Imbalance and balancing: Development of ecological flow networks

In this paper we address balancing process of ecological flow networks. In existing approaches, macroscopic objectives to which systems organize are assumed. Flow balance provides only constraints for the optimization. Since flow balance and objectives are separated from each other, it is impossible to address how the appearance of objectives is related to flow balance. Therefore, we take an alternative approach, in which we directly describe a dynamics of balancing process. We propose a simple mathematical formula for local balancing dynamics and show that it can generate a self-organizing property, which could be seen as a primitive objective.     

Scanning Strategies Do Not Modulate Face Identification: Eye-Tracking and Near-Infrared Spectroscopy Study

Background

During face identification in humans, facial information is sampled (seeing) and handled (processing) in ways that are influenced by the kind of facial image type, such as a self-image or an image of another face. However, the relationship between seeing and information processing is seldom considered. In this study, we aimed to reveal this relationship using simultaneous eye-tracking measurements and near-infrared spectroscopy (NIRS) in face identification tasks.

Methodology/Principal Findings

22 healthy adult subjects (8 males and 14 females) were shown facial morphing movies in which an initial facial image gradually changed into another facial image (that is, the subject''s own face was changed to a familiar face). The fixation patterns on facial features were recorded, along with changes in oxyhemoglobin (oxyHb) levels in the frontal lobe, while the subjects identified several faces. In the self-face condition (self-face as the initial image), hemodynamic activity around the right inferior frontal gyrus (IFG) was significantly greater than in the familiar-face condition. On the other hand, the scanning strategy was similar in almost all conditions with more fixations on the eyes and nose than on other areas. Fixation time on the eye area did not correlate with changes in oxyHb levels, and none of the scanning strategy indices could estimate the hemodynamic changes.

Conclusions/Significance

We conclude that hemodynamic activity, i.e., the means of processing facial information, is not always modulated by the face-scanning strategy, i.e., the way of seeing, and that the right IFG plays important roles in both self-other facial discrimination and self-evaluation.     

Psychological stress induced by 20 days bed rest

We investigated the changes of the psychological state during 20 days bed rest (BR) in 10 young participants,(5 males and 5 females, age; 19-24 yrs). Psychological assessment was accomplished by the following authorized 3 indices: 1) Zung's Self-rating Depression Scale, 2) Cornell Medical Index, and 3) Goldberg's General Health Questionnaire. Zung's Self-rating Depression Scale is a indicator for depression, and the other two indices were used for detecting signs of neurosis. The results from Zung's Self-rating Depression Scale and the General Health Questionnaire in this study indicated a tendency toward depression and neurosis developing during BR, respectively. The scores in the Cornell Medical Index did not change. Urinary excretion of 17-hydroxycorticosteroid increased significantly, indicating that BR immobilization induced an important psychological stress. We were unable to determine which factors caused the changes in psychological state during BR, immobilization insert or personal problems.     

Effect of a five minutes isokinetic one leg knee extension training on maximal oxygen uptake during 20 days of -6 degrees head-down tilting bed-rest in young male subjects

Due to prolonged bed rest (BR), maximal oxygen uptake (VO2max) might be decreased by above -8%, even if a moderate supine bicycle exercise (SBE) was performed for 45 to 60 minutes every day during BR. However, the decrement of VO2max was lowered to below -5% by isometric training and using a reverse gradient garment. Further it was rather slightly increased by SBE training with gradually increasing load from 40% to 90% VO2max. The facts suggest the dependency of the decrease of VO2max during BR on exercising muscle mass (MM) and strength. In the present study, therefore, the effects of isokinetic knee extension (Ik-KnE) training on VO2max, exercising MM and muscle contraction strength during BR were investigated. Then, the relationships between changes in VO2max and the muscle mass and strength were considered.     

Effects of 20 days bed rest on muscle morphology

Using ultrasound, muscle thickness and fascicle angles from aponeurosis were evaluated before, during and after 20 days bed rest (BR). Subjects were healthy adults (4 women and 4 men). Measurements were carried out before and after BR and after 10 weeks of recovery, respectively. Muscle measurements were taken at nine sites in trunk and upper and lower extremities, respectively. For the m. triceps brachii, m. vastus lateralis, and m. gastrocnemius medialis, fascicle angles from the aponeurosis as well as muscle thickness were measured. There was a high statistical significant correlation between muscle thickness and cross-sectional area for quadriceps muscles, suggesting applicability of muscle thickness for evaluation of muscle size. Muscle thickness decreased in muscles of the lower extremity by 2.1-4.4 % after bed rest. In triceps brachii and vastus lateralis muscles, there were no prominent changes in muscle thickness and fascicle angles. It was concluded that muscle morphology deteriorates with changes in muscle architecture by bed rest but the response is small and muscle-specific. It was also suggested that bed rest affects not only muscle mass but muscle tone as well.     

Effect of bed rest immobilization on metabolic turnover of bone and bone mineral density

Immobilization induces abnormal bone metabolism and severe decalcification of bone. To investigate the effect of middle-term immobilization on bone metabolism, we studied 10 young healthy males and females during bed rest for 20 days. Bone mineral density (BMD) rapidly decreased in both lumbar and metacarpal bones. No bone showed consistent BMD alterations, partial increase and partial decrease, and both lumbar and metacarpal bone showed similar rapid BMD change. Urinary excretion of pyridinoline tended to slightly increase by day 10, and to decline by day 20 (mean +/-SE: 34.2 +/-7.4, 26.3+/-4.6 nmol day-1, respectively). Neither alkaline phosphatase (isoform III) nor tartrate-resistant acid phosphatase, changed, suggesting that in the early stage of immobilization bone matrix in some part might increase or be resorbed without any activation of osteoblast or osteoclast, resulting in rapid calcification or decalcification, respectively.     

Comparing cardiovascular responses during exercise between head-down tilt pedaling with lower body negative pressure and upright cycling in man

If lower body negative pressure (LBNP) loaded on exercise in weightlessness environment is able to derive a comparable cardiovascular responses to these in the ground, it should be identified as an optimal LBNP for exercise in space. To investigate the LBNP, 7 young subjects were exercised 4 work rates stepping up every 50 watts from 50 watts to 200 watts every 5 minutes in the upright position or 6 degree head down tilt position with each LBNP of 20, 40, 60, 80, and 100 mmHg. Oxygen uptake during tilt exercise with over 60 mmHg LBNP was not different from it in upright exercise. Heart rate and systolic arterial pressure responses to exercise were very similar between tilt exercise with 60 mmHg LBNP and upright exercise. In conclusion, the optimal LBNP loaded on exercise in space should be around 60 mmHg.     

Minimal model of a cell connecting amoebic motion and adaptive transport networks

A cell is a minimal self-sustaining system that can move and compute. Previous work has shown that a unicellular slime mold, Physarum, can be utilized as a biological computer based on cytoplasmic flow encapsulated by a membrane. Although the interplay between the modification of the boundary of a cell and the cytoplasmic flow surrounded by the boundary plays a key role in Physarum computing, no model of a cell has been developed to describe this interplay. Here we propose a toy model of a cell that shows amoebic motion and can solve a maze, Steiner minimum tree problem and a spanning tree problem. Only by assuming that cytoplasm is hardened after passing external matter (or softened part) through a cell, the shape of the cell and the cytoplasmic flow can be changed. Without cytoplasm hardening, a cell is easily destroyed. This suggests that cytoplasmic hardening and/or sol-gel transformation caused by external perturbation can keep a cell in a critical state leading to a wide variety of shapes and motion.     

Flexibility in starfish behavior by multi-layered mechanism of self-organization

Understanding animal behavior as a product of natural selection sometimes result in an underestimation of the animal's adaptability: lower animals with poor mental capabilities are usually considered to simply exhibit innate behavioral patterns. Self-organized behavior may exhibit both stability of certain behavioral patterns and flexibility in adopting those patterns. Thus, the self-organization processes of starfish arm and tube feet movements are investigated, by observing obstacle avoidance behavior and tube feet of moving starfish. As starfish have no central nervous systems, their behaviors are the result of certain self-organization processes. Starfish have hierarchically constructed motor organs consisting of arms and tube feet. The collective behavior of the tube feet does not function only as simple fluctuations in the arms' coordination. As a result, starfish seem to exhibit more versatile behavioral changes than expected from the original model of a self-organized behavior.