and to whole body vertical tilts (vestibular stimulation). Among 96 VN neurons whose activity was modulated by vestibular stimulation, the firing rate of 65 neurons (67.7%) was also affected by passive hindlimb movement. VN neurons in conscious cats most commonly encoded hindlimb movement irrespective of the direction of movement (n = 33, 50.8%), in that they responded to all flexion and extension movements of the limb. Other VN neurons overtly encoded information about the direction of hindlimb movement (n = 27, 41.5%), and the remainder had more complex responses. These data confirm that hindlimb somatosensory and vestibular inputs converge onto VN neurons of the conscious cat, suggesting that VN neurons integrate somatosensory inputs from the limbs in computations that affect motor outflow to maintain balance.

Falls study: Proprioception, postural stability, and slips

The present study evaluated effects of exercise training on the proprioception sensitivity, postural stability, and the likelihood of slip-induced falls. Eighteen older adults (6 in balance, 6 in weight, and 6 in control groups) participated in this study. Three groups met three times per week over the course of eight weeks. Ankle and knee proprioception sensitivities and postural stability were measured. Slip-induced events were introduced for all participants before and after training. The results indicated that, overall, strength and postural stability were improved only in the training group, although proprioception sensitivity was improved in all groups. Training for older adults resulted in decreased likelihood of slip-induced falls. The study suggested that proprioception can be improved by simply being active, however, the results suggested that training would aid older adults in reducing the likelihood of slip-induced falls.

Velocity dependence of vestibular information for postural control on tilting surfaces

Vestibular information is known to be important for postural stability on tilting surfaces, but the relative importance of vestibular information across a wide range of surface tilt velocities is less clear. We compared how tilt velocity influences postural orientation and stability in nine subjects with bilateral vestibular loss and nine age-matched, control subjects. Subjects stood on a force platform that tilted 6 deg, toes-up at eight velocities (0.25 to 32 deg/s), with and without vision. Results showed that visual information effectively compensated for lack of vestibular information at all tilt velocities. However, with eyes closed, subjects with vestibular loss were most unstable within a critical tilt velocity range of 2 to 8 deg/s. Subjects with vestibular deficiency lost their balance in more than 90% of trials during the 4 deg/s condition, but never fell during slower tilts (0.25-1 deg/s) and fell only very rarely during faster tilts (16-32 deg/s). At the critical velocity range in which falls occurred, the body center of mass stayed aligned with respect to the surface, onset of ankle dorsiflexion was delayed, and there was delayed or absent gastrocnemius inhibition, suggesting that subjects were attempting to actively align their upper bodies with respect to the moving surface instead of to gravity. Vestibular information may be critical for stability at velocities of 2 to 8 deg/s because postural sway above 2 deg/s may be too fast to elicit stabilizing responses through the graviceptive somatosensory system, and postural sway below 8 deg/s may be too slow for somatosensory-triggered responses or passive stabilization from trunk inertia.

Methods for the assessment of neuromotor capacity in non-specific low back pain: Validity and applicability in everyday clinical practice

BACKGROUND

Physiotherapists and clinicians require methods that can be used in everyday practice for measuring proprioception of the trunk in individuals with non-specific low back pain (NSLBP).

OBJECTIVE

Our objective was to conduct a systematic literature review of methods used for assessment of proprioception of the trunk in individuals with non-specific low back pain.

METHOD

Data were obtained from MEDLINE, CINAHL, Embase, PEDro and CENTRAL databases from their inception to December 2011. Reference lists of the selected reviews were hand searched for other potentially relevant studies. Randomized and nonrandomized controlled studies proprioception of the trunk in individuals with low back pain were selected. Thirty-six studies satisfied the selection criteria and were included in this review.

RESULTS

Two reviewers independently selected the studies, conducted the quality assessment, and extracted data from each study. The Strobe scale was used to evaluate the scientific rigor of each selected study.

CONCLUSIONS

This systematic review covered all the relevant literature, but none of the included studies offered a valid, reliable and feasible method to assess neuromotor capacity in everyday physiotherapy clinical practice.

The association between muscle strength and activity limitations in patients with the hypermobility type of Ehlers-Danlos syndrome: the impact of proprioception

PURPOSE

The patients diagnosed with Ehlers-Danlos Syndrome Hypermobility Type (EDS-HT) are characterized by pain, proprioceptive inacuity, muscle weakness, potentially leading to activity limitations. In EDS-HT, a direct relationship between muscle strength, proprioception and activity limitations has never been studied. The objective of the study was to establish the association between muscle strength and activity limitations and the impact of proprioception on this association in EDS-HT patients.

METHODS

Twenty-four EDS-HT patients were compared with 24 controls. Activity limitations were quantified by Health Assessment Questionnaire (HAQ), Six-Minute Walk test (6MWT) and 30-s chair-rise test (30CRT). Muscle strength was quantified by handheld dynamometry. Proprioception was quantified by movement detection paradigm. In analyses, the association between muscle strength and activity limitations was controlled for proprioception and confounders.

RESULTS

Muscle strength was associated with 30CRT (r = 0.67, p = <0.001), 6MWT (r = 0.58, p = <0.001) and HAQ (r = 0.63, p= <0.001). Proprioception was associated with 30CRT (r = 0.55, p < 0.001), 6MWT (r = 0.40, p = <0.05) and HAQ (r = 0.46, p < 0.05). Muscle strength was found to be associated with activity limitations, however, proprioceptive inacuity confounded this association.

CONCLUSIONS

Muscle strength is associated with activity limitations in EDS-HT patients. Joint proprioception is of influence on this association and should be considered in the development of new treatment strategies for patients with EDS-HT. Implications for rehabilitation Reducing activity limitations by enhancing muscle strength is frequently applied in the treatment of EDS-HT patients. Although evidence regarding treatment efficacy is scarce, the current paper confirms the rationality that muscle strength is an important factor in the occurrence of activity limitations in EDS-HT patients. Although muscle strength is the most dominant factor that is associated with activity limitations, this association is confounded by proprioception. In contrast to common belief proprioception was not directly associated with activity limitations but confounded this association. Controlling muscle strength on the bases of proprioceptive input may be more important for reducing activity limitations than just enhancing sheer muscle strength.

Effects of Warm-Up and Fatigue on Knee Joint Position Sense and Jump Performance

The purpose of this study was to evaluate the effects of a warm-up and fatigue protocol on the vertical jump and knee joint position sense of sprinters. Thirty-two sprinters were randomly allocated to either a control group (CONT) or a plyometric group (PLYO) that performed a warm-up, followed by a high-intensity plyometric protocol. Absolute (AAE), relative (RAE), and variable (VAE) angular errors and vertical jump were evaluated before and after the warm-up, as well as after the plyometric protocol and again 5 min later. After the warm-up, athletes improved RAE and jump performance. After the plyometric protocol, scores on the RAE, VAE, and the vertical jump performance worsened compared to the control group and to the values obtained after the warm-up. Five minutes later, RAE and vertical jump continued to be impaired. AAE did not show significant differences. The vertical jump is improved after the warm-up, although it is deteriorated after high-intensity plyometry. Regarding knee proprioception, the lack of impairments in the AAE make unclear the effects of the plyometric exercises on knee proprioception.

Transmembrane channel-like (tmc) gene regulates Drosophila larval locomotion

Drosophila larval locomotion, which entails rhythmic body contractions, is controlled by sensory feedback from proprioceptors. The molecular mechanisms mediating this feedback are little understood. By using genetic knock-in and immunostaining, we found that the Drosophila melanogaster transmembrane channel-like (tmc) gene is expressed in the larval class I and class II dendritic arborization (da) neurons and bipolar dendrite (bd) neurons, both of which are known to provide sensory feedback for larval locomotion. Larvae with knockdown or loss of tmc function displayed reduced crawling speeds, increased head cast frequencies, and enhanced backward locomotion. Expressing Drosophila TMC or mammalian TMC1 and/or TMC2 in the tmc-positive neurons rescued these mutant phenotypes. Bending of the larval body activated the tmc-positive neurons, and in tmc mutants this bending response was impaired. This implicates TMC's roles in Drosophila proprioception and the sensory control of larval locomotion. It also provides evidence for a functional conservation between Drosophila and mammalian TMCs.

Baseline Time to Stabilization Identifies Anterior Cruciate Ligament Rupture Risk in Collegiate Athletes

BACKGROUND

There is a need for successful screening methods to identify athletes at increased risk of anterior cruciate ligament (ACL) injury. Previous research showed that collegiate athletes with ACL tears demonstrated slower time to stabilization during jump landing after reconstruction.

HYPOTHESIS

Collegiate athletes with baseline deficiencies in time to stabilization are at increased risk of subsequent ACL rupture.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

A total of 278 National Collegiate Athletic Association Division I college athletes (166 men, 112 women; mean age, 18.5 years; height, 178.8 cm; mass, 79.9 kg) in the high-risk sports of men's football; women's volleyball and field hockey; and men's and women's lacrosse, basketball, and soccer were measured to obtain baseline time to stabilization for backward, forward, medial, and lateral single-legged jump landing tasks. Athletes were followed for ACL rupture over a 4-year period. Independent t tests were used to evaluate differences in time to stabilization for each jump landing task between athletes with subsequent ACL rupture and uninjured athletes. Logistic regression models were used to assess time to stabilization as a predictor for ACL rupture.

RESULTS

Nine athletes sustained noncontact ACL ruptures (5 men, 4 women). These 9 athletes took significantly longer to stabilize compared with uninjured athletes during baseline backward jump landing (1.58 ± 0.39 and 1.09 ± 0.52 seconds, respectively; P = .0052). The odds of ACL rupture increased 3-fold (odds ratio, 2.95; 95% CI, 1.28-6.77) for every second increase in backward time to stabilization observed between injured and uninjured athletes.

CONCLUSION

Collegiate athletes with slower baseline backward time to stabilization were at increased risk of ACL rupture.

Biological and bionic hands: natural neural coding and artificial perception

The first decade and a half of the twenty-first century brought about two major innovations in neuroprosthetics: the development of anthropomorphic robotic limbs that replicate much of the function of a native human arm and the refinement of algorithms that decode intended movements from brain activity. However, skilled manipulation of objects requires somatosensory feedback, for which vision is a poor substitute. For upper-limb neuroprostheses to be clinically viable, they must therefore provide for the restoration of touch and proprioception. In this review, I discuss efforts to elicit meaningful tactile sensations through stimulation of neurons in somatosensory cortex. I focus on biomimetic approaches to sensory restoration, which leverage our current understanding about how information about grasped objects is encoded in the brain of intact individuals. I argue that not only can sensory neuroscience inform the development of sensory neuroprostheses, but also that the converse is true: stimulating the brain offers an exceptional opportunity to causally interrogate neural circuits and test hypotheses about natural neural coding.

Axiom, Anguish, and Amazement: How Autistic Traits Modulate Emotional Mental Imagery

Individuals differ in their ability to feel their own and others’ internal states, with those that have more autistic and less empathic traits clustering at the clinical end of the spectrum. However, when we consider semantic competence, this group could compensate with a higher capacity to imagine the meaning of words referring to emotions. This is indeed what we found when we asked people with different levels of autistic and empathic traits to rate the degree of imageability of various kinds of words. But this was not the whole story. Individuals with marked autistic traits demonstrated outstanding ability to imagine theoretical concepts, i.e., concepts that are commonly grasped linguistically through their definitions. This distinctive characteristic was so pronounced that, using tree-based predictive models, it was possible to accurately predict participants’ inclination to manifest autistic traits, as well as their adherence to autistic profiles – including whether they fell above or below the diagnostic threshold – from their imageability ratings. We speculate that this quasi-perceptual ability to imagine theoretical concepts represents a specific cognitive pattern that, while hindering social interaction, may favor problem solving in abstract, non-socially related tasks. This would allow people with marked autistic traits to make use of perceptual, possibly visuo-spatial, information for “higher” cognitive processing.

Improved interoceptive awareness in chronic low back pain: a comparison of Back school versus Feldenkrais method

PURPOSE

To determine the efficacy of the Feldenkrais method for relieving pain in patients with chronic low back pain (CLBP) and the improvement of interoceptive awareness.

METHOD

This study was designed as a single-blind randomized controlled trial. Fifty-three patients with a diagnosis of CLBP for at least 3 months were randomly allocated to the Feldenkrais (mean age 61.21 ± 11.53 years) or Back School group (mean age 60.70 ± 11.72 years). Pain was assessed using the visual analog scale (VAS) and McGill Pain Questionnaire (MPQ), disability was evaluated with the Waddel Disability Index, quality of life was measured with the Short Form-36 Health Survey (SF-36), and mind-body interactions were studied using the Multidimensional Assessment of Interoceptive Awareness Questionnaire (MAIA). Data were collected at baseline, at the end of treatment, and at the 3-month follow-up.

RESULTS

The two groups were matched at baseline for all the computed parameters. At the end of treatment (Tend), there were no significant differences between groups regarding chronic pain reduction (p = 0.290); VAS and MAIA-N sub scores correlated at Tend (R = 0.296, p = 0.037). By the Friedman analysis, both groups experienced significant changes in pain (p < 0.001) and disability (p < 0.001) along the investigated period.

CONCLUSIONS

The Feldenkrais method has comparable efficacy as Back School in CLBP. Implications for rehabilitation The Feldenkrais method is a mind-body therapy that is based on awareness through movement lessons, which are verbally guided explorations of movement that are conducted by a physiotherapist who is experienced and trained in this method. It aims to increase self-awareness, expand a person's repertoire of movements, and to promote increased functioning in contexts in which the entire body cooperates in the execution of movements. Interoceptive awareness, which improves with rehabilitation, has a complex function in the perception of chronic pain and should be investigated further in future research. The efficacy of the Feldenkrais method is comparable with that of BS for nonspecific chronic low back pain. The physician can recommend a body-mind rehabilitation approach, such as the Feldenkrais method, or an educational and rehabilitation program, such as BS, to the patient, based on his individual needs. The 2 rehabilitation approaches are equally as effective in improving interoceptive awareness.

Effects of Three Weeks of Whole-Body Vibration Training on Joint-Position Sense, Balance, and Gait in Children with Cerebral Palsy: A Randomized Controlled Study

Purpose : To observe the effects of whole-body vibration (WBV) training in conjunction with conventional physical therapy (PT) on joint-position sense (JPS), balance, and gait in children with cerebral palsy (CP). Methods: In this randomized controlled study, 24 children with CP were randomly selected either to continue their conventional PT or to receive WBV in conjunction with their conventional PT programme. Exposure to the intervention was intermittent (3 min WBV, 3 min rest) for 20 minutes, twice weekly for 3 weeks. JPS, balance, and gait were evaluated before and after treatment. Results: Ankle JPS was improved after 3 weeks of WBV training (p=0.014). Participants in the WBV group showed greater improvements in speed (F_1,21=5.221, p=0.035) and step width (F_1,21=4.487, p=0.039) than participants in the conventional PT group. Conclusion: Three weeks of WBV training was effective in improving ankle JPS and gait variables in children with CP.

Neuronal representation of saccadic error in macaque posterior parietal cortex (PPC)

Motor control, motor learning, self-recognition, and spatial perception all critically depend on the comparison of motor intention to the actually executed movement. Despite our knowledge that the brainstem-cerebellum plays an important role in motor error detection and motor learning, the involvement of neocortex remains largely unclear. Here, we report the neuronal computation and representation of saccadic error in macaque posterior parietal cortex (PPC). Neurons with persistent pre- and post-saccadic response (PPS) represent the intended end-position of saccade; neurons with late post-saccadic response (LPS) represent the actual end-position of saccade. Remarkably, after the arrival of the LPS signal, the PPS neurons’ activity becomes highly correlated with the discrepancy between intended and actual end-position, and with the probability of making secondary (corrective) saccades. Thus, this neuronal computation might underlie the formation of saccadic error signals in PPC for speeding up saccadic learning and leading the occurrence of secondary saccade.

DOI:http://dx.doi.org/10.7554/eLife.10912.001

Effects of tibialis anterior vibration on postural control when exposed to support surface translations

The sensory re-weighting theory suggests unreliable inputs may be down-weighted to favor more reliable sensory information and thus maintain proper postural control. This study investigated the effects of tibialis anterior (TA) vibration on center of pressure (COP) motion in healthy individuals exposed to support surface translations to further explore the concept of sensory re-weighting. Twenty healthy young adults stood with eyes closed and arms across their chest while exposed to randomized blocks of five trials. Each trial lasted 8 s, with TA vibration either on or off. After 2 s, a sudden backward or forward translation occurred. Anterior-posterior (A/P) COP data were evaluated during the preparatory (first 2 s), perturbation (next 3 s), and recovery (last 3 s) phases to assess the effect of vibration on perturbation response features. The knowledge of an impending perturbation resulted in reduced anterior COP motion with TA vibration in the preparatory phase relative to the magnitude of anterior motion typically observed during TA vibration. During the perturbation phase, vibration did not influence COP motion. However, during the recovery phase vibration induced greater anterior COP motion than during trials without vibration. The fact that TA vibration produced differing effects on COP motion depending upon the phase of the perturbation response may suggest that the immediate context during which postural control is being regulated affects A/P COP responses to TA vibration. This indicates that proprioceptive information is likely continuously re-weighted according to the context in order to maintain effective postural control.

Changes in muscle spindle firing in response to length changes of neighboring muscles

Skeletal muscle force can be transmitted to the skeleton, not only via its tendons of origin and insertion but also through connective tissues linking the muscle belly to surrounding structures. Through such epimuscular myofascial connections, length changes of a muscle may cause length changes within an adjacent muscle and hence, affect muscle spindles. The aim of the present study was to investigate the effects of epimuscular myofascial forces on feedback from muscle spindles in triceps surae muscles of the rat. We hypothesized that within an intact muscle compartment, muscle spindles not only signal length changes of the muscle in which they are located but can also sense length changes that occur as a result of changing the length of synergistic muscles. Action potentials from single afferents were measured intra-axonally in response to ramp-hold release (RHR) stretches of an agonistic muscle at different lengths of its synergist, as well as in response to synergist RHRs. A decrease in force threshold was found for both soleus (SO) and lateral gastrocnemius afferents, along with an increase in length threshold for SO afferents. In addition, muscle spindle firing could be evoked by RHRs of the synergistic muscle. We conclude that muscle spindles not only signal length changes of the muscle in which they are located but also local length changes that occur as a result of changing the length and relative position of synergistic muscles.

Impact of limiting visual input on gait: Individuals with Parkinson disease, age-matched controls, and healthy young participants

Normal and limited vision gait was investigated in individuals with Parkinson disease (PD), healthy older and healthy young individuals. Participants walked a GAITRite mat with normal vision or vision of lower limbs occluded. Results indicate individuals with PD walked more slowly, with shorter and wider steps, and spent more time in double support with limited vision as compared to full vision. Healthy young and old individuals took shorter steps but were otherwise unchanged between conditions.

Quantitative neuroanatomy for connectomics in Drosophila

Neuronal circuit mapping using electron microscopy demands laborious proofreading or reconciliation of multiple independent reconstructions. Here, we describe new methods to apply quantitative arbor and network context to iteratively proofread and reconstruct circuits and create anatomically enriched wiring diagrams. We measured the morphological underpinnings of connectivity in new and existing reconstructions of Drosophila sensorimotor (larva) and visual (adult) systems. Synaptic inputs were preferentially located on numerous small, microtubule-free 'twigs' which branch off a single microtubule-containing 'backbone'. Omission of individual twigs accounted for 96% of errors. However, the synapses of highly connected neurons were distributed across multiple twigs. Thus, the robustness of a strong connection to detailed twig anatomy was associated with robustness to reconstruction error. By comparing iterative reconstruction to the consensus of multiple reconstructions, we show that our method overcomes the need for redundant effort through the discovery and application of relationships between cellular neuroanatomy and synaptic connectivity.

DOI:http://dx.doi.org/10.7554/eLife.12059.001

The nervous system contains cells called neurons, which connect to each other to form circuits that send and process information. Each neuron receives and transmits signals to other neurons via very small junctions called synapses. Neurons are shaped a bit like trees, and most input synapses are located in the tiniest branches. Understanding the architecture of a neuron’s branches is important to understand the role that a particular neuron plays in processing information. Therefore, neuroscientists strive to reconstruct the architecture of these branches and how they connect to one another using imaging techniques.

One imaging technique known as serial electron microscopy generates highly detailed images of neural circuits. However, reconstructing neural circuits from such images is notoriously time consuming and error prone. These errors could result in the reconstructed circuit being very different than the real-life circuit. For example, an error that leads to missing out a large branch could result in researchers failing to notice many important connections in the circuit. On the other hand, some errors may not matter much because the neurons share other synapses that are included in the reconstruction.

To understand what effect errors have on the reconstructed circuits, neuroscientists need to have a more detailed understanding of the relationship between the shape of a neuron, its synaptic connections to other neurons, and where errors commonly occur. Here, Schneider-Mizell, Gerhard et al. study this relationship in detail and then devise a faster reconstruction method that uses the shape and other properties of neurons without sacrificing accuracy. The method includes a way to include data from the shape of neurons in the circuit wiring diagrams, revealing circuit patterns that would otherwise go unnoticed.

The experiments use serial electron microscopy images of neurons from fruit flies and show that, from the tiniest larva to the adult fly, neurons form synapses with each other in a similar way. Most errors in the reconstruction only affect the tips of the smallest branches, which generally only host a single synapse. Such omissions do not have a big effect on the reconstructed circuit because strongly connected neurons make multiple synapses onto each other.

Schneider-Mizell, Gerhard et al.'s approach will help researchers to reconstruct neural circuits and analyze them more effectively than was possible before. The algorithms and tools developed in this study are available in an open source software package so that they can be used by other researchers in the future.

DOI:http://dx.doi.org/10.7554/eLife.12059.002

Assessing performance, stability, and cleat comfort/support in collegiate club soccer players using prophylactic ankle taping and bracing

Soccer athletes at all levels of play are keenly aware of their equipment needs including cleat wear, and want to be protected from injury but without impeding on-field performance. Ankle injury is a common disorder that is prevalent in the sport of soccer and recent improvements in ankle prophylaxis interventions have proven effective. The aim of this study was to determine if the use of elastic taping or a neoprene sleeve alters performance, stability, and cleat comfort/support in soccer players compared to wearing a soccer cleat without any external support. Twenty male collegiate club soccer players were recruited and randomly assigned to the three conditions (untaped control, taped, neoprene sleeve). Performance testing and comfort/support assessment for each condition took place in one on-field test session, while stability testing was completed during a separate laboratory session. The only significant finding was improved inversion/eversion stability in both the tape and sleeve conditions as compared to the cleated condition. The addition of tape or a sleeve did not have an adverse effect on performance or comfort during functional and stability testing, and should therefore be considered as a method to decrease ankle injuries in soccer athletes as external supports provide increased stability in inversion/eversion range of motion.

Using Balance Tests to Discriminate Between Participants With a Recent Index Lateral Ankle Sprain and Healthy Control Participants: A Cross-Sectional Study

CONTEXT

The first step to identifying factors that increase the risk of recurrent ankle sprains is to identify impairments after a first sprain and compare performance with individuals who have never sustained a sprain. Few researchers have restricted recruitment to a homogeneous group of patients with first sprains, thereby introducing the potential for confounding.

OBJECTIVE

To identify impairments that differ in participants with a recent index lateral ankle sprain versus participants with no history of ankle sprain.

DESIGN

Cross-sectional study.

PATIENTS OR OTHER PARTICIPANTS

We recruited a sample of convenience from May 2010 to April 2013 that included 70 volunteers (age = 27.4 ± 8.3 years, height = 168.7 ± 9.5 cm, mass = 65.0 ± 12.5 kg) serving as controls and 30 volunteers (age = 31.1 ± 13.3 years, height = 168.3 ± 9.1 cm, mass = 67.3 ± 13.7 kg) with index ankle sprains.

MAIN OUTCOME MEASURE(S)

We collected demographic and physical performance variables, including ankle-joint range of motion, balance (time to balance after perturbation, Star Excursion Balance Test, foot lifts during single-legged stance, demi-pointe balance test), proprioception, motor planning, inversion-eversion peak power, and timed stair tests. Discriminant analysis was conducted to determine the relationship between explanatory variables and sprain status. Sequential discriminant analysis was performed to identify the most relevant variables that explained the greatest variance.

RESULTS

The average time since the sprain was 3.5 ± 1.5 months. The model, including all variables, correctly predicted a sprain status of 77% (n = 23) of the sprain group and 80% (n = 56) of the control group and explained 40% of the variance between groups ([Formula: see text] = 42.16, P = .03). Backward stepwise discriminant analysis revealed associations between sprain status and only 2 tests: Star Excursion Balance Test in the anterior direction and foot lifts during single-legged stance ([Formula: see text] = 15.2, P = .001). These 2 tests explained 15% of the between-groups variance and correctly predicted group membership of 63% (n = 19) of the sprain group and 69% (n = 48) of the control group.

CONCLUSIONS

Balance impairments were associated with a recent first ankle sprain, but proprioception, motor control, power, and function were not.

Skeletal ligament healing using the recombinant human amelogenin protein

Injuries to ligaments are common, painful and debilitating, causing joint instability and impaired protective proprioception sensation around the joint. Healing of torn ligaments usually fails to take place, and surgical replacement or reconstruction is required. Previously, we showed that in vivo application of the recombinant human amelogenin protein (rHAM⁺) resulted in enhanced healing of the tooth‐supporting tissues. The aim of this study was to evaluate whether amelogenin might also enhance repair of skeletal ligaments. The rat knee medial collateral ligament (MCL) was chosen to prove the concept. Full thickness tear was created and various concentrations of rHAM⁺, dissolved in propylene glycol alginate (PGA) carrier, were applied to the transected MCL. 12 weeks after transection, the mechanical properties, structure and composition of transected ligaments treated with 0.5 μg/μl rHAM⁺ were similar to the normal un‐transected ligaments, and were much stronger, stiffer and organized than control ligaments, treated with PGA only. Furthermore, the proprioceptive free nerve endings, in the 0.5 μg/μl rHAM⁺ treated group, were parallel to the collagen fibres similar to their arrangement in normal ligament, while in the control ligaments the free nerve endings were entrapped in the scar tissue at different directions, not parallel to the axis of the force. Four days after transection, treatment with 0.5 μg/μl rHAM⁺ increased the amount of cells expressing mesenchymal stem cell markers at the injured site. In conclusion application of rHAM⁺ dose dependently induced mechanical, structural and sensory healing of torn skeletal ligament. Initially the process involved recruitment and proliferation of cells expressing mesenchymal stem cell markers.

Proprioceptive acuity predicts muscle co-contraction of the tibialis anterior and gastrocnemius medialis in older adults' dynamic postural control

Older adults use a different muscle strategy to cope with postural instability, in which they 'co-contract' the muscles around the ankle joint. It has been suggested that this is a compensatory response to age-related proprioceptive decline however this view has never been assessed directly. The current study investigated the association between proprioceptive acuity and muscle co-contraction in older adults. We compared muscle activity, by recording surface electromyography (EMG) from the bilateral tibialis anterior (TA) and gastrocnemius medialis (GM) muscles, in young (aged 18-34) and older adults (aged 65-82) during postural assessment on a fixed and sway-referenced surface at age-equivalent levels of sway. We performed correlations between muscle activity and proprioceptive acuity, which was assessed using an active contralateral matching task. Despite successfully inducing similar levels of sway in the two age groups, older adults still showed higher muscle co-contraction. A stepwise regression analysis showed that proprioceptive acuity measured using variable error was the best predictor of muscle co-contraction in older adults. However, despite suggestions from previous research, proprioceptive error and muscle co-contraction were negatively correlated in older adults, suggesting that better proprioceptive acuity predicts more co-contraction. Overall, these results suggest that although muscle co-contraction may be an age-specific strategy used by older adults, it is not to compensate for age-related proprioceptive deficits.

Interrater and Intrarater Reliability and Validity of 3 Measurement Methods for Shoulder-Position Sense

CONTEXT

Joint-position sense (JPS) plays a critical role in the stability of shoulder joint. Restoration of JPS is essential to improve rehabilitation outcomes in individuals with shoulder injury. However, the number of affordable and reliable shoulder-JPS measurement methods for everyday clinical practice is limited.

OBJECTIVE

To estimate reliability and validity of 3 simple shoulder-JPS measurement methods.

DESIGN

Cross-sectional study.

PARTICIPANTS

25 healthy men and women.

MAIN OUTCOME MEASURE

Absolute-error scores of JPS in 3 ranges of shoulder flexion (low, mid, and high), measured with a laser pointer, an inclinometer, and a goniometer in 2 separate sessions (48 h apart).

RESULTS

Overall interrater and intrarater intraclass correlation coefficients were .86 and .78 for the laser pointer, .67 and .70 for the inclinometer, and .60 and .50 for the goniometer, respectively. There was excellent reliability in the low range for the laser pointer and inclinometer methods, but fair to good and poor reliability in mid- and high ranges, respectively. All methods showed strong validity.

CONCLUSION

The laser pointer and inclinometer JPS measurement methods are reliable and can be used by clinicians during rehabilitation of shoulder injuries.

Vibrotactile stimulation of fast-adapting cutaneous afferents from the foot modulates proprioception at the ankle joint

It has previously been shown that cutaneous sensory input from across a broad region of skin can influence proprioception at joints of the hand. The present experiment tested whether cutaneous input from different skin regions across the foot can influence proprioception at the ankle joint. The ability to passively match ankle joint position (17° and 7° plantar flexion and 7° dorsiflexion) was measured while cutaneous vibration was applied to the sole (heel, distal metatarsals) or dorsum of the target foot. Vibration was applied at two different frequencies to preferentially activate Meissner's corpuscles (45 Hz, 80 μm) or Pacinian corpuscles (255 Hz, 10 μm) at amplitudes ∼3 dB above mean perceptual thresholds. Results indicated that cutaneous input from all skin regions across the foot could influence joint-matching error and variability, although the strongest effects were observed with heel vibration. Furthermore, the influence of cutaneous input from each region was modulated by joint angle; in general, vibration had a limited effect on matching in dorsiflexion compared with matching in plantar flexion. Unlike previous results in the upper limb, we found no evidence that Pacinian input exerted a stronger influence on proprioception compared with Meissner input. Findings from this study suggest that fast-adapting cutaneous input from the foot modulates proprioception at the ankle joint in a passive joint-matching task. These results indicate that there is interplay between tactile and proprioceptive signals originating from the foot and ankle.

The Periaqueductal Gray Orchestrates Sensory and Motor Circuits at Multiple Levels of the Neuraxis

The periaqueductal gray (PAG) coordinates behaviors essential to survival, including striking changes in movement and posture (e.g., escape behaviors in response to noxious stimuli vs freezing in response to fear-evoking stimuli). However, the neural circuits underlying the expression of these behaviors remain poorly understood. We demonstrate in vivo in rats that activation of the ventrolateral PAG (vlPAG) affects motor systems at multiple levels of the neuraxis through the following: (1) differential control of spinal neurons that forward sensory information to the cerebellum via spino-olivo-cerebellar pathways (nociceptive signals are reduced while proprioceptive signals are enhanced); (2) alterations in cerebellar nuclear output as revealed by changes in expression of Fos-like immunoreactivity; and (3) regulation of spinal reflex circuits, as shown by an increase in α-motoneuron excitability. The capacity to coordinate sensory and motor functions is demonstrated in awake, behaving rats, in which natural activation of the vlPAG in fear-conditioned animals reduced transmission in spino-olivo-cerebellar pathways during periods of freezing that were associated with increased muscle tone and thus motor outflow. The increase in spinal motor reflex excitability and reduction in transmission of ascending sensory signals via spino-olivo-cerebellar pathways occurred simultaneously. We suggest that the interactions revealed in the present study between the vlPAG and sensorimotor circuits could form the neural substrate for survival behaviors associated with vlPAG activation.

SIGNIFICANCE STATEMENT

Neural circuits that coordinate survival behaviors remain poorly understood. We demonstrate in rats that the periaqueductal gray (PAG) affects motor systems at the following multiple levels of the neuraxis: (1) through altering transmission in spino-olivary pathways that forward sensory signals to the cerebellum, reducing and enhancing transmission of nociceptive and proprioceptive information, respectively; (2) by alterations in cerebellar output; and (3) through enhancement of spinal motor reflex pathways. The sensory and motor effects occurred at the same time and were present in both anesthetized animals and behavioral experiments in which fear conditioning naturally activated the PAG. The results provide insights into the neural circuits that enable an animal to be ready and able to react to danger, thus assisting in survival.

An Assessment of Six Muscle Spindle Models for Predicting Sensory Information during Human Wrist Movements

Background: The muscle spindle is an important sensory organ for proprioceptive information, yet there have been few attempts to use Shannon information theory to quantify the capacity of human muscle spindles to encode sensory input.

Methods: Computer simulations linked kinematics, to biomechanics, to six muscle spindle models that generated predictions of firing rate. The predicted firing rates were compared to firing rates of human muscle spindles recorded during a step-tracking (center-out) task to validate their use. The models were then used to predict firing rates during random movements with statistical properties matched to the ergonomics of human wrist movements. The data were analyzed for entropy and mutual information.

Results: Three of the six models produced predictions that approximated the firing rate of human spindles during the step-tracking task. For simulated random movements these models predicted mean rates of 16.0 ± 4.1 imp/s (mean ± SD), peak firing rates <50 imp/s and zero firing rate during an average of 25% of the movement. The average entropy of the neural response was 4.1 ± 0.3 bits and is an estimate of the maximum information that could be carried by muscles spindles during ecologically valid movements. The information about tendon displacement preserved in the neural response was 0.10 ± 0.05 bits per symbol; whereas 1.25 ± 0.30 bits per symbol of velocity input were preserved in the neural response of the spindle models.

Conclusions: Muscle spindle models, originally based on cat experiments, have predictive value for modeling responses of human muscle spindles with minimal parameter optimization. These models predict more than 10-fold more velocity over length information encoding during ecologically valid movements. These results establish theoretical parameters for developing neuroprostheses for proprioceptive function.

Extended use of Kinesiology Tape and Balance in Participants with Chronic Ankle Instability

CONTEXT

Participants with chronic ankle instability (CAI) have been shown to have balance deficits related to decreased proprioception and neuromuscular control. Kinesiology tape (KT) has been proposed to have many benefits, including increased proprioception.

OBJECTIVE

To determine if KT can help with balance deficits associated with CAI.

DESIGN

Cohort study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Thirty participants with CAI were recruited for this study.

INTERVENTION(S)

Balance was assessed using the Balance Error Scoring System (BESS). Participants were pretested and then randomly assigned to either the control or KT group. The participants in the KT group had 4 strips applied to the foot and lower leg and were instructed to leave the tape on until they returned for testing. All participants returned 48 hours later for another BESS assessment. The tape was then removed, and all participants returned 72 hours later to complete the final BESS assessment.

MAIN OUTCOME MEASURE(S)

Total BESS errors.

RESULTS

Differences between the groups occurred at 48 hours post-application of the tape (mean difference = 4.7 ± 1.4 errors, P < .01; 95% confidence interval = 2.0, 7.5) and at 72 hours post-removal of the tape (mean difference = 2.3 ± 1.1 errors, P = .04; 95% confidence interval = 0.1, 4.6).

CONCLUSIONS

The KT improved balance after it had been applied for 48 hours when compared with the pretest and with the control group. One of the most clinically important findings is that balance improvements were retained even after the tape had been removed for 72 hours.

Physiology of central pathways

The relative simplicity of the neural circuits that mediate vestibular reflexes is well suited for linking systems and cellular levels of analyses. Notably, a distinctive feature of the vestibular system is that neurons at the first central stage of sensory processing in the vestibular nuclei are premotor neurons; the same neurons that receive vestibular-nerve input also send direct projections to motor pathways. For example, the simplicity of the three-neuron pathway that mediates the vestibulo-ocular reflex leads to the generation of compensatory eye movements within ~5ms of a head movement. Similarly, relatively direct pathways between the labyrinth and spinal cord control vestibulospinal reflexes. A second distinctive feature of the vestibular system is that the first stage of central processing is strongly multimodal. This is because the vestibular nuclei receive inputs from a wide range of cortical, cerebellar, and other brainstem structures in addition to direct inputs from the vestibular nerve. Recent studies in alert animals have established how extravestibular signals shape these "simple" reflexes to meet the needs of current behavioral goal. Moreover, multimodal interactions at higher levels, such as the vestibular cerebellum, thalamus, and cortex, play a vital role in ensuring accurate self-motion and spatial orientation perception.

Upper limb joint position sense during shoulder flexion in healthy individuals: a pilot study to develop a new assessment method

BACKGROUND

Altered shoulder joint position sense (JPS) following shoulder injury has been demonstrated in the literature and may increase the risk of injury. A JPS assessment targeting the shoulder will provide the clinician with an objective marker. The present study aimed to develop an assessment method of JPS using an active relocation test (ART).

METHODS

In total, 40 healthy participants were recruited. A laser-pointer attached to the index finger during an ART allowed measurement (mm) of JPS by measuring the distance between the target and relocated position. Participants were blindfolded and stood an arm's length (approximately 1 m) away from the wall. Whilst keeping the wrist in neutral and elbow extended, the participant actively moved to the target position (90° glenohumeral flexion), held for 5 seconds, returned their arm to their side and actively returned to the target position. A mean was calculated from three trials to provide an ART score.

RESULTS

The mean (SD) dominant and nondominant ART score was 89.2 (SD 35.5) mm (95% confidence interval = 77.87 mm to 100.5 mm) and 94.1 (34.5) mm (95% confidence interval = 83.1 mm to 105.2 mm), respectively. Arm dominance did not significantly affect ART scores.

CONCLUSIONS

No significant difference was demonstrated between the dominant and nondominant arm using an ART assessing JPS acuity. Further studies are needed to establish inter-rater and intra-rater reliability.

The role of proprioception and neuromuscular stability in carpal instabilities

Carpal stability has traditionally been defined as dependent on the articular congruity of joint surfaces, the static stability maintained by intact ligaments, and the dynamic stability caused by muscle contractions resulting in a compression of joint surfaces. In the past decade, a fourth factor in carpal stability has been proposed, involving the neuromuscular and proprioceptive control of joints. The proprioception of the wrist originates from afferent signals elicited by sensory end organs (mechanoreceptors) in ligaments and joint capsules that elicit spinal reflexes for immediate joint stability, as well as higher order neuromuscular influx to the cerebellum and sensorimotor cortices for planning and executing joint control. The aim of this review is to provide an understanding of the role of proprioception and neuromuscular control in carpal instabilities by delineating the sensory innervation and the neuromuscular control of the carpus, as well as descriptions of clinical applications of proprioception in carpal instabilities.

Effect of Kinesiotape Applications on Ball Velocity and Accuracy in Amateur Soccer and Handball

Evidence supporting performance enhancing effects of kinesiotape in sports is missing. The aims of this study were to evaluate effects of kinesiotape applications with regard to shooting and throwing performance in 26 amateur soccer and 32 handball players, and to further investigate if these effects were influenced by the players’ level of performance. Ball speed as the primary outcome and accuracy of soccer kicks and handball throws were analyzed with and without kinesiotape by means of radar units and video recordings. The application of kinesiotapes significantly increased ball speed in soccer by 1.4 km/h (p=0.047) and accuracy with a lesser distance from the target by −6.9 cm (p=0.039). Ball velocity in handball throws also significantly increased by 1.2 km/h (p=0.013), while accuracy was deteriorated with a greater distance from the target by 3.4 cm (p=0.005). Larger effects with respect to ball speed were found in players with a lower performance level in kicking (1.7 km/h, p=0.028) and throwing (1.8 km/h, p=0.001) compared with higher level soccer and handball players (1.2 km/h, p=0.346 and 0.5 km/h, p=0.511, respectively). In conclusion, the applications of kinesiotape used in this study might have beneficial effects on performance in amateur soccer, but the gain in ball speed in handball is counteracted by a significant deterioration of accuracy. Subgroup analyses indicate that kinesiotape may yield larger effects on ball velocity in athletes with lower kicking and throwing skills.

Gaze stabilization in chronic vestibular-loss and in cerebellar ataxia: interactions of feedforward and sensory feedback mechanisms

During gaze shifts, humans can use visual, vestibular, and proprioceptive feedback, as well as feedforward mechanisms, for stabilization against active and passive head movements. The contributions of feedforward and sensory feedback control, and the role of the cerebellum, are still under debate. To quantify these contributions, we increased the head moment of inertia in three groups (ten healthy, five chronic vestibular-loss and nine cerebellar-ataxia patients) while they performed large gaze shifts to flashed targets in darkness. This induces undesired head oscillations. Consequently, both active (desired) and passive (undesired) head movements had to be compensated for to stabilize gaze. All groups compensated for active and passive head movements, vestibular-loss patients less than the other groups (P < 0.001, passive/active compensatory gains: vestibular-loss 0.23 ± 0.09/0.43 ± 0.12, healthy 0.80 ± 0.17/0.83 ± 0.15, cerebellar-ataxia 0.68 ± 0.17/0.77 ± 0.30, mean ± SD). The compensation gain ratio against passive and active movements was smaller than one in vestibular-loss patients (0.54 ± 0.10, P=0.001). Healthy and cerebellar-ataxia patients did not differ in active and passive compensation. In summary, vestibular-loss patients can better stabilize gaze against active than against passive head movements. Therefore, feedforward mechanisms substantially contribute to gaze stabilization. Proprioception alone is not sufficient (gain 0.2). Stabilization against active and passive head movements was not impaired in our cerebellar ataxia patients.

Increasing cutaneous afferent feedback improves proprioceptive accuracy at the knee in patients with sensory ataxia

Hereditary sensory and autonomic neuropathy type III (HSAN III) features disturbed proprioception and a marked ataxic gait. We recently showed that joint angle matching error at the knee is positively correlated with the degree of ataxia. Using intraneural microelectrodes, we also documented that these patients lack functional muscle spindle afferents but have preserved large-diameter cutaneous afferents, suggesting that patients with better proprioception may be relying more on proprioceptive cues provided by tactile afferents. We tested the hypothesis that enhancing cutaneous sensory feedback by stretching the skin at the knee joint using unidirectional elasticity tape could improve proprioceptive accuracy in patients with a congenital absence of functional muscle spindles. Passive joint angle matching at the knee was used to assess proprioceptive accuracy in 25 patients with HSAN III and 9 age-matched control subjects, with and without taping. Angles of the reference and indicator knees were recorded with digital inclinometers and the absolute error, gradient, and correlation coefficient between the two sides calculated. Patients with HSAN III performed poorly on the joint angle matching test [mean matching error 8.0 ± 0.8° (±SE); controls 3.0 ± 0.3°]. Following application of tape bilaterally to the knee in an X-shaped pattern, proprioceptive performance improved significantly in the patients (mean error 5.4 ± 0.7°) but not in the controls (3.0 ± 0.2°). Across patients, but not controls, significant increases in gradient and correlation coefficient were also apparent following taping. We conclude that taping improves proprioception at the knee in HSAN III, presumably via enhanced sensory feedback from the skin.

The Right Supramarginal Gyrus Is Important for Proprioception in Healthy and Stroke-Affected Participants: A Functional MRI Study

Human proprioception is essential for motor control, yet its central processing is still debated. Previous studies of passive movements and illusory vibration have reported inconsistent activation patterns related to proprioception, particularly in high-order sensorimotor cortices. We investigated brain activation specific to proprioception, its laterality, and changes following stroke. Twelve healthy and three stroke-affected individuals with proprioceptive deficits participated. Proprioception was assessed clinically with the Wrist Position Sense Test, and participants underwent functional magnetic resonance imaging scanning. An event-related study design was used, where each proprioceptive stimulus of passive wrist movement was followed by a motor response of mirror -copying with the other wrist. Left (LWP) and right (RWP) wrist proprioception were tested separately. Laterality indices (LIs) were calculated for the main cortical regions activated during proprioception. We found proprioception-related brain activation in high-order sensorimotor cortices in healthy participants especially in the supramarginal gyrus (SMG LWP z = 4.51, RWP z = 4.24) and the dorsal premotor cortex (PMd LWP z = 4.10, RWP z = 3.93). Right hemispheric dominance was observed in the SMG (LI LWP mean 0.41, SD 0.22; RWP 0.29, SD 0.20), and to a lesser degree in the PMd (LI LWP 0.34, SD 0.17; RWP 0.13, SD 0.25). In stroke-affected participants, the main difference in proprioception-related brain activation was reduced laterality in the right SMG. Our findings indicate that the SMG and PMd play a key role in proprioception probably due to their role in spatial processing and motor control, respectively. The findings from stroke--affected individuals suggest that decreased right SMG function may be associated with decreased proprioception. We recommend that clinicians pay particular attention to the assessment and rehabilitation of proprioception following right hemispheric lesions.