A goal-driven modular neural network predicts parietofrontal neural dynamics during grasping.

One of the primary ways we interact with the world is using our hands. In macaques, the circuit spanning the anterior intraparietal area, the hand area of the ventral premotor cortex, and the primary motor cortex is necessary for transforming visual information into grasping movements. However, no comprehensive model exists that links all steps of processing from vision to action. We hypothesized that a recurrent neural network mimicking the modular structure of the anatomical circuit and trained to use visual features of objects to generate the required muscle dynamics used by primates to grasp objects would give insight into the computations of the grasping circuit. Internal activity of modular networks trained with these constraints strongly resembled neural activity recorded from the grasping circuit during grasping and paralleled the similarities between brain regions. Network activity during the different phases of the task could be explained by linear dynamics for maintaining a distributed movement plan across the network in the absence of visual stimulus and then generating the required muscle kinematics based on these initial conditions in a module-specific way. These modular models also outperformed alternative models at explaining neural data, despite the absence of neural data during training, suggesting that the inputs, outputs, and architectural constraints imposed were sufficient for recapitulating processing in the grasping circuit. Finally, targeted lesioning of modules produced deficits similar to those observed in lesion studies of the grasping circuit, providing a potential model for how brain regions may coordinate during the visually guided grasping of objects.

Neural Dynamics of Variable Grasp-Movement Preparation in the Macaque Frontoparietal Network.

Our voluntary grasping actions lie on a continuum between immediate action and waiting for the right moment, depending on the context. Therefore, studying grasping requires an investigation into how preparation time affects this process. Two macaque monkeys (Macaca mulatta; one male, one female) performed a grasping task with a short instruction followed by an immediate or delayed go cue (0-1300 ms) while we recorded in parallel from neurons in the grasp preparation relevant area F5 that is part of the ventral premotor cortex, and the anterior intraparietal area (AIP). Initial population dynamics followed a fixed trajectory in the neural state space unique to each grip type, reflecting unavoidable movement selection, then diverged depending on the delay, reaching unique states not achieved for immediately cued movements. Population activity in the AIP was less dynamic, whereas F5 activity continued to evolve throughout the delay. Interestingly, neuronal populations from both areas allowed for a readout tracking subjective anticipation of the go cue that predicted single-trial reaction time. However, the prediction of reaction time was better from F5 activity. Intriguingly, activity during movement initiation clustered into two trajectory groups, corresponding to movements that were either "as fast as possible" or withheld movements, demonstrating a widespread state shift in the frontoparietal grasping network when movements must be withheld. Our results reveal how dissociation between immediate and delay-specific preparatory activity, as well as differentiation between cortical areas, is possible through population-level analysis.SIGNIFICANCE STATEMENT Sometimes when we move, we consciously plan our movements. At other times, we move instantly, seemingly with no planning at all. Yet, it's unclear how preparation for movements along this spectrum of planned and seemingly unplanned movement differs in the brain. Two macaque monkeys made reach-to-grasp movements after varying amounts of preparation time while we recorded from the premotor and parietal cortex. We found that the initial response to a grasp instruction was specific to the required movement, but not to the preparation time, reflecting required movement selection. However, when more preparation time was given, neural activity achieved unique states that likely related to withholding movements and anticipation of movement, shedding light on the roles of the premotor and parietal cortex in grasp planning.

Analysis of clinical benefit, harms, and cost-effectiveness of screening women for abdominal aortic aneurysm.

BACKGROUND: A third of deaths in the UK from ruptured abdominal aortic aneurysm (AAA) are in women. In men, national screening programmes reduce deaths from AAA and are cost-effective. The benefits, harms, and cost-effectiveness in offering a similar programme to women have not been formally assessed, and this was the aim of this study. METHODS: We developed a decision model to assess predefined outcomes of death caused by AAA, life years, quality-adjusted life years, costs, and the incremental cost-effectiveness ratio for a population of women invited to AAA screening versus a population who were not invited to screening. A discrete event simulation model was set up for AAA screening, surveillance, and intervention. Relevant women-specific parameters were obtained from sources including systematic literature reviews, national registry or administrative databases, major AAA surgery trials, and UK National Health Service reference costs. FINDINGS: AAA screening for women, as currently offered to UK men (at age 65 years, with an AAA diagnosis at an aortic diameter of ≥3·0 cm, and elective repair considered at ≥5·5cm) gave, over 30 years, an estimated incremental cost-effectiveness ratio of £30 000 (95% CI 12 000-87 000) per quality-adjusted life year gained, with 3900 invitations to screening required to prevent one AAA-related death and an overdiagnosis rate of 33%. A modified option for women (screening at age 70 years, diagnosis at 2·5 cm and repair at 5·0 cm) was estimated to have an incremental cost-effectiveness ratio of £23 000 (9500-71 000) per quality-adjusted life year and 1800 invitations to screening required to prevent one AAA-death, but an overdiagnosis rate of 55%. There was considerable uncertainty in the cost-effectiveness ratio, largely driven by uncertainty about AAA prevalence, the distribution of aortic sizes for women at different ages, and the effect of screening on quality of life. INTERPRETATION: By UK standards, an AAA screening programme for women, designed to be similar to that used to screen men, is unlikely to be cost-effective. Further research on the aortic diameter distribution in women and potential quality of life decrements associated with screening are needed to assess the full benefits and harms of modified options. FUNDING: UK National Institute for Health Research Health Technology Assessment programme.

Experiences of living with varicose veins: A systematic review of qualitative research.

AIM: To identify the symptoms and quality of life impacts that are important from the perspective of patients with varicose veins and to compare identified themes to items in varicose vein patient-reported outcome measures (PROMs). BACKGROUND: Varicose veins are common worldwide and are considered a chronic condition with implications for quality of life. Treatment is predominantly conservative; therefore, understanding patients' experiences of living with varicose veins is important to inform the provision of clinical care. PROMs are often used to collect data about patients' quality of life. DESIGN: Thematic synthesis of qualitative research reported according to ENTREQ guidelines. METHODS: Multiple electronic databases, including MEDLINE and CINAHL, were systematically searched to identify qualitative research examining experiences of adults with varicose veins. Thematic synthesis was then conducted on the included studies. RESULTS: Three studies met the inclusion criteria; the quality of the studies was high. The range and intensity of reported symptoms and participant's experiences of living with varicose veins were varied. Five overarching themes were identified: physical, psychological and social impact of varicose veins, adapting to varicose veins and reasons for seeking treatment. The overall key theme to emerge was adaptation, with patients demonstrating how they adapted to the various impacts. CONCLUSION: This review demonstrates that varicose veins have a wide range of symptoms and may have a significant impact on quality of life; people made significant adaptations to enable them to live their lives as fully as possible. RELEVANCE TO CLINICAL PRACTICE: Healthcare professionals need to be aware of the range of symptoms and their impact on quality of life. The use of PROMs to gather information about quality of life and symptoms is well established globally; however, PROMs currently used may not capture the full extent of the impact on patient's quality of life.

Effects of supervised exercise training on lower-limb cutaneous microvascular reactivity in adults with venous ulcers.

PURPOSE: To investigate the effects of a 12-week supervised exercise programme on lower-limb cutaneous microvascular reactivity in adults with venous leg ulceration. METHODS: Thirty-eight adults with unilateral venous ulceration who were being treated with lower-limb compression therapy (58% male; mean age 65 years; median ulcer size 5 cm2) were randomly allocated to exercise or control groups. Exercise participants (n = 18) were invited to attend thrice weekly sessions of lower-limb aerobic and resistance exercise for 12 weeks. Cutaneous microvascular reactivity was assessed in the gaiter region of ulcerated and non-ulcerated legs at baseline and 3 months using laser Doppler fluxmetry coupled with iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP). Cutaneous vascular conductance (CVC) was calculated as laser Doppler flux (AU)/mean arterial pressure (mmHg). RESULTS: Thirty-seven participants completed follow-up assessments. Median session attendance was 36 (range 2-36). Analyses of covariance revealed greater peak CVC responses to ACh in the exercise group at 3 months in both the ulcerated (adjusted difference = 0.944 AU/mmHg; 95% CI 0.504-1.384) and non-ulcerated (adjusted difference = 0.596 AU/mmHg; 95% CI 0.028-1.164) legs. Peak CVC responses to SNP were also greater in the exercise group at 3 months in the ulcerated leg (adjusted difference = 0.882 AU/mmHg; 95% CI 0.274-1.491), but not the non-ulcerated leg (adjusted difference = 0.392 AU/mmHg; 95% CI - 0.377 to 1.161). CONCLUSION: Supervised exercise training improves lower-limb cutaneous microvascular reactivity in adults with venous leg ulceration.

Exercise fidelity and progression in a supervised exercise programme for adults with venous leg ulcers.

Despite exercise being included in the recommended advice for patients with venous leg ulcers, there is a fear shared by clinicians and patients that exercise may be either inappropriate or harmful and actually delay rather than promote healing. Therefore, before implementing a larger-scale study exploring the effects of a supervised exercise programme in patients with venous ulcers being treated with compression therapy, it is important to assess exercise safety as well as fidelity and progression in a feasibility study. Eighteen participants randomised in the exercise group were asked to undertake 36 (3 times/week for 12 weeks) 60-min exercise sessions, each comprising moderate-intensity aerobic, resistance, and flexibility exercise components. For the purposes of this paper, we analysed the data collected during the exercise sessions. The overall session attendance rate was 79%, with 13 of 18 participants completing all sessions. No in-session adverse events were reported; 100% aerobic components and 91% of resistance components were completed within the desired moderate-intensity target. Similarly, 81% of aerobic components and 93% of flexibility components were completed within the prescribed duration targets. Our data showed that patients with venous ulcers could safely follow a supervised exercise programme incorporating moderate-intensity aerobic, resistance, and flexibility components.

Neural Population Dynamics during Reaching Are Better Explained by a Dynamical System than Representational Tuning.

Recent models of movement generation in motor cortex have sought to explain neural activity not as a function of movement parameters, known as representational models, but as a dynamical system acting at the level of the population. Despite evidence supporting this framework, the evaluation of representational models and their integration with dynamical systems is incomplete in the literature. Using a representational velocity-tuning based simulation of center-out reaching, we show that incorporating variable latency offsets between neural activity and kinematics is sufficient to generate rotational dynamics at the level of neural populations, a phenomenon observed in motor cortex. However, we developed a covariance-matched permutation test (CMPT) that reassigns neural data between task conditions independently for each neuron while maintaining overall neuron-to-neuron relationships, revealing that rotations based on the representational model did not uniquely depend on the underlying condition structure. In contrast, rotations based on either a dynamical model or motor cortex data depend on this relationship, providing evidence that the dynamical model more readily explains motor cortex activity. Importantly, implementing a recurrent neural network we demonstrate that both representational tuning properties and rotational dynamics emerge, providing evidence that a dynamical system can reproduce previous findings of representational tuning. Finally, using motor cortex data in combination with the CMPT, we show that results based on small numbers of neurons or conditions should be interpreted cautiously, potentially informing future experimental design. Together, our findings reinforce the view that representational models lack the explanatory power to describe complex aspects of single neuron and population level activity.

Predicting Reaction Time from the Neural State Space of the Premotor and Parietal Grasping Network.

Neural networks of the brain involved in the planning and execution of grasping movements are not fully understood. The network formed by macaque anterior intraparietal area (AIP) and hand area (F5) of the ventral premotor cortex is implicated strongly in the generation of grasping movements. However, the differential role of each area in this frontoparietal network is unclear. We recorded spiking activity from many electrodes in parallel in AIP and F5 while three macaque monkeys (Macaca mulatta) performed a delayed grasping task. By analyzing neural population activity during action preparation, we found that state space analysis of simultaneously recorded units is significantly more predictive of subsequent reaction times (RTs) than traditional methods. Furthermore, because we observed a wide variety of individual unit characteristics, we developed the sign-corrected average rate (SCAR) method of neural population averaging. The SCAR method was able to explain at least as much variance in RT overall as state space methods. Overall, F5 activity predicted RT (18% variance explained) significantly better than AIP (6%). The SCAR methods provides a straightforward interpretation of population activity, although other state space methods could provide richer descriptions of population dynamics. Together, these results lend support to the differential role of the parietal and frontal cortices in preparation for grasping, suggesting that variability in preparatory activity in F5 has a more potent effect on trial-to-trial RT variability than AIP. SIGNIFICANCE STATEMENT: Grasping movements are planned before they are executed, but how is the preparatory activity in a population of neurons related to the subsequent reaction time (RT)? A population analysis of the activity of many neurons recorded in parallel in macaque premotor (F5) and parietal (AIP) cortices during a delayed grasping task revealed that preparatory activity in F5 could explain a threefold larger fraction of variability in trial-to-trial RT than AIP. These striking differences lend additional support to a differential role of the parietal and premotor cortices in grasp movement preparation, suggesting that F5 has a more direct influence on trial-to-trial variability and movement timing, whereas AIP might be more closely linked to overall movement intentions.

Pentoxifylline for intermittent claudication.

BACKGROUND: Intermittent claudication (IC) is a symptom of peripheral arterial disease (PAD) and is associated with high morbidity and mortality. Pentoxifylline, one of many drugs used to treat IC, acts by decreasing blood viscosity, improving erythrocyte flexibility and promoting microcirculatory flow and tissue oxygen concentration. Many studies have evaluated the efficacy of pentoxifylline in treating individuals with PAD, but results of these studies are variable. This is an update of a review first published in 2012. OBJECTIVES: To determine the efficacy of pentoxifylline in improving the walking capacity (i.e. pain-free walking distance and total (absolute, maximum) walking distance) of individuals with stable intermittent claudication, Fontaine stage II. SEARCH METHODS: For this update, the Cochrane Vascular Group Trials Search Co-ordinator searched the Specialised Register (last searched April 2015) and the Cochrane Register of Studies (2015, Issue 3). SELECTION CRITERIA: All double-blind, randomised controlled trials (RCTs) comparing pentoxifylline versus placebo or any other pharmacological intervention in patients with IC Fontaine stage II. DATA COLLECTION AND ANALYSIS: Two review authors separately assessed included studies,. matched data and resolved disagreements by discussion. Review authors assessed the methodological quality of studies by using the Cochrane 'Risk of bias' tool and collected results related to pain-free walking distance (PFWD) and total walking distance (TWD). Comparison of studies was based on duration and dose of pentoxifylline. MAIN RESULTS: We included in this review 24 studies with 3377 participants. Seventeen studies compared pentoxifylline versus placebo. In the seven remaining studies, pentoxifylline was compared with flunarizine (one study), aspirin (one study), Gingko biloba extract (one study), nylidrin hydrochloride (one study), prostaglandin E1 (two studies) and buflomedil and nifedipine (one study). The quality of the evidence was generally low, with large variability in reported findings.. Most included studies did not report on random sequence generation and allocation concealment, did not provide adequate information to allow selective reporting to be judged and did not report blinding of assessors. Heterogeneity between included studies was considerable with regards to multiple variables, including duration of treatment, dose of pentoxifylline, baseline walking distance and participant characteristics; therefore, pooled analysis was not possible.Of 17 studies comparing pentoxifylline with placebo, 14 reported TWD and 11 reported PFWD; the difference in percentage improvement in TWD for pentoxifylline over placebo ranged from 1.2% to 155.9%, and in PFWD from -33.8% to 73.9%. Testing the statistical significance of these results generally was not possible because data were insufficient. Most included studies suggested improvement in PFWD and TWD for pentoxifylline over placebo and other treatments, but the statistical and clinical significance of findings from individual trials is unclear. Pentoxifylline generally was well tolerated; the most commonly reported side effects consisted of gastrointestinal symptoms such as nausea. AUTHORS' CONCLUSIONS: Given the generally poor quality of published studies and the large degree of heterogeneity evident in interventions and in results, the overall benefit of pentoxifylline for patients with Fontaine class II intermittent claudication remains uncertain. Pentoxifylline was shown to be generally well tolerated.Based on total available evidence, high-quality data are currently insufficient to reveal the benefits of pentoxifylline for intermittent claudication.

Endovascular repair of abdominal aortic aneurysm.

BACKGROUND: An abnormal dilatation of the abdominal aorta is referred to as an abdominal aortic aneurysm (AAA). Due to the risk of rupture, surgical repair is offered electively to individuals with aneurysms greater than 5.5 cm in size. Traditionally, conventional open surgical repair (OSR) was considered the first choice approach. However, over the past two decades endovascular aneurysm repair (EVAR) has gained popularity as a treatment option. This article intends to review the role of EVAR in the management of elective AAA. OBJECTIVES: To assess the effectiveness of EVAR versus conventional OSR in individuals with AAA considered fit for surgery, and EVAR versus best medical care in those considered unfit for surgery. This was determined by the effect on short, intermediate and long-term mortality, endograft related complications, re-intervention rates and major complications. SEARCH METHODS: The Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator (TSC) searched the Specialised Register (January 2013) and the Cochrane Central Register of Controlled Trials (CENTRAL) (2012, Issue 12). The TSC also searched trial databases for details of ongoing or unpublished studies. SELECTION CRITERIA: Prospective randomised controlled trials (RCTs) comparing EVAR with OSR in individuals with AAA considered fit for surgery. and comparing EVAR with best medical care in individuals considered unfit for surgery. We excluded studies with inadequate data or using an inadequate randomisation technique. DATA COLLECTION AND ANALYSIS: Three reviewers independently evaluated trials for appropriateness for inclusion and extracted data using pro forma designed by the Cochrane PVD Group. We assessed the quality of trials using The Cochrane Collaboration's 'Risk of bias' tool. We entered collected data in to Review Manager (version 5.2.3) for analysis. Where direct comparisons could be made, we determined odds ratios (OR). We tested studies for heterogeneity and, when present, we used a random-effects model; otherwise we used a fixed-effect model. We tabulated data that could not be collated. MAIN RESULTS: Four high-quality trials comparing EVAR with OSR (n = 2790) and one high-quality trial comparing EVAR with no intervention (n = 404) fulfilled the inclusion criteria. In individuals considered fit for surgery, a pooled analysis, including 1362 individuals randomised to EVAR and 1361 randomised to OSR, found short-term mortality (including 30-day or inhospital mortality, excluding deaths prior to intervention) with EVAR to be significantly lower than with OSR (1.4% versus 4.2%, OR 0.33, 95% confidence interval (CI) 0.20 to 0.55; P < 0.0001). Using intention-to-treat analysis (ITT) there was no significant difference in mortality at intermediate follow-up (up to four years from randomisation), with 221 (15.8%) and 237 (17%) deaths in the EVAR (n = 1393) and OSR (n = 1390) groups, respectively (OR 0.92, 95% CI 0.75 to 1.12; P = 0.40). There was also no significant difference in long-term mortality (beyond four years), with 464 (37.3%) deaths in the EVAR and 470 (37.8%) deaths in the OSR group (OR 0.98, 95% CI 0.83 to 1.15; P = 0.78). Similarly, there was no significant difference in aneurysm-related mortality between groups, either at the intermediate- or long-term follow up.Studies showed that both EVAR and OSR were associated with similar incidences of cardiac deaths (OR 1.14, 95% CI 0.86 to 1.52; P = 0.36) and fatal stroke rate (OR 0.81, 95% CI 0.42 to 1.55; P = 0.52). The long-term reintervention rate was significantly higher in the EVAR group than in the OSR group (OR 1.98, 95% CI 1.12 to 3.51; P = 0.02; I(2) = 85%). Results of the reintervention analysis should be interpreted with caution due to significant heterogeneity. Operative complications, health-related quality of life and sexual dysfunction were generally comparable between the EVAR and OSR groups. However, there was a slightly higher incidence of pulmonary complications in the OSR group compared with the EVAR group (OR 0.36, 95% CI 0.17 to 0.75; P = 0.006).In individuals considered unfit for conventional OSR, the one included trial found no difference between the EVAR and no-intervention groups with regard to all-cause mortality at final follow up, with 21.0 deaths per 100 person-years in the EVAR group and 22.1 deaths per 100 person years in the no-intervention group (adjusted hazard ratio (HR) with EVAR 0.99, 95% CI 0.78 to 1.27; P = 0.97). Aneurysm-related deaths were, however, significantly higher in the no-intervention group than in the EVAR group (adjusted HR 0.53, 95% CI 0.32 to 0.89; P = 0.02). There was no difference in myocardial events (HR 1.07, 95% CI 0.60 to 1.91) between the groups in this study. AUTHORS' CONCLUSIONS: In individuals considered fit for conventional surgery, EVAR was associated with lower short-term mortality than OSR. However, this benefit from EVAR did not persist at the intermediate- and long-term follow ups. Individuals undergoing EVAR had a higher reintervention rate than those undergoing OSR. Most of the reinterventions undertaken following EVAR, however, were catheter-based interventions associated with low mortality. Operative complications, health-related quality of life and sexual dysfunction were generally comparable between EVAR and OSR. However, there was a slightly higher incidence of pulmonary complications in the OSR group than in the EVAR group.In individuals considered unfit for open surgery, the results of a single trial found no overall short- or long-term benefits of EVAR over no intervention with regard to all-cause mortality, but individuals may differ and individual preferences should always be taken into account.

Surgery for varicose veins: use of tourniquet.

BACKGROUND: Varicose vein surgery is a common surgical procedure but there is no consensus regarding the best surgical technique. The use of tourniquets during varicose vein surgery has been advocated as a means of reducing the potential for blood loss during the operation. OBJECTIVES: To identify whether the use of a tourniquet should be recommended when undertaking surgery for the management of primary varicose veins. SEARCH METHODS: For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched April 2013) and the CENTRAL (2013, Issue 3). SELECTION CRITERIA: All studies described as randomised controlled trials that examined the use of tourniquets during surgery for patients with primary varicose veins were included. DATA COLLECTION AND ANALYSIS: Data from eligible studies were extracted and summarised independently by two authors. All studies were cross-checked independently by the authors. MAIN RESULTS: No additional studies were included or excluded in the updated review. Twenty papers detailing 18 trials were considered. Only three trials were randomised controlled trials and were included in the review. The remaining fifteen studies were excluded for various reasons. All three included trials had a small sample size and reported the trial design, outcome measures and analysis poorly. There were also variations in the outcome measures used between the trials. In addition, there was no consistency on the reporting of mean and medians for blood loss during the operation. It was therefore not possible to pool the data to perform meta-analysis. However, the reported blood loss when using a tourniquet was between 0 and 16 ml compared to between 107 to 133 ml when not using a tourniquet (P < 0.01). AUTHORS' CONCLUSIONS: Although there were significant quality issues with the available evidence, the use of a tourniquet would appear to reduce blood loss during surgery. There were no reported differences between the use or non-use of a tourniquet in terms of complications and morbidity. However, the available trials were not of sufficient size to detect rarer complications such as nerve damage.

Conflicting perspectives during guidelines development are an important source of implementation failure.

In recent years many countries have created national bodies that provide evidence-based guidance and policy relating to the commissioning and provision of healthcare services. However, such guidance often fails to be consistently implemented. The differing perspectives from which guidance is developed is suggested as a significant contributor to these failures. A societal perspective is, necessarily, taken by policy makers, while patients and their healthcare professionals are primarily concerned with an individual perspective. This is particularly likely to impair implementation where national policy objectives, such as cost effectiveness, equity, or the promotion of innovation, are embodied in the guidance, while patients and healthcare professionals may consider it appropriate to over-ride these, based upon individual circumstances and preferences. This paper examines these conflicts with reference to guidance issued by the National Institute of Health and Care Excellence in England. Conflicts are identified between the objectives, values, and preferences of those who develop and those who implement such guidance, with consequent difficulties in providing helpful personalised recommendations. The implications of this for the development and implementation of guidance are discussed and recommendations are made regarding the ways in which such guidance is framed and disseminated.

Myomatrix arrays for high-definition muscle recording.

Neurons coordinate their activity to produce an astonishing variety of motor behaviors. Our present understanding of motor control has grown rapidly thanks to new methods for recording and analyzing populations of many individual neurons over time. In contrast, current methods for recording the nervous system's actual motor output - the activation of muscle fibers by motor neurons - typically cannot detect the individual electrical events produced by muscle fibers during natural behaviors and scale poorly across species and muscle groups. Here we present a novel class of electrode devices ("Myomatrix arrays") that record muscle activity at unprecedented resolution across muscles and behaviors. High-density, flexible electrode arrays allow for stable recordings from the muscle fibers activated by a single motor neuron, called a "motor unit", during natural behaviors in many species, including mice, rats, primates, songbirds, frogs, and insects. This technology therefore allows the nervous system's motor output to be monitored in unprecedented detail during complex behaviors across species and muscle morphologies. We anticipate that this technology will allow rapid advances in understanding the neural control of behavior and in identifying pathologies of the motor system.

Myomatrix arrays for high-definition muscle recording.

Neurons coordinate their activity to produce an astonishing variety of motor behaviors. Our present understanding of motor control has grown rapidly thanks to new methods for recording and analyzing populations of many individual neurons over time. In contrast, current methods for recording the nervous system's actual motor output - the activation of muscle fibers by motor neurons - typically cannot detect the individual electrical events produced by muscle fibers during natural behaviors and scale poorly across species and muscle groups. Here we present a novel class of electrode devices ('Myomatrix arrays') that record muscle activity at unprecedented resolution across muscles and behaviors. High-density, flexible electrode arrays allow for stable recordings from the muscle fibers activated by a single motor neuron, called a 'motor unit,' during natural behaviors in many species, including mice, rats, primates, songbirds, frogs, and insects. This technology therefore allows the nervous system's motor output to be monitored in unprecedented detail during complex behaviors across species and muscle morphologies. We anticipate that this technology will allow rapid advances in understanding the neural control of behavior and identifying pathologies of the motor system.

Pentoxifylline for intermittent claudication.

BACKGROUND: Intermittent claudication (IC) is a symptom of peripheral arterial occlusive disease (PAD). It is associated with high morbidity and mortality. Pentoxifylline is one of many drugs used to treat IC. Pentoxifylline decreases blood viscosity, improves erythrocyte flexibility, and increases microcirculatory flow and tissue oxygen concentration.Many studies have evaluated the efficacy of pentoxifylline in treating PAD but the results of these studies are very variable. OBJECTIVES: To determine the efficacy of pentoxifylline in improving the walking capacity (that is pain-free walking distance and the total (absolute, maximum) walking distance) of patients with stable intermittent claudication, Fontaine stage II. SEARCH METHODS: The Cochrane Peripheral Vascular Diseases Group searched their Specialised Register (last searched January 2011) and CENTRAL (2011, Issue 1). In addition, we searched MEDLINE (Week 2 January 2011) and EMBASE (2011 Week 03). ClinicalTrials.gov and Current Controlled Trials were searched for ongoing or unpublished trials. SELECTION CRITERIA: All double blind, randomised controlled trials (RCTs) comparing pentoxifylline to placebo or any other pharmacological intervention in patients with IC Fontaine stage II. DATA COLLECTION AND ANALYSIS: Included studies were assessed separately by two review authors. Data were matched and disagreements resolved by discussion. The quality of the studies was assessed using the Jadad score and the Cochrane risk of bias tool. Results relating to pain-free walking distance (PFWD) and total walking distance (TWD) were collected. Studies were compared based on the duration and dose of pentoxifylline. MAIN RESULTS: Twenty-three studies with 2816 participants were included in this review. There was considerable heterogeneity between the included studies with regards to multiple variables including duration of treatment, dose of pentoxifylline, baseline walking distance and patient characteristics, and therefore pooled analysis was not possible. The quality of the included studies was generally low. There was very large variability in the reported findings between the individual studies. In a total of 17 studies which compared pentoxifylline with placebo, of which 14 reported TWD and 11 reported PFWD, the difference in percentage improvement in TWD for pentoxifylline over placebo ranged from 1.2% to 155.9%, and for PFWD the difference ranged from -33.8% to 73.9%. Testing for statistical significance of these results was generally not possible due to the lack of data. There was no statistically significant difference in ankle brachial pressure index (ABI) between the pentoxifylline and placebo groups. Pentoxifylline was generally well tolerated. AUTHORS' CONCLUSIONS: Given the generally poor quality of the published studies and the large degree of heterogeneity in the interventions and the results, the overall benefit of pentoxifylline for patients with Fontaine class II intermittent claudication remains uncertain. Pentoxifylline is generally well tolerated.  Based on the totality of the available evidence, it is possible that pentoxifylline could have a place in the treatment of IC as a means of improving walking distance and as a complimentary treatment assuming all other essential measures such as lifestyle change, exercise and treatment for secondary prevention have been taken into account. However, the response to pentoxifylline should be assessed on an individual basis.

Varicose veins treatment in England: population-based study of time trends and disparities related to demographic, ethnic, socioeconomic, and geographical factors.

BACKGROUND: Varicose vein (VV) treatments have changed significantly in recent years leading to potential disparities in service provision. The aim of this study was to examine the trends in VV treatment in England and to identify disparities in the provision of day-case and inpatient treatments related to deprivation, ethnicity, and other demographic, and geographical factors. METHOD: A population-based study using linked hospital episode statistics for England categorized VV procedures and compared population rates and procedure characteristics by ethnicity, deprivation quintile, and geographical area. RESULTS: A total of 311 936 people had 389 592 VV procedures between 2006/07 and 2017/18, with a further 63 276 procedures between 2018/19 and 2020/21. Procedure rates have reduced in all but the oldest age groups, whereas endovenous procedures have risen to more than 60 per cent of the total in recent years. In younger age groups there was a 20-30 per cent reduction in procedure rates for the least-deprived compared with the most-deprived quintiles. Non-white ethnicity was associated with lower procedure rates. Large regional and local differences were identified in standardized rates of VV procedures. In the most recent 5-year interval, the North-East region had a three-fold higher rate than the South-East region with evidence of greater variation between commissioners in overall rates, the proportion of endovenous procedures, and policies regarding bilateral treatments. CONCLUSIONS: There are substantial geographical variations in the provision of treatment for VVs, which are not explained by demographic differences. These have persisted, despite the publication of guidelines from the National Institute for Health and Care Excellence, and many commissioners, and providers would seem to implement policies that are contrary to this guidance. Lower rates of procedures in less-deprived areas may reflect treatments carried out in private practice, which are not included in these data.

Rapid motor responses quickly integrate visuospatial task constraints.

We have recently shown that subjects can appropriately modulate their rapid motor responses (traditionally termed reflexes) to move their hand to a spatial target when the target is displayed ~2 s before a mechanical perturbation (Pruszynski et al. in J Neurophysiol 100:224-238, 2008). The goal of this study was to investigate how quickly visual information can be used to modulate rapid motor responses to an impending mechanical perturbation. Following a 2 s to 10 ms target preview delay (PD), a perturbation either displaced the subject's hand into or out of the previewed target. We also included a condition, where the target appeared after perturbation onset (target PD = +90 ms). In all cases, subjects were instructed to react as quickly as possible to the perturbation by reaching into the displayed target. Our results indicate that subjects began to incorporate visual information into their rapid motor responses with PDs as small as 70 ms. Interestingly, subjects reacted faster when the target was presented ~150 ms before the perturbation than when they had 2 s to prepare a response. Using receiver operative characteristic (ROC) analysis, we examined modulation of muscle activity as a function of preview delay in three predefined epochs. No modulation was found in the short-latency epoch (R1; 20-45 ms). In contrast, both the long-latency (45-105 ms) and voluntary (120-180 ms) epochs were modulated at essentially the same time, 140 ms from visual presentation of the target to the beginning of each respective epoch.

Effects of upper-limb exercise on lower-limb cutaneous microvascular function in post-surgical varicose-vein patients.

Regular walking exercise attenuates lower-limb cutaneous microvascular endothelial dysfunction in post-surgical varicose-vein patients. This study assessed the effects of upper-limb exercise training on lower-limb cutaneous microvascular function in this patient group. Six post-surgical (4-5 weeks) varicose-vein patients completed an 8-week arm-crank exercise training programme. Changes in cutaneous microvascular function of the lower leg were assessed using laser Doppler flowmetry and iontophoretic administration of endothelial-dependent and -independent agonists [acetylcholine (ACh) and sodium nitroprusside (SNP), respectively]. At 8 weeks, median lower-limb cutaneous vasodilator responsives to ACh and SNP remained unchanged relative to baseline (e.g. 6 mC: 37 (interquartile range 24-63) vs. 40 (20-71) PU and 35 (23-48) vs. 38 (21-64) PU, respectively for the supine position). Upper-limb exercise appears ineffective for improving lower-limb cutaneous microvascular function in post-surgical varicose-vein patients. Therefore, limb specificity appears an important factor in optimal exercise prescription for these patients.

A systematic review of health-related quality of life instruments used for people with venous ulcers: an assessment of their suitability and psychometric properties.

AIMS AND OBJECTIVES: To review the quality of life questionnaires used to measure the impact of venous ulceration and to evaluate their psychometric properties. BACKGROUND: Venous leg ulcers have a negative impact on quality of life. Health-related quality of life can be measured using structured questionnaires. Nurses are the primary care providers for patients with venous ulceration and are ideally placed to assess and develop these types of questionnaires. There may also be an opportunity to use such quality of life instruments to measure the impact of nursing interventions in other areas where nurses are the key care providers. DESIGN: Systematic review. METHOD: Studies were sought that used quality of life instruments to evaluate the impact of venous ulceration. Fourteen electronic bibliographical databases and 11 Internet-based health services research related resources were searched. In addition, grey literature was sought and the reference lists of relevant articles checked. Data were extracted regarding the type of instrument used, sample, number of items and domains and psychometric performance of the instrument. RESULTS: The initial search identified a total of 338 potential citations. After review, a total of 31 studies were included: 17 used generic and 14 used disease-specific instruments. Five different types of generic and seven disease-specific instruments were identified. There was significant heterogeneity between the studies in terms of study design, aetiology of ulceration and times of assessment. The disease-specific instruments showed limitations in relation to their applicability to venous ulcer patients because of flaws in design or validation. CONCLUSIONS: The literature on quality of life related to venous ulceration failed to sufficiently distinguish between those with different causes of leg ulceration. There appeared to be problems with the ability of current quality of life instruments to detect changes in quality of life related to ulcer healing. Relevance to clinical practice. There appears to be an opportunity for nurses to develop a health-related quality of life health-related quality of life instruments to evaluate their impact on patient outcomes. Such instruments could potentially allow nursing interventions to be assessed more effectively than the recently proposed nursing metrics.