Evaluation of Divers' Neuropsychometric Effectiveness and High-Pressure Neurological Syndrome via Computerized Test Battery Package and Questionnaires in Operational Setting

[Effects of Extreme Environments on Human Sleep]

Recently, with the rapid growth of the global population and the exhaustion of resources, exploration activities in extreme environments such as the polar regions, the outer space, the deep sea, the deep underground and highlands are becoming increasingly more frequent. This in-depth exploration of the external environment and the consequent dramatic changes in lifestyles impact on sleep, a basic life activity of humans, in ways that cannot be overlooked. the basic life activity of human beings. Sleep, a basic life activity and the result of the evolution of organisms to adapt to their environment, is closely associated with sleep homeostasis and endogenous rhythms. However, external environmental changes and lifestyle shifts in extreme environments have had a significant impact on the patterns and the quality of sleep in humans. Furthermore, this impact can lead to many physiological and psychological problems, posing a great threat to human health. In this review, we delved into the specific effects of different extreme natural environments and enclosed environments on sleep, elaborating on how these environments alter the patterns and the quality of sleep in humans. In addition, we summarized the changes in human sleep under extreme environments to help gain a better understanding of the mechanisms by which these specific environments impact human sleep. It is expected that this review will provide a solid theoretical foundation for optimizing long-term survival strategies in extreme environments and help humans adapt to and overcome the challenges posed by extreme environments more effectively.

Cortical neurite microstructural correlates of time perception in healthy older adults

The human experience is significantly impacted by timing as it structures how information is processed. Nevertheless, the neurological foundation of time perception remains largely unresolved. Understanding cortical microstructure related to timing is crucial for gaining insight into healthy aging and recognizing structural alterations that are typical of neurodegenerative diseases associated with age. Given the importance, this study aimed to determine the brain regions that are accountable for predicting time perception in older adults using microstructural measures of the brain. In this study, elderly healthy adults performed the Time-Wall Estimation task to measure time perception through average error time. We used support vector regression (SVR) analyses to predict the average error time using cortical neurite microstructures derived from orientation dispersion and density imaging based on multi-shell diffusion magnetic resonance imaging (dMRI). We found significant correlations between observed and predicted average error times for neurite arborization (ODI) and free water (FISO). Neurite arborization and free water properties in specific regions in the medial and lateral prefrontal, superior parietal, and medial and lateral temporal lobes were among the most significant predictors of timing ability in older adults. Further, our results revealed that greater branching along with lower free water in cortical structures result in shorter average error times. Future studies should assess whether these same networks are contributing to time perception in older adults with mild cognitive impairment (MCI) and whether degeneration of these networks contribute to early diagnosis or detection of dementia.

Assessing Critical Flicker Fusion Frequency: Which Confounders? A Narrative Review

The critical flicker fusion frequency (cFFF) refers to the frequency at which a regularly recurring change of light stimuli is perceived as steady. The cFFF threshold is often assessed in clinics to evaluate the temporal characteristics of the visual system, making it a common test for eye diseases. Additionally, it serves as a helpful diagnostic tool for various neurological and internal diseases. In the field of diving/hyperbaric medicine, cFFF has been utilized to determine alertness and cognitive functions. Changes in the cFFF threshold have been linked to the influence of increased respiratory gas partial pressures, although there exist inconsistent results regarding this effect. Moreover, the use of flicker devices has produced mixed outcomes in previous studies. This narrative review aims to explore confounding factors that may affect the accuracy of cFFF threshold measurements, particularly in open-field studies. We identify five broad categories of such factors, including (1) participant characteristics, (2) optical factors, (3) smoking/drug use, (4) environmental aspects, and (5) breathing gases and partial pressures. We also discuss the application of cFFF measurements in the field of diving and hyperbaric medicine. In addition, we provide recommendations for interpreting changes in the cFFF threshold and how they are reported in research studies.

Neuropsychological and Neurophysiological Mechanisms behind Flickering Light Stimulus Processing

The aim of this review is to summarise current knowledge about flickering light and the underlying processes that occur during its processing in the brain. Despite the growing interest in the topic of flickering light, its clinical applications are still not well understood. Studies using EEG indicate an appearing synchronisation of brain wave frequencies with the frequency of flickering light, and hopefully, it could be used in memory therapy, among other applications. Some researchers have focused on using the flicker test as an indicator of arousal, which may be useful in clinical studies if the background for such a relationship is described. Since flicker testing has a risk of inducing epileptic seizures, however, every effort must be made to avoid high-risk combinations, which include, for example, red-blue light flashing at 15 Hz. Future research should focus on the usage of neuroimaging methods to describe the specific neuropsychological and neurophysiological processes occurring in the brain during the processing of flickering light so that its clinical utility can be preliminarily determined and randomised clinical trials can be initiated to test existing reports.

Vascular Function Recovery Following Saturation Diving

Background and Objectives: Saturation diving is a technique used in commercial diving. Decompression sickness (DCS) was the main concern of saturation safety, but procedures have evolved over the last 50 years and DCS has become a rare event. New needs have evolved to evaluate the diving and decompression stress to improve the flexibility of the operations (minimum interval between dives, optimal oxygen levels, etc.). We monitored this stress in saturation divers during actual operations. Materials and Methods: The monitoring included the detection of vascular gas emboli (VGE) and the changes in the vascular function measured by flow mediated dilatation (FMD) after final decompression to surface. Monitoring was performed onboard a diving support vessel operating in the North Sea at typical storage depths of 120 and 136 msw. A total of 49 divers signed an informed consent form and participated to the study. Data were collected on divers at surface, before the saturation and during the 9 h following the end of the final decompression. Results: VGE were detected in three divers at very low levels (insignificant), confirming the improvements achieved on saturation decompression procedures. As expected, the FMD showed an impairment of vascular function immediately at the end of the saturation in all divers but the divers fully recovered from these vascular changes in the next 9 following hours, regardless of the initial decompression starting depth. Conclusion: These changes suggest an oxidative/inflammatory dimension to the diving/decompression stress during saturation that will require further monitoring investigations even if the vascular impairement is found to recover fast.

Critical Flicker Fusion Frequency: A Narrative Review

This review presents the current knowledge of the usage of critical flicker fusion frequency (CFF) in human and animal model studies. CFF has a wide application in different fields, especially as an indicator of cortical arousal and visual processing. In medicine, CFF may be helpful for diagnostic purposes, for example in epilepsy or minimal hepatic encephalopathy. Given the environmental studies and a limited number of other methods, it is applicable in diving and hyperbaric medicine. Current research also shows the relationship between CFF and other electrophysiological methods, such as electroencephalography. The human eye can detect flicker at 50-90 Hz but reports are showing the possibility to distinguish between steady and modulated light up to 500 Hz. Future research with the use of CFF is needed to better understand its utility and application.