Competition between movement plans increases motor variability: evidence of a shared resource for movement planning.

Do movement plans, like representations in working memory, share a limited pool of resources? If so, the precision with which each individual movement plan is specified should decrease as the total number of movement plans increases. To explore this, human participants made speeded reaching movements toward visual targets. We examined if preparing one movement resulted in less variability than preparing two movements. The number of planned movements was manipulated in a delayed response cueing procedure that limited planning to a single target (experiment 1) or hand (experiment 2) or required planning of movements toward two targets (or with two hands). For both experiments, initial movement direction variability was higher in the two-plan condition than in the one-plan condition, demonstrating a cost associated with planning multiple movements, consistent with the limited resource hypothesis. In experiment 3, we showed that the advantage in initial variability of preparing a single movement was present only when the trajectory could be fully specified. This indicates that the difference in variability between one and two plans reflects the specification of full motor plans, not a general preparedness to move. The precision cost related to concurrent plans represents a novel constraint on motor preparation, indicating that multiple movements cannot be planned independently, even if they involve different limbs.This research was supported by the Wellcome Trust and the Van Coeverden Adriani Stichting.This is the author accepted manuscript. The final version is available from the American Physiological Society via http://dx.doi.org/10.1152/jn.00113.201

Prosthesis Prescription Protocol of the Arm (PPP-Arm):The implementation of a national prosthesis prescription protocol

Background and aim: In order to create more uniformity in the prescription of upper limb prostheses by Dutch rehabilitation teams, the development and implementation of a Prosthesis Prescription Protocol of the upper limb (PPP-Arm) was initiated. The aim was to create a national digital protocol to structure, underpin, and evaluate the prescription of upper limb prostheses for clients with acquired or congenital arm defects. Technique: Prosthesis Prescription Protocol of the Arm (PPP-Arm) was developed on the basis of the International Classification of Functioning and consisted of several layers. All stakeholders (rehabilitation teams, orthopedic workshops, patients, and insurance companies) were involved in development and implementation. A national project coordinator and knowledge brokers in each team were essential for the project. Discussion: PPP-Arm was successfully developed and implemented in nine Dutch rehabilitation teams. The protocol improved team collaboration, structure, and completeness of prosthesis prescriptions and treatment uniformity and might be interesting for other countries as well

Family history information and common chronic disease prevention: Type 2 diabetes as an example

Timmermans, D.R.M. [Promotor]Henneman, L. [Copromotor

The existence of an insulin-stimulated glucose and non-essential but not essential amino acid substrate interaction in diabetic pigs

<p>Abstract</p> <p>Background</p> <p>The generation of energy from glucose is impaired in diabetes and can be compensated by other substrates like fatty acids (Randle cycle). Little information is available on amino acids (AA) as alternative energy-source in diabetes. To study the interaction between insulin-stimulated glucose and AA utilization in normal and diabetic subjects, intraportal hyperinsulinaemic euglycaemic euaminoacidaemic clamp studies were performed in normal (n = 8) and streptozotocin (120 mg/kg) induced diabetic (n = 7) pigs of ~40-45 kg.</p> <p>Results</p> <p>Diabetic vs normal pigs showed basal hyperglycaemia (19.0 ± 2.0 vs 4.7 ± 0.1 mmol/L, <it>P </it>< .001) and at the level of individual AA, basal concentrations of valine and histidine were increased (<it>P </it>< .05) whereas tyrosine, alanine, asparagine, glutamine, glutamate, glycine and serine were decreased (<it>P </it>< .05). During the clamp, diabetic vs normal pigs showed reduced insulin-stimulated glucose clearance (4.4 ± 1.6 vs 16.0 ± 3.0 mL/kg·min, <it>P </it>< .001) but increased AA clearance (166 ± 22 vs 110 ± 13 mL/kg· min, <it>P </it>< .05) at matched arterial euglycaemia (5-7 mmol/L) and euaminoacidaemia (2.8-3.5 mmol/L). The increase in AA clearance was mainly caused by an increase in non-essential AA clearance (93.6 ± 13.8 vs 46.6 ± 5.4 mL/kg·min, <it>P </it>< .01), in particular alanine (14.2 ± 2.4 vs 3.2 ± 0.4 mL/kg·min, <it>P </it>< .001)<b/>. Essential AA clearance was largely unchanged (72.9 ± 8.5 vs 63.3 ± 8.5 mL/kg· min), however clearances of threonine (<it>P </it>< .05) and tyrosine (<it>P </it>< .01) were increased in diabetic vs normal pigs (8.1 ± 1.3 vs 5.2 ± 0.5, and 14.3 ± 2.5 vs 6.4 ± 0.7 mL/kg· min, respectively).</p> <p>Conclusions</p> <p>The ratio of insulin-stimulated glucose versus AA clearance was decreased 5.4-fold in diabetic pigs, which was caused by a 3.6-fold decrease in glucose clearance and a 2.0-fold increase in non-essential AA clearance. In parallel with the Randle concept (glucose - fatty acid cycle), the present data suggest the existence of a glucose and non-essential AA substrate interaction in diabetic pigs whereby reduced insulin-stimulated glucose clearance seems to be partly compensated by an increase in non-essential AA clearance whereas essential AA are preferentially spared from an increase in clearance.</p

Cerebellar tDCS Dissociates the Timing of Perceptual Decisions from Perceptual Change in Speech

Neuroimaging studies suggest that the cerebellum might play a role in both speech perception and speech perceptual learning. However, it remains unclear what this role is: does the cerebellum directly contribute to the perceptual decision? Or does it contribute to the timing of perceptual decisions? To test this, we applied transcranial direct current stimulation (tDCS) to the right cerebellum during a speech perception task. Participants experienced a series of speech perceptual tests designed to measure and then manipulate their perception of a phonetic contrast. One group received cerebellar tDCS during speech perceptual learning and a different group received "sham" tDCS during the same task. Both groups showed similar learning-related changes in speech perception that transferred to a different phonetic contrast. For both trained and untrained speech perceptual decisions, cerebellar tDCS significantly increased the time it took participants to indicate their decisions with a keyboard press. The results suggest that cerebellar tDCS disrupted the timing of perceptual decisions, while leaving the eventual decision unaltered. In support of this conclusion, we use the drift diffusion model to decompose the data into processes that determine the outcome of perceptual decision-making and those that do not. The modeling suggests that cerebellar tDCS disrupted processes unrelated to decision-making. Taken together, the empirical data and modeling demonstrate that right cerebellar tDCS dissociates the timing of perceptual decisions from perceptual change. The results provide initial evidence in healthy humans that the cerebellum critically contributes to speech timing in the perceptual domain

Visuomotor transformation for interception: catching while fixating

Catching a ball involves a dynamic transformation of visual information about ball motion into motor commands for moving the hand to the right place at the right time. We previously formulated a neural model for this transformation to account for the consistent leftward movement biases observed in our catching experiments. According to the model, these biases arise within the representation of target motion as well as within the transformation from a gaze-centered to a body-centered movement command. Here, we examine the validity of the latter aspect of our model in a catching task involving gaze fixation. Gaze fixation should systematically influence biases in catching movements, because in the model movement commands are only generated in the direction perpendicular to the gaze direction. Twelve participants caught balls while gazing at a fixation point positioned either straight ahead or 14° to the right. Four participants were excluded because they could not adequately maintain fixation. We again observed a consistent leftward movement bias, but the catching movements were unaffected by fixation direction. This result refutes our proposal that the leftward bias partly arises within the visuomotor transformation, and suggests instead that the bias predominantly arises within the early representation of target motion, specifically through an imbalance in the represented radial and azimuthal target motion

Circulating interleukin-6 receptor in patients with sepsis syndrome

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