Impact of online visual feedback on motor acquisition and retention when learning to reach in a force field

When subjects learn a novel motor task, several sources of feedback (proprioceptive, visual or auditory) contribute to the performance. Over the past few years, several studies have investigated the role of visual feedback in motor learning, yet evidence remains conflicting. The aim of this study was therefore to investigate the role of online visual feedback (VFb) on the acquisition and retention stages of motor learning associated with training in a reaching task. Thirty healthy subjects made ballistic reaching movements with their dominant arm toward two targets, on 2 consecutive days using a robotized exoskeleton (KINARM). They were randomly assigned to a group with (VFb) or without (NoVFb) VFb of index position during movement. On day 1, the task was performed before (baseline) and during the application of a velocity-dependent resistive force field (adaptation). To assess retention, participants repeated the task with the force field on day 2. Motor learning was characterized by: (1) the final endpoint error (movement accuracy) and (2) the initial angle (iANG) of deviation (motor planning). Even though both groups showed motor adaptation, the NoVFb-group exhibited slower learning and higher final endpoint error than the VFb-group. In some condition, subjects trained without visual feedback used more curved initial trajectories to anticipate for the perturbation. This observation suggests that learning to reach targets in a velocity-dependent resistive force field is possible even when feedback is limited. However, the absence of VFb leads to different strategies that were only apparent when reaching toward the most challenging target.

Comparison of strength measurements under single-joint and multi-joint conditions in hemiparetic individuals

Objective: It has been suggested that the measurement of strength is inappropriate in patients with stroke, in large part because of the presence of abnormal synergy patterns. The aim of the present study was to characterize force production during multi-joint maximal exertion involving different combinations of activation between shoulder and elbow flexors and extensors.

Design: Cross-sectional study.

Setting: Rehabilitation centre.

Subjects: A convenience sample of 16 chronic hemiparetic stroke subjects.

Main outcome measures: Maximal torques in flexion and extension at the shoulder and the elbow were measured using static dynamometers (single-joint condition). In addition, the maximal forces produced at the wrist were measured in four directions in the sagittal plane requiring different torque combinations between shoulder and elbow flexors and extensors (multi-joint condition).

Results: No difference was found across directions for the ratios of maximal forces (paretic/nonparetic) in the multi-joint condition (p = 0.227; mean ratios (9±SD) for each direction ranging from 0.599±0.23 to 0.689±0.27), suggesting that the ability to produce force did not change as a function of the required torque combination. In addition, relative torques (% of the maximal torque in the single-joint condition) exerted during the multi-joint exertions were similar on the paretic and the nonparetic side.

Conclusions: These results do not support the assumption that force production is limited by abnormal synergy patterns between flexors and extensors at the shoulder and the elbow in hemiparetic patients.

Experimental tonic hand pain modulates the corticospinal plasticity induced by a subsequent hand deafferentation

Sensorimotor reorganization is believed to play an important role in the development and maintenance of phantom limb pain, but pain itself might modulate sensorimotor plasticity induced by deafferentation. Clinical and basic research support this idea, as pain prior to amputation increases the risk of developing post-amputation pain. The aim of this study was to examine the influence of experimental tonic cutaneous hand pain on the plasticity induced by temporary ischemic hand deafferentation. Sixteen healthy subjects participated in two experimental sessions (Pain, No Pain) in which transcranial magnetic stimulation was used to assess corticospinal excitability in two forearm muscles (flexor carpi radialis and flexor digitorum superficialis) before (T0, T10, T20, and T40) and after (T60 and T75) inflation of a cuff around the wrist. The cuff was inflated at T45 in both sessions and in the Pain session capsaicin cream was applied on the dorsum of the hand at T5. Corticospinal excitability was significantly greater during the Post-inflation phase (p=0.002) and increased similarly in both muscles (p=0.861). Importantly, the excitability increase in the Post-inflation phase was greater for the Pain than the No-Pain condition (p=0.006). Post-hoc analyses revealed a significant difference between the two conditions during the Post-inflation phase (p=0.030) but no difference during the Pre-inflation phase (p=0.601). In other words, the corticospinal facilitation was greater when pain was present prior to cuff inflation. These results indicate that pain can modulate the plasticity induced by another event, and could partially explain the sensorimotor reorganization often reported in chronic pain populations.

Micafungin as primary antifungal prophylaxis in patients presenting with acute myeloid leukemia

OBJECTIVE

To study the efficacy and safety of micafungin for prophylaxis of invasive fungal infections in patients undergoing induction chemotherapy for acute myeloid leukemia.

PATIENTS AND METHODS

A prospective observational single-center study of 41 patients from the hematology department between May 2012 and April 2015. Micafungin was administered once daily from the first day of induction chemotherapy to the end of the neutropenic phase.

RESULTS

Neither Candida nor Aspergillus infection was documented in our 41 patients from the first day of micafungin infusion to the end of the neutropenic phase. Patients were followed for three months after discontinuation of micafungin and none of them contracted an invasive fungal infection. Only one patient presented with grade III-IV hepatic and ionic toxicities.

CONCLUSION

Micafungin is associated with a good safety profile and is an interesting option for preventing invasive fungal infections in the high-risk population of patients presenting with hematological disorders.

Perceived and Valued Roles of Adults with Severe Mental Health Problems

The purpose of this article is to convey the findings of two studies related to the perception of past, present and future roles, the value attributed to these roles as well as the role patterns. Both studies were conducted with adults who have schizophrenia and are involved in a rehabilitation or work program. Data were collected from two sources: 1) secondary analysis of a study related to the methodology for validating the French translation (Hachey, Jumoorty, & Mercier, 1995) of the “Role Checklist”, (Barris, Oakley, & Kielhofner, 1988) and 2) a research project on the perception of roles and quality of life. Results showed that the dominant roles assumed by participants regardless of time were family member, friend, home maintainer and hobbyist. The most valued roles were those of friend, worker, and family member. The discussion will address the questions asked and elucidate the role patterns. The conclusion underlines the importance, for occupational therapists and health professionals, of including roles in the daily lives of their clients, taking into consideration the ones they value most highly.

DNA metabarcoding diet analysis for species with parapatric vs sympatric distribution: a case study on subterranean rodents

Closely related sympatric species commonly develop different ecological strategies to avoid competition. Ctenomys minutus and C. flamarioni are subterranean rodents parapatrically distributed in the southern Brazilian coastal plain, showing a narrow sympatric zone. To gain understanding on food preferences and possible competition for food resources, we evaluated their diet composition performing DNA metabarcoding analyzes of 67 C. minutus and 100 C. flamarioni scat samples, collected along the species geographical ranges. Thirteen plant families, mainly represented by Poaceae, Araliaceae, Asteraceae and Fabaceae, were identified in the diet of C. minutus. For C. flamarioni, 10 families were recovered, with a predominance of Poaceae, Araliaceae and Asteraceae. A significant correlation between diet composition and geographical distance was detected in C. minutus, whereas the diet of C. flamarioni was quite homogeneous throughout its geographical distribution. No significant differences were observed between males and females of each species. However, differences in diet composition between species were evident according to multivariate analysis. Our results suggest some level of diet partitioning between C. flamarioni and C. minutus in the sympatric region. While the first species is more specialized on few plant items, the second showed a more varied and heterogeneous diet pattern among individuals. These differences might have been developed to avoid competition in the region of co-occurrence. Resource availability in the environment also seems to influence food choices. Our data indicate that C. minutus and C. flamarioni are generalist species, but that some preference for Poaceae, Asteraceae and Araliaceae families can be suggested for both rodents.

[F0 characteristics in Parkinsonian speech: Contrast between the effect of hypodopaminergy due to Parkinson's disease and that of the therapeutic delivery of L-Dopa]

Voice and speech impairments are frequent in Parkinson's disease, particularly when the disease is at an advanced stage. These impairments affect spoken communication and may become a serious disability for someone with Parkinson's disease. Many studies based on auditory-perceptual or acoustic methods have been carried out to characterize dysarthria. The heterogeneity of evaluation methods and experimental bias however make results difficult to understand. For instance, in terms of phonatory impairments and with regard to F0, results are contradictory: PD speech may be characterized by either higher F0 or lower F0 compared to control subjects, or there may be no difference at all between the two population. In this study, we aim to provide a conceptual and methodological framework which allows for interpreting the results obtained from 44 speakers (29 PD and 15 control subjects) in relation to physiological (gender, age, PD subjects' pharmacologic state) and linguistic (speech production tasks) constraints. For the present corpus, we did not observe any F0 mean difference between the two groups. Our results however reveal a significant increase in F0 mean in PD subjects under L-dopa. We assume a double and opposite effect on F0 mean during drug withdrawal: low sub-glottal pressure, due to PD, results in a decrease in F0, while laryngeal rigidity leads to an increase in F0. These two effects thus mutually annihilate. Under L-Dopa, however, the drug effect increases sub-glottal pressure, which combined with an increase in F0 due to rigidity, leads to a global increase in F0.

Characteristics of major Escherichia coli reductases involved in aerobic nitro and azo reduction

AIMS

Escherichia coli is able to reduce azo compounds such as methyl red (MR) and nitro compounds such as 7-nitrocoumarin-3-carboxylic acid (7NCCA). The aim of this study was to clarify the specificity of the major E. coli reductases.

METHODS AND RESULTS

Enzymatic assays with pure enzymes obtained after cloning, overproduction and purification under native or denaturing conditions were performed on three enzymes: AzoR, NfsA and NfsB. Their dependence on putative cofactors such as flavin mononucleotide (FMN), NADH and NADPH was studied as well as the reductase capacity of E. coli mutants depleted for one, two or three of the corresponding genes.

CONCLUSIONS

AzoR was able to reduce both MR and 7NCCA, whereas NfsA and NfsB could only reduce the nitro compound. AzoR and NfsB were strictly FMN dependent in contrast to NfsA. At a low oxygen concentration, the three proteins were not mandatory for azo reduction and nitro reduction, but in optimal aerobic conditions, azoR was essential for MR reduction, and an nfsA/nfsB combination was important for 7NCCA reduction. Overexpression of azoR gene was able to compensate for the loss of nfsA and nfsB under aerobic conditions.

SIGNIFICANCE AND IMPACT OF STUDY

These data provide new insights into the substrate specificity of major E. coli nitroreductases and demonstrate that oxygen is an important parameter to take into account in studies of nitroreductase activity.

Sarcoplasmic reticulum: a key factor in cardiac contractility of sea bass Dicentrarchus labrax and common sole Solea solea during thermal acclimations

This study investigated the effects of acclimation temperature upon (i) contractility of ventricular strips (ii) calcium movements in ventricular cardiomyocytes during excitation-contraction coupling (ECC), and (iii) the role of the sarcoplasmic reticulum (SR) in myocardial responses, in two marine teleosts, the sea bass (Dicentrarchus labrax) and the common sole (Solea solea). Because of the different sensitivities of their metabolism to temperature variation, both species were exposed to different thermal ranges. Sea bass were acclimated to 10, 15, 20, and 25 °C, and common sole to 6, 12, 18, and 24 °C, for 1 month. Isometric tension developed by ventricular strips was recorded over a range of physiological stimulation frequencies, whereas the depolarization-induced calcium transients were recorded on isolated ventricular cells through hyperpotassic solution application (at 100 mM). The SR contribution was assessed by ryanodine (RYAN) perfusion on ventricular strips and by caffeine application (at 10 mM) on isolated ventricular cells. Rates of contraction and relaxation of ventricular strip, in both species, increased with increasing acclimation temperature. At a low range of stimulation frequency, ventricular strips of common sole developed a positive force-frequency relationship at high acclimation temperature. In both the species, SR Ca(2+)-cycling was dependent on fish species, acclimation temperature and pacing frequency. The SR contribution was more important to force development at low acclimation temperatures in sea bass but at high acclimation temperatures in common sole. The results also revealed that high acclimation temperature causes an increase in the maximum calcium response amplitude on ventricular cells in both the species. Although sea bass and common sole occupy similar environments and tolerate similar environmental temperatures, this study indicated that sea bass and common sole can acclimatize to new thermal conditions, adjusting their cellular process in a different manner.

Influence of the amount of use on hand motor cortex representation: effects of immobilization and motor training

Converging evidence from animal and human studies has revealed that increased or decreased use of an extremity can lead to changes in cortical representation of the involved muscles. However, opposite experimental manipulations such as immobilization and motor training have sometimes been associated with similar cortical changes. Therefore, the behavioral relevance of these changes remains unclear. The purpose of this study was to observe the effect of the amount of use on hand muscle motor cortex representation by contrasting the effect of unspecific motor training and immobilization. Nine healthy volunteers were tested prior and after a 4-day exposure to two experimental conditions using a randomized cross-over design: a motor training condition (to play Guitar Hero 2h/day with the tested (nondominant) hand on the fret board) and an immobilization condition (to wear an immobilization splint 24h/day). Before and after each condition, motor cortex representation of the nondominant first dorsal interosseous (FDI) muscle was mapped using image-guided transcranial magnetic stimulation (TMS). At the behavioral level, results show that the training condition led to a 20% improvement in the trained task, while the immobilization condition resulted in a 36% decrease in the FDI maximal voluntary contraction. At the neurophysiological level, corticospinal excitability (e.g. Motor-evoked potential amplitude) was found to be decreased in response to immobilization, while no change was observed in response to motor training. No change was found for other TMS variables (motor thresholds or map location/volume/area) in either condition. In conclusion, our results indicate that a 4-day decrease, but not increase, in the amount of use of nondominant hand muscles is sufficient to induce a change in corticospinal excitability. The lack of a training effect might be explained by the use of an unspecific task (that is nevertheless representative of "real-life" training situations) and/or by insufficient duration/intensity to induce long-lasting changes.