Inter-Joint Coordination Deficits Revealed in the Decomposition of Endpoint Jerk During Goal-Directed Arm Movement After Stroke

It is well documented that neurological deficits after stroke can disrupt motor control processes that affect the smoothness of reaching movements. The smoothness of hand trajectories during multi-joint reaching depends on shoulder and elbow joint angular velocities and their successive derivatives as well as on the instantaneous arm configuration and its rate of change. Right-handed survivors of unilateral hemiparetic stroke and neurologically-intact control participants held the handle of a two-joint robot and made horizontal planar reaching movements. We decomposed endpoint jerk into components related to shoulder and elbow joint angular velocity, acceleration, and jerk. We observed an abnormal decomposition pattern in the most severely impaired stroke survivors consistent with deficits of inter-joint coordination. We then used numerical simulations of reaching movements to test whether the specific pattern of inter-joint coordination deficits observed experimentally could be explained by either a general increase in motor noise related to weakness or by an impaired ability to compensate for multi-joint interaction torque. Simulation results suggest that observed deficits in movement smoothness after stroke more likely reflect an impaired ability to compensate for multi-joint interaction torques rather than the mere presence of elevated motor noise

Submovements During Reaching Movements after Stroke

Neurological deficits after cerebrovascular accidents very frequently disrupt the kinematics of voluntary movements with the consequent impact in daily life activities. Robotic methodologies enable the quantitative characterization of specific control deficits needed to understand the basis of functional impairments and to design effective rehabilitation therapies. In a group of right handed chronic stroke survivors (SS) with right side hemiparesis, intact proprioception, and differing levels of motor impairment, we used a robotic manipulandum to study right arm function during discrete point-to-point reaching movements and reciprocal out-and-back movements to visual targets. We compared these movements with those of neurologically intact individuals (NI). We analyzed the presence of secondary submovements in the initial (i.e. outward) trajectory portion of the two tasks and found that the SS with severe impairment (F

Apprendistato: quadro comparato e buone prassi

Il volume affronta da un punto di vista comparato gli aspetti principali connessi al contratto di apprendistato. Il punto di partenza sono le analisi e gli spunti offerti dalle istituzioni comunitarie per una maggiore diffusione dei rapporti di apprendistato, in un’ottica di aumento dell’occupazione giovanile e di contrasto alla dispersione scolastica. La pubblicazione mette in relazione cinque aspetti: definizione e ruolo dell’apprendistato; soggetti regolatori; retribuzione; durata del percorso; monte ore formativo. Per ciascuna di queste voci si evidenziano le peculiarità dei sistemi in vigore in Italia, Francia, Spagna, Regno Unito, Germania, Danimarca e Svezia

Lower limb stiffness estimation during running: the effect of using kinematic constraints in muscle force optimization algorithms

The focus of this paper is on the effect of muscle force optimization algorithms on the human lower limb stiffness estimation. By using a forward dynamic neuromusculoskeletal model coupled with a muscle short-range stiffness model we computed the human joint stiffness of the lower limb during running. The joint stiffness values are calculated using two different muscle force optimization procedures, namely: Toque-based and Torque/Kinematic-based algorithm. A comparison between the processed EMG signal and the corresponding estimated muscle forces with the two optimization algorithms is provided. We found that the two stiffness estimates are strongly influenced by the adopted algorithm. We observed different magnitude and timing of both the estimated muscle forces and joint stiffness time profile with respect to each gait phase, as function of the optimization algorithm used

Phase transitions between single- and double-layered smectic structures in binary mixtures of cyano-mesogens

Binary mixtures of mesogens which exhibit respectively single-layered (A 1), double layered (A2) and partially double layered (A d) smectic phases show abrupt A2-A1 or A2-Ad transitions as a function of concentration. Double layered structures imply the formation of dimerized entities and the possibility of dimerization is discussed in terms of the amphiphilic nature of the molecules in the binary mixture (symmetrical and dissymmetrical polar mesogens). The results are analysed with respect to the thermal stability of the A 2 phase when defects are introduced in the polar interface by adding non-polar symmetrical mesogens.Des mélanges binaires de mésogènes présentant respectivement des phases smectiques monocouches (A1), bicouches (A2) et partiellement bicouches (Ad) permettent de mettre en évidence en fonction de la concentration des transitions brusques A2-A1 ou A 2-Ad. La structure bicouche implique un processus de dimérisation des entités mésogènes qui est discuté en fonction du caractère amphipathique des molécules (molécules polaires symétriques et dissymétriques). La stabilité de la phase bicouche est également analysée lorsque l'on introduit une perturbation au niveau de l'interface polaire par adjonction de molécules non polaires

The effect of pain on human time perception

This thesis explored the effect of pain on human temporal perception. This aim was achieved firstly by systematically testing the way in which pain experience affects duration estimates, and memory for duration and secondly by examining whether it was possible to reduce perceived duration of pain in clinical and no clinical population. Chapter 5 examined the effect of different pain intensities on perceived duration when pain was the to-be-timed stimulus (i.e., task-relevant) and when pain was in the background (i.e., task-irrelevant). Participants were required to verbally estimate the duration of no pain, low pain and high pain electro-cutaneous stimulations and the duration of a neutral visual stimulus whilst being exposed to no pain, low pain and high pain thermal stimulation. Increases in the intensity of the electro-cutaneous stimulation were associated with longer verbal estimates, reflecting a multiplicative effect. However, low pain thermal stimulation did not affect the perceived duration of the visual stimulus and high pain thermal stimulation led to shorter verbal estimates. The lengthening effect of pain therefore appeared to be limited to circumstances when pain was task-relevant. Chapter 6 examined whether changes in physiological arousal mediated the effect of task-relevant and task-irrelevant pain on time perception. Participants’ physiological activity (skin conductance level and high frequency heart rate variability) was measured while they were asked to verbally estimate the duration of an electro-cutaneous stimulation at different intensities and a neutral stimulus whilst perceiving a thermal stimulation at different intensities. The lengthening effect of task-relevant pain on time perception, although did not replicate the multiplicative effect, was mediated by sympathetic arousal, supporting previous suggestions that temporal distortions due to pain are caused by changes in the arousal level. However, task-irrelevant pain did not affect verbal estimates of participants, despite it increased their physiological arousal, and there was no relationship between physiological arousal and verbal estimates. This suggests that changes in arousal do not affect time perception when arousal arises from sources other than the to-be-timed stimulus. Chapter 7 examined whether pain enhanced or disrupted the memorization of duration by using a temporal generalisation task. Participants were required to encode the duration of a tone whilst experiencing neutral or painful thermal stimulation and to recall the duration immediately after learning or after a delay. Delay affected neutral and pain related durations in a comparable way, suggesting that pain does not have any unique effect on the memorization of duration: pain does not enhance nor disrupt the memorization of duration information. Chapter 8 tested whether a mindfulness intervention could reduce the lengthening effect of pain in heathy people and in chronic pain patients. Participants were asked to estimate the duration of visual, vibrotactile and electro-cutaneous stimuli before and after practicing mindfulness meditation for a week. Healthy participants gave similar verbal estimates before and after the intervention, suggesting that mindfulness was not able to modulate the perceived duration in any stimulus modality. In chronic pain patients mindfulness practice led to longer verbal estimates in any stimulus modality including pain, suggesting that mindfulness was not an appropriate intervention to reduce the lengthening effect of pain, however, caution should be taken when interpreting this latter finding due to the small sample. Together the finding of this thesis show that task relevant pain distorts time, in part due to its capacity to increase sympathetic nervous system activity. Pain, however, appears to have no influence on memory for duration. Furthermore, interventions which reduce the intensity of pain do not appear to be effective in reducing the perceived duration of pain. Further research is therefore required to understand how the lengthening effect of pain can be mitigated in clinical and non-clinical settings

Characterizing historical transformation trajectories of the forest landscape in Rome's metropolitan area (Italy) for effective planning of sustainability goals

With the aim at developing a landscape dynamics framework for environmental planning and management and testing the effectiveness of protected areas in achieving the 2030 Agenda of the United Nations sustainability goals, we characterized the historical transformation trajectories of forest area changes from 1936 to 2010 in the Metropolitan City of Rome Capital (Italy). Remote sensing-based products coupled with landscape pattern metrics and fragmentation analysis have been implemented, comparing different historical forest maps. The results show a remarkable forest area gain – from 17.6% to 25.5% – thanks to 68,299 ha of recently established forest. Statistical descriptors showed that the highest relative gain occurred in mountain zones, confirming a wide European forest recovery pattern in marginal areas from past deforestation and overexploitation. Deforestation mainly occurred in the flat and hilly areas where almost 26,000 ha of forests were lost since 1936. In summary, two main forest landscape dynamics were reconstructed: (I) the increase of forest cover fragmentation in the lowland areas; and (II) the rise in the forest area in the interior sectors of the mountain landscape, mainly within protected areas. Restoring the forest ecosystem's bioecological integrity has been highlighted as an urgent action for biodiversity conservation and carbon mitigation. In lowland areas, the study revealed the urgent need to establish new protected areas and rewilding spaces as landscape metrics are relatively below the sustainability targets for healthy forest ecosystems. The proposed framework can be used for testing the effectiveness of environmental planning and management in other forest landscapes to achieve the Agenda 2030 goals