Postural Reflex

Spinal cord injury (SCI) can result in paralysis of trunk muscles, which can affect sitting balance. The objective of this study was to analyze trunk muscle coordination of individuals with thoracic SCI and compare it to able-body individuals. A total of 27 individuals were recruited and subdivided into: (a) high thoracic SCI; (b) low thoracic SCI; and (c) able-body groups. Participants were seated and asked to lean their trunk in eight directions while trunk muscle activity was recorded. Muscle coordination was assessed using the non-negative matrix factorization (NMF) method to extract muscle modules, which are the synergistic trunk muscle activations, and their directional activation patterns...

Neuro-anatomical evidence supports the potential for threat-related factors, such as fear, anxiety and vigilance, to influence brainstem motor nuclei controlling eye movements, as well as the vestibular nuclei. However, little is known about how threat influences human ocular responses, such as eye saccades (ES), smooth pursuit eye tracking (SP), and optokinetic nystagmus (OKN), and whether these responses can be facilitated above normal baseline levels with a natural source of threat. This study was designed to examine the effects of height-induced postural threat on the gain of ES, SP and OKN responses in humans...

Considering the emerging advantages related to virtual reality implementation in clinical rehabilitation, the aim of the present study was to discover possible (i) improvements achievable in unilateral vestibular hypofunction patients using a self-assessed head-mounted device (HMD)-based gaming procedure when combined with a classical vestibular rehabilitation protocol (HMD group) as compared with a group undergoing only vestibular rehabilitation and (ii) HMD procedure-related side effects. Therefore, 24 vestibular rehabilitation and 23-matched HMD unilateral vestibular hypofunction individuals simultaneously underwent a 4-week rehabilitation protocol...

The ability to modulate the mechanical properties of our limbs contributes to our ability to interact with the physical world in a consistent and predictable manner. An individual joint's contributions to whole limb mechanics can be quantified by its joint impedance, which characterizes the torque generated about a joint in response to external perturbations of position. A number of studies have estimated joint impedance during movement and have shown that it can be much lower than it is during posture. However, the mechanisms contributing to these differences remain unknown partly because conditions known to affect impedance, including muscle activation and joint angles, have not been carefully controlled across studies...

Dynamic joint stiffness determines the relation between joint position and torque, and plays a vital role in the control of posture and movement. Dynamic joint stiffness can be quantified during quasi-stationary conditions using disturbance experiments, where small position perturbations are applied to the joint and the torque response is recorded. Dynamic joint stiffness is composed of intrinsic and reflex mechanisms that act and change together, so that nonlinear, mathematical models and specialized system identification techniques are necessary to estimate their relative contributions to overall joint stiffness...

Postural reflexes are essential for locomotion and postural stability, and may play an important role in the etiology of chronic back pain. It has recently been theoretically predicted, and with the help of unilateral perturbations of the trunk experimentally confirmed that the sensorimotor control must lower the reflex amplitude for increasing reflex delays to maintain spinal stability. The underlying neuromuscular mechanism for the compensation of postural perturbations, however, is not yet fully understood...

[Purpose] The purpose of this study was to examine the effects of the measurement posture and stimulation intensity on the nociceptive flexion reflex (RIII reflex). [Subjects and Methods] Thirty normal female adult subjects were selected for this study. Their RIII reflexes were measured in three positions and with three degrees of stimulation intensity. The measurement posture was randomly selected. The analysis items were the stimulation intensity of the induced RIII reflex, the amplitude of the RIII reflex, and the numeric rating scale (NRS)...

BACKGROUND: While the positive effect of balance training on age-related impairments in postural stability is well-documented, the neural correlates of such training adaptations in older adults remain poorly understood. This study therefore aimed to shed more light on neural adaptations in response to balance training in older adults. METHODS: Postural stability as well as spinal reflex and cortical excitability was measured in older adults (65-80 years) before and after 5 weeks of balance training (n = 15) or habitual activity (n = 13)...

PURPOSE: This study examined whether spinal excitability, as measured by the soleus Hoffmann reflex (H-reflex), is scaled to the difficulty level of the dual-task being performed. METHODS: Twenty-two participants completed a combination of three balance task and three secondary cognitive (visuo-motor) task difficulty levels for a total of nine dual-task conditions. An additional eight participants were tested while performing the same three balance task difficulty levels on its own (i...

BACKGROUND: Constipation is considered as one of the most common non-motor manifestations in cerebral palsy (CP). Along with other reasons, spasticity also contributes in developing constipation in CP, by decreasing mobility of trunk and lower extremities and abdominal viscera. Stretching exercises of upper extremities, trunk and lower extremities are routine management of spasticity in CP children. The objective of the study was to determine the role of stretching exercises in improving constipation symptoms in children with spastic cerebral palsy and to explore the association between spasticity and constipation among cerebral palsy children...

BACKGROUND: Postural core instability is associated with poor dynamic balance and a high risk of serious falls. Both neurodevelopmental treatment (NDT) and dynamic neuromuscular stabilization (DNS) core stabilization exercises have been used to improve core stability, but the outcomes of these treatments remain unclear. OBJECTIVE: This study was undertaken to examine the therapeutic effects of NDT and DNS core stabilization exercises on muscular activity, core stability, and core muscle thickness...

BACKGROUND: Baseline visual acuity (VA) loss from static to dynamic head conditions assessed using the Dynamic Visual Acuity Testing (DVAT) have not been established in NCAA football players. DVAT assesses the Vestibulo-Ocular Reflex (VOR) which is measured in Logarithm of the Minimum Angle of Resolution (logMAR). Decreased VA beyond baseline measures may detect VOR impairment and impact treatment protocols and assist in return to play decisions post-concussion. HYPOTHESIS/PURPOSE: To establish normative VA mean scores during a static head posture as well as dynamically during the DVAT with a head speed of 150 deg/s in the pitch (vertical) and yaw (horizontal) planes rotating 20 degrees in each direction...

BACKGROUND AND PURPOSE: The MR Parkinsonism index helps in differentiating progressive supranuclear palsy from Parkinson disease and multisystem atrophy. Pontomesencephalic involvement is common in neurologic Wilson disease, but there is no prior study evaluating the MR Parkinsonism index and its indices in Wilson disease. We report the MR Parkinsonism index and its indices in Wilson disease and correlate these changes with clinical severity and postural reflex. MATERIALS AND METHODS: Thirteen individuals with neurologic Wilson disease were included, and their clinical details, including neurologic severity, postural reflex abnormality, and location of signal changes on MR imaging, were noted...

Clinicians increasingly use smartphone medical applications. There is no evidence to support the validity and reliability of applications used to assess the neuromusculoskeletal system. The aim of this study was to systematically review the quality of studies as well as the validity and reliability of using a smartphone as a clinical assessment tool for the neuromusculoskeletal system. Areas covered: PubMed, CINAHL and Embase were searched. A manual search was also conducted. Additionally, forward snowballing of relevant articles was performed in Scopus and Web of Science...

AIM: To study the prevalence of cardiac autonomic neuropathy (CAN) in patients with Type 2 diabetes mellitus at high risk for foot ulcers. MATERIALS AND METHODS: We screened patients attending diabetic clinic for identifying patients at high risk for foot ulcers. Those with foot risk category 1, 2 and 3 as per criteria of Foot Care Interest Group were subjected to battery of cardiovascular autonomic reflex tests. Those with one abnormal test were termed as probable CAN and those with two abnormal tests as definite CAN...

We studied the short-latency (SL) postural effects of axial impulses in 11 subjects (22 ± 2 years old). Recordings were made bilaterally from soleus and tibialis anterior (TA) muscles. We confirmed that with leaning anteriorly and posteriorly, reflex EMG increases occurred in both muscle groups at short latency following brief perturbations applied over C7 or the sternum (soleus mean latencies 57.5 and 66.4 ms; TA mean 51.7 and 55.4 ms, respectively). While the size of the SL reflexes was affected by the direction of lean when standing we found that light touch did not affect the amplitudes or latencies significantly...

AIM: The objective was to evaluate in treated heart failure (HF) patients whether multidrug therapy interferes with the cardiovascular autonomic response to postural stress. METHODS AND RESULTS: Blood pressure (BP; Finapres), heart rate (HR), stroke volume, and total peripheral resistance (TPR) responses to standing up were measured in 33 HF patients and 10 healthy age-matched controls. Ten hypertensive (HT) patients treated with a similar combination of drugs but without heart failure served as reference subjects to account for use of medication...

OBJECTIVE: To investigate the influence of vestibular function on dynamic postural stability assessed by the functional reach test (FRT) and the timed up and go test (TUG). STUDY DESIGN: Retrospective study. SETTING: Tertiary referral center. SUBJECTS AND METHODS: The FRT and TUG were performed in 399 patients with dizziness. The effects of peripheral vestibular dysfunction assessed by the caloric test and cervical vestibular evoked myogenic potentials (cVEMPs) to air-conducted sound (500 Hz, tone burst) on the results of FRT and TUG were analyzed...

In many animals intersegmental reflexes are important for postural and movement control but are still poorly undesrtood. Mathematical methods can be used to model the responses to stimulation, and thus go beyond a simple description of responses to specific inputs. Here we analyse an intersegmental reflex of the foot (tarsus) of the locust hind leg, which raises the tarsus when the tibia is flexed and depresses it when the tibia is extended. A novel method is described to measure and quantify the intersegmental responses of the tarsus to a stimulus to the femoro-tibial chordotonal organ...

Rapid and reflexive responses to threats are present across phylogeny. The neural circuitry mediating reflexive defense reactions has been well-characterized in a variety of species, for example, in rodents and cats, the detection of and species-typical response to threats is mediated by a network of structures including the midbrain tectum (deep and intermediate layers of the superior colliculus [DLSC]), periaqueductal gray (PAG), and forebrain structures such as the amygdala and hypothalamus. However, relatively little is known about the functional architecture of defense circuitry in primates...