Trunk Angle Modulates Feedforward and Feedback Control during Single-Limb Squatting

Trunk positioning and unexpected perturbations are high-risk conditions at the time of anterior cruciate ligament injury. The influence of trunk positioning on motor control responses to perturbation during dynamic performance is not known. We tested the influence of trunk position on feedforward and feedback control during unexpected perturbations while performing a novel single-limb squatting task. We also assessed the degree that feedforward control was predictive of feedback responses. In the flexed trunk condition, there were increased quadriceps (p < 0.026) and gluteus medius long-latency reflexes (p < 0.001) and greater quadriceps-to-hamstrings co-contraction during feedforward (p = 0.017) and feedback (p = 0.007) time bins. Soleus long-latency reflexes increased more than 100% from feedforward muscle activity regardless of trunk condition. Feedforward muscle activity differentially predicted long-latency reflex responses depending on the muscle (R2: 0.47–0.97). These findings support the concept that trunk positioning influences motor control responses to perturbation and that feedback responses may be invariant to the feedforward control strategy.

Sensorimotor feedback loops are selectively sensitive to reward

While it is well established that motivational factors such as earning more money for performing well improve motor performance, how the motor system implements this improvement remains unclear. For instance, feedback-based control, which uses sensory feedback from the body to correct for errors in movement, improves with greater reward. But feedback control encompasses many feedback loops with diverse characteristics such as the brain regions involved and their response time. Which specific loops drive these performance improvements with reward is unknown, even though their diversity makes it unlikely that they are contributing uniformly. This lack of mechanistic insight leads to practical limitations in applications using reward, such as clinical rehabilitation, athletic coaching, and brain-inspired robotics. We systematically tested the effect of reward on the latency (how long for a corrective response to arise?) and gain (how large is the corrective response?) of eight distinct sensorimotor feedback loops in humans. Only the feedback responses known to rely on prefrontal associative cortices showed sensitivity to reward, while feedback responses that relied mainly on premotor and sensorimotor cortex did not show sensitivity to reward. Our results may have implications regarding feedback control performance in pathologies showing a cognitive decline, or on athletic coaching. For instance, coaching methodologies that rely on reinforcement or "reward shaping" may need to specifically target aspects of movement that rely on reward-sensitive feedback responses.

Exploring Supervisory Feedback Formulation on Academic Writing of Research Proposals and Postgraduates’ Responses to Feedback: A Case Study

Despite the emphasis on effective supervisory feedback formulation on postgraduates’ academic writing, our understanding of effective feedback forms may not be comprehensive without mentoring students’ responses to feedback. Therefore, the current case study explores feedback formulation on research proposal writing and two postgraduates’ responses to feedback in a Malaysian university. Data were collected from written feedback, students’ commenting responses to feedback, their text revisions, and follow-up interviews. The feedback is formulated as directive, referential, and expressive, and it addresses issues related to content, organization, linguistic accuracy, and appropriateness in research proposal writing. The two postgraduates engaged in cognitive (e.g., confusion), metacognitive (e.g., reading feedback), and affective (e.g., appreciating feedback) responses to feedback. They integrated most of the feedback in revising their writing and made additional text revisions. Although this study is primarily qualitative in nature, simple descriptive quantitative measures were applied to the data to determine the prevalence of feedback forms, responding and revision patterns. The study provides useful suggestions for supervisory feedback practices.

Emerging roles of calcium-sensing receptor in the local regulation of intestinal transport of ions and calcium

Whether the intestinal mucosal cells are capable of sensing calcium concentration in the lumen and pericellular interstitium remains enigmatic for decades. Most calcium-regulating organs, such as parathyroid gland, kidney and bone, are capable of using calcium-sensing receptor (CaSR) to detect plasma calcium and trigger appropriate feedback responses to maintain calcium homeostasis. Although both CaSR transcripts and proteins are abundantly expressed in the crypt and villous enterocytes of the small intestine as well as the surface epithelial cells of the large intestine, the studies of CaSR functions have been limited to amino acid sensing and regulation of epithelial fluid secretion. Interestingly, several lines of recent evidence have indicated that the enterocytes use CaSR to monitor luminal and extracellular calcium levels, thereby reducing the activity of transient receptor potential channel, subfamily V, member 6, and inducing paracrine and endocrine feedback responses to restrict calcium absorption. Recent investigations in zebra fish and rodents have also suggested the role of fibroblast growth factor (FGF)-23 as an endocrine and/or paracrine factor participating in the negative control of intestinal calcium transport. In this review article, besides the CaSR-modulated ion transport, we elaborate the possible roles of CaSR and FGF-23 as well as their crosstalk as parts of a negative feedback loop for counterbalancing the seemingly unopposed calciotropic effect of 1,25-dihydroxyvitamin D3 on the intestinal calcium absorption.

The Development of Auditing Standards at the PCAOB and Related Audit Practitioner Input

The Public Company Accounting Oversight Board (PCAOB; Board) maintains that constituent feedback plays an essential and dynamic role in its audit standard-setting process. We examine a major source of constituent feedback, responses to standard-setting questions, using a sample drawn from the original proposals of fourteen PCAOB auditing standards. We find that after receiving comment letter feedback to the standard-setting questions, the Board revises approximately half of its guidance tied to those questions before it finalizes auditing standards-a finding consistent with the Board's assertion that it carefully considers constituent perspectives as it develops new regulation. We also explore the related comment letters of eight professional auditing firms subject to the PCAOB's annual inspection program and discover varying levels of opposition to and support for the PCAOB's proposed authoritative guidance. We observe PCAOB revision to authoritative guidance highly contested by the firms in more than three-fourths of cases of standard-setting questions and PCAOB non-revision to guidance highly supported by the firms in more than ninety percent of cases.