Coupling of upper and lower limb pattern generators during human crawling at different arm/leg speed combinations

A crawling paradigm was performed by healthy adults to examine inter-limb coupling patterns and to understand how central pattern generators (CPGs) for the upper and lower limbs are coordinated. Ten participants performed hands-and-feet crawling on two separate treadmills, one for the upper limbs and another one for the lower limbs, the speed of each of them being changed independently. A 1:1 frequency relationship was often maintained even when the treadmill speed was not matched between the upper and lower limbs. However, relative stance durations in the upper limbs were only affected by changes of the upper limb treadmill speed, suggesting that although absolute times are adjusted, the relative proportions of stances and swing do not adapt to changes in lower limb treadmill speeds. With large differences between treadmill speeds, changes in upper and lower limb coupling ratio tended to occur when the upper limbs stepped at slower speeds than the lower limbs, but more rarely the other way around. These findings are in sharp contrast with those in the cat, where forelimbs always follow the rhythm of the faster moving hindlimbs. However, the fact that an integer frequency ratio is often maintained between the upper and lower limbs supports evidence of coupled CPG control. We speculate that the preference for the upper limb to decrease step frequency at lower speeds in humans may be due to weaker ascending propriospinal connections and/or a larger influence of cortical control on the upper limbs which allows for an overriding of spinal CPG control

Planar Covariation of Hindlimb and Forelimb Elevation Angles during Terrestrial and Aquatic Locomotion of Dogs

The rich repertoire of locomotor behaviors in quadrupedal animals requires flexible inter-limb and inter-segmental coordination. Here we studied the kinematic coordination of different gaits (walk, trot, gallop, and swim) of six dogs (Canis lupus familiaris) and, in particular, the planar covariation of limb segment elevation angles. The results showed significant variations in the relative duration of rearward limb movement, amplitude of angular motion, and inter-limb coordination, with gait patterns ranging from a lateral sequence of footfalls during walking to a diagonal sequence in swimming. Despite these differences, the planar law of inter-segmental coordination was maintained across different gaits in both forelimbs and hindlimbs. Notably, phase relationships and orientation of the covariation plane were highly limb specific, consistent with the functional differences in their neural control. Factor analysis of published muscle activity data also demonstrated differences in the characteristic timing of basic activation patterns of the forelimbs and hindlimbs. Overall, the results demonstrate that the planar covariation of inter-segmental coordination has emerged for both fore- and hindlimbs and all gaits, although in a limb-specific manner

Drawing ellipses in water: evidence for dynamic constraints in the relation between velocity and path curvature

Several types of continuous human movements comply with the so-called Two-Thirds Power Law (2/3-PL) stating that velocity (V) is a power function of the radius of curvature (R) of the endpoint trajectory. The origin of the 2/3-PL has been the object of much debate. An experiment investigated further this issue by comparing two-dimensional drawing movements performed in air and water. In both conditions, participants traced continuously quasi-elliptic trajectories (period T = 1.5 s). Other experimental factors were the movement plane (horizontal/vertical), and whether the movement was performed free-hand, or by following the edge of a template. In all cases a power function provided a good approximation to the V-R relation. The main result was that the exponent of the power function in water was significantly smaller than in air. This appears incompatible with the idea that the power relationship depends only on kinematic constraints and suggests a significant contribution of dynamic factors. We argue that a satisfactory explanation of the observed behavior must take into account the interplay between the properties of the central motor commands and the visco-elastic nature of the mechanical plant that implements the commands

Planar covariance of upper and lower limb elevation angles during hand–foot crawling in healthy young adults

MacLellan MJ, Catavitello G, Ivanenko YP, Lacquaniti F. Planar covariance of upper and lower limb elevation angles during hand–foot crawling in healthy young adults. Experimental Brain Research. 2017;235(11):3287-3294

An atypical, pigment-producing Metschnikowia strain from a leukaemia patient

A yeast strain was isolated from the sputum sample of a leukaemia patient in the Spirito Santo Hospital of Pescara, Italy. The fungus produced a pigment that formed a reddish halo around colonies, and was identified and deposited as a Metschnikowia spp. (accession number IHEM 25107-GenBank accession number JQ921016) in the BCCM/IHEM collection of biomedical fungi and yeasts (Bruxelles, Belgium). Although the physiology of the strain was close to that of Metschnikowia sinensis, the D1/D2 sequence did not correspond to any previously described Metschnikowia species. Phylogeny of the genus Metschnikowia is complex and requires far more analysis. We present the first non-M. pulcherrima Metschnikowia spp. isolate recovered from a human, and emphasize the role of man as a transient carrier of environmental yeasts, the pathogenicity of which still needs to be defined</p