Short-Term Effect of Crural Fasciotomy on Kinematic Variability and Propulsion During Level Locomotion

Treadmill locomotion can be characterized by consistent step-to-step kinematics despite the redundant degrees of freedom. The authors investigated the effect of disrupting the crural fascia in decerebrate cats to determine if the crural fascia contributed to kinematic variability and propulsion in the limb. Crural fasciotomy resulted in statistically significant decreases in velocity and acceleration in the joint angles during level walking, before, during, and after paw-off, particularly at the ankle. A further finding was an increase in variance of the limb segment trajectories in the frontal plane. The crural fascia therefore provides force transmission and reduction in kinematic variability to the limb during locomotion.     

Horizontal Plane Head Stabilization During Locomotor Tasks

Frequency characteristics of head stabilization were examined during locomotor tasks in healthy young adults (N = 8) who performed normal walking and 3 walking tasks designed to produce perturbations primarily in the horizontal plane. In the 3 walking tasks, the arms moved in phase with leg movement, with abnormally large amplitude, and at twice the frequency of leg movement. Head-in-space angular velocity was examined at the predominant frequencies of trunk motion. Head movements in space occurred at low frequencies (< 4.0 Hz) in all conditions and at higher frequencies (> 4.0 Hz) when the arms moved at twice the frequency of the legs. Head stabilization strategies were determined from head-on-trunk with respect to trunk frequency profiles derived from angular velocity data. During natural walking at low frequencies (< 3.0 Hz), head-on-trunk movement was less than trunk movement. At frequencies 3.0 Hz or greater, equal and opposite compensatory movement ensured head stability. When arm swing was altered, compensatory movement guaranteed head stability at all frequencies. Head stabilization was successful for frequencies up to 10.0 Hz during locomotor tasks Maintaining head stability at high frequencies during voluntary tasks suggests that participants used feedforward mechanisms to coordinate head and trunk movements. Maintenance of head stability during dynamic tasks allows optimal conditions for vestibulo-ocular reflex function.     

Behaviour and gaze analyses during a goal-directed locomotor task

The objectives of the current study were: (a) to determine whether perception–action coupling controlled behaviours when walking through moving doors and (b) to determine how vision contributed to this behaviour. Participants (N = 6) walked along a 7-m path toward two motor-driven doors, which moved at rates ranging between 20 and 40 cm/s. Each door was independently driven such that both moved at the same velocity (symmetrical) or at different velocities (asymmetrical). The results showed that in both door movement conditions the participants controlled their approach velocity by slowing down prior to crossing the doors. The decrease in walking velocity produced greater velocity variability in the final stages prior to crossing the doors and high success rates. The results from the gaze behaviours showed that fixation durations were significantly longer when the doors moved asymmetrically, suggesting that the visual information from this unpredictable environment took longer to process. However, the fixation patterns were similar between the two door movement conditions. Regardless of the door movement condition, the participants spent about 60% of each trial fixating environmental objects (i.e., left door, right door, or aperture). The majority of fixations were directed towards one of the doors at the beginning of the trial and then shifted towards the aperture in the final phase. The participants were using perception–action coupling to control their behaviours in the final phase in order to steer locomotion through the aperture.     

Modulation of Gait During Visual Adaptation to Dark

The authors investigated the modulation of gait during dark adaptation. Twenty-five women (mean age = 72 years, SD = 5 years) walked back and forth on an arbitrarily uneven walkway during normal lighting at speeds ranging from slow to fast. Participants then performed 20 trials at preferred speed after sudden reduction of lighting; the authors compared those trials with point estimates at equivalent speeds representing normal lighting. The authors estimated speed, cadence, mediolateral trunk acceleration, and mediolateral interstep trunk-acceleration variability for each trial. Participants compensated for sudden reduction of lighting by reducing their walking speed. Compared with performance at equivalent speeds during normal lighting, cadence, trunk acceleration, and interstep trunk-acceleration variability initially increased. All variables showed an asymptotic approximation toward normal values during 60-90 s of walking in subdued lighting. The authors suggest that the sudden transition from normal to marginal lighting, rather than marginal lighting itself, may challenge locomotor control.     

Test-dependent expression of behavioral syndromes: A study of aggressiveness,activity, and stress of chub

Aggressiveness has been one of the behavioral traits most examined with various standard testing methods. We used two distinct methods (the mirror and the real opponent tests) to evaluate individual aggression and relate it to the activity and individual stress of chub (Squalius cephalus L.). Three hypotheses were formulated and tested: (a) there is a significant positive relationship between the aggressiveness of individuals measured with the mirror and the real opponent tests, indicating their convergent validity; (b) the irregularities in response to the aggressiveness and activity tests lead to the context-specific expression of the behavioral syndromes; and (c) there is a significant positive relationship between the stress induced in individuals by both tests of aggressiveness, demonstrating individually consistent stress-coping strategies. The first and the second hypothesis were confirmed, while the third hypothesis was rejected. Our results suggest that particular tests of aggressiveness could act as a situation with high strength, leaving little variation between individual responses. Thus, we propose that for the proper interpretation of various studies using different tests to study identical behavioral traits, it is important to consider the convergent validity of not only the tested behavioral traits but also the individual stress responses. The chub also showed stress relieve through aggressiveness, suggesting the species as a prospective animal model to the study interaction between the stress and the aggressiveness. A detailed aggression ethogram of chub was provided to facilitate the use of this specie in future studies.     

Iterative Spatial Updating During Forward Linear Walking Revealed Using a Continuous Pointing Task

Abstract

The continuous pointing task uses target-directed pointing responses to determine how perceived distance traveled is estimated during forward linear walking movements. To more precisely examine the regulation of this online process, the current study measured upper extremity joint angles and step-cycle kinematics in full vision and no-vision continuous pointing movements. Results show perceptual under-estimation of traveled distance in no-vision trials compared to full vision trials. Additionally, parsing of the shoulder plane of elevation trajectories revealed discontinuities that reflected this perceptual under-estimation and that were most frequently coupled with the early portion of the right foot swing phase of the step-cycle. This suggests that spatial updating may be composed of discrete iterations that are associated with gait parameters.     

Newborns modulate their crawling in response to their native language but not another language

Human newborns can propel themselves to their mother's breast when positioned skin to skin on her abdomen just after birth. For decades, researchers have considered this primitive crawling behavior a spinal reflex, immune to supra spinal control. However, recent research suggests that neonatal crawling is already responsive to visual and olfactory stimuli processed at a supra spinal level. Here we report that a few hours post birth, French newborns can also modulate their crawling in response to their native language – a source of information that is processed supra-spinally. The crawling patterns of 23 French-born newborns were recorded on video and via an infrared motion capture system during two randomly ordered 2-min trials. The newborns were secured on a mini skateboard to facilitate arm and leg movements during their crawling propulsion. They heard a repetitive sequence of the same sentences either in French, their native language, or in English, a rhythmically different and hence discriminable unfamiliar language, on each trial. In French, compared to English, crawling was enhanced, with significantly more arm and leg steps and significantly more and larger trunk rotations in the cephalo-caudal axis. Moreover, newborns rotated their heads and trunk toward the appropriate loud speaker when hearing French but not English. These preliminary findings suggest that newborn crawling is not a simple stereotyped reflex under spinal control, but a complex pattern that can be modulated in response to higher-order, supra-spinally processed stimuli. The findings open fascinating questions about the range of stimuli to which newborn crawling is responsive.