The Impact of Oral Promethazine on Human Whole-Body Motion Perceptual Thresholds

The effect of inherent and incidental constraints on bimanual force control in simulated Martian gravity

The ability to coordinate actions between the limbs is important for many operationally relevant tasks associated with space exploration. A future milestone in space exploration is sending humans to Mars. Therefore, an experiment was designed to examine the influence of inherent and incidental constraints on the stability characteristics associated with the bimanual control of force in simulated Martian gravity. A head-up tilt (HUT)/head-down tilt (HDT) paradigm was used to simulate gravity on Mars (22.3° HUT). Right limb dominant participants (N = 11) were required to rhythmically coordinate patterns of isometric forces in 1:1 in-phase and 1:2 multifrequency patterns by exerting force with their right and left limbs. Lissajous displays were provided to guide task performance. Participants performed 14 twenty-second practice trials at 90° HUT (Earth). Following a 30-min rest period, participants performed 2 test trials for each coordination pattern in both Earth and Mars conditions. Performance during the test trials were compared. Results indicated very effective temporal performance of the goal coordination tasks in both gravity conditions. However, results indicated differences associated with the production of force between Earth and Mars. In general, participants produced less force in simulated Martian gravity than in the Earth condition. In addition, force production was more harmonic in Martian gravity than Earth gravity for both limbs, indicating that less force distortions (adjustments, hesitations, and/or perturbations) occurred in the Mars condition than in the Earth condition. The force coherence analysis indicated significantly higher coherence in the 1:1 task than in the 1:2 task for all force frequency bands, with the highest level of coherence in the 1-4 Hz frequency band for both gravity conditions. High coherence in the 1-4 Hz frequency band is associated with a common neural drive that activates the two arms simultaneously and is consistent with the requirements of the two tasks. The results also support the notion that neural crosstalk stabilizes the performance of the 1:1 in-phase task. In addition, significantly higher coherence in the 8-12 Hz frequency bands were observed for the Earth condition than the Mars condition. Force coherence in the 8-12 Hz bands is associated with the processing of sensorimotor information, suggesting that participants were better at integrating visual, proprioceptive, and/or tactile feedback in Earth than for the Mars condition. Overall, the results indicate less neural interference in Martian gravity; however, participants appear to be more effective at using the Lissajous displays to guide performance under Earth's gravity.

Intra-individual consistency of vestibular perceptual thresholds

Vestibular perceptual thresholds quantify sensory noise associated with reliable perception of small self-motions. Previous studies have identified substantial variation between even healthy individuals' thresholds. However, it remains unclear if or how an individual's vestibular threshold varies over repeated measures across various time scales (repeated measurements on the same day, across days, weeks, or months). Here, we assessed yaw rotation and roll tilt thresholds in four individuals and compared this intra-individual variability to inter-individual variability of thresholds measured across a large age-matched cohort each measured only once. For analysis, we performed simulations of threshold measurements where there was no underlying variability (or it was manipulated) to compare to that observed empirically. We found remarkable consistency in vestibular thresholds within individuals, for both yaw rotation and roll tilt; this contrasts with substantial inter-individual differences. Thus, we conclude that vestibular perceptual thresholds are an innate characteristic, which validates pooling measures across sessions and potentially serves as a stable clinical diagnostic and/or biomarker.

Your Vestibular Thresholds May Be Lower Than You Think: Cognitive Biases in Vestibular Psychophysics

PURPOSE

Recently, there has been a surge of interest in measuring vestibular perceptual thresholds, which quantify the smallest motion that a subject can reliably perceive, to study physiology and pathophysiology. These thresholds are sensitive to age, pathology, and postural performance. Threshold tasks require decisions to be made in the presence of uncertainty. Since humans often rely on past information when making decisions in the presence of uncertainty, we hypothesized that (a) perceptual responses are affected by their preceding trial; (b) perceptual responses tend to be biased opposite of the "preceding response" because of cognitive biases but are not biased by the "preceding stimulus"; and (c) when fits do not account for this cognitive bias, thresholds are overestimated. To our knowledge, these hypotheses are unaddressed in vestibular and direction-recognition tasks.

CONCLUSIONS

Results in normal subjects supported each hypothesis. Subjects tended to respond opposite of their preceding response (not the preceding stimulus), indicating a cognitive bias, and this caused an overestimation of thresholds. Using an enhanced model (MATLAB code provided) that considered these effects, average thresholds were lower (5.5% for yaw, 7.1% for interaural). Since the results indicate that the magnitude of cognitive bias varies across subjects, this enhanced model can reduce measurement variability and potentially improve the efficiency of data collection.

The Influence of Altered-Gravity on Bimanual Coordination: Retention and Transfer

Many of the activities associated with spaceflight require individuals to coordinate actions between the limbs (e.g., controlling a rover, landing a spacecraft). However, research investigating the influence of gravity on bimanual coordination has been limited. The current experiment was designed to determine an individual's ability to adapt to altered-gravity when performing a complex bimanual force coordination task, and to identify constraints that influence coordination dynamics in altered-gravity. A tilt table was used to simulate gravity on Earth [90° head-up tilt (HUT)] and microgravity [6° head-down tilt (HDT)]. Right limb dominant participants (N = 12) were required to produce 1:1 in-phase and 1:2 multi-frequency force patterns. Lissajous information was provided to guide performance. Participants performed 14, 20 s trials at 90° HUT (Earth). Following a 30-min rest period, participants performed, for each coordination pattern, two retention trials (Earth) followed by two transfer trials in simulated microgravity (6° HDT). Results indicated that participants were able to transfer their training performance during the Earth condition to the microgravity condition with no additional training. No differences between gravity conditions for measures associated with timing (interpeak interval ratio, phase angle slope ratio) were observed. However, despite the effective timing of the force pulses, there were differences in measures associated with force production (peak force, STD of peak force mean force). The results of this study suggest that Lissajous displays may help counteract manual control decrements observed during microgravity. Future work should continue to explore constraints that can facilitate or interfere with bimanual control performance in altered-gravity environments.

Vestibular Precision at the Level of Perception, Eye Movements, Posture, and Neurons

Precision and accuracy are two fundamental properties of any system, including the nervous system. Reduced precision (i.e., imprecision) results from the presence of neural noise at each level of sensory, motor, and perceptual processing. This review has three objectives: (1) to show the importance of studying vestibular precision, and specifically that studying accuracy without studying precision ignores fundamental aspects of the vestibular system; (2) to synthesize key hypotheses about precision in vestibular perception, the vestibulo-ocular reflex, posture, and neurons; and (3) to show that groups of studies that are thoughts to be distinct (e.g., perceptual thresholds, subjective visual vertical variability, neuronal variability) are actually "two sides of the same coin" - because the methods used allow results to be related to the standard deviation of a Gaussian distribution describing the underlying neural noise. Vestibular precision varies with age, stimulus amplitude, stimulus frequency, body orientation, motion direction, pathology, medication, and electrical/mechanical vestibular stimulation, but does not vary with sex. The brain optimizes precision during integration of vestibular cues with visual, auditory, and/or somatosensory cues. Since a common concern with precision metrics is time required for testing, we describe approaches to optimize data collection and provide evidence that fatigue and session effects are minimal. Finally, we summarize how precision is an individual trait that is correlated with clinical outcomes in patients as well as with performance in functional tasks like balance. These findings highlight the importance of studying vestibular precision and accuracy, and that knowledge gaps remain.

Research on basketball sports neural network model based on nonlinear classification

Intelligent video analysis has broad application prospects. How to automatically analyze and identify human behavior in video has attracted extensive attention from researchers at home and abroad. Moreover, researching effective video behavior recognition algorithms and designing efficient behavior recognition systems has important theoretical and practical value. This paper studies the nonlinear classification technique and applies the video behavior recognition algorithm to basketball recognition. Moreover, this paper studies the classical convolutional neural network model and several improvements. In addition, this paper explains the advantages of convolutional neural networks in feature extraction compared with traditional neural networks and analyzes the performance of the algorithm by designing actual experiments. The research results show that the algorithm can quickly identify multiple players on the field, and the method can effectively deal with occlusion and other issues with high accuracy and real-time.

Visual recognition and performance prediction of athletes based on target tracking EIA algorithm

In the past, the research of target tracking was often to track problems in a static background, and the tracking scenes were often stable, and the targets were special. However, target tracking is often a tracking problem in the face of realistic complex scenes, and the target and scene are more complex. Therefore, the target tracking algorithm still faces many challenges in practical applications, especially in sports visual feature recognition. Based on the needs of sports feature recognition, this study combines the EIA algorithm to construct a feature recognition model. Moreover, for the shortcomings of the compressed sensing tracking algorithm that cannot accurately and comprehensively describe the target shape through a single target feature, the multi-feature adaptive fusion method is used to visualize the target appearance model, thus improving the accuracy of target tracking. In addition, this study design experiments to analyze the performance of the algorithm model. The research results show that the algorithm model of this study has certain recognition effects.

Performance analysis of sports training based on random forest algorithm and infrared motion capture

Because sports video has a wide audience and huge market potential, research with the main goal of sports video content analysis has become a hot spot in the field of video analysis. Although after more than ten years of hard work, the current achievements are still far from the expectations of people. In this study, the sports video is taken as the analysis object, and for the shortcoming that when the VIRE positioning algorithm uses linear interpolation to calculate the virtual label, the error between the obtained RSSI value and the actual value is larger, this paper uses quadratic interpolation to improve it. Moreover, this study explores the threshold setting of the algorithm and proposes a threshold setting method, so that the adjacent map thresholds of each reader are not necessarily consistent, and the resulting adjacent label map is more accurate. In addition, this experiment uses the algorithm model designed in this study combined with the qualysis infrared capture system to capture the tennis serve. Finally, this study conducts model algorithm performance analysis through comparative analysis. The research results show that the algorithm of this study has certain practical effects.

Application of improved random forest algorithm and fuzzy mathematics in physical fitness of athletes

The comprehensive indicators of the physical fitness of young athletes and the specific modes of transportation, working and leisure activities as explanatory variables are not in line with the normal distribution. Moreover, there is a high correlation between explanatory variables, and fitting traditional regression models does not meet the assumptions, and multiple collinearity problems will occur, and good results will not be obtained. The random forest regression model has excellent performance in overcoming these difficulties. Therefore, the random forest regression model is constructed to evaluate the impact of various factors on the physical fitness of young people. This paper studies the impact of various factors on the health level of young people’s body and combines the source data and research goals to establish a comprehensive evaluation index system and an influential factor indicator system. In addition, this paper uses AHP to conduct comprehensive evaluation, and obtains the comprehensive physical quality of young people, and gives corresponding suggestions according to the actual situation.

Research on sports retrieval recognition of action based on feature extraction and SVM classification algorithm

The feature extraction speed of the traditional athlete motion retrieval algorithm is slow, and it often takes dozens of minutes or even hours to analyze a video. The speed of this feature extraction obviously cannot meet the needs of big data video analysis. In response to these two problems exposed by Action Bank under large-scale data, this paper proposes to apply the template learning method based on spectral clustering to Action Bank, which replaces the cumbersome manual selection template step and is easy to generalize to different databases. Moreover, in view of the disadvantage of slow speed of extracting Action Bank features, this paper proposes a fast algorithm for accumulating Action Bank. In addition, this study uses the lookup table method instead of the time-consuming steps of the correlation distance calculation in template matching, which greatly accelerates the time of feature extraction. Finally, this study design experiments to analyze the performance of the algorithm. Through research, it can be seen that the algorithm of this study can be applied to athletes’ sports retrieval and has certain recognition effects.

Challenges to the central nervous system during human spaceflight missions to Mars

Space travel presents a number of environmental challenges to the central nervous system, including changes in gravitational acceleration that alter the terrestrial synergies between perception and action, galactic cosmic radiation that can damage sensitive neurons and structures, and multiple factors (isolation, confinement, altered atmosphere, and mission parameters, including distance from Earth) that can affect cognition and behavior. Travelers to Mars will be exposed to these environmental challenges for up to 3 years, and space-faring nations continue to direct vigorous research investments to help elucidate and mitigate the consequences of these long-duration exposures. This article reviews the findings of more than 50 years of space-related neuroscience research on humans and animals exposed to spaceflight or analogs of spaceflight environments, and projects the implications and the forward work necessary to ensure successful Mars missions. It also reviews fundamental neurophysiology responses that will help us understand and maintain human health and performance on Earth.

The motor vertical in the absence of gravicentric cues

When participants are asked to flip an omnidirectional switch "down", the direction of their responses depends mainly on gravicentric, less so on egocentric and least on visual cues about the vertical (Lackner and DiZio, Exp. Brain Res. 130:2-26, 2000). Here we evaluate response direction when gravicentric cues are not available. Participants flipped an omnidirectional switch "down" when gravito-inertial force acted orthogonally to the response plane on earth (session E), and when it was near zero during parabolic flights (session P). We found that the relative weight of visual cues was similar in both sessions, and it was similar to that in an earlier study where participants stood upright. Across all three data sets, the weight of visual cues averaged 0.09. The relative weight of egocentric cues was also similar in both sessions, averaging 0.87; however, it was significantly lower in the earlier study with upright participants, where it averaged 0.43. We further found that informative and noninformative tactile stimulation had no substantial effects on response direction, which suggests that the earlier reported anchoring effect of tactile signals for the perceived vertical may not extend to the motor vertical. We conclude that the absence of gravicentric cues is compensated by a higher weight of egocentric cues, but not by a higher weight of visual cues. As a consequence, astronauts, divers and persons who work on ground in a horizontal body posture may mishandle equipment because of their strong reliance on egocentric cues.

Perception of threshold-level whole-body motion during mechanical mastoid vibration

BACKGROUND

Vibration applied on the mastoid has been shown to be an excitatory stimulus to the vestibular receptors, but its effect on vestibular perception is unknown.

OBJECTIVE

Determine whether mastoid vibration affects yaw rotation perception using a self-motion perceptual direction-recognition task.

METHODS

We used continuous, bilateral, mechanical mastoid vibration using a stimulus with frequency content between 1 and 500 Hz. Vestibular perception of 10 healthy adults (M±S.D. = 34.3±12 years old) was tested with and without vibration. Subjects repeatedly reported the perceived direction of threshold-level yaw rotations administered at 1 Hz by a motorized platform. A cumulative Gaussian distribution function was fit to subjects' responses, which was described by two parameters: bias and threshold. Bias was defined as the mean of the Gaussian distribution, and equal to the motion perceived on average when exposed to null stimuli. Threshold was defined as the standard deviation of the distribution and corresponded to the stimulus the subject could reliably perceive.

RESULTS

The results show that mastoid vibration may reduce bias, although two statistical tests yield different conclusions. There was no evidence that yaw rotation thresholds were affected.

CONCLUSIONS

Bilateral mastoid vibration may reduce left-right asymmetry in motion perception.

Human perception of whole body roll-tilt orientation in a hypogravity analog: underestimation and adaptation

Overestimation of roll tilt in hypergravity ("G-excess" illusion) has been demonstrated, but corresponding sustained hypogravic conditions are impossible to create in ground laboratories. In this article we describe the first systematic experimental evidence that in a hypogravity analog, humans underestimate roll tilt. We studied perception of self-roll tilt in nine subjects, who were supine while spun on a centrifuge to create a hypogravity analog. By varying the centrifuge rotation rate, we modulated the centripetal acceleration (G_C) at the subject's head location (0.5 or 1 G_C) along the body axis. We measured orientation perception using a subjective visual vertical task in which subjects aligned an illuminated bar with their perceived centripetal acceleration direction during tilts (±11.5-28.5°). As hypothesized, based on the reduced utricular otolith shearing, subjects initially underestimated roll tilts in the 0.5 G_C condition compared with the 1 G_C condition (mean perceptual gain change = -0.27, P = 0.01). When visual feedback was given after each trial in 0.5 G_C, subjects' perceptual gain increased in approximately exponential fashion over time (time constant = 16 tilts or 13 min), and after 45 min, the perceptual gain was not significantly different from the 1 G_C baseline (mean gain difference between 1 G_C initial and 0.5 G_C final = 0.16, P = 0.3). Thus humans modified their interpretation of sensory cues to more correctly report orientation during this hypogravity analog. Quantifying the acute orientation perceptual learning in such an altered gravity environment may have implications for human space exploration on the moon or Mars. NEW & NOTEWORTHY Humans systematically overestimate roll tilt in hypergravity. However, human perception of orientation in hypogravity has not been quantified across a range of tilt angles. Using a centrifuge to create a hypogravity centripetal acceleration environment, we found initial underestimation of roll tilt. Providing static visual feedback, perceptual learning reduced underestimation during the hypogravity analog. These altered gravity orientation perceptual errors and adaptation may have implications for astronauts.

Human manual control precision depends on vestibular sensory precision and gravitational magnitude

Precise motion control is critical to human survival on Earth and in space. Motion sensation is inherently imprecise, and the functional implications of this imprecision are not well understood. We studied a "vestibular" manual control task in which subjects attempted to keep themselves upright with a rotational hand controller (i.e., joystick) to null out pseudorandom, roll-tilt motion disturbances of their chair in the dark. Our first objective was to study the relationship between intersubject differences in manual control performance and sensory precision, determined by measuring vestibular perceptual thresholds. Our second objective was to examine the influence of altered gravity on manual control performance. Subjects performed the manual control task while supine during short-radius centrifugation, with roll tilts occurring relative to centripetal accelerations of 0.5, 1.0, and 1.33 G_C (1 G_C = 9.81 m/s²). Roll-tilt vestibular precision was quantified with roll-tilt vestibular direction-recognition perceptual thresholds, the minimum movement that one can reliably distinguish as leftward vs. rightward. A significant intersubject correlation was found between manual control performance (defined as the standard deviation of chair tilt) and thresholds, consistent with sensory imprecision negatively affecting functional precision. Furthermore, compared with 1.0 G_C manual control was more precise in 1.33 G_C (-18.3%, P = 0.005) and less precise in 0.5 G_C (+39.6%, P < 0.001). The decrement in manual control performance observed in 0.5 G_C and in subjects with high thresholds suggests potential risk factors for piloting and locomotion, both on Earth and during human exploration missions to the moon (0.16 G) and Mars (0.38 G). NEW & NOTEWORTHY The functional implications of imprecise motion sensation are not well understood. We found a significant correlation between subjects' vestibular perceptual thresholds and performance in a manual control task (using a joystick to keep their chair upright), consistent with sensory imprecision negatively affecting functional precision. Furthermore, using an altered-gravity centrifuge configuration, we found that manual control precision was improved in "hypergravity" and degraded in "hypogravity." These results have potential relevance for postural control, aviation, and spaceflight.

Variability in the Vestibulo-Ocular Reflex and Vestibular Perception

The vestibular system enables humans to estimate self-motion, stabilize gaze and maintain posture, but these behaviors are impacted by neural noise at all levels of processing (e.g., sensory, central, motor). Despite its essential importance, the behavioral impact of noise in human vestibular pathways is not completely understood. Here, we characterize the vestibular imprecision that results from neural noise by measuring trial-to-trial vestibulo-ocular reflex (VOR) variability and perceptual just-noticeable differences (JNDs) in the same human subjects as a function of stimulus intensity. We used head-centered yaw rotations about an Earth-vertical axis over a broad range of motion velocities (0-65°/s for VOR variability and 3-90°/s peak velocity for JNDs). We found that VOR variability increased from approximately 0.6°/s at a chair velocity of 1°/s to approximately 3°/s at 65°/s; it exhibited a stimulus-independent range below roughly 1°/s. Perceptual imprecision ("sigma") increased from 0.76°/s at 3°/s to 4.7°/s at 90°/s. Using stimuli that manipulated the relationship between velocity, displacement and acceleration, we found that velocity was the salient cue for VOR variability for our motion stimuli. VOR and perceptual imprecision both increased with stimulus intensity and were broadly similar over a range of stimulus velocities, consistent with a common noise source that affects motor and perceptual pathways. This contrasts with differing perceptual and motor stimulus-dependent imprecision in visual studies. Either stimulus-dependent noise or non-linear signal processing could explain our results, but we argue that afferent non-linearities alone are unlikely to be the source of the observed behavioral stimulus-dependent imprecision.

Allocating less attention to central vision during vection is correlated with less motion sickness

Visually induced motion sickness (VIMS) is a common discomfort response associated with vection-provoking stimuli. It has been suggested that susceptibility to VIMS depends on the ability to regulate visual performance during vection. To test this, 29 participants, with VIMS susceptibility assessed by Motion Sickness Susceptibility Questionnaire, were recruited to undergo three series of sustained attention to response tests (SARTs) while watching dot pattern stimuli known to provoke roll-vection. In general, SARTs performance was impaired in the central visual field (CVF), but improved in peripheral visual field (PVF), suggesting the reallocation of attention during vection. Moreover, VIMS susceptibility was negatively correlated with the effect sizes, suggesting that participants who were less susceptible to VIMS showed better performance in attention re-allocation. Finally, when trained to re-allocation attention from the CVF to the PVF, participants experienced more stable vection. Findings provide a better understanding of VIMS and shed light on possible preventive measures. Practitioner Summary: Allocating less visual attention to central visual field during visual motion stimulation is associated with stronger vection and higher resistance to motion sickness. Virtual reality application designers may utilise the location of visual tasks to strengthen and stabilise vection, while reducing the potential of visually induced motion sickness.

Neurovestibular Symptoms in Astronauts Immediately after Space Shuttle and International Space Station Missions

OBJECTIVES

(1) To assess vestibular changes and related sensorimotor difficulties, especially instability of posture and gait, among astronauts immediately after they return from space and to compare the effects experienced after short- and long-duration space missions. (2) To determine whether any difficulties experienced were severe enough to impair the astronauts' ability to leave the spacecraft in the event of an emergency.

STUDY DESIGN

Prospective cohort study.

SETTING

National Aeronautics and Space Administration's Kennedy Space Center and Johnson Space Center.

SUBJECTS AND METHODS

Fourteen crewmembers of 3 Space Shuttle missions that lasted about 1 week and 18 crewmembers of 8 International Space Station missions that lasted about 6 months were given brief vestibular examinations 1 to 5 hours after landing. These examinations focused on the presence of vestibular and motor coordination difficulties, as well as motion sickness and motion sensations. Standardized tests included the observation of abnormal eye movements, finger-to-nose pointing, standing up from a seated position, postural stability, and tandem gait.

RESULTS

Unsteady walking and postural instabilities were observed after short- and long-duration missions. Motion sickness symptoms were observed after long-duration missions but not after short-duration missions. The symptom most frequently reported by the astronauts was an exaggerated perceived motion associated with sudden head movements during reentry and after landing.

CONCLUSION

The severity of the observed abnormalities would limit the ability of crewmembers during the first 5 hours after landing and increase the time required to leave the spacecraft during this period.