Motor adaptation via distributional learning.

Objective. Both artificial and biological controllers experience errors during learning that are probabilistically distributed. We develop a framework for modeling distributions of errors and relating deviations in these distributions to neural activity.Approach. The biological system we consider is a task where human subjects are required to learn to minimize the roll of an inverted T-shaped object with an unbalanced weight (i.e. one side of the object is heavier than the other side) during lift. We also collect BOLD activity during this process. For our experimental setup, we define the state of the system to be the maximum magnitude roll of the object after lift onset and give subjects the goal of achieving the zero state.Main Results. We derive a model for this problem from a variant of Temporal Difference Learning. We then combine this model with Distributional Reinforcement Learning (DRL), a framework that involves defining a value distribution by treating the reward as stochastic. This model transforms the goal of the controller from achieving a target state, to achieving a distribution over distances from the target state. We call it a Distributional Temporal Difference Model (DTDM). The DTDM allows us to model errors in unsuccessfully minimizing object roll using deviations in the value distribution when the center of mass of the unbalanced object is changed. We compute deviations in global neural activity and show that they vary continuously with deviations in the value distribution. Different aspects might contribute to this global shift or signal difference, including a difference in grasp and lift force at lift onset, as well as sensory feedback of error/roll after lift onset. We predict that there exists a coordinated, global response to errors that incorporates all of this information, which is encoding the DTDM objective and used on subsequent trials enabling success. We validate the utility of the DTDM as a model for biological adaptation by using it to engineer a robotic controller to solve a similar problem.Significance. We develop a novel theoretical framework and show that it can be used to model a non-trivial motor learning task. Because this theoretical framework is consistent with state-of-the-art reinforcement learning, we can also use it to program a robot to perform a similar task. These results suggest a way to model the multiple subsystems composing global neural activity in a way that transfers well to engineering artificial intelligence.

Operating Room Inefficiencies Attributable to Errors in Surgical Case Scheduling and Surgeon Procedure Heterogeneity.

This study examined effects of scheduling errors on operating room efficiency and surgeon procedure heterogeneity on the rate of incorrectly scheduled cases. Operative cases in an academic center over 11 months were categorized as correctly or incorrectly scheduled. Surgeon heterogeneity was the number of unique procedures performed. Delays were greater for misbooked first cases (median 9 minutes late (interquartile range [IQR] 2-24) vs 4 (IQR 0-13), P < .01). For subsequent cases, turnover time was longer if misbooked (47 minutes (IQR 33-69) vs 39 (IQR 28-55), P < .01). Overall, the difference between actual and scheduled length was greater for misbooked cases (26 minutes (IQR -15 to +79) vs 6 (IQR -17 to +38), P < .01). Highest heterogeneity surgeons had higher risk of incorrect scheduling compared with the lowest (odds ratio = 1.97, 95% confidence interval [1.34-2.98], P < .01). Scheduling errors led to delays in first starts, unexpectedly longer cases, and prolonged turnovers. Highest heterogeneity surgeons were at greatest risk for misbooking.

Chiari I malformation associated with atlanto-occipital assimilation presenting as orthopnea and cough syncope: a case report and review of literature.

Although it is not uncommon for patients with Chiari I malformations to present with respiratory complaints, cough syncope is a rare presenting symptom. We report an adult patient who harbored both a Chiari I malformation and atlanto-occipital assimilation who complained of cough syncope, orthopnea, and central sleep apnea. The patient underwent decompressive craniectomy of the posterior fossa and cervical level 2 laminectomy. However, due to a possible initial underappreciation of the profound narrowing of the foramen magnum as a result of these concomitant pathologies, the patient may have had continued impaired cerebrospinal fluid flow, leading to a symptomatic pseudomeningocele and requiring a more extensive decompression that included a cervical level 3 laminectomy as well as a temporary lumbar drain. On 2-year follow-up, he has remained asymptomatic.

Chiari I malformation associated with atlanto-occipital assimilation presenting as orthopnea and cough syncope.

Although it is not uncommon for patients with Chiari I malformations to present with respiratory complaints, cough syncope is a rare presenting symptom. We report an adult patient who had both a Chiari I malformation and atlanto-occipital assimilation, and complained of cough syncope, orthopnea, and central sleep apnea. The patient underwent decompressive craniectomy of the posterior fossa and a cervical level 2 laminectomy. However, due to an initial under-appreciation of the profound narrowing of the foramen magnum as a result of these concomitant pathologies, the patient had continued impaired cerebrospinal fluid flow, leading to a symptomatic pseudomeningocele and required a more extensive decompression that included a cervical level 3 laminectomy as well as a temporary lumbar drain. On 2 year follow-up, he remained asymptomatic.

Daily functioning and quality of life in children with sickle cell disease pain: relationship with family and neighborhood socioeconomic distress.

UNLABELLED: The aim of this study was to examine the relationship between individual/family and neighborhood socioeconomic distress, pain, and functional outcomes in children with sickle cell disease (SCD). We hypothesized that both individual economic distress as well as residence in neighborhoods of severe economic distress would predict children's level of pain-related functional disability and health-related quality of life (HRQOL). Participants (mean age, 12.14 years; 57% male, n = 56) were recruited from an outpatient hematology clinic at a Midwestern tertiary referral hospital. Questionnaires assessing pain, depression, functional disability, and HRQOL were completed by children and their caregivers. Individual socioeconomic data including parental education and family income were reported by caregivers. Neighborhood socioeconomic distress was identified using publicly available census tract data and was based on neighborhood poverty, female head of household, male unemployment, and high school dropout levels. Multivariate regression analyses revealed that individual/family socioeconomic distress was a significant predictor of children's functional disability and physical and psychosocial HRQOL. Neighborhood socioeconomic distress emerged as a significant independent predictor of physical HRQOL only, where living in a distressed neighborhood predicted diminished physical HRQOL. Findings suggest that individual socioeconomic status and neighborhood economic distress play similar but independent roles in predicting children's functional outcomes related to SCD pain. PERSPECTIVE: Little is known about the influence of either individual/family or neighborhood socioeconomic factors on pain and functioning in children with SCD. Our findings suggest that socioeconomic distress defined at both the individual level and at the neighborhood/community level are significant independent predictors of pain-related disability and HRQOL in children with SCD.