Publications by authors named "S Villard"

[Methemoglobinemia].

Rev Med Interne

August 2024

Methemoglobinemia (MetHb) refers to the state of oxidation of the iron ion "ferrous" (Fe to iron "ferric" (Fe) within the heme molecule that makes up hemoglobin (Hb). This state is physiological if its level remains controlled. The ferrous state of the heme molecule occurs in the event of significant oxidative stress.

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The task of processing speech masked by concurrent speech/noise can pose a substantial challenge to listeners. However, performance on such tasks may not directly reflect the amount of listening effort they elicit. Changes in pupil size and neural oscillatory power in the alpha range (8-12 Hz) are prominent neurophysiological signals known to reflect listening effort; however, measurements obtained through these two approaches are rarely correlated, suggesting that they may respond differently depending on the specific cognitive demands (and, by extension, the specific type of effort) elicited by specific tasks.

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In speech-on-speech listening experiments, some means for designating which talker is the "target" must be provided for the listener to perform better than chance. However, the relative strength of the segregation variables designating the target could affect the results of the experiment. Here, we examine the interaction of two source segregation variables-spatial separation and talker gender differences-and demonstrate that the relative strengths of these cues may affect the interpretation of the results.

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Numerous studies have been carried out on the potential effects of an extremely low frequency (ELF-0-300 Hz) magnetic field (MF) on human health. However, there is limited data on the effect of a high exposure level to ELF MFs for a prolonged period. Therefore, the objective of this pilot work was to demonstrate the feasibility of a study evaluating the stress hormone concentrations resulting from a 10-min exposure to a 60 Hz MF of several tens of thousands of µT.

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Electric fields from both extremely low-frequency magnetic fields (ELF-MF) and alternating current (AC) stimulations impact human neurophysiology. As the retinal photoreceptors, vestibular hair cells are graded potential cells and are sensitive to electric fields. Electrophosphene and magnetophosphene literature suggests different impacts of AC and ELF-MF on the vestibular hair cells.

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