Arm Choice Research Articles

Measuring Habitual Arm Use Post-stroke With a Bilateral Time-Constrained Reaching Task

Background: Spontaneous use of the more-affected arm is a meaningful indicator of stroke recovery. The Bilateral Arm Reaching Test (BART) was previously developed to quantify arm use by measuring arm choice to targets projected over a horizontal hemi-workspace. In order to improve clinical validity, we constrained the available movement time, thereby promoting more spontaneous decision making when selecting between the more-affected and less affected arm during the BART.Methods: Twenty-two individuals with mild to moderate hemiparesis were tested with the time-based BART in three time-constraint conditions: no-time constraint, medium, and fast conditions. Arm use was measured across three sessions with a 2-week interval in a spontaneous choice block, in which participants were instructed to use either the more-affected or the less-affected arm to reach targets. We tested the effect of time-constraint condition on the more-affected arm use, external validity of the BART with the Actual Amount of Use Test (AAUT), and test-retest reliability across the three test sessions.Results: The fast condition in the time-based BART showed reduced use of the more-affected arm compared to the no-time constraint condition P < 0.0001) and the medium condition P = 0.0006; Tukey post hoc analysis after mixed-effect linear regression). In addition, the fast condition showed strong correlation with the AAUT r = 0.829, P < 0.001), and excellent test-retest reliability (ICC = 0.960, P < 0.0001).Conclusion: The revised BART with a time-restricted fast condition provides an objective, accurate, and repeatable measure of spontaneous arm use in individuals with chronic stroke hemiparesis.

An Automated T-maze Based Apparatus and Protocol for Analyzing Delay- and Effort-based Decision Making in Free Moving Rodents.

Many neurological and psychiatric patients demonstrate difficulties and/or deficits in decision making. Rodent models are helpful to produce a deeper understanding of the neurobiological causes underlying the decision-making problems. A cost-benefit based T-maze task is used for measuring decision making in which rodents choose between a high reward arm (HRA) and a low reward arm (LRA). There are two paradigms of the T-maze decision-making task, one in which the cost is a time delay and the other in which it is physical effort. Both paradigms require a tedious and labor-intensive management of experimental animals, multiple doors, pellet reward, and arm choice recordings. In the current work, we invented an apparatus based on traditional T-maze with full automation for pellet delivery, door management and choice recordings. This automated setup can be used for the evaluation of both delay- and effort-based decision making in rodents. With the protocol described here, our lab investigated the decision-making phenotypes of multiple genetically modified mice. In the representative data, we showed that the mice with ablated medial habenular showed aversions of both delay and effort and tended to choose the immediate and effortless reward. This protocol helps to decrease the variability caused by experimenter intervention and to enhance experiment efficiency. In addition, chronic silicon probe or microelectrode recording, fiber-optic imaging and/or manipulation of neural activity can be easily applied during the decision-making task using the setup described here.

An Automated T-maze Based Apparatus and Protocol for Analyzing Delay- and Effort-based Decision Making in Free Moving Rodents

Many neurological and psychiatric patients demonstrate difficulties and/or deficits in decision making. Rodent models are helpful to produce a deeper understanding of the neurobiological causes underlying the decision-making problems. A cost-benefit based T-maze task is used for measuring decision making in which rodents choose between a high reward arm (HRA) and a low reward arm (LRA). There are two paradigms of the T-maze decision-making task, one in which the cost is a time delay and the other in which it is physical effort. Both paradigms require a tedious and labor-intensive management of experimental animals, multiple doors, pellet reward, and arm choice recordings. In the current work, we invented an apparatus based on traditional T-maze with full automation for pellet delivery, door management and choice recordings. This automated setup can be used for the evaluation of both delay- and effort-based decision making in rodents. With the protocol described here, our lab investigated the decision-making phenotypes of multiple genetically modified mice. In the representative data, we showed that the mice with ablated medial habenular showed aversions of both delay and effort and tended to choose the immediate and effortless reward. This protocol helps to decrease the variability caused by experimenter intervention and to enhance experiment efficiency. In addition, chronic silicon probe or microelectrode recording, fiber-optic imaging and/or manipulation of neural activity can be easily applied during the decision-making task using the setup described here.

Design and rationale of the effect of early nutritional therapy on frailty, functional outcomes and recovery of malnourished medical inpatients trial (EFFORT): a pragmatic, multicenter, randomized-controlled trial

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; Malnutrition is highly prevalent and strongly associated with clincial outcomes of medical inpatients. Still, the benefit of nutritional treatment to prevent adverse outcomes in medical inpatients at risk for malnutrition remains unproven. We describe the trial methods of the largest yet nutritional trial in medical inpatients including the rationale for key design decisions regarding the nutritional strategy, eligibility criteria, choice of control arm, and endpoints.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; The Effect of early nutritional therapy on Frailty, Functional Outcomes and Recovery of malnourished medical inpatients Trial (EFFORT) is an investigator-initiated, non-commercial, open-label RCT to compare the effects of an intensified nutritional therapy (intervention group) with a control group on medical outcomes. We include adult medical inpatients at risk of malnutrition based on a Nutritional Risk Screening 2002 (NRS) score of ≥3 points with an expected length of stay of ≥5 days. An individualized systematic nutritional assessment by study dieticians is done to define nutritional targets and to establish an implementation plan. Patients in the intervention group receive individualized early nutritional therapy based on a previously published consensus algorithm, while control group patients receive standard hospital nutrition. The study is powered to compare clinical outcomes (composite adverse outcome and mortality) in the 2 study arms as well as to address several mechanistical questions.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Conclusion:&lt;/strong&gt; EFFORT aims to close important gaps in the literature regarding the controversy about benefit and possible harm of nutritional therapy in medical inpatients at risk for malnutrition.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Trial Registration: &lt;/strong&gt;ClinicalTrials.gov NCT02517476; registered July 30, 2015.&lt;/p&gt;

Rethinking non-inferiority: a practical trial design for optimising treatment duration.

BackgroundTrials to identify the minimal effective treatment duration are needed in different therapeutic areas, including bacterial infections, tuberculosis and hepatitis C. However, standard non-inferiority designs have several limitations, including arbitrariness of non-inferiority margins, choice of research arms and very large sample sizes.MethodsWe recast the problem of finding an appropriate non-inferior treatment duration in terms of modelling the entire duration–response curve within a pre-specified range. We propose a multi-arm randomised trial design, allocating patients to different treatment durations. We use fractional polynomials and spline-based methods to flexibly model the duration–response curve. We call this a ‘Durations design’. We compare different methods in terms of a scaled version of the area between true and estimated prediction curves. We evaluate sensitivity to key design parameters, including sample size, number and position of arms.ResultsA total sample size of ~ 500 patients divided into a moderate number of equidistant arms (5–7) is sufficient to estimate the duration–response curve within a 5% error margin in 95% of the simulations. Fractional polynomials provide similar or better results than spline-based methods in most scenarios.ConclusionOur proposed practical randomised trial ‘Durations design’ shows promising performance in the estimation of the duration–response curve; subject to a pending careful investigation of its inferential properties, it provides a potential alternative to standard non-inferiority designs, avoiding many of their limitations, and yet being fairly robust to different possible duration–response curves. The trial outcome is the whole duration–response curve, which may be used by clinicians and policymakers to make informed decisions, facilitating a move away from a forced binary hypothesis testing paradigm.

Reference Arm for Blood Pressure Measurement in Stroke Survivors

Background: Averting recurrent stroke among stroke survivors requires a choice of the appropriate arm for blood pressure (BP) measurement, especially among high - risk survivors. Objectives: This study aimed at determining the appropriate arm for BP measurement in stroke survivors. Methods: This cross sectional study comprised of 100 volunteer and willing stroke survivors enrolled using the convenient sampling technique from 2 public hospitals in Maiduguri, Nigeria. Each participant’s BP was measured as stipulated by previous studies. Descriptive statistics were used to summarize the socio - demographics and clinical characteristics of the stroke survivors. Student’s t - test for independent samples was used to compare mean BP between unaffected and affected arms of the participants. Results: Mean age and age range of the participants in years were 53.8 + 17.7 and 20 to 90, respectively. Participants that had had a stroke within the previous 7 months accounted for 69.0% of cases. Spastic stroke constituted 71%. Sides of the body afflicted with stroke were equally distributed. A significant difference (p = 0.017) existed in blood pressure between unaffected and affected arms of stroke survivors. Conclusions: Health workers involved in the management of stroke patients were advised to take blood pressure measurement from both the affected and non-affected arms; the arm with the higher value should be taken as the reference arm.

Effect of Exposure to Lead Acetate on Neurobehavior and Learning in the Kitten

Objective: Elevated aggression and poor intelligence scores occur in children with BLLs (Blood Lead Levels) lower than 10 μg/dL while Pb-exposed cats show increased aggressive behavior with BLLs of 10 μg/dL. This increased aggression in cats may be associated with the development of hyper-spiny neurons observed in the motor cortex, hippocampus and cerebellum of kittens with BLLs<1.2 μg/dL. These results suggest that lead ingestion by kittens might result in learning and behavioral deficits similar to those observed in lead-burdened children. Methods: To test this, kittens were treated (20 mg/kg/day, lead acetate or distil water via esophageal intubation) from Postnatal Day (PND) 1 to 7. At 8 and 10 weeks of age, the kittens were tested in a reversal T-maze, an open-field, and a free-fall test. Results: 8 weeks old Pb-treated kittens showed a delay in learning as demonstrated by a significant higher number of Incorrect Arm Choices (IACs) in the T-maze that returned to control levels in 10 weeks old kittens. No differences occurred between the two groups at 8 and 10 weeks of age in the open-field or free-fall tests. Conclusion: The impairment in the reversal T-maze suggests a Pb-induced delay in learning, which compares favourably with current understanding of delayed learning in Pb-poisoned children.

Risk of cancer in patients with psoriasis on biological therapies: a systematic review.

Biological therapies are highly effective in psoriasis, but have profound effects on innate and adaptive immune pathways that may negatively impact on cancer immunosurveillance mechanisms. To investigate the risk of cancer in patients with psoriasis treated with biological therapy. We searched MEDLINE, Embase, and the Cochrane Library (up to August 2016) for randomized controlled trials, prospective cohort studies and systematic reviews that reported cancer incidence in people exposed to biological therapy for psoriasis compared with a control population. Eight prospective cohort studies met our inclusion criteria. All the evidence reviewed related to tumour necrosis factor inhibitors (TNFi) with the exception of one study on ustekinumab. An increased risk of nonmelanoma skin cancer (NMSC), particularly squamous cell carcinoma, was reported with TNFi compared with both a general United States population and a rheumatoid arthritis population treated with TNFi. No evidence for increased risk of cancers (reported as all cancers, lymphoma, melanoma, prostate, colorectal and breast cancer) other than NMSC was identified. There were important limitations to the studies identified including choice of comparator arms, inadequate adjustment for confounding factors and failure to account for latency periods of cancer. There remains a need for ongoing pharmacovigilance in relation to cancer risk and biological therapy; the NMSC signal requires further investigation to determine the risk specifically attributable to biological therapy using prospectively collected data with adjustment for known NMSC risk factors.

Design and rationale of the Procalcitonin Antibiotic Consensus Trial (ProACT), a multicenter randomized trial of procalcitonin antibiotic guidance in lower respiratory tract infection

BackgroundOveruse of antibiotics is a major public health problem, contributing to growing antibiotic resistance. Procalcitonin has been reported to be commonly elevated in bacterial, but not viral infection. Multiple European trials found procalcitonin-guided care reduced antibiotic use in lower respiratory tract infection, with no apparent harm. However, applicability to US practice is limited due to trial design features impractical in the US, between-country differences, and residual safety concerns.MethodsThe Procalcitonin Antibiotic Consensus Trial (ProACT) is a multicenter randomized trial to determine the impact of a procalcitonin antibiotic prescribing guideline, implemented with basic reproducible strategies, in US patients with lower respiratory tract infection.DiscussionWe describe the trial methods using the Consolidated Standards of Reporting Trials (CONSORT) framework, and the rationale for key design decisions, including choice of eligibility criteria, choice of control arm, and approach to guideline implementation.Trial registrationClinicalTrials.gov NCT02130986. Registered May 1, 2014.

INNOVATIVE CLINICAL TRIAL DESIGNS

Since the middle of the 20th century, randomised controlled trials have provided the strongest level of evidence to inform the treatment of all diseases. In particular, trials in the 1970s...

Rats in a levered T-maze task show evidence of time-place discriminations in two different measures.

It is difficult for rats to learn to go to an arm of a T-maze to receive food that is dependent on the time of day, unless the amount of food in each daily session is different. In the same task, rats show evidence of time-place discriminations if they are required to press levers in the arms of the T-maze, but learning is only evident when the first lever press is considered, and not the first arm visited. These data suggest that rats struggle to use time as a discriminative stimulus unless the rewards/events differ in some dimension, or unless the goal locations can be visited prior to making a response. If both of these conditions are met in the same task, it might be possible to compare time-place learning in two different measures that essentially indicate performance before and after entering the arms of the T-maze. In the present study, we investigated time-place learning in rats with a levered T-maze task in which the amounts of food varied depending on the time of day. The first arm choices and first lever presses both indicated that the rats had acquired time-place discriminations, and both of these measures became significantly different from chance during the same block. However, there were subtle differences between the two measures, which suggest that time-place discrimination is aided by visiting the goal locations.

How do you design randomised trials for smaller populations? A framework.

How should we approach trial design when we can get some, but not all, of the way to the numbers required for a randomised phase III trial?We present an ordered framework for designing randomised trials to address the problem when the ideal sample size is considered larger than the number of participants that can be recruited in a reasonable time frame. Staying with the frequentist approach that is well accepted and understood in large trials, we propose a framework that includes small alterations to the design parameters. These aim to increase the numbers achievable and also potentially reduce the sample size target. The first step should always be to attempt to extend collaborations, consider broadening eligibility criteria and increase the accrual time or follow-up time. The second set of ordered considerations are the choice of research arm, outcome measures, power and target effect. If the revised design is still not feasible, in the third step we propose moving from two- to one-sided significance tests, changing the type I error rate, using covariate information at the design stage, re-randomising patients and borrowing external information.We discuss the benefits of some of these possible changes and warn against others. We illustrate, with a worked example based on the Euramos-1 trial, the application of this framework in designing a trial that is feasible, while still providing a good evidence base to evaluate a research treatment.This framework would allow appropriate evaluation of treatments when large-scale phase III trials are not possible, but where the need for high-quality randomised data is as pressing as it is for common diseases.

Important issues in the justification of a control treatment in paediatric drug trials.

The value of comparative effectiveness trials in informing clinical and policy decisions depends heavily on the choice of control arm (comparator). Our objective is to identify challenges in comparator reasoning and to determine justification criteria for selecting a control arm in paediatric clinical trials. A literature search was completed to identify existing sources of guidance on comparator selection. Subsequently, we reviewed a randomly selected sample of comparators selected for paediatric investigation plans (PIPs) adopted by the Paediatric Committee of the European Medicines Agency in 2013. We gathered descriptive information and evaluated their review process to identify challenges and compromises between regulators and sponsors with regard to the selection of the comparator. A tool to help investigators justify the selection of active controls and placebo arms was developed using the existing literature and empirical data. Justifying comparator selection was a challenge in 28% of PIPs. The following challenging paediatric issues in the decision-making process were identified: use of off-label medications as comparators, ethical and safe use of placebo, duration of placebo use, an undefined optimal dosing strategy, lack of age-appropriate safety and efficacy data, and drug dosing not supported by extrapolation of safety/efficacy evidence from other populations. In order to generate trials that will inform clinical decision-making and support marketing authorisations, researchers must systemically and transparently justify their selection of the comparator arm for their study. This report highlights key areas for justification in the choice of comparator in paediatric clinical trials.

THE CONCERNS OF BLOOD PRESSURE MONITORING IN ARTERIAL HYPERTENSION OUTPATIENTS

Aim. To analyze correctness of office blood pressure (BP) measurement by physicians and home-based BP monitoring (HBPM) — by the patients, and to assess the efficacy of patients teaching for correct BP self-measurement and control. Material and methods. Totally, 46 physicians questioned (32 local internists and 14 general practitioners with experience 2-27 years) and 290 patients with arterial hypertension (AH). Results. It was revealed that the following parameters were not unified: choice of arm, size of a cuff, times BP measured, time interval for repeated measurement, recording of BP by patients and physicians. These parameters did not suffice totally the Russian guidelines on diagnostics and treatment of arterial hypertension. About a half of BP patients by themselves corrected antihypertension treatment and dealt with the “crises”. Conclusion. Education of patients for BP measurement rules must be performed in “AH schools” and in offices (prevention departments) under supervision of local internists and general practitioners. Such events, as regular update of sphygmomanometers and supply physicians by cuffs of various size, will help to achieve better BP measurement quality in office, as in screening.

Heterometallic CuII–DyIII Clusters of Different Nuclearities with Slow Magnetic Relaxation

The synthesis, structures, and magnetic properties of two heterometallic Cu(II)-Dy(III) clusters are reported. The first structural motif displays a pentanuclear Cu(II)4Dy(III) core, while the second one reveals a nonanuclear Cu(II)6Dy(III)3 core. We employed o-vanillin-based Schiff base ligands combining o-vanillin with 3-amino-1-propanol, H2vap, (2-[(3-hydroxy-propylimino)-methyl]-6-methoxy-phenol), and 2-aminoethanol, H2vae, (2-[(3-hydroxy-ethylimino)-methyl]-6-methoxy-phenol). The differing nuclearities of the two clusters stem from the choice of imino alcohol arm in the Schiff bases, H2vap and H2vae. This work is aimed at broadening the diversity of Cu(II)-Dy(III) clusters and to perceive the consequence of changing the length of the alcohol arm on the nuclearity of the cluster, providing valuable insight into promising future synthetic directions. The underlying topological entity of the pentanuclear Cu4Dy cluster is reported for the first time. The investigation of magnetic behaviors of 1 and 2 below 2 K reveals slow magnetic relaxation with a significant influence coming from the variation of the alcohol arm affecting the nature of magnetic interactions.

Dissociable contribution of nucleus accumbens and dorsolateral striatum to the acquisition of risk choice behavior in the rat

While a growing body of research has suggested that the mesocorticolimbic dopamine systems play a key role in decision making under risk, how the nucleus accumbens (NAC) is involved in the acquisition of risk choice behavior remains unclear. This study used a T-maze task to assess risk-based decision making in which the rat was required to assess the risk by choosing to enter either a small and certain reward arm or a large but uncertain reward arm of the maze. The latter option, when chosen, resulted in provision of 2, 4, or 8 sweeten pellets with a probability (p) of 0.5, 0.25, or 0.125, respectively. Thus the latter arm provided three different conditions of reward ratio, compared to the choice of former arm, which always provided 1 pellet with p=1. This risk choice task was then run with the expected value being equality between the binary choice options. The experimental rats first received an excitoneurotoxic lesion affecting either the NAC or the dorsolateral striatum (DLS) and this was followed by post-lesion behavioral examination. The sham lesion control rats acquired a stable risk choice with regard to each reward ratio over a 10-day test. The pattern of choice behavior appeared in risk-seeking when p=0.5 to obtain 2 pellets, and was risk-averse when larger reward resulted in lower p. The NAC lesion significantly disrupted the acquisition of the aforementioned risk choice behavior and apparently shifted the choice into a risk-averse style for all three reward ratios. No such effect was observed in the rats with DLS lesions. Neither the gross motor action nor the discrimination of different reward magnitudes was impaired by the lesions affecting either the NAC or DLS as assessed by an additional experiment. These findings suggest that firstly there is heterogeneity between NAC and DLS with respect to risk-based decision making, and that secondly the NAC is involved and critical to the acquisition of behavioral choice under risk, specially when the expected value of the reward under the two choice options is equal.

Spatial radial maze procedures and setups to dissociate local and distal relational spatial frameworks in humans

BackgroundRadial maze tasks have been used to assess optimal foraging and spatial abilities in rodents. The spatial performance was based on a capacity to rely on a configuration of local and distant cues. We adapted maze procedures assessing the relative weight of local cues and distant landmarks for arm choice in humans. New methodThe procedure allowed testing memory of places in four experimental setups: a fingertip texture-groove maze, a tactile screen maze, a virtual radial maze and a walking size maze. During training, the four reinforced positions remained fixed relative to local and distal cues. During subsequent conflict trials, these frameworks were made conflictive in the prediction of reward locations. ResultsThree experiments showed that the relative weight of local and distal relational cues is affected by different factors such as cues’ nature, visual access to the environment, real vs. virtual environment, and gender. A fourth experiment illustrated how a walking maze can be used with people suffering intellectual disability. Comparison with existing methodsIn our procedure, long-term (reference) and short-term (working) memory can be assessed. It is the first radial task adapted to human that enables dissociating local and distal cues, to provides an indication as to their relative salience. Our mazes are moveable and easily used in limited spaces. Tasks are performed with realistic and spontaneous though controlled exploratory movements. ConclusionOur tasks enabled highlighting the use of different strategies. In a clinical perspective, considering the use of compensatory strategies should orient towards adapted behavioural rehabilitation.

Mothers Understand And Can do it (MUAC): a comparison of mothers and community health workers determining mid-upper arm circumference in 103 children aged from 6months to 5years.

BackgroundMid-upper arm circumference (MUAC) was recently endorsed and recommended for screening for acute malnutrition in the community. The objective of this study was to determine whether a colour-banded MUAC strap would allow minimally trained mothers to screen their own children for malnutrition, without locating the mid-point of the left upper arm by measurement, as currently recommended.MethodsA non-randomised non-blinded evaluation of mothers’ performance when measuring MUAC after minimal training, compared with trained Community Health Workers (CHW) following current MUAC protocols. The study was conducted in 2 villages in Mirriah, Zinder region, Niger where mothers classified one of their children (n = 103) aged 6–59 months (the current age range for admission into community malnutrition programs) using the MUAC tape.ResultsMothers’ had a sensitivity and specificity for classification of their child’s nutritional status of > 90% and > 80% respectively for global acute malnutrition (GAM, defined by a MUAC < 125 mm) and > 73% and > 98% for severe acute malnutrition (SAM, defined by a MUAC < 115 mm). The few children misclassified as not having SAM, were classified as having moderate acute malnutrition (MAM). The choice of arm did not influence the classification results; weighted Kappa of 0.88 for mothers and 0.91 for CHW represent almost perfect agreement. Errors occurred at the class boundaries and no gross errors were made.ConclusionsAdvanced SAM is associated with severe complications, which often require hospital admission or cause death. Mothers (with MUAC tapes costing $0.06) can screen their children frequently allowing early diagnosis and treatment thereby becoming the focal point in scaling-up community management of acute malnutrition.Trial registrationThe trial is registered with clinicaltrials.gov (Trial number NCT01790815)

Learning about cognition risk with the radial-arm maze in the developmental neurotoxicology battery

Cognitive dysfunction has been found in epidemiological studies to be among the most sensitive impairments associated with developmental exposure to a variety of environmental contaminants from heavy metals to polyhalogenated hydrocarbons and pesticides. These chemicals have been also shown to impair cognitive function after developmental exposure in experimental animal models. The radial-arm maze (RAM) has proven to be a sensitive and reliable way to assess both learning and memory in a variety of species, most often in rats and mice. The RAM is a very adaptable test method that takes advantage of rodents' instinct to explore new places in the environment to forage. That is, rodents do not need to be trained to run through the maze; they will normally do this from the initial session of testing. Training with differential reinforcement for arm choices provides a more rigorous test of learning and memory. The RAM is quite adaptable for assessing various aspects of cognition. Although the RAM has been mostly used to assess spatial learning and memory, it can be configured to assess non-spatial memory as well. Both working and reference memory can be easily distinguished. The RAM can be run with both appetitive (food reinforced) and aversive (water escape) motivators. The RAM has been found to be sensitive to a wide variety of developmental toxicants including heavy metals such as mercury and pesticides such as chlorpyrifos. There is an extremely rich literature especially with rats showing the effects of many types of brain lesions and drug effects so that the participation of a wide variety of neural systems in RAM performance is known. These systems, notably the hippocampus and frontal cortex, and acetylcholine and glutamate neurotransmitter systems, are the same neural systems that have been shown in humans to be critical for learning and memory. This considerably aids the interpretation of neurobehavioral toxicity studies.

Effort, success, and nonuse determine arm choice.

How do humans choose one arm or the other to reach single targets in front of the body? Current theories of reward-driven decisionmaking predict that choice results from a comparison of "action values," which are the expected rewards for possible actions in a given state. In addition, current theories of motor control predict that in planning arm movements, humans minimize an expected motor cost that balances motor effort and endpoint accuracy. Here, we test the hypotheses that arm choice is determined by comparison of action values comprising expected effort and expected task success for each arm, as well as a handedness bias. Right-handed subjects, in either a large or small target condition, were first instructed to use each hand in turn to shoot through an array of targets and then to choose either hand to shoot through the same targets. Effort was estimated via inverse kinematics and dynamics. A mixed-effects logistic-regression analysis showed that, as predicted, both expected effort and expected success predicted choice, as did arm use in the preceding trial. Finally, individual parameter estimation showed that the handedness bias correlated with mean difference between right- and left-arm success, leading to overall lower use of the left arm. We discuss our results in light of arm nonuse in individuals' poststroke.