In this paper, we introduce an electrode for measuring auditory evoked potentials by employing the advantages of polyimide (PI), which is a well-known substrate material for producing flexible electrodes using MEMS technology. The PI multimicroelectrode array has four fingers that include 16 electrodes in order to achieve sufficient adhesion to the curved surface of the animal skull. For high-quality signal acquisition, we optimized the device to decrease crosstalk and improve contact impedance by adding ground channels and fabricating a raised electrode structure. In addition, implantation of the device was facilitated by the addition of an alignment site to ensure optimal positioning and enable signal measurement from the specific part of the cerebral cortex in charge of auditory sensing. After the implantation of the PI electrode on the skull surface, electrical signals were measured following stimulation at different stimulus frequencies (5 or 10 kHz). Unlike other techniques, administration of this PI electrode is less invasive, reducing patient recovery time dramatically in comparison with other electrocorticographic operations. Furthermore, as the exterior of the brain would not be exposed at any point, the chance of infection is minimized.
This study aimed to investigate the effects of a marine exercise retreat program on thyroid-related hormone levels. A total of 62 middle-aged euthyroid women participated in a 6-day marine exercise retreat program. Using thyroid-stimulating hormone (TSH) and free thyroxine (fT4) hormone levels, the participants were divided into high and low-hormone-level groups. Despite decreased TSH and fT4 levels after the program, the factors influencing changes in each group were different. TSH levels were influenced by changes in the normalized low frequency (nLF) of heart rate variability and carbon monoxide (CO) from all the participants, and changes in body fat percentage, nLF, and nitrogen dioxide (NO2) exposure level in the high TSH group. fT4 levels were influenced by changes in body mass index (BMI), NO2 exposure, and particulate matter diameter of 10 µm or less (PM10) exposure in all participants. Changes in BMI and CO exposure influenced the low fT4 group. Lastly, changes in the exercise stress test affected the high fT4 group. Thus, the marine exercise retreat program affected euthyroid thyroid-related hormone levels, and influencing factors differ depending on the initial value of the hormone.
Recent studies have reported that the cortisol awakening response (CAR) is associated with various health risks. The different indices used to represent the CAR include the average cortisol levels in the morning immediately after waking (AVE); the total area under the curve of cortisol levels with respect to ground (AUCg); and the area under the curve of cortisol levels with respect to increase (AUCi). However, it is unclear which physiological phenomenon each index reflects. This study investigated the factors, such as stress, circadian rhythm, sleep, and obesity, affecting the CAR through a marine retreat-based healing program in which the anticipated stress of the participants could be controlled to some degree. Fifty-one menopausal women in their 50s and 60s were included, who performed beach yoga and Nordic walking for four days at an uncontaminated beach. The baseline CAR indices showed that the AVE and AUCg were significantly higher in the high sleep efficiency group than in the low sleep efficiency group. However, the AUCi decreased substantially with increasing age. The changes in the AVE, AUCg, and AUCi were calculated through the program, and it was found that the AVE and AUCg increased significantly more in the obese group than in the normal and overweight groups. The obese group also showed significantly decreased serum triglyceride and BDNF (brain-derived neurotrophic factor) levels compared to the low BMI group. Thus, it was confirmed that AVE and AUCg reflected physiological phenomena affected by factors such as sleep efficiency and obesity, whereas the AUCi was affected by factors such as age. In addition, the marine retreat program can improve the low levels of CAR associated with obesity and aging.
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