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71.
Curtis J. Condon Su-Hua Chang Albert S. Feng 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,168(6):709-725
Summary Response characteristics of 130 single neurons in the superior olivary nucleus of the northern leopard frog (Rana pipiens pipiens) were examined to determine their selectivity to various behaviorally relevant temporal parameters [rise-fall time, duration, and amplitude modulation (AM) rate of acoustic signals. Response functions were constructed with respect to each of these variables. Neurons with different temporal firing patterns such as tonic, phasic or phasic-burst firing patterns, participated in time domain analysis in specific manners. Phasic neurons manifested preferences for signals with short rise-fall times, thus possessing low-pass response functions with respect to this stimulus parameter; conversely, tonic and phasic-burst units were non-selective and possessed all-pass response functions. A distinction between temporal firing patterns was also observed for duration coding. Whereas phasic units showed no change in the mean spike count with a change in stimulus duration (i.e., all-pass duration response functions), tonic and phasic-burst units gave higher mean spike counts with an increase in stimulus duration (i.e., primary-like high-pass response functions). Phasic units manifested greater response selectivity for AM rate than did tonic or phasic-burst units, and many phasic units were tuned to a narrow range of modulation rates (i.e., band-pass). The results suggest that SON neurons play an important role in the processing of complex acoustic patterns; they perform extensive computations on AM rate as well as other temporal parameters of complex sounds. Moreover, the response selectivities for rise-fall time, duration, and AM rate could often be shown to contribute to the differential responses to complex synthetic and natural sounds.Abbreviations
SON
superior olivary nucleus
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DMN
dorsal medullary nucleus
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TS
torus semicircularis
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FTC
frequency threshold curve
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BF
best excitatory frequency
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PAM
pulsatile amplitude modulation
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SAM
sinusoidal amplitude modulation
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SQAM
square-wave amplitude modulation
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MTF
modulation transfer function
-
PSTH
peri-stimulus time histogram 相似文献
72.
Residuals for relative risk regression 总被引:2,自引:0,他引:2
73.
青海省海北地区高寒草甸鸟类群落结构的季节变化 总被引:17,自引:1,他引:16
本研究地区,高寒草甸鸟类群落由22种鸟组成,它们隶属于2目9科,其中留鸟11种,迁徙鸟8种。在当地繁殖的鸟19种,冬候鸟2种。各项鸟类群落指标呈现明显季节变化,一般从早春开始上升,到夏季达到高峰,然后逐渐下降至隆冬的最低点。 相似文献
74.
On the evolution of non-specific mutualism 总被引:2,自引:0,他引:2
Richard Law Suzanne Koptur 《Biological journal of the Linnean Society. Linnean Society of London》1986,27(3):251-267
It has been argued that mutualisms are non-specific when mutualistic interactions are weak and transient, and become more specific as interactions increase in strength. However, this runs counter to the observation that there exist tightly linked mutualisms of great antiquity that are highly nonspecific. Here we argue that mutualism generates positive, interspecific, frequency-dependent selection, which acts as a cohesive evolutionary force, discouraging evolution of specificity. A simple mathematical model is constructed to analyse the evolution of a community consisting of two guilds of species with mutualistic between-guild interactions, two competing species in each guild and two genetically distinct phenotypes within each species. With some simplifying assumptions, the trajectories in the neighbourhood of the only interior equilibrium point are determined analytically in terms of interactions between individuals. These show that the equilibrium is locally stable (no evolution) when there is little differentiation between phenotypes in mutualistic and interspecific, competitive interactions. On the other hand, when there is strong differentiation between phenotypes in their mutualistic interactions, the equilibrium is unstable and the community starts to evolve towards non-specificity. There are, however, two forces counteracting this tendency which, if sufficiently potent, cause evolution towards specificity. The first is generated by strong differentiation between phenotypes in interspecific competition; the second is caused by specificity which already exists between species in their mutualistic interactions. Thus, the tendency for non-specificity or specificity to evolve depends on the interplay between antagonistic and mutualistic interactions in the community. We illustrate these results with some numerical examples and, finally, survey some data on specificity of mutualisms in the light of the analysis. 相似文献
75.
棕色固氮菌在正常培养过程中所产生的含肽物质,有络合特征峰出现。含肽物质与钼(V)络合的EPR信号g值为1.94。与钼酸盐的络合稳定常数K为2.5×10~9。棕色固氮菌变种UW1(Av1~-,Av2~-),UW38(Av1~-,Av2~ )和UW91(Av1~ ,Av2~-)都能产生类似的含肽物质。培养基中钼的存在是含肽物质产生和分泌所必需的,含肽物质排出的量与培养基中钼的水准呈正相关。不能积累钼的变种UW71在高钼培养基中只能限量地分泌含肽物质。氨培养条件下仍能产生和分泌含肽物质。这种含肽物质与该菌粗提液中的某种成分(除固氮酶组分外)具同源性,它既能从菌体中分泌出来,又能进入菌体,在菌体和培养液之间往返运行,可能在该菌钼酸盐运输中起载体作用。 相似文献
76.
77.
78.
Summary Using the monotone dependence function (mdf) together with correlation coefficient it was found that the Ma-DNA content as well as total protein content are regularly, linearly, positively and strongly dependent in sister cells (proter-opisthe) ofChilodonella steini. Additionally it was shown that proter-opisthe ordering is irrelevant to Ma-DNA and protein contents.Analysis of sister cell generation times (TG) confirmed the existence of regular, linear, positive and strong codependence.The relations between Ma-DNA and total protein contents, between protein content and TG, and between Ma-DNA content and TG were also described. There is a weak, linear dependence between Ma-DNA and total protein contents. Relations of TG and Ma-DNA content or TG and total protein content are non-linear and not even monotone. Low and high levels of DNA or proteins are connected with long generation times. 相似文献
79.
Most previously published electromyographic (EMG) studies have indicated that the temporalis muscles in humans become almost
electrically quiet during incisai biting. These data have led various workers to conclude that these muscles may contribute
little to the incisai bite force. The feeding behavior and comparative anatomy of the incisors and temporalis muscles of certain
catarrhine primates, however, suggest that the temporalis muscle is an important and powerful contributor to the bite force
during incision. One purpose of this study is to analyze the EMG activity of the masseter and temporalis muscles in both humans
and macaques with the intention of focusing on the conflict between published EMG data on humans and inferences of muscle
function based on the comparative anatomy and behavior of catarrhine primates. The EMG data collected from humans in the present
study indicate that, in five of seven subjects, the masseter,anterior temporalis, and posterior temporalis muscles are very active during apple incision (i.e., relative to EMG activity
levels during apple and almond mastication). In the other two human subjects the EMG levels of these muscles are lower during
incision than during mastication, but in no instance are these muscles ever close to becoming electrically quiet. The EMG
data on macaques indicate that, in all six subjects, the masseter, anterior temporalis, and posterior temporalis muscles are
very active during incision. These data are in general agreement with inferences on muscle function that have been drawn from
the comparative anatomy and behavior of primates, but they do not agree with previous experimental data. The reason for this
disagreement is probably due to differences in the experimental procedure. In previous studies subjects simply bit isometrically
on their incisors and the resulting EMG pattern was compared to the pattern associated with powerful clenching in centric
occlusion. In the present study the subjects incised into actual food objects, and the resulting EMG pattern was compared
to the pattern associated with mastication of various foods. It is not surprising that these two procedures result in markedly
different EMG patterns, which in turn result in markedly different interpretations of jaw-muscle function. In an attempt to
explain the evolution of the postorbital septum in anthropoids, it has been suggested that the anterior temporalis is more
active than the masseter during incision (Cachel, 1979). The human and macaque EMG data do not support this hypothesis; during
incision, the two muscles show no consistent differences in humans and the masseter appears to be in fact more active than
the anterior temporalis in macaques. 相似文献
80.
Regulation of the loss of frost hardiness in Pinus radiata by photoperiod and temperature 总被引:2,自引:1,他引:1
Abstract. In controlled environments, the interactive effects of warm (16: 8°C, day: night) and cool (12: 4°C, day: night) temperatures and long (13.5 h) and short (10 h) photoperiods on the dehardening of seedlings of Pinus radiata D. Don were investigated. In another experiment, the effect of four photoperiods from 9 to 14 h was examined. In a third, dehardening at constant temperatures from 5 to 17°C was followed. There was no evidence for an interaction between photoperiod and temperature. Dehardening was temporarily delayed by photoperiods below about 10 h, but there was no other quantitative effect of photoperiod. At constant temperatures, the rate of dehardening was initially constant but declined as the minimum summer frost hardiness was reached. In the initial phase the rate of dehardening was a linear function of temperature, increasing from 0.05°C day−1 at 8°C to 0.30 °C day−1 at 17°C. Temperature controlled the loss of frost hardiness by regulating the rate of dehardening. 相似文献