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Response Threshold (response + threshold)

Distribution by Scientific Domains

Medical Sciences	75%

Selected Abstracts

How does the pitch and pattern of a signal affect auditory arousal thresholds?

JOURNAL OF SLEEP RESEARCH, Issue 2 2009
DOROTHY BRUCK
Summary How arousal thresholds vary with different sounds is a critical issue for emergency awakenings, especially as sleepers are dying in fires despite having a working smoke alarm. Previous research shows that the current high-pitched (3000+ Hz) smoke alarm signal is significantly less effective than an alternative signal, the 520 Hz square wave, in all populations tested. However, as the number of sounds tested has been small further research is needed. Here we measured auditory arousal thresholds (AATs) across signals with a range of characteristics to determine the most effective waking signal. Thirty-nine young adults participated over three nights. In Part A, nine signals were presented in stage 4 sleep with ascending decibel levels. Signals were short beeps in the low- to mid-frequency range with different spectral complexities: square waves, pure tones, whoops and white noise. Part B manipulated temporal patterns, inserting silences of 0, 10 and 21 s after each 12 s of beeps. It was found that the low-frequency (400 and 520 Hz) square waves yielded significantly lower AATs than the alternatives. A trend was found across the three temporal manipulations, with a 10 s intervening silence showing some advantage. These findings support earlier research indicating that the best sound for awakening from deep sleep is a low-frequency square wave. It is argued that the signal with the lowest response threshold when awake may be the same as the most arousing signal when asleep, especially where the sleeper processes the signal as meaningful. [source]

The Effect of CO2 and KTP laser on the cat saccule and utricle

THE LARYNGOSCOPE, Issue 8 2009
Larry Lundy MD
Abstract Objectives/Hypothesis: To assess the potential carbon dioxide (CO2) and potassium-titanyl-phosphate (KTP) laser-related trauma to the saccule and utricle in a cat model. Study Design: Basic science experiment utilizing cat model. Methods: Twelve adult male cats were divided into two groups,CO2 and KTP,to assess the potential saccule and/or utricle trauma with direct discharge of laser energy into the vestibule after the stapes was removed. Both groups were subdivided to assess the effects with acute sacrifice and three-month survival. Bone conduction auditory brain-stem response thresholds were used to monitor auditory function. Clinical observation was used to monitor vestibular function. The temporal bones were harvested, processed, and stained with hematoxylin and eosin (H&E) in all animals with the uninvolved side serving as the control. Results: None of the animals demonstrated changes in bone conduction auditory brain-stem responses. None of the animals in the survival group demonstrated clinical vestibular dysfunction. Saccular and utricular wall rupture was observed in all animals sacrificed acutely. None of the saccular and utricular wall ruptures were of a size and location that could be attributed to laser trauma, and none of the saccular and utricular wall ruptures were associated with neuroepithelial trauma. Conclusions: There is no evidence of a difference between the CO2 and KTP laser in potential laser-related trauma. Using bone-conducting auditory brain-stem response threshold and clinical monitoring of vestibular function, there was no evidence of clinical auditory or vestibular dysfunction. The histologic evidence of saccular and utricular wall rupture is more consistent with stapes extraction trauma than laser-related trauma. Laryngoscope, 2009 [source]

Life-cycle exposure of fathead minnows (Pimephales promelas) to an ethinylestradiol concentration below 1 ng/L reduces egg fertilization success and demasculinizes males

ENVIRONMENTAL TOXICOLOGY, Issue 2 2005
Joanne L. Parrott
Abstract Forty-eight hours after fertilization, fathead minnow (Pimephales promelas) eggs were exposed to the synthetic estrogen 17,-ethinylestradiol (EE2) at nominal concentrations of 0.32 and 0.96 ng/L and measured concentrations of 3.5, 9.6, and 23 ng/L. The fish were observed through the larval, juvenile, and adult stages. Growth, secondary sex characteristics, the liver somatic index, the gonadosomatic index, and fecundity were examined after several lengths of exposure. No significant changes were seen in fry or juvenile growth from 8 to 30 days posthatch (dph). An increase in the ovipositor index (a female secondary sex characteristic) was the most sensitive early response at 60 dph and was seen in fish exposed to EE2 concentrations , 3.5 ng/L. Continuation of the EE2 exposure until 150 dph, through maturation and reproduction, allowed measurement of two sensitive end points: decreased egg fertilization and sex ratio (skewed toward females), both of which were significantly affected at the lowest EE2 concentration tested, 0.32 ng/L. The next most sensitive end point was demasculinization (decreased male secondary sex characteristic index) of males exposed to an EE2 concentration of 0.96 ng/L. The effects of low concentrations of EE2 (0.32 and 0.96 ng/L) were manifested in male fish (decreased male sex characteristics and reduced egg fertilization success), whereas female fish showed no changes in the gonadosomatic index. Exposure to higher EE2 concentrations negatively affected females, as shown by a reduced gonadosomatic index at 150 dph in fish exposed to ,3.5 ng/L EE2. Although there were some end points that showed changes at 60 dph, the reproductive end points and external sex characteristics measured in mature fish at 150 dph were more sensitive, with response thresholds of EE2 ranging from 0.32 to 0.96 ng/L. The concentrations of EE2 that negatively affected fathead minnows were similar to or lower than those detected in many municipal wastewater effluents. In conclusion, life-cycle exposure of fathead minnows proved to be a very sensitive bioassay, and responses were seen at concentrations of less than 1 ng/L, which are environmentally relevant concentrations of EE2. © 2005 Government of Canada. Exclusive worldwide publication rights in the article have been transferred to John Wiley & Sons, Inc. Environ Toxicol 20: 131,141, 2005. [source]