Genecology and ecophysiology of the maintenance of foliar phenotypic polymorphisms of Leptospermum recurvum (Myrtaceae) under oscillating atmospheric desiccation in the tropical-subalpine zone of Mount Kinabalu, Borneo

We investigated genecology and ecophysiological mechanisms of the polymorphism of leaf trichome density of Leptospermum recurvum Hook. f. (Myrtaceae) in the deglaciated summit zone above 3, 000 m a.s.l. of Mt. Kinabalu, Borneo. Various phenotypes with variable foliar trichome densities occurred sympatrically in the same population, and the composition of coexisting phenotypes varied substantially among populations. We conducted a common garden experiment by sowing seeds from multiple maternal trees of different leaf trichome densities. We found a significant relation between pubescence of maternal trees and offspring, which indicated that leaf trichome density had a genetic basis. Microsatellite analysis revealed that there was no barrier to gene flows among phenotypes or among populations, and very low neutral genetic differentiation among populations with high gene flows for both directions of phenotypes. The soils in the sites dominated by pubescent trees were significantly more desiccated than in the sites dominated by glabrous trees during a short drought. Glabrous trees had a significantly greater mortality rate than pubescent trees after an intensive El Niño drought (13.7 vs. 3.9%) in the same sites where both phenotypes occurred sympatrically. Pubescent individuals demonstrated a significantly greater photosynthetic water-use efficiency than glabrous individuals. El Niño droughts could cause large difference in soil moisture among sites and that a greater desiccation stress removed glabrous phenotypes as one end of divergent natural selection to form pubescent populations. These results implied that the process shaping the phenotypic polymorphisms involved strong gene flows combined with ongoing divergent selection

Slowed response to peripheral visual stimuli during strenuous exercise

Recently, we proposed that strenuous exercise impairs peripheral visual perception because visual responses to peripheral visual stimuli were slowed during strenuous exercise. However, this proposal was challenged because strenuous exercise is also likely to affect the brain network underlying motor responses. The purpose of the current study was to resolve this issue. Fourteen participants performed a visual reaction-time (RT) task at rest and while exercising at 50% (moderate) and 75% (strenuous) peak oxygen uptake. Visual stimuli were randomly presented at different distances from fixation in two task conditions: the Central condition (2° or 5° from fixation) and the Peripheral condition (30° or 50° from fixation). We defined premotor time as the time between stimulus onset and the motor response, as determined using electromyographic recordings. In the Central condition, premotor time did not change during moderate (167 ± 19 ms) and strenuous (168 ± 24 ms) exercise from that at rest (164 ± 17 ms). In the Peripheral condition, premotor time significantly increased during moderate (181 ± 18 ms, P < 0.05) and strenuous exercise (189 ± 23 ms, P < 0.001) from that at rest (173 ± 17 ms). These results suggest that increases in Premotor Time to the peripheral visual stimuli did not result from an impaired motor-response network, but rather from impaired peripheral visual perception. We conclude that slowed response to peripheral visual stimuli during strenuous exercise primarily results from impaired visual perception of the periphery

Central and peripheral visual reaction time of soccer players and nonathletes

Visual reaction time of 20 soccer players and 13 nonathlete university students was measured using three different sizes of stimulus in central and peripheral vision.The results were summarized as follows: 1) Central visual reaction time of soccer players increased significantly with a decrease in size of a stimulus, while peripheral visual reaction time of nonathletes increased significantly with a decrease in size of the stimulus.2) In soccer players the correlation between peripheral visual reaction time and central visual reaction time was higher when the size of the stimulus was small. In nonathletes，however，correlation of the same parameters was higher when the size of the stimulus was large. These results suggest that soccer players have a higher ability of peripheral visual perception to the smaller object than nonathletes，that might enable to make quick judgement and decision to the far distant ball in the soccer field

Cognitive performance is associated with cerebral oxygenation and peripheral oxygen saturation, but not plasma catecholamines, during graded normobaric hypoxia

What is the central question of this study? What are the mechanisms responsible for the decline in cognitive performance following exposure to acute normobaric hypoxia? What are the main findings and their importance? We found that 1) performance of a complex central executive task (n-back) was reduced FiO 0.12; 2) there was a strong correlation between performance of the n-back task and reductions in SpO and cerebral oxygenation; and 3) plasma adrenaline, noradrenaline, cortisol, and copeptin were not correlated with cognitive performance. It is well established that hypoxia impairs cognitive function; however, the physiological mechanisms responsible for these effects have received relatively little attention. This study examined the effects of graded reductions in fraction of inspired oxygen (FiO ) on oxygen saturation (SpO ), cerebral oxygenation, cardiorespiratory variables, activity of the sympathoadrenal system (adrenaline, noradrenaline) and hypothalamic-pituitary-adrenal axis (cortisol, copeptin), and cognitive performance. Twelve healthy males (mean [SD], age: 22 [4] yrs, height: 178 [5] cm, mass: 75 [9] kg, FEV /FVC ratio: 85 [5] %) completed a 4-task battery of cognitive tests to examine inhibition, selective attention (Eriksen Flanker), executive function (n-back) and simple and choice reaction time (Deary-Liewald). Tests were completed before and following 60 minutes of exposure to FiO 0.2093, 0.17, 0.145, and 0.12. Following 60 minutes of exposure response accuracy in the n-back task was significantly reduced in FiO 0.12 compared to baseline (82 [9] vs. 93 [5] %; p < 0.001) and compared to all other conditions at the same time point (FiO 0.2093: 92 [3] %, FiO 0.17: 91 [6] %, FiO 0.145: 85 [10] %, FiO 12: 82 [9] %; all p < 0.05). The performance of the other tasks was maintained. Δ accuracy and Δ reaction time of the n-back task was correlated with both Δ SpO (r (9) = 0.66; p < 0.001 and r (9) = - 0.36; p = 0.037 respectively) and Δ cerebral oxygenation (r (7) = 0.55; p < 0.001 and r (7) = - 0.38; p = 0.045 respectively). Plasma adrenaline, noradrenaline, cortisol and copeptin were not significantly elevated in any condition or correlated with any of the tests of cognitive performance. These findings suggest that reductions in peripheral oxygen saturation and cerebral oxygenation, and not increased activity of the sympathoadrenal system and hypothalamic-pituitary-adrenal axis, as previously speculated, are responsible for a decrease in cognitive performance during normobaric hypoxia

The effects of sleep deprivation, acute hypoxia, and exercise on cognitive performance: A multi-experiment combined stressors study

Introduction: Both sleep deprivation and hypoxia have been shown to impair executive function. Conversely, moderate intensity exercise is known to improve executive function. In a multi-experiment study, we tested the hypotheses that moderate intensity exercise would ameliorate any decline in executive function after i) three consecutive nights of partial sleep deprivation (PSD) (Experiment 1) and ii) the isolated and combined effects of a single night of total sleep deprivation (TSD) and acute hypoxia (Experiment 2). Methods: Using a rigorous randomised controlled crossover design, 12 healthy participants volunteered in each experiment (24 total, 5 females). In both experiments seven executive function tasks (2-choice reaction time, logical relations, manikin, mathematical processing, 1-back, 2-back, 3-back) were completed at rest and during 20 min semi-recumbent, moderate intensity cycling. Tasks were completed in the following conditions: before and after three consecutive nights of PSD and habitual sleep (Experiment 1) and in normoxia and acute hypoxia (FIO2 = 0.12) following one night of habitual sleep and one night of TSD (Experiment 2). Results: Although the effects of three nights of PSD on executive functions were inconsistent, one night of TSD (regardless of hypoxic status) reduced executive functions. Significantly, regardless of sleep or hypoxic status, executive functions are improved during an acute bout of moderate intensity exercise. Conclusion: These novel data indicate that moderate intensity exercise improves executive function performance after both PSD and TSD, regardless of hypoxic status. The key determinants and/or mechanism(s) responsible for this improvement still need to be elucidated. Future work should seek to identify these mechanisms and translate these significant findings into occupational and skilled performance settings

シュウヘン シヤ ノ ハンノウ ジカン ニ カンスル セイリ シンリガクテキ ケンキュウ

京都大学0048新制・課程博士博士(人間・環境学)甲第10953号人博第240号15||195(吉田南総合図書館)新制||人||60(附属図書館)UT51-2004-G800京都大学大学院人間・環境学研究科人間・環境学専攻(主査)教授 森谷 敏夫, 教授 田口 貞善, 助教授 小田 伸午学位規則第4条第1項該当Doctor of Human and Environmental StudiesKyoto UniversityDA