Automaticity with Balance in Dual-Task Tests in Healthy Adolescents

BACKGROUND/CONTEXT: The hallmark of healthy postural control in adolescents is automaticity which is the ability of the nervous system to successfully coordinate posture with minimal use of attention-demanding executive control resources. Automaticity plays an important role in adolescents because it is necessary to perform motor skills, motor learning and reduce the risk of sport injury. Research has shown in dual-task (DT) paradigms that the ability to use postural control and cognitive skills of the brain uses both local and global functional connectivity in the Prefrontal Cortex, which controls a healthy adolescent\u27s ability to perform a dual-task test with adequate balance. PURPOSE: The purpose of our study is to examine if healthy adolescents show strong functional connectivity to compensate for the deficit in their postural control. Automaticity can be measured by presenting a healthy adolescent with a dual-task test, and observing if the brain activity is impacted in the Prefrontal Cortex (PFC), inferring a significant deficit in their postural control. The use of force plates are used to measure the sway area and the average velocity of the participants when they are given a single-task test and a dual-task test. Smaller sway area and average velocity presents a better performance in the local and global functional connectivity between regions of the brain. We hypothesized that there is no significant difference in terms of single or dual-task tests in their functional connectivity. METHODS: 15 healthy adolescents (12 male (80%), age: 16.33±0.94 years, height: 1.69±0.10 m, mass: 64.08±9.81 kg) were recruited. Activity of the left/right prefrontal cortex (dorsal lateral and dorsal medial regions) were monitored using fNIRS, sampling rate of 20.3 Hz. The AMTI force plate is used to measure the center of pressure (CoP), sampling rate of 2000 Hz. Participants performed two standing trials on force plates for 30 seconds in single task (ST) and dual task (DT: concurrent cognitive task subtracting by 7’s) conditions. There was a 10-second quiet standing before each trial to serve as the baseline for the fNIRS signals. Our dependent variable included the HbO2 level, local and global efficiency of the prefrontal cortex and the 95% sway area and average CoP velocity. Three two-way MANOVA with repeated measures were used to examine the task difference (alpha level = 0.05). OUTCOMES: There was no significant task effect on balance performance (F3,12 = 4.048, p = 0.033). Post pairwise tests indicated that single-task tests presented a smaller average CoP velocity in the anterior posterior (p = 0.037, ST vs DT: 6.78 ± 2.39 vs. 10.22 ± 5.80 cm/s) and medial lateral (p = 0.048, ST vs DT: 4.38 ± 1.44 vs. 6.31 ± 3.79 cm/s) directions than in dual-task test. There was no significant task effect on HbO2 level, local and global efficiency (p \u3e 0.05). IMPACT: There was no significant task effect on brain efficiency in balance performance. We observed a worse balance performance under dual-task tests compared to single-task tests while the functional connectivity remains the same. These results suggest that adolescents are still developing their automaticity in balance when compared to the healthy young adults who would have the same balance performance under the dual-task tests

Functional Connectivity in Gait Under Dual-Task Paradigm in Healthy Adolescents

PURPOSE: Functional connectivity can be viewed as the mechanism used to coordinate different neural networks in order to perform a complex task. Dual-task walking requires an individual to walk, while simultaneously performing a secondary task. The purpose of this study was to determine the level of functional connectivity and neuro-efficiency in adolescents under the dual-task walking. We hypothesized that we would see an increase in local and global efficiency within adolescents when transitioning from a single task gait test to a dual task gait test. METHODS: 15 healthy adolescents (12 male, age: 16.33±0.94 years, height: 1.69±0.10 m, mass: 64.08±9.81 kg) were recruited. The brain activity of the left and right prefrontal cortex (dorsal lateral, and dorsal media) were measured by fNIRS, the sampling rate of 20.3 Hz. Vicon motion capture system was used to record kinematic data, the sampling rate of 100 Hz. The first test was a single task gait test in which the subject walked at a self-selected speed between two cones 15 meters apart for 2 minutes with 10 seconds of standing as the baseline for fNIRS measures. Subjects were then tested under a dual-task paradigm (serially subtracting 7’s from randomly presented 2 or 3-digit numbers). The primary outcome measures include normalized local and global efficiency, gait speed, and stride length. Two two-way MANOVA with repeated measures were used to examine the task difference (alpha level = 0.05). RESULTS: There was a significant task effect on gait performance (F3,12 = 6.430, p = 0.008). Post hoc pairwise tests indicated that single-task presented greater average walking velocity (p \u3c 0.001, ST vs. DT: 1.33 ± 0.18 vs. 1.23 ± 0.20 m/s) and shorter stride time (p = 0.002, ST vs. DT: 1.11 ± 0.10 vs. 1.14 ± 0.12 s) than dual-task. There was no significant task effect on brain activity and neural efficiency (p \u3e 0.05). CONCLUSION: There was a significant difference in gait speed between adolescents and young adults. This is due to the task complexity affecting adolescents significantly more than adults. Young adults don’t see a change in speed but do see an increase in PFC activation. Adolescents having lower levels of functional connectivity compared to young adults could be due to the number/size of functionally connected regions measured within adolescence. Children are still developing day by day, indicating that the strength of functional connectivity seemingly develops as they age. With this information we can conclude that functional connectivity continuously changes while going through your adolescent years

An Element-wise RSAV Algorithm for Unconstrained Optimization Problems

We present a novel optimization algorithm, element-wise relaxed scalar auxiliary variable (E-RSAV), that satisfies an unconditional energy dissipation law and exhibits improved alignment between the modified and the original energy. Our algorithm features rigorous proofs of linear convergence in the convex setting. Furthermore, we present a simple accelerated algorithm that improves the linear convergence rate to super-linear in the univariate case. We also propose an adaptive version of E-RSAV with Steffensen step size. We validate the robustness and fast convergence of our algorithm through ample numerical experiments.Comment: 25 pages, 7 figure