Biomedical subjects

Marco Schieppati

Publications and source records attributed to Marco Schieppati.

At least 19 recordsLinked to original sources

PubMed2007

Postural responses to continuous unilateral neck muscle vibration in standing patients with cervical dystonia.

Several observations support the notion that integration of neck proprioceptive input is impaired in cervical dystonia (CD). An example is the inconsistent or opposite to normal effect of lateral neck muscle vibration on body rotation during stepping. We hypothesized that lateral neck vibration produces abnormal responses also in a static task. Normal subjects and patients with CD stood quietly with eyes closed, without or with vibration applied to the sternocleidomastoid muscle, and center of foot pressure and body sway were recorded by a dynamometric platform. Patients had a larger than normal sway under control condition. They showed little or no postural responses to vibration. When body tilt occurred, it was rarely in the frontal plane as in normal subjects, but in the sagittal plane. No relationship existed between vibration-induced tilt during stance and body rotation during stepping. Therefore, in CD, proprioceptive neck input is less used for the construction of the postural vertical during quiet stance than it is used for the definition of the subjective straight ahead during a dynamic task.

Adult↗

PubMed2007

Balance control in Sensory Neuron Disease.

OBJECTIVE: Balance control under static and dynamic conditions was assessed in patients with Sensory Neuron Disease (SND) in order to shed further light on the pathophysiology of ataxia. METHODS: Fourteen patients with diabetic polyneuropathy and 11 with SND underwent clinical and neurophysiological evaluation, stabilometric recording of body sway during quiet stance with and without vision, stereometric analysis of body segment displacement while riding a platform translating in anterior-posterior direction with and without vision (dynamic condition), and EMG recording of leg muscle responses to abrupt stance perturbation produced by rotation of a supporting platform. The findings were compared to those of age matched normal subjects. RESULTS: Clinical and neurophysiological evaluation revealed a more severe motor impairment in patients with diabetes than SND, while sensory impairment was superimposable. Some patients with SND had vestibular dysfunction of diverse severity. Body sway during stance was larger in patients with SND than diabetes with and without vision. In the stance perturbation condition, the latency of the long-loop EMG response to platform rotation was disproportionately increased with respect to the spinal response in the SND but not in diabetic patients. Under dynamic condition, patients with SND oscillated more than diabetic patients and several of them easily lost balance with eyes closed. CONCLUSIONS: Patients with SND show severe unsteadiness under both static and dynamic conditions, particularly with eyes closed. The patchy sensory loss of SND, disrupting sensation from territories other than the lower limbs and possibly including the vestibular nerve, could be responsible for this instability. Ataxia is correlated to the abnormal latency of the muscle responses to stance perturbation. Since increased response latencies cannot be attributed to a vestibular deficit, the deterioration of equilibrium control would be ascribed mainly to the degeneration of the central branch of the afferent fibres. SIGNIFICANCE: Measures of body balance under quiet stance and dynamic conditions can provide relevant diagnostic information as to the pathophysiology and severity of ataxia and viability of the central branch of the sensory fibres, and help in separating patients with peripheral neuropathy from patients with loss of sensory neurones.

Aged↗

PubMed2006

Stance- and locomotion-dependent processing of vibration-induced proprioceptive inflow from multiple muscles in humans.

We performed a whole-body mapping study of the effect of unilateral muscle vibration, eliciting spindle Ia firing, on the control of standing and walking in humans. During quiet stance, vibration applied to various muscles of the trunk-neck system and of the lower limb elicited a significant tilt in whole body postural orientation. The direction of vibration-induced postural tilt was consistent with a response compensatory for the illusory lengthening of the stimulated muscles. During walking, trunk-neck muscle vibration induced ample deviations of the locomotor trajectory toward the side opposite to the stimulation site. In contrast, no significant modifications of the locomotor trajectory could be detected when vibrating various muscles of the lower as well as upper limb. The absence of correlation between the effects of muscle vibration during walking and standing dismisses the possibility that vibration-induced postural changes can account for the observed deviations of the locomotor trajectory during walking. We conclude that the dissimilar effects of trunk-neck and lower limb muscle vibration during walking and standing reflect a general sensory-motor plan, whereby muscle Ia input is processed according to both the performed task and the body segment from which the sensory inflow arises.

Action Potentials↗

PubMed2006

Time to reconfigure balancing behaviour in man: changing visual condition while riding a continuously moving platform.

While balancing on a continuously antero-posterior (A-P) translating platform (10 cm, 0.5 Hz), the head normally oscillates with the platform without vision but is stabilized in space with vision. We estimated the time to shift from one to the other balancing behaviour when visual condition changed at some stage during the balancing trials. Ten subjects performed randomly 50 balancing trials (each lasting 18 s): 10 trials with eyes open (EO), 10 with eyes closed (EC), 15 in which participants started with EO and closed their eyes (condition EO-->EC) in response to an acoustic signal delivered during the trial, and 15 starting with EC and closing their eyes (EC-->EO) in response to the same signal. No other specific instruction was given. Displacements of malleolus, hip and head, and EMG from leg and axial muscles were recorded. Indexes of amplitude of A-P head and hip oscillation and of amplitude of EMG activity were computed. All variables were larger with EC than EO. On changing visual condition during the trial, the pattern of head and hip movement and of muscle activity turned into that appropriate for the new visual condition in a time-interval ranging from about 1 to 2.5 s. For each subject, the mean latency of the change in the balancing behaviour was assessed by statistical methods. On average, the latencies of kinematics and EMG changes proved to be longer for the EO-->EC condition than vice versa. Further, the latencies of the changes were also measured across all EO-->EC and EC-->EO individual trials. These values were clustered around particular epochs of the first few oscillation cycles following the shift in visual condition. The results show that subjects can rapidly adapt their balancing behaviour to the new visual condition. However, they appear to refrain from releasing the new behaviour were this unfit, and unfastened it at appropriate time in the next platform translation cycle. These findings reveal the temporal and spatial features of the automatic release of the new balancing strategy in response to a shift in the ongoing sensory set, and emphasize the swiftness in the change in balancing behaviour when subjects pass from a non-visual to a visual reference frame.

Adult↗

PubMed2006

Neck muscle fatigue and postural control in patients with whiplash injury.

OBJECTIVES: To examine if patients with whiplash injury show identifiable increases in neck muscle fatigability and associated increase in postural body sway after contractions of dorsal neck muscles, and if physiotherapy treatment reduces these effects. METHODS: Sway was measured during stance in 13 patients before and after 5 min of isometric dorsal neck muscle contractions and after recovery, pre- and post-physiotherapy, using a force platform. Amplitude and median frequency of neck muscle EMG were calculated during the contracting period. After each stance trial, patients gave a subjective score of sway. RESULTS: Pre-treatment, seven patients showed EMG signs of fatigue (increases in amplitude, decreases in median frequency) and increases in sway (eyes closed) after contractions. The other patients showed neither fatigue nor increased sway. Post-treatment, no signs of fatigue or imbalance were recorded in all patients, for the same levels of muscle contraction. CONCLUSIONS: As in normal human subjects, increases in sway are associated with signs of neck muscle fatigue in some whiplash injury patients. Physiotherapy decreases the susceptibility to fatigue of neck muscles and is an effective choice of treatment of subjective instability and sway. SIGNIFICANCE: This study demonstrates a pathophysiological link between neck muscle fatigue and impaired postural control, and also that physiotherapy can relieve symptoms and signs of impaired neck muscle function by reducing muscle fatigability.

Adult↗

PubMed2006

The posture-related interaction between Ia-afferent and descending input on the spinal reflex excitability in humans.

The separate and combined depressive effects induced by vibration and standing on the soleus H-reflex have been studied by administering Achilles' tendon vibration in prone position and during stance. Without vibration, H-reflex amplitude was larger under prone than standing condition. Vibration reduced the reflex both in prone position and even more during stance. When vibration was superimposed to inclined stance (greater EMG background), the reflex was reduced of the same absolute amount as when it was superimposed to normal stance. When vibration was superimposed on stance with minimal or no background EMG, the reflex disappeared. These results confirm that both upright posture and vibration have a strong depressive effect on the H-reflex. They also show that muscle activity during stance is enough for overcoming the reflex depression. These findings provide information about the origin of the disfacilitatory effects on the monosynaptic reflex pathway, contribute to the understanding of the posture-related mechanisms responsible for the modulation of the spinal reflex excitability, and allow arguing in favour of a minor but adaptable role for the short latency stretch reflex in the control of quiet unperturbed stance.

Adult↗

PubMed2006

Balance in Parkinson's disease under static and dynamic conditions.

We tested balance performance in 15 on phase Parkinson's disease (PD) patients (8 nonfallers, PD-NF; 7 fallers, PD-F) during quiet stance (stabilometry) and on a platform continuously moving in the anteroposterior direction (dynamic test). Neither stabilometry (eyes open or closed) nor the dynamic test (eyes open) separated PD-F from PD-NF. With the dynamic test, eyes closed, PD-F with respect to PD-NF showed larger head oscillations, smaller cross-correlation between head and malleolus motion (more so in patients with low Unified Parkinson's Disease Rating Scale, or UPDRS), and larger delays of head with respect to platform motion. Further, across all PD patients, head displacement increased with the equivalent levodopa dose, indicating a trend for medication to worsen balancing capacity while improving UPDRS. The dynamic test is a sensitive tool for detecting instability in PD-F since absence of visual flow selectively impairs both association between body segment movements and anticipatory adjustments.

Accidental Falls↗

PubMed2006

Balance control in peripheral neuropathy: are patients equally unstable under static and dynamic conditions?

The aim of this investigation was to assess the potentially different effects of impaired proprioceptive input in balance control under static and dynamic conditions in neuropathic patients. We recruited 20 normal subjects and 27 patients affected by neuropathies known to affect to a different extent large and medium size afferent fibres. The patients comprised 5 with Charcot-Marie-Tooth disease type 1A (CMT1A), 8 with CMT type 2 (CMT2) and 14 with Diabetes polyneuropathy (Diabetics). Measurement of balance during quiet stance on a stabilometric platform showed that sway area (SA) was larger in the CMT2 and Diabetics than normal subjects or in CMT1A, under both eyes open and closed conditions. The estimated conduction velocity (CV) of the group II afferent fibres was lower in CMT2 and Diabetics than in normal subjects and CMT1A. Across all patients, SA increased as a function of the slowing of group II CV. During a dynamic balance task the head A-P displacement was only slightly increased in the patient groups with respect to normals, despite the increased delay at which the head followed displacement of the feet. The unpredictably good performance of all patient groups under dynamic condition, which was at variance with their imbalance during quiet stance, may indicate that these patients learnt to exploit anticipatory postural strategies.

Adult↗

PubMed2005

Coordinated modulation of locomotor muscle synergies constructs straight-ahead and curvilinear walking in humans.

We describe the muscle synergies accompanying steering of walking along curved trajectories, in order to analyze the simultaneous control of progression and balance-threatening emerging forces. For this purpose, we bilaterally recorded in ten subjects the electromyograms (EMGs) of a representative sample of leg and trunk muscles (n=16) during continuous walking along one straight and two curved trajectories at natural speed. Curvilinear locomotion involved a graded, limb-dependent modulation of amplitude and timing of activity of the muscles of the legs and trunk. The turn-related modulation of the motor pattern was highly coordinated amongst muscles and body sides. For all muscles, linear relationships were detected between the spatial and temporal features of muscle EMG activity. The largest modulation of EMG was observed in gastrocnemius medialis and lateralis muscles, which showed opposite changes in timing and amplitude during curve-walking. Moreover, amplitude and timing characteristics of muscle activities were significantly correlated with the spatial and temporal gait adaptations that are associated with curvilinear locomotion. The present results reveal that fine-modulation of the muscle synergies underlying straight-ahead locomotion is enough to generate the adequate propulsive forces to steer walking and maintain balance. These findings suggest that the turn-related command operates by modulation of the phase relationships between the tightly coupled neuronal assemblies that drive motor neuron activity during walking. This would produce the invariant templates for locomotion kinematics that are at the base of human navigation in space.

Adult↗

PubMed2005

Head stabilization on a continuously oscillating platform: the effect of a proprioceptive disturbance on the balancing strategy.

When standing and balancing on a continuously and predictably moving platform, body equilibrium relies on both anticipatory control and proprioceptive feedback. We have vibrated different postural muscles of the body to assess any effect of confounding the proprioceptive input on balance during such unstable conditions. Low and high platform oscillation frequencies were used, because different strategies are used to withstand the two perturbations. Eyes open (EO) and closed (EC) conditions were also tested, to assess whether the stabilizing effect of vision is independent from the proprioceptive disturbance. Subjects (n = 14) performed two series of trials, EO and EC: (1) quiet erect stance, (2) stance on the platform translating at 0.2 or 0.6 Hz sinusoidally in the anteroposterior (A-P) direction (dynamic conditions). Continuous bilateral vibration (90 Hz) was produced by two vibrators fixed to the following homonymous muscles: dorsal neck, quadriceps, biceps femoris, tibialis anterior, and triceps surae. Acquisition of body segments' displacement began 10 s after the start of platform translation. From markers fixed to head, hip, and malleolus, we computed the A-P oscillation of head and hip, body orientation in space, and cross-correlation (CC) and time-delay between malleolus and head trajectories. The results were (a) the head A-P oscillation was smaller with EO than EC, under both quiet stance and dynamic conditions; (b) vibration of tibialis and triceps surae, but not of other muscles, slightly increased head and body A-P oscillation with EC under dynamic conditions; (c) at 0.2 Hz but not at 0.6 Hz, for all visual and vibration conditions, there was a significant association between head and feet; (d) at 0.2 Hz, EC, neck muscle vibration increased this association, whereas vibration of the other muscles induced a major time delay in the oscillation of head compared with feet; (e) vibration of either neck or tibialis induced forward body leaning, while vibration of either triceps surae or biceps femoris induced backward leaning, with both EO and EC, under both static and dynamic conditions; (f) the head A-P oscillation, however, under dynamic conditions was not dependent on body leaning. The relatively scarce effects of proprioceptive disturbance on head stabilization and multijoint coordination (in spite of effects on body orientation similar to those observed during stance) speak for a major role of anticipatory control in the dynamic equilibrium task. However, the significant vibration-induced time delay in segments' coordination at low translation frequency, EC, suggests that the normally patterned Ia input promotes continuous adjustments of the feed-forward control mode.

Adaptation, Physiological↗

PubMed2005

Reflex contribution of spindle group Ia and II afferent input to leg muscle spasticity as revealed by tendon vibration in hemiparesis.

OBJECTIVE: Foot dorsiflexion evokes a short- (SLR) and a medium-latency EMG response (MLR) in the soleus of standing subjects. SLR is mediated by spindle group Ia, while group II fibres contribute to MLR through an oligosynaptic circuit. We studied the effects of Achilles' tendon vibration on both responses in spastic patients to disclose any abnormal excitability of these pathways. METHODS: SLR and MLR were evoked in 11 hemiparetics and 11 normals. The vibration-induced changes in both responses were correlated to the Ashworth score of the affected leg. RESULTS: There were no differences between normals and patients in the size of control SLR or MLR. Vibration decreased SLR to 70% in normal subjects, but increased it to 110% in patients, in both affected and unaffected leg. Vibration did not affect MLR in normals, but increased it to 165% on the affected and 120% on the unaffected side of patients. Ashworth score was solely correlated with the degree of vibration-induced increase of MLR. CONCLUSIONS: While the lack of inhibitory effect of vibration on SLR confirms a reduced inhibitibility of the monosynaptic reflex, the increased MLR indicates a disinhibition of group II pathway in patients, connected to the loss of descending control on group II interneurones. Spastic hypertonia depends on release of group II rather than group Ia reflex pathways. SIGNIFICANCE: These findings give a neurophysiological support for the pharmacological treatment of spastic hypertonia and suggest a method for the assessment of its effects.

Adult↗

PubMed2005

Lack of on-going adaptations in the soleus muscle activity during walking in patients affected by large-fiber neuropathy.

The aim of this study was to investigate the contribution of feedback from large-diameter sensory fibers to the adaptation of soleus muscle activity after small ankle trajectory modifications during human walking. Small-amplitude and slow-velocity ankle dorsiflexion enhancements and reductions were applied during the stance phase of the gait cycle to mimic the normal variability of the ankle trajectory during walking. Patients with demyelination of large sensory fibers (Charcot-Marie-Tooth type 1A and antibodies to myelin-associated glycoprotein neuropathy) and age-matched controls participated in this study. The patients had absent light-touch sense in the toes and feet and absent quadriceps and Achilles tendon reflexes, indicating functional loss of large sensory fibers. Moreover, their soleus stretch reflex response consisted of a single electromyographic (EMG) burst with delayed onset and longer duration (P < 0.01) than the short- and medium-latency reflex responses observed in healthy subjects. In healthy subjects, the soleus EMG gradually increased or decreased when the ankle dorsiflexion was, respectively, enhanced or reduced. In the patients, the soleus EMG increased during the dorsiflexion enhancements; however, the velocity sensitivity of this response was decreased compared with the healthy volunteers. When the dorsiflexion was reduced, the soleus EMG was unchanged. These results indicate that the enhancement of the soleus EMG is mainly sensitive to feedback from primary and secondary muscle spindle afferents and that the reduction may be mediated by feedback from the group Ib pathways. This study provides evidence for the role of sensory feedback in the continuous adaptation of the soleus activity during the stance phase of human walking.

Adaptation, Physiological↗

PubMed2004

Neck muscle fatigue and spatial orientation during stepping in place in humans.

Neck proprioceptive input, as elicited by muscle vibration, can produce destabilizing effects on stance and locomotion. Neck muscle fatigue produces destabilizing effects on stance, too. Our aim was to assess whether neck muscle fatigue can also perturb the orientation in space during a walking task. Direction and amplitude of the path covered during stepping in place were measured in 10 blindfolded subjects, who performed five 30-s stepping trials before and after a 5-min period of isometric dorsal neck muscle contraction against a load. Neck muscle electromyogram amplitude and median frequency during the head extensor effort were used to compute a fatigue index. Head and body kinematics were recorded by an optoelectronic system, and stepping cadence was measured by sensorized insoles. Before the contraction period, subjects normally stepped on the spot or drifted forward. After contraction, some subjects reproduced the same behavior, whereas others reduced their forward progression or even stepped backward. The former subjects showed minimal signs of fatigue and the latter ones marked signs of fatigue, as quantified by the dorsal neck electromyogram index. Head position and cadence were unaffected in either group of subjects. We argue that the abnormal fatigue-induced afferent input originating in the receptors transducing the neck muscle metabolic state can modulate the egocentric spatial reference frame. Notably, the effects of neck muscle fatigue on orientation are opposite to those produced by neck proprioception. The neck represents a complex source of inputs capable of modifying our orientation in space during a locomotor task.

Adaptation, Physiological↗

PubMed2004

Neck proprioception and spatial orientation in cervical dystonia.

Neck muscle vibration is known to influence body orientation and posture during locomotion and stance in normal subjects. To verify the hypothesis that neck proprioceptive input can be misinterpreted in patients with cervical dystonia (CD), lateral continuous vibration was applied to the sternocleidomastoid muscle during both stepping-in-place and quiet stance, with eyes closed. The orienting responses of CD patients were compared with those of normal subjects. Vibration effects on body orientation during stepping and stance were apparently different from normal, since no effects were seen when all patients' data collapsed were analysed. However, while some patients did not respond to vibratory stimuli regardless of the vibrated side, others had a 'good' side, the stimulation of which produced effects on body orientation similar to those observed in normal subjects. Homogeneous groups within the patient population were identified, based on the vibration-induced responses under stepping conditions. The different orienting or postural responses observed in CD patients were correlated with disease-related features such as spontaneous head position, maximum range of voluntary head yaw, presence or absence of a botulinum toxin treatment and disease duration. Our data suggest that, in CD patients, the reference system used in the control of body orientation in space is either refractory to the lateralized proprioceptive neck input or modified such that the input from both sides produces an orientation shift in the same sense. This would depend on the pathogenesis of the disease or on an adaptive process connected to the head abnormal posture. It seems that this refractoriness spreads to both sides of the neck with the advancement of the disease, thereby possibly entraining a progressive shift from a reference system based on the head to a more reliable egocentric reference.

Adult↗

PubMed2004

Botulinum toxin in post-stroke patients: stiffness modifications and clinical implications.

OBJECTIVE: To objectively quantify stiffness and clinical changes in the upper limb of poststroke patients following botulinum toxin (BT) injection. METHODS: Eighteen consecutive chronic post-stroke spastic patients were injected Botulinum toxin A in the forearm flexor spastic muscles. Spasticity was clinically evaluated with the Ashworth scale. Stiffness was measured with indices (passive stiffness index (ISI) and total stiffness index (TSI) obtained by mechanical wrist displacements induced by a torque motor,which could also provide the stretch reflex threshold speed (SRTS) from flexor muscles. Functional status was measured with the Barthel index and a specific hand ability scale, pain with a visual analogue scale (VAS). The ranges of voluntary wrist extension (EROM) and flexion (FROM) and wrist isometric extension and flexion (IE-IF) strength were also calculated. RESULTS: IE and EROM significantly increased, being respectively p < 0.01 and p < 0.05; also SRTS was augmented (p < 0.001),while TSI showed lower values (p < 0.001); the Ashworth score decreased at least one point. Hand function for selected tasks improved in 50% of patients, the Barthel index only in 4 (22 %), forearm pain was completely relieved in 3 patients (17 %). CONCLUSIONS: BT can be considered a valid therapeutic tool in all spastic patients, because of immediate advantages: reduction of muscle hypertonia, pain relief, improvement in selected motor performances.

Adult↗

PubMed2004

Group II spindle fibres and afferent control of stance. Clues from diabetic neuropathy.

OBJECTIVE: Since patients with large-fibre neuropathy do not show abnormal body sway during stance, the hypothesis was tested that postural control is not impaired until myelinated fibres of medium size are affected. METHODS: In 22 diabetic neuropathic patients and 13 normals, we recorded: (1) body sway area (SA), (2) stretch responses of soleus (Sol) and flexor digitorum brevis (FDB) to toe-up rotation of a platform, (3) Sol and FDB H reflex and FDB F wave, (4) conduction velocity (CV) of tibial, deep peroneal and sural nerve. In patients, detection thresholds for vibration, cooling (CDT), warming and heat-pain (HPDT) were assessed. RESULTS: Body SA was increased in patients with respect to normals. Toe-up rotation elicited short- (SLR) and medium-latency (MLR) responses in Sol and FDB in all normals. In patients, SLR was absent in FDB and reduced in Sol, and MLR was delayed in both muscles; the FDB H reflex was absent. The CV of tibial nerve group II afferent fibres, as estimated from the afferent time of FDB MLR, was reduced in patients. All sensory detection thresholds were increased. Stepwise multiple regression showed that increased SA was explained by increased latency of MLR, decreased CV of group II fibres and augmented CDT and HPDT. CONCLUSIONS: Unsteadiness in diabetic neuropathy is related to alterations in medium-size myelinated afferent fibres, possibly originating from spindle secondary terminations.

Aged↗

PubMed2004

A new hip-knee-ankle-foot sling: kinematic comparison with a traditional ankle-foot orthosis.

In this study, we performed a kinematic analysis of a new, low-cost sling for the lower limb, compared to a common ankle-foot orthosis (AFO). Gait with no orthosis, with the AFO, and with the new sling was analyzed in one hemiplegic subject. Both the AFO and the sling reduced the mean angle and ROM (range of movement) of the ankle and the vertical displacement of the center of mass. The sling, but not the AFO, restored the normal sequence heel-strike, forefoot contact of the affected side. The sling, but not the AFO, reduced the affected limb stance and stride duration, increased stride length, and improved walking speed. In conclusion, the proposed sling for the lower limb equally improved the affected ankle kinematics in contrast to the traditional AFO, and it also improved some gait variables in this hemiplegic subject.

Aged↗

PubMed2003

Tuning of a basic coordination pattern constructs straight-ahead and curved walking in humans.

We tested the hypothesis that common principles govern the production of the locomotor patterns for both straight-ahead and curved walking. Whole body movement recordings showed that continuous curved walking implies substantial, limb-specific changes in numerous gait descriptors. Principal component analysis (PCA) was used to uncover the spatiotemporal structure of coordination among lower limb segments. PCA revealed that the same kinematic law accounted for the coordination among lower limb segments during both straight-ahead and curved walking, in both the frontal and sagittal planes: turn-related changes in the complex behavior of the inner and outer limbs were captured in limb-specific adaptive tuning of coordination patterns. PCA was also performed on a data set including all elevation angles of limb segments and trunk, thus encompassing 13 degrees of freedom. The results showed that both straight-ahead and curved walking were low dimensional, given that 3 principal components accounted for more than 90% of data variance. Furthermore, the time course of the principal components was unchanged by curved walking, thereby indicating invariant coordination patterns among all body segments during straight-ahead and curved walking. Nevertheless, limb- and turn-dependent tuning of the coordination patterns encoded the adaptations of the limb kinematics to the actual direction of the walking body. Absence of vision had no significant effect on the intersegmental coordination during either straight-ahead or curved walking. Our findings indicate that kinematic laws, probably emerging from the interaction of spinal neural networks and mechanical oscillators, subserve the production of both straight-ahead and curved walking. During locomotion, the descending command tunes basic spinal networks so as to produce the changes in amplitude and phase relationships of the spinal output, sufficient to achieve the body turn.

Adaptation, Physiological↗