Absence Of Movement Research Articles

How does adaptive consumer movement affect population dynamics in consumer–resource metacommunities with homogeneous patches?

This article uses simple models to explore the impact of adaptive movement by consumers on the population dynamics of a consumer–resource metacommunity consisting of two identical patches. Consumer–resource interactions within a patch are described by the Rosenzweig–MacArthur predator–prey model, and these dynamics are assumed to be cyclic in the absence of movement. The per capita movement rate from one patch to the other is an increasing function of the difference between the per capita birth minus death rate in the destination patch and that in the currently occupied patch. Several variations on this model are considered. Results show that adaptive movement frequently creates anti-phase cycles in the two patches; these suppress the predator–prey cycle and lead to low temporal variation of the total population sizes of both species. Paradoxically, even when movement is very sensitive to the fitness difference between patches, perfect synchrony of patches is often much less likely than in comparable systems with random movement. Under these circumstances adaptive movement of consumers often generates differences in the average properties of the two patches. In addition, mean global densities and responses to global perturbations often differ greatly from similar systems with no movement or random movement.

A Robotic Model of the Human Neuro-Musculo-Skeletal System

A pair of muscles powering the human joint in an antagonistic configuration exemplifies the main difference between standard industrial robots and biological motor systems. Since muscles have a natural stiffness that varies with the muscle activation level, the central nervous system can generate stable equilibrium postures, towards which the arm is attracted, by properly regulating the activation levels of antagonistic muscles [1] The elastic properties of muscles contribute to the finite stiffness/compliance properties of the limb, to the stability of the neuro-musculo-skeletal system in the face of significant feedback delays and even allow for the generation of target movements in absence of sensory feedback, by shifting the equilibrium point [2]. Control theories based on the presence of the EP in biological motor systems [3] suggest that movements are programmed as a shift of equilibrium positions rather than through an explicit computation of forces. Thus, there is no need to solve the “inverse dynamics problem” for calculating the torque required to move the arm on the desired trajectory. The implementation of a given neuroscientific hypothesis on a real mechanical system could provide a tool under the full control of the experimenter, reproducing the main functional features of the human arm and being able to interact with the same physical environment of the human. To this end we developed the NEURARM platform, a bio-mimetic planar robotic arm reproducing key features of the human arm as identified at the level of joints and muscles. In particular:

Prior Knowledge Improves Decoding of Finger Flexion from Electrocorticographic Signals

Brain–computer interfaces (BCIs) use brain signals to convey a user’s intent. Some BCI approaches begin by decoding kinematic parameters of movements from brain signals, and then proceed to using these signals, in absence of movements, to allow a user to control an output. Recent results have shown that electrocorticographic (ECoG) recordings from the surface of the brain in humans can give information about kinematic parameters (e.g., hand velocity or finger flexion). The decoding approaches in these studies usually employed classical classification/regression algorithms that derive a linear mapping between brain signals and outputs. However, they typically only incorporate little prior information about the target movement parameter. In this paper, we incorporate prior knowledge using a Bayesian decoding method, and use it to decode finger flexion from ECoG signals. Specifically, we exploit the constraints that govern finger flexion and incorporate these constraints in the construction, structure, and the probabilistic functions of the prior model of a switched non-parametric dynamic system (SNDS). Given a measurement model resulting from a traditional linear regression method, we decoded finger flexion using posterior estimation that combined the prior and measurement models. Our results show that the application of the Bayesian decoding model, which incorporates prior knowledge, improves decoding performance compared to the application of a linear regression model, which does not incorporate prior knowledge. Thus, the results presented in this paper may ultimately lead to neurally controlled hand prostheses with full fine-grained finger articulation.

The effects of acute stress and acute corticosterone administration on the immobility response in rats

The immobility response is an innate antipredatory behavior in a broad variety of species. The immobility response varies in its postural components but in general is characterized by an absence of movement and a relative unresponsiveness to stimuli. Experimentally in rats, clamping the neck followed by body inversion and manual restrain elicits a response called “immobility by clamping the neck”. Stress reactions protect animals against predators and are characterized by activation of the sympathetic and hypothalamic–pituitary–adrenal systems. However, in mammals, the role of acute stress as a modulator of immobility response has been less studied. The aim of our study was to assess the effects of acute stress and the injection of corticosterone (5 mg/kg, ip) on immobility by clamping the neck in rats. We observed that either previous acute stress caused by forced exposure to elevated open platform or application of a heat-pain stimulus to the rat's tail during the immobility increased the duration of the immobility response caused by clamping the neck. Also, the corticosterone produced a rapid increase (15 min after injection) in the duration of this immobility response. Our results show that the acute stress, in rats, is a facilitator of the immobility response and suggest a possible nongenomic rapid action of corticosterone over brain structures that control this behavior.

Can changing the mechanical environment increase the speed of fracture healing? A pilot study in tibial fractures

We hypothesed that fracture healing could be speeded up by changing the mechanical environment from initial rigidity followed by micromovements (dynamization) to initial macromovement followed by rigidity. We based this hypothesis on two tenets. Firstly, callus requires movement for its formation and its production is limited to the first few weeks after fracture. Secondly, that callus would mature faster in the absence of movement (based on theoretical reasoning and supported by a prior rabbit experiment). An external fixator was built that would allow axial macromovements (up to 5 mm) and then compression to produce a rigid configuration. Permission from the Helsinki Ethical Committee was obtained for a pilot trial. 15 patients with an isolated closed (12 patients) or open grade 1 (3 patients) tibial fracture were treated. The average time of removal of the fixator was 11 weeks (range seven to 15.4 weeks) which was faster than other comparable series. This trial indicates that it is possible to speed up the healing of tibial fractures by changing the mechanical regimes used today of initial rigidity followed by dynamization to one of initial macromovement followed by rigidity.

Electrophysiological Analysis of Transmission Via Spinal Pathways After Vertebral Trauma

Complex electrophysiological examination of the state of spinal neuronal mechanisms was carried out in patients after complicated vertebral trauma (n = 52). Electromyographic responses of the muscles of the upper and lower limbs evoked by stimulation of the peripheral nerves, effects of magnetic stimulation (MS) of the brain cortex (transcranial MS, TMS) and spinal roots, and somatosensory evoked potentials (SSEPs) were recorded. Partial disorders of the motor functions of the lower limbs were observed in 21 patients. Subjects with complete absence of movements of the limbs demonstrated two variants of the patterns of electrophysiological phenomena. In 21 patients, evoked potentials were entirely absent, while reduced MS-evoked motor responses (MS MRs) and SSEPs could be observed in 10 subjects. The presence of these potentials was indicative of partial preservation of the cerebrospinal pathways after damage to the spinal cord. Thus, estimation of the results of complex electrophysiological examination allows one to objectively verify the state and dynamics of transmission via the spinal pathways, to make justified the tactics of treatment, and to estimate the efficacy of the measures directed toward recovery of the lost functions of spinal mechanisms.

Anything Goes, Nothing Sticks: Radical Stillness and Archival Impulse

Anything Goes, Nothing Sticks: Radical Stillness and Archival Impulse

Between Motion and Rest: Encountering Bodies in/on Display

Between Motion and Rest: Encountering Bodies in/on Display

Effect of cervical dynamics on adjacent segment degeneration after anterior cervical fusion with cages

The objective of this study is to evaluate the effect of anterior cervical discectomy and fusion (ACDF) on the motion of the cervical spine and dynamic stress (tendency to kyphosis) on adjacent segments and on the overall spinal alignment which may predispose to symptomatic disc diseases at other levels. Twenty consecutive patients underwent ACDF with a mean follow-up of 28 months (range 13-38). Preoperative and postoperative clinical assessments were done by using the neck disability index (NDI) and the Japanese Orthopedic Association (JOA) score. In all cases, at the last follow-up control, a neuro-radiographic assessment [cervical spine static and dynamic X-ray and magnetic resonance imaging (MRI)] was done. The angle of the operated disc space, the disc space angle of contiguous segments, and their range of motion (ROM) and the kyphotic Cobb angle (C2-7) were measured by computer software. The study was done at Sant'Andrea Hospital, Rome, Italy in the period from November 2003 to November 2005. We observed that: the mean Cobb angle improved significantly (p < 0.001) from 3.4 degrees (kyphosis) to postoperative 14.5 degrees. This normalization of angle showed a direct effect on improvement of myelopathic patients, but it had a statistically nonsignificant effect on adjacent segments degeneration (ASD). The mean segmental ROM of adjacent segments did not show significant instability. The mean was 11.1 degrees at upper and 10.2 degrees at lower levels (close to normal). In six cases, the ROM was higher than normal: five of these patients demonstrated symptomatic adjacent segment pathology. Postoperative improvement of mean JOA and NDI scores was statistically significant (p < 0.001). Anyway, symptomatic ASD was observed in five patients (20%): in four of them, the higher disc spaces and in one, the lower disc spaces were involved. In four cases, the preoperative MRI showed slight and asymptomatic disc degeneration at the same levels involved subsequently. This ASD was significantly related to the increased ROM at the segments involved. Follow-up X-rays showed solid fusion with absence of movement in all but one case (at 13-month follow-up), who showed slight movement in the operated level in spite of clinical improvement. The follow-up MRI showed, in all cases, good decompression in the treated levels. Compensatory increase in ROM of the contiguous motion segments in patients subjected to ACDF may lead to ASD especially in those cases with asymptomatic adjacent subclinical degenerative disease. If these preliminary results will be confirmed by larger series, it could be reasonable in young selected patients with soft disc herniation to adopt total disc arthroplasty instead of fusion after cervical micro-discectomy.

Stacking and Not Solely Topology of T3 Loops Controls Rigidity and Ammonium Ion Movement within d(G4T3G4)2 G-Quadruplex

A solution state NMR study has shown that d(G4T3G4) in the presence of (15)NH4(+) ions folds into a single bimolecular G-quadruplex structure in which its G-tracts are antiparallel and the two T3 loops span along the edges of the outer G-quartets on the opposite sides of the G-quadruplex core. This head-to-tail topology is in agreement with the topology of the G-quadruplex recently found in the X-ray crystal structure formed by d(G4T3G4) in the presence of K(+) ions [Neidle et al. J. Am. Chem. Soc. 2006, 128, 5480]. In contrast, the presence of K(+) ions in solution resulted in a complex ensemble of G-quadruplex structures. Molecular models based on NMR data demonstrate that thymine loop residues efficiently base-base stack on the outer G-quartets and in this way stabilize a single structure in the presence of (15)NH4(+) ions. The use of heteronuclear NMR enabled us to localize three (15)NH4(+) ion binding sites between pairs of adjacent G-quartets and study the kinetics of their movement. Interestingly, no (15)NH4(+) ion movement within the G-quadruplex was detected at 25 degrees C. At 35 degrees C we were able to observe slow movement of (15)NH4(+) ions from the outer binding sites to bulk solution with the characteristic residence lifetime of 1.2 s. The slow movement of (15)NH4(+) ions from the outer binding sites into bulk solution and the absence of movement from the inner binding site were attributed to steric hindrance imposed by the T3 loops and the rigidity of the G-quadruplex.

Thinking about movement hurts: The effect of motor imagery on pain and swelling in people with chronic arm pain

Chronic painful disease is associated with pain on movement, which is presumed to be caused by noxious stimulation. We investigated whether motor imagery, in the absence of movement, increases symptoms in patients with chronic arm pain. Thirty-seven subjects performed a motor imagery task. Pain and swelling were measured before, after, and 60 minutes after the task. Electromyography findings verified no muscle activity. Patients with complex regional pain syndrome (CRPS) were compared with those with non-CRPS pain. Secondary variables from clinical, psychophysical, and cognitive domains were related to change in symptoms using linear regression. Motor imagery increased pain and swelling. For CRPS patients, pain (measured on a 100-mm visual analog scale) increased by a mean +/- SD of 5.3 +/- 3.9 mm and swelling by 8% +/- 5%. For non-CRPS patients, pain increased by 1.4 +/- 4.1 mm and swelling by 3% +/- 4%. There were no differences between groups (P > 0.19 for both). Increased pain and swelling related positively to duration of symptoms and performance on a left/right judgment task that interrogated the body schema, autonomic response, catastrophic thoughts about pain, and fear of movement (r > 0.42, P < 0.03 for all). Motor imagery increased pain and swelling in patients with chronic painful disease of the arm. The effect increased in line with the duration of symptoms and seems to be modulated by autonomic arousal and beliefs about pain and movement. The results highlight the contribution of cortical mechanisms to pain on movement, which has implications for treatment.

Differential behavioral effects of partial bilateral lesions of ventral tegmental area or substantia nigra pars compacta in rats

Akinesia (or absence of movement) is a prominent feature of Parkinson's disease. Akinetic symptoms, however, are also observed in depression and schizophrenia, which support the hypothesis that akinesia involves more than only motor behavior. A common feature of these disorders is the disruption of dopamine homeostasis in the CNS. Here we aimed at relating the respective involvement of the nigrostriatal and mesocortical dopaminergic pathways to akinesia. We investigated in the rat the relative effects of selective bilateral partial lesions of substantia nigra pars compacta (SNc) or ventral tegmental area (VTA) which did not affect locomotion, on fine motor, motivational and cognitive behaviors. Motor impairments were measured by the evaluation of fine motor control in the stepping test and in the paw reaching test. Cognitive functions were assessed by various paradigms: spontaneous alternation in the Y maze and object exploration task. Motivational behavior was evaluated by the 100-pellets test. The results suggested that specific behavioral impairments are obtained following selective lesions of either SNc or VTA. SNc-lesioned rats exhibited deficits in fine motor functions as previously described in animal models of Parkinson's disease, whereas VTA-lesioned rats demonstrated traits of perseveration without significant motor impairments.

Water shrews detect movement, shape, and smell to find prey underwater

American water shrews (Sorex palustris) are aggressive predators that feed on a variety of terrestrial and aquatic prey. They often forage at night, diving into streams and ponds in search of food. We investigated how shrews locate submerged prey using high-speed videography, infrared lighting, and stimuli designed to mimic prey. Shrews attacked brief water movements, indicating motion is an important cue used to detect active or escaping prey. They also bit, retrieved, and attempted to eat model fish made of silicone in preference to other silicone objects showing that tactile cues are important in the absence of movement. In addition, water shrews preferentially sniffed model prey fish and crickets underwater by exhaling and reinhaling air through the nostrils, suggesting olfaction plays an important role in aquatic foraging. The possibility of echolocation, sonar, or electroreception was investigated by testing for ultrasonic and audible calls above and below water and by presenting electric fields to foraging shrews. We found no evidence for these abilities. We conclude that water shrews detect motion, shape, and smell to find prey underwater. The short latency of attacks to water movements suggests shrews may use a flush-pursuit strategy to capture some prey.

A New Bio‐Inspired Robot Based on Senseless Motion; Theoretical Study and Preliminary Technological Results

Over the last few years, there has been considerable interest in developing autonomous robots that are able to move in constrained environments, inspired by the motion of lower animal forms such as parasites, worms, insects and even snakes and eels. In this paper, we describe a new design and concept of autonomous microrobot based on senseless motion. The “senseless motion” is the movement in absence of an external perception system. In a lot of living species, rhythmic movements, finalized to locomotion, are produced by oscillating circuits in the central nervous system. We reproduced this motion using a voice‐coil actuator embedded with its control hardware in a cylinder presents on its external surface a skate‐like structure produces a differential friction in order to move the robot on different substrates. Preliminary experiments have been carried out on several materials in order to measure the frictional forces produced by the robot during its motion and to verify the repeatability of senseless motion.

Nerve Sources for Facial Reanimation With Muscle Transplant in Patients With Unilateral Facial Palsy

Ninety-one patients with long-standing unilateral facial palsy and submitted to reanimation of the face with muscle transplant were divided into 3 nonrandomized groups: group I: 2-stage facial reanimation, cross face followed by gracilis muscle transplant, 58 patients; group II: 1-stage reanimation with latissimus dorsi muscle transplant, 11 patients (a branch of the facial nerve on the nonparalyzed side of the face was used as the nerve source for reanimation in groups I and II); group III: 1-stage reanimation with gracilis muscle transplant and neural coaptation of the respective nerve and the ipsilateral masseteric branch of the trigeminal nerve, 22 patients. No microvascular complications were observed. The average interval between surgery and initial muscle contractions was 11.1 months, 7.2 months, and 3.7 months in group I, group II, and group III, respectively. The quality (intensity and shape) of the smile, voluntary or involuntary, obtained on the reanimated side in relation to the unaffected side was considered good or excellent in 53.4%, 54.5%, and 86.3% of the patients in groups I, II, and III, respectively. In group I, the average age of the patients with excellent or good results (19.8 + 10.5 years) was significantly lower than that of the patients with fair or poor results or absence of movement (36.5 + 13.3 years). The smile was considered emotional or involuntary in 34% of the patients in group I and 45% in group II. Most of the patients in each group were only able to produce "voluntary smiles". Crossed synkinesis with lip puckering was observed in 48% of the patients in group I and 90% in group II. The results obtained with 1-stage facial reanimation with masseteric nerve were more uniform and predictable than those obtained with the other techniques evaluated in this study.

The Role of Behavioral Dynamics in Determining the Patch Distributions of Interacting Species

The effect of the behavioral dynamics of movement on the population dynamics of interacting species in multipatch systems is studied. The behavioral dynamics of habitat choice used in a range of previous models are reviewed. There is very limited empirical evidence for distinguishing between these different models, but they differ in important ways, and many lack properties that would guarantee stability of an ideal free distribution in a single-species system. The importance of finding out more about movement dynamics in multispecies systems is shown by an analysis of the effect of movement rules on the dynamics of a particular two-species-two-patch model of competition, where the population dynamical equilibrium in the absence of movement is often not a behavioral equilibrium in the presence of adaptive movement. The population dynamics of this system are explored for several different movement rules and different parameter values, producing a variety of outcomes. Other systems of interacting species that may lack a dynamically stable distribution among patches are discussed, and it is argued that such systems are not rare. The sensitivity of community properties to individual movement behavior in this and earlier studies argues that there is a great need for empirical investigation to determine the applicability of different models of the behavioral dynamics of habitat selection.

Behavior and measures of respiration in rabbits differing in terms of movement activity in an open field

Analysis of the behavior of 19 Chinchilla rabbits the first time they were placed in an open field allowed them to be divided into three groups differing in terms of investigative movement activity (passive rabbits accounted for 37%, active for 21%, and intermediate for 42%). On repeat placing in the open field, passive rabbits increased and active rabbits decreased their levels of activity. Correlations were found between the rabbits' behavior in the open field and the nature of their external respiration in the absence of movements in the comfort situation. Passive rabbits, as compared with intermediate and active animals, showed longer respiratory cycles, expirations, and breath holds in expiration. Animals with a predominance of right-hand turns in the open field showed shorter respiratory cycles and expirations than animals with a predominance of left-hand turns. These studies led to the conclusion that the characteristics of external respiration can serve as a predictive factor for the passive-defensive strategy of behavior in rabbits in emotionally negative situations.

Aiming for the future: prospective action difficulty, prescribed difficulty, and Fitts’ law

A main purpose of the current investigation was to determine if Fitts' index of difficulty [log(2)(2A/W)] could be taken as an index of subjective difficulty in prospective action. In two experiments, participants viewed 12 target displays with values of log(2)(2A/W) (prescribed difficulty) ranging between 1.0 and 6.5 bits. Following each 15 s trial, participants provided magnitude estimates reflecting the difficulty that someone else would experience if they actually had to make targeted movements during the trial. The prospective difficulty estimates were always made in the absence of movement. In Experiment 1, target displays were presented to participants on their own video monitor, while in Experiment 2, all participants concurrently viewed scaled-up target displays projected onto a large screen. There were three main findings: First, in both experiments, the prospective-prescribed relation was strong and positive. This finding warrants two conclusions: Fitts' index of difficulty can be taken as an index of subjective difficulty in prospective action, and subjective estimates of performance difficulty result from the monitoring of feedforward control signals generated in the absence of movement-related feedback. Second, even with the large differences in the target display scale of Experiments 1 and 2, difficulty estimates were equivalent at common prescribed difficulty levels. In other words, the results of Experiment 1 were successfully replicated in Experiment 2. This finding demonstrates the generality of the prospective-prescribed relation. Third, nonlinearities in the prospective-prescribed relation resembled those seen in functions describing the increases in movement time that accompany increases in prescribed difficulty (Fitts' law). This observation suggests that the prospective difficulty estimates were based on the value of a temporal parameter in an implicit mental simulation of the action.

Padronização das técnicas de secção do nervo facial e de avaliação da mímica facial em ratos

OBJETIVOS: Padronização da técnica de secção do nervo facial extratemporal em ratos e elaboração de uma escala de avaliação da mímica facial desses animais antes e após essa secção. TIPO DE ESTUDO: Experimental. MÉTODO: Vinte ratos Wistar foram anestesiados com xilasina e ketamina e submetidos à secção do nervo facial próximo à sua emergência pelo forame mastóideo na pele. Todos os animais foram avaliados. Foram observados: fechamento ocular, reflexo de piscamento, movimentação e posicionamento das vibrissas, e foi elaborada uma escala de avaliação e graduação destes parâmetros. RESULTADOS: O tronco do nervo facial foi encontrado entre a margem tendinosa do músculo clavotrapézio e a cartilagem auricular. O tronco foi seccionado proximal à sua saída pelo forame mastóideo e os cotos foram suturados com nylon 9-0. Foi elaborada uma escala de avaliação e graduação da mímica facial independente para olho e vibrissa e a somatória dos parâmetros, como forma de avaliar a face paralisada. A ausência de piscamento e de fechamento ocular recebeu valor 1; a presença de contração do músculo orbicular, sem reflexo de piscamento, valor 2; fechamento ocular de 50% através de reflexo de piscamento, valor 3, o fechamento de 75%, valor 4. A presença de reflexo de piscamento com fechamento ocular completo recebeu valor 5. A ausência de movimento e posição posterior das vibrissas recebeu pontuação 1; tremor leve e posição posterior, pontuação 2; tremor maior e posição posterior, pontuação 3 e movimento normal com posição posterior, pontuação 4. A movimentação simétrica das vibrissas, com posição anterior recebeu pontuação 5. CONCLUSÃO: O rato apresenta anatomia que permite fácil acesso ao nervo facial extratemporal, possibilitando secção e sutura desse nervo de forma padronizada. Também foi possível estabelecer uma escala de avaliação e graduação da mímica facial dos ratos com paralisia facial a partir da observação clínica desses animais.

Standardization of techniques used in facial nerve section and facial movement evaluation in rats

SummaryAimstandardization of the technique to section the extratemporal facial nerve in rats and creation of a scale to evaluate facial movements in these animals before and after surgery.Study designExperimental.Methodtwenty Wistar rats were anesthetized with ketamine xylazine and submitted to sectioning of the facial nerve near its emergence through the mastoid foramen. Eye closure and blinking reflex, vibrissae movement and positioning were observed in all animals and a scale to evaluate these parameters was then created.ResultsThe facial nerve trunk was found between the tendinous margin of the clavotrapezius muscle and the auricular cartilage. The trunk was proximally sectioned as it exits the mastoid foramen and the stumps were sutured with a 9-0-nylon thread. An evaluation and graduation scale of facial movements, independent for eye and vibrissae, was elaborated, together with a sum of the parameters, as a means to evaluate facial palsy. Absence of eye blinking and closure scored 1; the presence of orbicular muscle contraction, without blinking reflex, scored 2; 50% of eye closure through blinking reflex, scored 3, 75% of closure scored 4. The presence of complete eye closure and blinking reflex scored 5. The absence of movement and posterior position of the vibrissae scored 1; slight shivering and posterior position scored 2; greater shivering and posterior position, scored 3 and normal movement with posterior position, scored 4; symmetrical movement of he vibrissae, with anterior position, scored 5.ConclusionThe rat anatomy allows easy access to the extratemporal facial nerve, allowing its sectioning and standardized suture. It was also possible to establish an evaluation and graduation scale of the rat facial movements with facial palsy based on the clinical observation of these animals.