OLFACTORY RESPONSIVENESS TO DIACETYL

Odor thresholds in the headspace over aqueous solutions of diacetyl (butane-2,3-dione) were measured in quadruplicate by a forced-choice procedure in 53 individuals. Mean individual thresholds varied over a factor of 256, with the group average at .005 μg/ml. Thresholds showed a modest negative correlation with suprathreshold intensity ratings. Intensity ratings were distributed bimodally, consistent with the existence of insensitive and sensitive groups and suggesting the possibility of a specific anosmia for this compound.     

Quantitative Studies of Stimulus Coding in First-Order Vibrissa Afferents of Rats. 1. Receptive Field Properties and Threshold Distributions

We examined stimulus-response relationships of vibrissa-activated mechanosensory neurons of the rat's fifth (trigeminal) ganglion. Single-unit activity was recorded with tungsten microelectrodes. The vibrissae were deflected with a variety of parametrically controlled stimulus waveforms.

We found that the receptive field of each vibrissa-activated neuron consisted of a single vibrissa. Few, if any, unambiguous examples of spontaneous activity were observed in these neurons. Even if true spontaneous activity was present, its observed incidence was low, as were the measured discharge rates.

Thresholds of individual neurons were usually quite discrete; often a 1-2% increase in pulse magnitude (angular displacement) above a level to which the neuron did not respond caused it to discharge on every trial. The distribution of thresholds for the sample was continuous with a median of about 1° and a range of over three orders of magnitude. The most sensitive neurons responded to deflections of less than 0.1°. Many neurons responded to a single suprathreshold pulse with more than one spike. We found no consistent relationships among the thresholds of the additional evoked discharges of an individual neuron other than that the total number of evoked spikes either increased or stayed the same, but never decreased, as stimulus magnitude increased.

About one-third of the neurons examined had velocity thresholds below 3°/sec. Above that value, thresholds were distributed continuously throughout a range of over three orders of magnitude. The median velocity threshold was about 100°/sec. The broad and continuous distributions of both magnitude and velocity thresholds suggest that a population of vibrissa-activated neurons can code stimulus strength smoothly and continuously over a wide range, even though individual neurons may be poorly suited to do so.     

Effects of linoleic acid on sweet, sour, salty, and bitter taste thresholds and intensity ratings of adults

Evidence supporting a taste component for dietary fat has prompted study of plausible transduction mechanisms. One hypothesizes that long-chain, unsaturated fatty acids block selected delayed-rectifying potassium channels, resulting in a sensitization of taste receptor cells to stimulation by other taste compounds. This was tested in 17 male and 17 female adult (mean +/- SE age = 23.4 +/- 0.7 yr) propylthiouracil tasters with normal resting triglyceride concentrations (87.3 +/- 5.6 mg/day) and body mass index (23.3 +/- 0.4 kg/m(2)). Participants were tested during two approximately 30-min test sessions per week for 8 wk. Eight stimuli were assessed in duplicate via an ascending, three-alternative, forced-choice procedure. Qualities were randomized over weeks. Stimuli were presented as room-temperature, 5-ml portions. They included 1% solutions of linoleic acid with added sodium chloride (salty), sucrose (sweet), citric acid (sour), and caffeine (bitter) as well as solutions of these taste compounds alone. Participants also rated the intensity of the five strongest concentrations using the general labeled magnitude scale. The suprathreshold samples were presented in random order with a rinse between each. Subjects made the ratings self-paced while wearing nose clips. It was hypothesized that taste thresholds would be lower and absolute intensity ratings or slopes of intensity functions would be higher for the stimuli mixed with the linoleic acid. Thresholds were compared by paired t-tests and intensity ratings by repeated measures analysis of variance. Thresholds were significantly higher (i.e., lower sensitivity) for the sodium chloride, citric acid, and caffeine solutions with added fatty acid. Sweet, sour, and salty intensity ratings were lower or unchanged by the addition of a fatty acid. The two highest concentrations of caffeine were rated as weaker in the presence of linoleic acid. These data do not support a mechanism for detecting dietary fats whereby fatty acids sensitize taste receptor cells to stimulation by taste compounds.     

Evidence for human orosensory (taste?) sensitivity to free fatty acids

Accumulating evidence suggests dietary fatty acids (FAs) may be sensed in the oral cavity. However, the effective cues have not been characterized. In particular, influences from other sensory cues have hampered identification of an independent gustatory contribution. Experiment 1 examined techniques to minimize the formation of FA oxidation products and improve the homogeneity of water/lipid emulsions to be used as stimuli in Experiment 2, a psychophysical study to determine FA detection thresholds in humans. Through sonication of chilled samples held in polypropylene labware and the addition of 0.01% ethylenediaminetetraacetic acid, calcium disodium salt, homogenous emulsions of unoxidized linoleic and oleic FAs were obtained. Spectrophotometric analysis revealed no oxidation product formation over a 24-h period. Coupled with these techniques, a masking approach was used to minimize other sensory cues imparted from linoleic, oleic, and stearic FAs. Concentration ranges from 0.00028% to 5% (w/v) were prepared in mixtures with 5% mineral oil (w/v) and 5% gum acacia (w/v) to mask lubricity and viscosity effects, respectively. Testing was conducted under red light with nares blocked to eliminate visual and olfactory cues. Oral rinses with 20 ppm capsaicin were administered to desensitize participants to selected irritation effects prior to remeasuring linoleic acid detection thresholds. To determine if the effective stimulus was an oxidation product, oxidized linoleic acid was included among the test stimuli. Detection thresholds were obtained using a 3-alternative, forced-choice ascending-concentration presentation procedure. The mean detection threshold for linoleic acid pre-desensitization was 0.034 +/- 0.008%, for linoleic acid post-desensitization was 0.032 +/- 0.007%, for oleic 0.022 +/- 0.003%, for stearic 0.032 +/- 0.005%, and oxidized linoleic 0.025 +/- 0.005%. The results suggest that linoleic, oleic, stearic, and oxidized linoleic acids are detectable in the oral cavity of humans with minimal input from the olfactory, capsaicin, and viscosity-assessing tactile systems.     

Simulated microgravity [bed rest] has little influence on taste,odor or trigeminal sensitivity

Anecdotal evidence suggests that astronauts' perceptions of foods in space flight may differ from their perceptions of the same foods on Earth. Fluid shifts toward the head experienced in space may alter the astronauts' sensitivity to odors and tastes, producing altered perceptions. Our objective was to determine whether head-down bed rest, which produces similar fluid shifts, would produce changes in sensitivity to taste, odor or trigeminal sensations. Six subjects were tested three times prior to bed rest, three times during bed rest and two times after bed rest to determine their threshold sensitivity to the odors isoamylbutyrate and menthone, the tastants sucrose, sodium chloride, citric acid, quinine and monosodium glutamate, and to capsaicin. Thresholds were measured using a modified staircase procedure. Self-reported congestion was also recorded at each test time. Thresholds for monosodium glutamate where slightly higher during bed rest. None of the other thresholds were altered by bed rest.     

AngⅡ通过激活Notch1/Sox2通路对肝星状细胞LX2的活化和增殖的作用

目的探讨AngⅡ通过靶向调控Notch1/Sox2肝星状细胞LX2细胞的增殖。 方法通过CCK8检测AngⅡ对肝星状细胞增殖能力的影响,通过羟脯氨酸酸法检测AngⅡ对肝星状细胞胶原合成能力的影响,并通过脂质体转染siRNA-Notch1构建Notch1低表达细胞模型,通过CCK8检测敲低Notch1对AngⅡ诱导的肝星状细胞LX2增殖的影响,通过Western Blot检测敲低Notch1对AngⅡ诱导的肝星状细胞LX2蛋白表达的影响。所有的检测结果都进行生物学重复。采用方差分析和t检验进行统计学分析。 结果CCK8结果显示,AngⅡ（5、10、20、40、80 nmol/L）预处理A450值分别为0.67±0.06、0.88±0.07、0.98±0.07、1.08±0.07、1.23±0.07,较对照组0.57±0.05上升,差异具有统计学意义（F = 45.76,P < 0.01）,羟脯氨酸检查结果显示,AngⅡ（10、20、40 nmol/L）预处理组羟脯氨酸浓度分别为（2.60±0.20）、（3.47±0.25）、（4.17±0.21）mg/L,羟脯氨酸浓度较对照组（1.90±0.10）mg/L上升,差异具有统计学意义（F = 75.18,P < 0.01）。Western Blot结果显示,AngⅡ10、20、40 nmol/L组Notch1蛋白表达水平分别为0.20±0.02、0.54±0.04、0.82±0.03,与正常对照组0.11±0.02发生升高,差异具有统计学意义（F = 400.50,P < 0.01）。Notch1干扰后,CCK8结果显示,siRNA-Notch1+AngⅡ组（10、20、40 nmol/L）A450值分别为0.53±0.06、0.83±0.03、1.03±0.03,与siRNA-NC+ AngⅡ对照组0.97±0.06,1.43±0.06,1.73±0.06比较发生降低（P < 0.01）。进一步Western Blot结果显示,Notch1敲低组（AngⅡ+ siRNA-Notch1）Notch1、HES1和Sox2蛋白表达水平分别为1.47±0.12、0.77±0.06和0.50±0.10,分别与AngⅡ对照组2.83±0.15、2.20±0.10和1.17±0.06比较,差异具有统计学意义（P < 0.01）。 结论AngⅡ通过激活Notch1/Sox2信号促进肝星状细胞LX2增殖。     

VISUAL HAZE DETECTION THRESHOLD ASSESSMENT BY ASCENDING METHOD OF LIMITS AND A TRANSFORMED STAIRCASE PROCEDURE IN APPLE JUICE SIMULATIONS UNDER " STORE LIKE" CONDITIONS

Visual haze detection thresholds were assessed in thirty panelists by two methods: the ascending method of limits and a transformed staircase procedure (UDTR, from Wetherill and Levitt 1965). The 3AFC test was used as the response procedure for both methods. Experimental samples consisted of an apple juice simulation (water with food coloring). Haze was added to the samples using formazin, and was calibrated to eleven levels ranging from 0.75–13.30NTU. Haze detection thresholds under store-like conditions (3.55 ± 0.57 [mean ± S.E.] and 3.16 ± 0.50 NTU by the two methods, respectively) were higher than those found previously under more controlled viewing conditions. No differences were found between methods, genders, or order of method presentation ( p > 0.05); a practice effect showed a slight improvement in detection thresholds between sessions ( p = 0.05). Nonparametric tests confirmed the similarities in the threshold estimates from the two methods. The two methods estimated visual haze detection thresholds equally well. However, the ascending method of limits may be preferred method due to the shorter time involved in administration.     

辣椒碱对烟粉虱的生物活性及生长发育和生殖力的影响

在实验室条件下研究了辣椒碱对烟粉虱的生物活性及生长发育和生殖力的影响.结果表明:辣椒碱对烟粉虱各虫态均有杀虫活性,且随辣椒碱浓度的增大活性增强;辣椒碱浸叶法/浸虫法处理对烟粉虱成虫、卵和若虫的毒力(LC50分别为3525.79、1603.29和1526.27mg·L-1))均高于内吸法处理(LC50分别为5360.04、2359.19和5897.43 mg.L-1),两种处理方法下辣椒碱对烟粉虱卵的毒力均明显高于对成虫的毒力;2000和4000 mg·L-1浓度辣椒碱对烟粉虱成虫具有明显的拒食作用,烟粉虱在该两种浓度辣椒碱处理过的棉花叶上取食24 h的蜜露分泌量均显著低于取食非处理棉花叶后的蜜露分泌量;辣椒碱各试验浓度对烟粉虱成虫均表现出较强的产卵忌避作用,当辣椒碱处理浓度达4000 mg·L-1时,对烟粉虱的选择性产卵忌避率和非选择性产卵忌避率分别高达94.2％和83.0％.500、1000和2000 mg·L-1辣椒碱浸渍处理对烟粉虱存活卵和若虫的发育历期、成虫羽化率均没有影响,但辣椒碱4000mg·L-1处理明显延长烟粉虱若虫发育历期、降低成虫羽化率.不同浓度辣椒碱处理均明显抑制烟粉虱生殖力,且这种抑制作用随辣椒碱浓度的增大而增强.     

Disinfection of bacteria in water systems by using electrolytically generated copper:silver and reduced levels of free chlorine

As an alternative disinfectant to chlorination, electrolytically generated copper:silver (400 and 40 micrograms/L copper and silver, respectively) with and without free chlorine (0.3 mg/L) was evaluated over a period of 4 weeks in indoor and outdoor water systems (100 L tap water with natural body flora and urine). Numbers of total coliform, pseudomonas, and staphylococci were all less than drinking water standards in systems treated with copper:silver and free chlorine and systems treated with free chlorine alone (1.0 mg/L). No significant differences (p less than or equal to 0.05) in bacterial numbers were observed between systems with copper:silver and free chlorine and those with free chlorine alone. Overall, free-chlorine treatments (0.3 or 1.0 mg/L) showed significantly lower heterotrophic plate numbers than those without free chlorine. When challenged with a natural Staphylococcus sp. isolate, water with copper:silver and free chlorine had a 2.4 log10 reduction in bacterial numbers within 2 min, while free chlorine alone or copper:silver alone showed 1.5 and 0.03 log10 reductions, respectively. Addition of copper:silver to water systems may allow the concentration of free chlorine to be reduced while still providing comparable sanitary quality of the water.     

农林复合系统滇龙胆茎叶化学计量特征研究

以农林复合系统种植的滇龙胆(Gentiana rigescens Franch.ex Hemsl.)为材料,采用高效液相色谱法建立不同栽培系统滇龙胆茎、叶的色谱指纹图谱,并测定其主要活性成分马钱苷酸、獐牙菜苦苷、龙胆苦苷和当药苷含量,研究不同栽培系统滇龙胆茎、叶化学计量特征。采用相关性分析、指纹图谱相似度分析、偏最小二乘判别分析(PLS-DA)、变量投影重要性准则(VIP)等方法进行化学数据分析。结果显示,滇龙胆主要活性成分马钱苷酸含量为(1.85±0.92)mg/g~(7.43±7.64)mg/g,獐牙菜苦苷含量为(1.03±0.17)mg/g~(1.58±0.50)mg/g,龙胆苦苷含量为(15.28±11.34)mg/g~(24.59±7.84)mg/g,当药苷含量为(4.10±1.64)mg/g~(31.67±22.70)mg/g,且叶片中4种活性成分的总含量高于茎;不同栽培系统中,与尼泊尔桤木间作的滇龙胆茎、叶活性成分总含量最高,而与核桃间作的滇龙胆茎、叶活性成分总含量最低。相关性分析显示,植株相同部位和不同部位间的环烯醚萜和裂环烯醚萜含量呈显著(P0.05)或极显著(P0.01)正相关。指纹图谱相似度分析表明,不同栽培系统滇龙胆茎指纹图谱相似度介于0.989~0.992之间、叶指纹图谱相似度为0.988~0.996,相同部位样品化学成分种类相似。PLS-DA分析结果表明,茎和叶片整体化学计量特征具有明显差异;单作及林药间作的样品被区分为不同类群,不同间作模式下滇龙胆茎、叶化学成分具显著差异,叶片高效液相色谱指纹图谱可用于区分不同栽培系统滇龙胆样品。本研究结果可为农林复合系统滇龙胆有效成分含量研究及滇龙胆资源的合理开发利用提供科学依据。     

Obese Women Have Lower Monosodium Glutamate Taste Sensitivity and Prefer Higher Concentrations Than Do Normal‐weight Women

The goal of this study was to determine whether obese women exhibit altered umami and sweet taste perception compared to normal‐weight women. A total of 57 subjects (23 obese and 34 normal weight) participated in a 2‐day study separated by 1 week. Half of the women in each group were evaluated using monosodium glutamate (MSG; prototypical umami stimulus) on the first test day and sucrose on the second test day; the order was reversed for the remaining women. We used two‐alternative forced‐choice staircase procedures to measure taste detection thresholds, forced‐choice tracking technique to measure preferences, the general Labeled Magnitude Scale (gLMS) to measure perceived intensity of suprathreshold concentrations, and a triangle test to measure discrimination between 29 mmol/l MSG and 29 mmol/l NaCl. Obese women required higher MSG concentrations to detect a taste and preferred significantly higher MSG concentrations in a soup‐like vehicle. However, their perception of MSG at suprathreshold concentrations, their ability to discriminate MSG from salt, and their preference for sucrose were similar to that observed in normal‐weight women. Regardless of their body weight category, 28% of the women did not discriminate 29 mmol/l MSG from 29 mmol/l NaCl (nondiscriminators). Surprisingly, we found that, relative to discriminators, nondiscriminators perceived less savoriness when tasting suprathreshold MSG concentrations and less sweetness from suprathreshold sucrose concentrations but had similar MSG and sucrose detection thresholds. Taken together, these data suggest that body weight is related to some components of umami taste and that different mechanisms are involved in the perception of threshold and suprathreshold MSG concentrations.     

Population-specific behavioral electrosensitivity of the European blind cave salamander,Proteus anguinus

In nine salamanders from different Slovenian populations of the urodele Proteus anguinus, including three specimens of its ‘black’ variety, P anguinus parkelj, thresholds of an overt avoidance response to electrical field stimuli were estimated as a function of frequency (continuous sine-waves in water). Thresholds down to 0.3 mV/cm (ca 100 nA/cm²) and up to 2 mV/cm (670 nA/cm²), at ‘best frequencies’ of around 30 Hz were found. Sensitivity covered a total frequency range of below 1 Hz, excluding DC, up to 1–2 kHz with up to 40 dB higher thresholds. Thresholds and tuning curves are compared with those of a Proteus population raised in captivity for more than 35 years. The biological significance and the apparently still ongoing evolution of the electrical sense in urodeles, ie in the genus Proteus, are interpreted in terms of comparative sensory physiology and ethological ecology as a result of more recent evolutionary diversification during and since glaciation in the Pleistocene.     

Frequency and site-dependent variations in vibration detection thresholds on the face

An adaptive psychophysical procedure was used to estimate the vibration detection threshold at seven spatially matched sites on the two sides of the face and at one scalp site. Repeated measurements over six testing sessions were made for stimuli vibrating at 1, 10 and 100 Hz for each of 21 neurologically healthy, young adult females. Approximately 14 stimulus trials were required to obtain each estimate of the threshold amplitude. Thresholds varied as a function of frequency (p < 0.0001), side (p < 0.001) and site (p < 0.0001). Compared to stimulation at 100 Hz at which the estimates were lowest, thresholds were 3.1 times greater at 10 Hz and 5.4 times greater at 1 Hz. Thresholds were lowest on the vermilion and highest on the cheek and chin. The preauricular skin and scalp exhibited an intermediate level of sensitivity. Whereas thresholds were comparable on the two sides of the face for stimulation at 1 Hz, they averaged 1.33 times greater on the right side for stimulation at 10 and 100Hz. Moreover, thresholds obtained during the last two sessions were 16% higher than those obtained during the first two sessions (p < 0.02), suggesting that subjects on average became more conservative in reporting the presence of the stimulus. The sensitivity in discriminating differences in tactile function favors use of the rapidly administered testing procedure in a clinical setting.     

Frequency and site-dependent variations in vibration detection thresholds on the face

An adaptive psychophysical procedure was used to estimate the vibration detection threshold at seven spatially matched sites on the two sides of the face and at one scalp site. Repeated measurements over six testing sessions were made for stimuli vibrating at 1, 10 and 100 Hz for each of 21 neurologically healthy, young adult females. Approximately 14 stimulus trials were required to obtain each estimate of the threshold amplitude. Thresholds varied as a function of frequency ( p < 0.0001), side ( p < 0.001) and site ( p < 0.0001). Compared to stimulation at 100 Hz at which the estimates were lowest, thresholds were 3.1 times greater at 10 Hz and 5.4 times greater at 1 Hz. Thresholds were lowest on the vermilion and highest on the cheek and chin. The preauricular skin and scalp exhibited an intermediate level of sensitivity. Whereas thresholds were comparable on the two sides of the face for stimulation at 1 Hz, they averaged 1.33 times greater on the right side for stimulation at 10 and 100 Hz. Moreover, thresholds obtained during the last two sessions were 16% higher than those obtained during the first two sessions ( p < 0.02), suggesting that subjects on average became more conservative in reporting the presence of the stimulus. The sensitivity in discriminating differences in tactile function favors use of the rapidly administered testing procedure in a clinical setting.     

Water-relation parameters of giant and normal cells of Capsicum annuum pericarp

Abstract. Measurements of the water-relation parameters of the giant subepidermal cells (volume, V = 0.119 to 1.658 mm³; = 0.53±0.35 mm³, SD, n = 23) and the smaller mesocarp parenchyma cells ( V = 0.10 to 0.79×10⁻³ mm³; = 0.36±0.27×10⁻³ mm³, SD, n = 6) of the inner pericarp surface of Capsicum annuum L. were made using the Jülich pressure probe. The volumetric elastic modulus ɛ for the large cells was between 1.5 and 27 MPa for a pressure range of 0.09 to 0.41 MPa. For the small cells ɛ was 0.1 to 0.6 MPa for a pressure range of 0.22 to 0.39 MPa. The turgor pressure P , the half-time of water exchange T _1/2, and the hydraulic conductivity L _p were as follows, with SD and number of replicates: large cells, P = 0.27±0.06 MPa (23), T _1/2=2.7±2.2 s (46), L _p=5.8±3.7 pm s⁻¹ Pa⁻ (46); small cells, P = 0.33±0.07 MPa (6), T _1/2= 33±10s (12), L _p=0.21±0.07 pm s⁻¹ Pa⁻¹ (12). The determination of these basic water-relation parameters is considered as a prerequisite for future ecotoxicological and phytopathological studies. The differences between the large and the small cells are discussed in relation to a desirable biophysical definition of succulence. Further, for the large cells a pressure and volume dependence of ɛ was demonstrated.     

Gustatory perception of isohumulones: influence of sex and thiourea taster status

Detection thresholds for NaCl and a purified isohumulones preparationdid not differ between thiourea tasters and non-tasters. However,suprathreshold concentrations of isohumulones in water (butnot in beer) were perceived as more intense by tasters. Femaleshad significantly lower NaCl thresholds and tended to perceiveisohumulones in water as more intense.     

Administration of capsiate, a non-pungent capsaicin analog, promotes energy metabolism and suppresses body fat accumulation in mice

We investigated the effects of a single oral administration of capsiate, which is found in the fruits of a non-pungent cultivar of pepper, CH-19 Sweet, and has the same structure as capsaicin except for replacement of NH by O in the alkyl chain, on the thermogenesis and fat accumulation in mice. The oxygen consumption and serum adrenalin concentration were higher in both the capsaicin (10 mg/kg-body weight) and capsiate (10 mg/kg-body weight) groups than those in the control group. We also examined the effects of 2 weeks of administration of capsaicin and capsiate on body fat accumulation. Eevery day for 2 weeks administration of capsiate (10, 50 mg/kg-body weight/day) markedly suppressed body fat accumulation as well as capsaicin (10 mg/kg-body weight/day). These results suggest that capsiate promotes energy metabolism and suppresses body fat accumulation as does capsaicin.     

Methods for determining auditory evoked brain-stem response thresholds in human newborns

Previous investigators have reported that newborn auditory evoked brain-stem responses (ABRs) are 20–30 dB higher than adult psychophysical thresholds to the same stimuli. These investigators reduced the intensity of the stimulus until they no longer reported an ABR to the stimulus. We adapted 2 widely used psychophysical methods, the up-down-transformed response (UDTR) method and the method of constant stimuli, for ABR threshold determination of human newborns. Response judgments were made blindly. ABR thresholds of healthy normal newborns by both procedures were no more than 10–15 dB higher than adult psychophysical thresholds. The differences between the newborn ABR thresholds we reported and those in the literature were probably explained by different procedures including the method used to estimate adult psychophysical thresholds. The correlations between ABR thresholds and suprathreshold ABR latencies and amplitudes and latency and amplitude/intensity functions were modest at best. In normal newborns suprathreshold ABR measurements are of little value in predicting ABR thresholds.     

Correspondence between evoked vocal responses and auditory thresholds in Pleurodema thaul (Amphibia; Leptodactylidae)

Thresholds for evoked vocal responses and thresholds of multiunit midbrain auditory responses to pure tones and synthetic calls were investigated in males of Pleurodema thaul, as behavioral thresholds well above auditory sensitivity have been reported for other anurans. Thresholds for evoked vocal responses to synthetic advertisement calls played back at increasing intensity averaged 43 dB RMS SPL (range 31–52 dB RMS SPL), measured at the subjects’ position. Number of pulses increased with stimulus intensities, reaching a plateau at about 18–39 dB above threshold and decreased at higher intensities. Latency to call followed inverse trends relative to number of pulses. Neural audiograms yielded an average best threshold in the high frequency range of 46.6 dB RMS SPL (range 41–51 dB RMS SPL) and a center frequency of 1.9 kHz (range 1.7–2.6 kHz). Auditory thresholds for a synthetic call having a carrier frequency of 2.1 kHz averaged 44 dB RMS SPL (range 39–47 dB RMS SPL). The similarity between thresholds for advertisement calling and auditory thresholds for the advertisement call indicates that male P. thaul use the full extent of their auditory sensitivity in acoustic interactions, likely an evolutionary adaptation allowing chorusing activity in low-density aggregations.     

The development of hearing sensitivity in altricial birds: the absolute thresholds of the generation of evoked potentials]

Thresholds of field L auditory evoked potentials EP were studied in 1.5-9-day-old nestlings of pied flycatcher in response to pure tone signals of different frequencies. According to the tendencies of age dynamics of auditory EP thresholds (2-9 days of life) all hearing range was divided into three separate channels: low-frequency (0.3-1.0 kHz), intermediate-(1.5-4.0 kHz) and high-frequency (5.0-8.0 kHz) ones. The widening of the hearing range in its high-frequency part was demonstrated on days 4-5 of life. The development of auditory sensitivity was shown to continue within all three channels in postembryonic period (days 2-9 post-hatching), each of the channels being characterized by its own age dynamics of auditory EP thresholds. Reproduction of tape-recorded species song during days 1-3 post-hatching resulted in significant decrease of auditory EP thresholds.