Subjecting Elite Athletes to Inspiratory Breathing Load Reveals Behavioral and Neural Signatures of Optimal Performers in Extreme Environments

Background: It is unclear whether and how elite athletes process physiological or psychological challenges differently than healthy comparison subjects. In general, individuals optimize exercise level as it relates to differences between expected and experienced exertion, which can be conceptualized as a body prediction error. The process of computing a body prediction error involves the insular cortex, which is important for interoception, i.e. the sense of the physiological condition of the body. Thus, optimal performance may be related to efficient minimization of the body prediction error. We examined the hypothesis that elite athletes, compared to control subjects, show attenuated insular cortex activation during an aversive interoceptive challenge. Methodology/Principal Findings: Elite adventure racers (n = 10) and healthy volunteers (n = 11) performed a continuous performance task with varying degrees of a non-hypercapnic breathing load while undergoing functional magnetic resonance imaging. The results indicate that (1) non-hypercapnic inspiratory breathing load is an aversive experience associated with a profound activation of a distributed set of brain areas including bilateral insula, dorsolateral prefrontal cortex and anterior cingulated; (2) adventure racers relative to comparison subjects show greater accuracy on the continuous performance task during the aversive interoceptive condition; and (3) adventure racers show an attenuated right insula cortex response during and following the aversive interoceptive condition of non-hypercapnic inspirator

Hearing function in a hyperbaric environment

Navy divers\u27 hearing function was assessed as part of three saturation deep dives to 1,000 feet of sea water (fsw) to determine explanations for threshold shifts observed under hyperbaric conditions. Across the three deep dives, different aspects of the ear were evaluated, including air- and bone-conduction pure-tone thresholds, real ear probe microphone measurements, auditory evoked potentials, and central auditory processing assessments. Attempts to measure middle ear function and cochlear function (through otoacoustic emissions) were unsuccessful. Baseline measurements were obtained at 0 fsw in air before and after the saturation deep dives. Results showed that some aspects of hearing function remained unchanged with increases in depth. In general, audiometric thresholds at depth were similar to those measured on the surface at 500, 1,000, 2,000, 3,000, and 4,000 Hz. However, hearing sensitivity actually improved at depth at 6,000 and 8,000 Hz. The use of a specially designed sound booth for a pressurized heliox environment yielded significantly lower ambient noise levels and improved the accuracy of threshold measurement. Auditory evoked potential measurements and central auditory processing function were relatively unaffected by changes in depth. Significant changes at depth were seen in ear canal resonance which shifted up in frequency; this finding was attributed to the effect of helium on the hearing mechanism. Because objective measurement of middle ear and inner ear function were not methodologically possible, questions still remain regarding the interpretation of middle and inner ear function at depth. Nonetheless, our overall findings suggest that most aspects of hearing functioning are similar under high atmospheric pressures and in heliox as they are on the surface, with the exception of shifts in ear canal resonance and improvements in audiometric thresholds at high frequencies

The effect of oxidation on the mineralogy and magnetic properties of olivine

Although nucleation of magnetite and/or hematite along dislocations upon oxidation of olivine has been observed by many workers, the effect of oxidation on the magnetic properties of the sample with specific mineralogical alterations has not been studied. Therefore, we investigate this problem using a set of time series 1 bar oxidation experiments at 600 and 900 °C. Results show rapid olivine oxidation and alteration at both 600 and 900 °C, forming magnetite and hematite associated with a change from paramagnetic to ferromagnetic behavior after oxidation. Magnetite and hematite nucleate along dislocations and impurities in the crystal structure, along with surface coatings and within cracks in the crystals. Fresh, unaltered mantle xenoliths containing magnetite have been interpreted as having formed in cold tectonic regimes in the mantle, rather than through oxidation during or after ascent. Mantle xenoliths rapidly ascend through the mantle with estimates of the ascent of up to 90 km/h (3 GPa/h) based on the diffusion profile of water in mantle olivine. The rates correspond to xenoliths ascending through the mantle over hours and not days or weeks. Our results show that olivine oxidation and alteration can occur in days to weeks at 600 °C and within minutes at 900 °C. Therefore, if the xenolithic material is transported to the surface in a cold magma (at temperatures ≤600 °C), then the timescale of ascent is likely not long enough for oxidation to cause magnetite formation or a ferromagnetic signature to occur. However, if the material is transported in a hot oxidized basaltic magma (with temperatures ≥900 °C), then oxidation can cause magnetite formation and a ferromagnetic signature

Impaired cortical processing of inspiratory loads in children with chronic respiratory defects

<p>Abstract</p> <p>Background</p> <p>Inspiratory occlusion evoked cortical potentials (the respiratory related-evoked potentials, RREPs) bear witness of the processing of changes in respiratory mechanics by the brain. Their impairment in children having suffered near-fatal asthma supports the hypothesis that relates asthma severity with the ability of the patients to perceive respiratory changes. It is not known whether or not chronic respiratory defects are associated with an alteration in brain processing of inspiratory loads. The aim of the present study was to compare the presence, the latencies and the amplitudes of the P1, N1, P2, and N2 components of the RREPs in children with chronic lung or neuromuscular disease.</p> <p>Methods</p> <p>RREPs were recorded in patients with stable asthma (n = 21), cystic fibrosis (n = 32), and neuromuscular disease (n = 16) and in healthy controls (n = 11).</p> <p>Results</p> <p>The 4 RREP components were significantly less frequently observed in the 3 groups of patients than in the controls. Within the patient groups, the N1 and the P2 components were significantly less frequently observed in the patients with asthma (16/21 for both components) and cystic fibrosis (20/32 and 14/32) than in the patients with neuromuscular disease (15/16 and 16/16). When present, the latencies and amplitudes of the 4 components were similar in the patients and controls.</p> <p>Conclusion</p> <p>Chronic ventilatory defects in children are associated with an impaired cortical processing of afferent respiratory signals.</p