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This study investigates developmental changes in active usage of a contact surface and pressure distribution beneath infants’ foot during learning of upright posture. We started studying longitudinally on 22 female and 22 male infants at their 12.5th months (1st trimester, T1) and kept on screening the same subjects at every three months (19 females and 12 males at 15.5th months (T2), 17 females and 7 males at 18.4th months (T3)), in Gazi University Hospital, Social Pediatrics Department. Each trial was fulfilled by an infant standing on a pressure pad placed on top of a force plate to collect the pressure distribution data beneath the feet for 15 sec at T1, and 25-sec at T2 and T3 and was repeated at least three times. Data collection sessions were also recorded with the camera. We expected to monitor the developmental changes at an infant’s standing experience during their 2nd-year epoch through time-frequency domain analysis metrics on the overall CoPx and CoPy signals.The stabilogram plots showed noticeable shrinkage both in AP and ML directions. The phase plane plots showed shrinkage of the pattern in both CoPx and CoPy signals, and the amplitude of the frequency density function estimates and the frequency spectrum of CoP decreased significantly by time from T1 to T3. In the next part of the study, the image processing analysis have been done on pressure pad matrices. Time and frequency domain metrics of contact area, weight, pressure, and moment arms of front, mid, and hind regions of each foot have been estimated. In the frequency domain metrics there were significant shifts of the power of pressure distribution and moment arms to the lower frequencies due to the trimesters. We observed high frequency pressure vibration at the Mid foot at all trimesters. Further, we revealed higher frequency manifestations of moment arm at Fore foot in regional CoPx, which may be pointing to the role of the Fore foot as the controller and Mid foot as the load transmitter. Moreover, nonlinear dynamic analyses have been performed and led us to calculate the characteristic metrics of the m-dimensional attractor dynamics constructed in phase space by estimating critical τ (time-delay operator) from the CoPx signal through S-average displacement method. Further, Approximate Entropy (ApEn) metric was calculated by using critical τestimates, which showed an increase in ApEn, from T1 to T3. These metrics, which define the characteristics of the developmental stages of motor learning, will help to illuminate the evolution of upright stance.

This study investigates how the combination of robot-mediated haptic interaction and cerebellar neuromodulation can improve task performance and promote motor skill development in healthy individuals using a robotic exoskeleton worn on the index finger. The authors propose a leader-follower type of mirror game where participants can follow a leader in a two-dimensional virtual reality environment while the exoskeleton tracks the index finger motion using an admittance filter. The game requires two primary learning phases: the initial phase focuses on mastering the pinching interface, while the second phase centers on predicting the leader’s movements. Cerebral transcranial direct current stimulation (tDCS) with anodal polarity is applied to the subjects during the game. It is shown that the subjects’ performance improves as they play the game. The combination of tDCS with finger exoskeleton significantly enhances task performance. Our research indicates that modulation of the cerebellum during the mirror game improves the motor skills of healthy individuals. The results also indicate potential uses for motor neurorehabilitation in hemiplegia patients.

The aim of this study was to investigate the microstructure, mechanical and biological properties of biphasic hydroxyapatite--Tricalcium phosphate (HT) and HT substituted with constant fluoride (F−) and varying strontium (Sr2+) amounts. All the samples were synthesized via precipitation method and sintered at 1100°C for 1 h. It was observed that the relative density of the sintered strontium and fluoride doped HT slightly increased. For microstructural analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) examinations were performed. Remarkable amounts of β-TCP and CaO phases were detected in XRD analysis which could be due to the Ca/P ratio less than 1.67. Lattice parameters increased due to substitutions of ions. In SEM analysis, smaller grains were observed for HT doped with ions. In FTIR analysis, the characteristic bands of HA and β-TCP were exhibited. Increased Sr2+ ion contents resulted in increased microhardness values. The highest microhardness value was obtained for the HT doped with 5%Sr2+ and 1%F−. In order to evaluate the cytocompatibility of doped HT, in vitro cytotoxicity tests were performed using Saos-2 cells. Higher initial cell attachment was observed on Sr2+ and F−doped HT discs than observed on pure HT.SEM analysis was conducted to examine the morphology of the cells on the surface of the samples. And it was observed that the surface of all discs was covered with cell layers showing perfect cell-material interaction.HT doped with 5%Sr2+ and 1%F−had the optimum structural, mechanical and biocompatibility properties and can be suggested as a good biomaterial for biomedical applications.

Previous studies suggest that low-dimensional control underlies motor unit activity, with low-frequency oscillations in common synaptic inputs serving as the primary determinant of muscle force production. In this study, we used principal component analysis (PCA) and factor analysis (FA) to investigate the relationship between low-dimensional motor unit components and force oscillations during repetitive isometric tasks with similar force profiles. We assessed the consistency of these components across trials in both individual (tibialis anterior; first dorsal interosseous) and synergistic muscles (vastus medialis, VM; vastus lateralis, VL). Participants performed 15 trials of a force-matching learning task. Three post-skill acquisition trials were selected for analysis to ensure high similarity in force profiles. Motor units were decomposed from high-density surface electromyograms, tracked across trials, and their smoothed discharge rates were decomposed into low-dimensional components using PCA and FA. Parallel analysis indicated that a single component could explain the smoothed discharge rates for the individual muscles and two components for VM-VL. Importantly, the first component explained most of the variance (∼70%) in smoothed discharge rates across all muscles. The first motor unit component also showed significantly higher correlations with force oscillations than the second component and remained highly consistent across trials. These findings were further supported by a non-linear framework combining network- and information-theoretic tools, which revealed high motor unit network density in the first component of all muscles. Collectively, these results suggest that, during isometric contractions, motor unit activity is primarily controlled by a single dominant shared synaptic input that closely mirrors force oscillations.