普氏蹄蝠下丘单反应和双反应神经元加工多普勒频移补偿信号的特点及生理机制

恒频-调频(constant frequency-frequency modulation,CF-FM)蝙蝠独特的多普勒频移补偿(Doppler-shift compensation,DSC)行为可保证其对回声信息的精确提取.那么听中枢加工DSC信号的适应性机制是什么?本实验模拟CF-FM蝙蝠DSC后的回声定位信号,研究下丘(inferior colliculus,IC)神经元加工DSC信号的特点及生理机制.实验共获得117个IC神经元,在CF-FM声刺激下,神经元表现为single-on(SO,n=83)和double-on(DO,n=34)两种反应模式.无论是在蝙蝠的正向还是负向补偿过程中,SO和DO神经元对回声反应恢复到50%时的双声刺激间隔(inter-pulse interval,IPI)值,均会随补偿条件的改变而发生变化.当双声刺激由无补偿转变为最佳补偿条件时,两类神经元的50%IPI显著缩短(P0.001),但SO神经元50%IPI缩短率超过70%的神经元数目较DO神经元多,且偏好正向补偿的IC神经元中,SO神经元的平均DSC范围也要显著宽于DO神经元(P0.05).该研究结果提示,IC中SO神经元可能较DO神经元更能充分利用蝙蝠DSC行为,来提高对回声反应的恢复能力,以最大程度地获取猎物信息并准确判断与猎物的相对速度.     

声刺激时程和模式影响大蹄蝠下丘神经元的恢复周期

本文旨在探讨声刺激时程及模式参量对恒频-调频(constant frequency-frequency modulation,CF-FM)蝙蝠下丘(inferior colliculus,IC)神经元恢复周期的影响。实验选用5只听力正常的大蹄蝠为实验动物,采用不同时程或不同模式的双声刺激,记录IC神经元的反应和恢复周期。结果共记录到169个IC声敏感神经元。依据神经元恢复率达到50%时的双声刺激间隔(interpulse interval,IPI)将神经元恢复周期分为三种类型:快速恢复型(fast,F),50%IPI为0～15ms;短时恢复型(short,S),50%IPI为15.1～30ms;长时恢复型(long,L),50%IPI30ms。在2、5和7ms时程的CF声刺激下,神经元50%IPI平均值随声刺激时程的增加,分别为(30.2±27.6)、(39.9±29.1)和(49.4±34.7)ms,F和S型神经元比例逐渐下降,而L型神经元比例逐渐上升。当声刺激模式由2msCF声转变为2msFM声时,F、S和L三种类型神经元比例分别由32.3%、41.5%、26.2%转变为47.7%、24.6%、27.7%,平均恢复周期缩短,由(30.2±27.6)减至(23.9±19.0)ms(P0.05,n=65)。与7msCF声刺激相比,5+2msCF-FM声刺激使F型神经元比例上升(18.2%→29.1%),S型神经元(29.1%→27.3%)和L型神经元(52.7%→43.6%)比例下降,平均恢复周期缩短,由(49.4±34.7)减至(36.3±29.4)ms(P0.05,n=55)。结果提示,CF-FM蝙蝠回声定位信号中的CF和FM成分在蝙蝠导航和捕食过程中分别扮演不同的角色,其中终末相中的FM成分主要使F型神经元数量增多,平均恢复周期缩短。FM成分在蝙蝠靠近靶物的过程中发挥重要作用以快速处理高脉冲重复率回声信息,它有利于准确计算目标距离和识别目标表面质地。     

单频刺激声稳态诱发反应的可靠性研究

目的:通过测试正常听力青年男女的听觉多频稳态诱发反应ASSR和单频刺激声稳态诱发反应探求单频刺激声稳态诱发反应的可靠性。方法:选取32名64耳听力正常的青年人作为受试者,对其进行纯音听阈、ASSR及四个0.5、1、2、4k Hz单频刺激声稳态诱发反应阈值测试,并记录0.5、1、2和4k Hz四个频率纯音阈值及ASSR及四个单频刺激声稳态诱发反应阈值。结果:ASSR在0.5、1、2和4k Hz四个频率的反应阈值与纯音听阈阈值相关性系数分别为0.64、0.81、0.79、0.85;0.5k Hz单频刺激声稳态诱发反应阈值与ASSR阈值具有明显统计学差异,其余3个单频刺激声稳态诱发反应阈值与ASSR阈值没有统计学差异,0.5k Hz单频刺激声稳态诱发反应阈值与纯音听阈阈值相关性系数为0.81。结论:ASSR阈值与纯音听阈具有较好的相关性,0.5k Hz单频刺激声稳态诱发反应可以提高0.5k Hz ASSR阈值与纯音听阈的相关性。     

外侧丘系腹核在声信号加工和听觉上行传导中的作用

外侧丘系腹核(ventral nucleus of the lateral lemniscus,VNLL)是中枢听觉通路中连接耳蜗核等低位脑干和中脑下丘(inferior colliculus,IC)的重要核团,其神经元能够对声信号的不同参数进行检测与加工,进而形成多样的声反应特性。VNLL神经元对频率反应的调谐曲线有多种类型,但其锐化程度一般较低,对频率的分析亦不够精确;有关强度调谐的放电率函数分为两种类型:单调型与非单调型,它们对强度的加工和编码往往受到发放模式的影响;不同发放模式的VNLL神经元对时程的编码能力不同,其中起始型具有精确的时间特性,适合编码声刺激的起始时间信息,对蝙蝠的回声定位非常重要。VNLL接受来自低位核团的输入,并发出上行的抑制性投射至IC,在IC神经元的声信息检测过程中发挥重要作用。近来研究认为VNLL快速的抑制性投射延迟IC神经元的首次发放潜伏期,VNLL延迟的抑制性投射介导IC神经元的发放模式,但VNLL抑制性输入如何在IC进行整合,并增强IC神经元检测声信号能力的机制并不清楚,且缺乏VNLL对IC进行实时调控作用的直接证据。这些问题的研究有助于进一步认识上行输入在声信号加工过程中的作用,同时也是本实验室今后的研究重点。本文结合本实验室相关研究,围绕VNLL对听觉信号的加工和上行传导进行综述。     

菲菊头蝠的下丘神经元基本声反应特性

自由声场刺激条件下,采用单单位胞外微电极记录方法,研究了一种未被研究过的恒频/调频(CF/FM)蝙蝠———菲菊头蝠(Rhinolophuspusillus)的下丘神经元基本声反应特性,其结果发现,在所得的110个下丘神经元中,发放类型包括相位型(54·5%)、紧张型(25·5%)、持续型(7·3%)、梳齿型(7·3%)和暂停型(5·4%)等5种类型。记录深度在208~1855(829·0±328·1)μm之间,最佳频率在16·7~75·6(38·9±15·7)kHz之间,最小阈值在5~74(34·7±13·6)dBSPL之间,阈上10dBSPL潜伏期在5·0~27·5(15·2±3·9)ms之间。最佳频率随记录深度的增加而增大(r=0·9578,P<0·001);记录的54个频率调谐曲线(FTCs)均为开放型,其中52个为单峰型,2个为双峰型。52个单峰型FTC的Q10-dB值介于1·56~31·61之间,并且大部分是狭窄型(Q10-dB值>5),占69·2%(36/52),少部分为宽阔型(Q10-dB值<5),占30·8%(16/52)。2个双峰型神经元FTC在低频处为宽阔型,高频处为狭窄型,Q10-dB值分别为1·95、8和2·89、6·51。共获得34个神经元的强度-发放率函数(RIFs),可分为单调型、非单调型和饱和型。结合先前所研究的FM蝙蝠———普通伏翼蝠(Pipistrellusabramus)下丘神经元的基本声反应特性,比较分析了CF/FM蝙蝠与FM蝙蝠下丘神经元的声反应差异及其行为学意义。     

菲菊头蝠的下丘神经元基本声反应特性

自由声场刺激条件下，采用单单位胞外微电极记录方法，研究了一种未被研究过的恒频/调频(CF/FM)蝙蝠——菲菊头蝠(Rhinolophus pusillus)的下丘神经元基本声反应特性，其结果发现，在所得的110个下丘神经元中，发放类型包括相位型(54.5%)、紧张型(25.5%)、持续型(7.3%)、梳齿型(7.3%)和暂停型(5.4%)等5种类型。记录深度在208～1 855(829.0±328.1)μm之间，最佳频率在16.7～75.6(38.9±15.7)kHz之间，最小阈值在5～74(34.7±13.6)dB SPL之间，阈上10 dB SPL潜伏期在5.0～27.5(15.2±3.9)ms之间。最佳频率随记录深度的增加而增大(r=0.957 8，P<0.001)；记录的54个频率调谐曲线(FTCs)均为开放型，其中52个为单峰型，2个为双峰型。52个单峰型FTC的Q_10-dB值介于1.56～31.61之间，并且大部分是狭窄型(Q _10-dB值>5)，占69.2%(36/52)，少部分为宽阔型(Q _10-dB值<5)，占30.8%(16/52)。2个双峰型神经元FTC在低频处为宽阔型，高频处为狭窄型，Q _10-dB值分别为1.95、8和2.89、6.51。共获得34个神经元的强度－发放率函数(RIFs)，可分为单调型、非单调型和饱和型。结合先前所研究的FM蝙蝠——普通伏翼蝠(Pipistrellus abramus)下丘神经元的基本声反应特性，比较分析了CF/FM蝙蝠与FM蝙蝠下丘神经元的声反应差异及其行为学意义。     

普氏蹄蝠下丘CF-CF联合敏感神经元的声反应

为了研究普氏蹄蝠(Hipposideros pratti)下丘(IC)中恒频-恒频(CF-CF)联合敏感神经元声反应特性,以及易化型和抑制型CF-CF联合敏感神经元在IC高频表征区神经元中所占的比例,实验记录了普氏蹄蝠IC神经元在不同频率和声强下的单声反应以及在不同延迟下的双声反应。本实验采用在体细胞内电生理技术从7只听力正常的蝙蝠上共获得77个IC声敏感神经元。所获得的数据经过处理并应用Sigma Plot 10.0软件作图。研究结果显示,77个神经元中37(48.1%)个为CF-CF联合敏感神经元,且多数为抑制型(24/37),少数为(13/37)易化型。实验结果说明普氏蹄蝠IC中既存在易化型也存在抑制型CF-CF联合敏感神经元,其中抑制型CF-CF联合敏感神经元比易化型所占比例更高。这些CF-CF联合敏感神经元有助于蝙蝠在巡航过程中处理回声信息时进行频谱和时相的整合。     

回声定位蝙蝠及其声通讯

综述了回声定位蝙蝠种类及其发声方式,回声定位信号的主要类型及回声定位信号声学特征,多普勒频移对长CF／FM蝙蝠的主要作用,简介了蝙蝠求偶和母婴识别等内声通讯行为,提出了一些尚待解决的重要问题。     

恒频-调频蝙蝠下丘神经元的恢复周期决定声脉冲跟随率

为探究恒频-调频蝙蝠下丘神经元恢复周期特点及其对声脉冲跟随率的影响,实验采用模拟的大蹄蝠(Hipposideros armiger)自然状态下的恒频-调频发声信号为声刺激,在5只听力正常的大蹄蝠上记录了下丘神经元的声反应和恢复周期(n = 93)．结果发现,根据神经元恢复率达50%时的双声刺激间隔(inter pulse interval,IPI),可将其分为长时恢复型(long recovery,LR;47.4%)、中等时间恢复型(moderate recovery,MR;35.1%)和短时恢复型(short recovery,SR;17.5%)．每种类型依据其恢复率随IPI增加而呈现的不同变化又可进一步分为单IPI反应区神经元,多IPI反应区神经元,以及单调IPI反应神经元．LR,MR和SR型神经元恢复率达50%时的平均IPI分别为(64.0 ± 24.8),(19.6 ± 5.8)和(7.1 ± 2.4) ms (P < 0.001),相对应的平均理论每秒声脉冲数分别为(18.2 ± 7.0),(55.4 ± 15.7)和(171.3 ± 102.9) Hz (P < 0.001)．结果提示,单IPI和多IPI反应区神经元具有特殊IPI反应特性,能对蝙蝠捕食和巡航期间所处的时相做出准确判断,而单调IPI反应神经元对IPI变化的敏感性较强,但时相判断性较差．另外LR,MR和SR型神经元恢复周期和理论脉冲跟随率的平均结果均能与这种蝙蝠回声定位期间3个时相的发声行为相匹配,且神经元恢复周期参与决定声脉冲跟随率,满足了蝙蝠巡航、捕食的行为学需要．     

γ-氨基丁酸能抑制对大棕蝠听皮层神经元声反应特性的影响

为了探讨γ－氨基丁酸（γ-aminobutyric acid,GABA)能抑制对大棕蝠(Eptesicus fuscus)听皮层(auditory cortex,AC)神经元声反应特性的影响,采用多管微电极电泳方法,观察了8只大棕蝠AC神经元去ABA能抑制前后声刺激诱发的反应。结果显示,微电泳GABAa受体拮抗剂荷包牡丹碱(bicuculline,Bic)去ABA能抑制可改变声刺激诱发的反应模式;极大地增加神经元冲动发放率,缩短反应的潜伏期和降低反应的最小阈值;不同程度地改变强度－发放率和强度－潜伏期函数。结果提示：1、GABA能抑制对AC神经元声信号处理起重要作用;2、GABA能抑制可改变AC神经元兴奋性支配或输入的效应,并因此定型AC神经元的声反应性质,即发放模式、阈值、强度－发放率和强度－潜伏期函数;3、GABA能抑制为AC神经元的声诱发活动提供一种调制性抑制。     

Peripheral specialization for fine analysis of doppler-shifted echoes in the auditory system of the "CF-FM" bat Pteronotus parnellii.

Pteronotus parnellii uses the second harmonic (61-62 kHz) of the CF component in its orientation sounds for Doppler-shift compensation. The bat's inner ear is mechanically specialized for fine analysis of sounds at about 61-62 kHz. Because of this specialization, cochlear microphonics (CM) evoked by 61-62 kHz tone bursts exhibit prominent transients, slow increase and decrease in amplitude at the onset and cessation of these stimuli. CM-responses to 60-61 kHz tone bursts show a prominent input-output non-linearity and transients. Accordingly, a summated response of primary auditory neurones (N1) appears not only at the onset of the stimuli, but also at the cessation. N1-off is sharply tuned at 60-61 kHz, while N1-on is tuned at 63-64 kHz, which is 2 kHz higher than the best frequency of the auditory system because of the envelope-distortion originating from sharp mechanical tuning. Single peripheral neurones sensitive to 61-62 kHz sounds have an unusually sharp tuning curve and show phase-locked responses to beats of up to 3 kHz. Information about the frequencies of Doppler-shifted echoes is thus coded by a set of sharply tuned neurones and also discharges phase-locked to beats. Neurones with a best frequency between 55 and 64 kHz show not only tonic on-responses but also off-responses which are apparently related to the mechanical off-transient occuring in the inner ear and not to a rebound from neural inhibition.     

不同的声音强度对大鼠听皮层神经元特征频率可塑性的影响

目的：探讨声音强度对大鼠听皮层神经元特征频率可塑性的影响。方法：采用常规电生理学细胞外记录技术,测定不同声刺激强度下,听皮层神经元的特征频率和调谐曲线,比较条件刺激前后的变化。结果：在条件刺激声频率和神经元的特征频率相差±1.0kHz范围内,条件刺激诱导的神经元特征频率可塑性与条件刺激强度有关,较高的刺激强度比较低刺激强度诱导的特征频率可塑性概率高;特征频率可塑性的概率与神经元的频率调谐曲线类型相关,但这种相关几乎不受条件刺激声强度影响。结论：条件声刺激强度可明显影响大鼠听皮层神经元特征频率的可塑性。     

Intraoperative Electroretinograms before and after Core Vitrectomy

Purpose

To evaluate retinal function by intraoperative electroretinograms (ERGs) before and after core vitrectomy.

Design

Retrospective consecutive case series.

Method

Full-field photopic ERGs were recorded prior to the beginning and just after core vitrectomy using a sterilized contact lens electrode in 20 eyes that underwent non-complicated vitreous surgery. A light-emitted diode was embedded into the contact lens, and a stimulus of 150 ms on and 350 ms off at 2 Hz was delivered. The amplitudes and latencies of the a-, b-, and d-waves, photopic negative response (PhNR), and oscillatory potentials (OPs) were analyzed. The intraocular temperature at the mid-vitreous was measured at the beginning and just after the surgery with a thermoprobe.

Results

The intraocular temperature was 33.2 ± 1.3°C before and 29.4 ± 1.7°C after the vitrectomy. The amplitudes of the PhNR and OPs were significantly smaller after surgery, and the latencies of all components were prolonged after the surgery. These changes were not significantly correlated with the changes of the temperature.

Conclusion

Retinal function is reduced just after core vitrectomy in conjunction with significant temperature reduction. The differences in the degree of alterations of each ERG component suggests different sensitivity of each type of retinal neuron.     

Peripheral auditory tuning for fine frequency analysis by the CF-FM bat,Rhinolophus ferrumequinum

Summary For echolocation,Rhinolophus ferrumequinum emits orientation sounds, each of which consists of a long constant-frequency (CF) component and short frequency-modulated (FM) components. The CF component is about 83 kHz and is used for Doppler-shift compensation. In this bat, single auditory nerve fibers and cochlear nuclear neurons tuned at about 83 kHz show low threshold and very sharp filter characteristics. The slopes of their tuning curves ranged between 1,000 and 3,500 dB/octave and their Q-10 dB values were between 20 and 400, 140 on the average (Figs. 3–5). The peripheral auditory system is apparently specialized for the reception and fine frequency analysis of the CF component in orientation sounds and Doppler-shift compensated echoes. This specialization is not due to suppression or inhibition comparable to lateral inhibition, but due to the mechanical specialization of the cochlea. Peripheral auditory neurons with the best frequency between 77 and 87 kHz showed not only on-responses, but also off-responses to tonal stimuli (Figs. 1, 2, and 6). The off-responses with a latency comparable to that of N₁-off were not due to a rebound from either suppression or inhibition, but probably due to a mechanical transient occurring in the cochlea at the cessation of a tone burst.We thank Alexander von Humboldt Stiftung, Deutsche Forschungsgemeinschaft (Grant No. Ne146/6-8), Stiftung Volkswagenwerk (Grant No. 111858), and American National Science Foundation (Grant No. 40018 and BMS 75-17077) for their support for our cooperative work.     

正常小儿胫神经诱发短潜伏时头皮体感区电位及脑瘫对该电位的影响

本研究观察了20例正常小儿和49例脑瘫小儿的下肢胫后神经刺激性短潜伏时头皮体感诱发电位(PTN-SSEP)。正常小儿在刺激后出现6个反应波(P18、N23、P31、N42、P54和N68),大脑左右两体感头皮的SSEP波形相似;时相基本相等,t检验表明两侧间无差异;电压除波P31外其余波也无显著差异。脑瘫小儿PTN-SSEP异常率达91.84％,有4种类型:正常型占8.16％、混合异常型57.14％、反应低下型6.12％及电压不对称型28.57％。经统计患儿左右头皮的SSEP、潜伏时和电压均有显著差异(P<0.05),其中P31和N42电压差值>50％。与正常小儿比较,患儿双侧反应降低,多数波潜伏时延长。患侧电压损失率>50％(P<0.001),波P18、N23和P31的潜伏时差异显著。结果提示.(1)正常小儿体感通路反应稳定,左右侧活动基本对称;(2)脑瘫小儿体感通路左右侧活动不对称,患侧传导机能下降,体感皮层反应减退。     

Middle-latency auditory evoked potentials during induction of thiopentone anaesthesia in pigs.

A method is described for measuring middle-latency auditory evoked potentials (MLAEP) in consciously awake, non-sedated pigs during the induction of thiopentone anaesthesia (0.6 ml/kg, 2.5% thiopentone solution). It was done by using autoregressive modelling with an exogenous input (ARX). The ability to perceive pain during the induction was compared with (1) the changes in latencies and amplitudes of the MLAEP, (2) the change in a depth of anaesthesia index based on the ARX-model and (3) the change in the 95% spectral edge frequency. The pre-induction MLAEP was easily recordable and looked much like the one in man, dogs and rats. The temporal resolution in the ARX method was sufficiently high to describe the fast changes occurring during induction of thiopentone anaesthesia. As previously reported from studies in man, dogs and rats, induction of thiopentone anaesthesia resulted in significantly increased latencies and decreased amplitudes of the MLAEP trace as well as in a significantly reduced depth of anaesthesia index and spectral edge frequency. None of the changes, however, related well to the ability to react to a painful stimulus. Whether an ARX-based depth of anaesthesia index designed especially for pigs might be better than the present index (designed for man) for assessing depth of anaesthesia must await the results of further studies.     

Dynamic response of the peripheral chemoreflex loop to changes in end-tidal O2.

We studied the peripheral ventilatory response dynamics to changes in end-tidal O2 tension (PETO2) in 13 cats anesthetized with alpha-chloralose-urethan. The arterial O2 tension in the medulla oblongata was kept constant using the technique of artificial perfusion of the brain stem. At constant end-tidal CO2 tension, 72 ventilatory on-responses due to stepwise changes in PETO2 from hyperoxia (45-55 kPa) to hypoxia (4.7-9.0 kPa) and 62 ventilatory off-responses due to changes from hypoxia to hyperoxia were assessed. We fitted two exponential functions with the same time delay to the breath-by-breath ventilation and found a fast and a slow component in 85% of the ventilatory on-responses and in 76% of the off-responses. The time constant of the fast component of the ventilatory on-response was 1.6 +/- 1.5 (SD) s, and that of the off-response was 2.4 +/- 1.3 s; the gain of the on-response was smaller than that of the off-response (P = 0.020). For the slow component, the time constant of the on-response (72.6 +/- 36.4 s) was larger (P = 0.028) than that of the off-response (43.7 +/- 28.3 s), whereas the gain of the on-response exceeded that of the off-response (P = 0.031). We conclude that the ventilatory response of the peripheral chemoreflex loop to stepwise changes in PETO2 contains a fast and a slow component.     

Modifications of event-related evoked potentials in physiological and pathological aging of the brain

We compared the parameters of acoustic event-related evoked potentials (ERP; tone stimulation) in healthy young and healthy aged persons with those in patients suffering from Alzheimer’s disease (groups 1–3, respectively). It was found that the mean peak latencies (PL) of the components P1-N2 in group 1 were longer than those in group 2, and the absolute values of the amplitudes of these components were more negative. In Alzheimer patients (group 3), the PL of the components P1–P2 were much longer than those in group 2, and their peak-to-peak amplitudes dropped. The latencies of a simple sensorimotor reaction in groups 1–3 progressively increased (about three times). The ERP observed in two modes (“blackground” and “attention,” the latter with the performance of the sensorimotor reaction) were subjected to spectral analysis. Possible reasons for and mechanisms of those modifications of evoked potentials, which relate to physiological and pathological aging of the brain, are discussed.     

Functional features of electroreceptors (small pit organs) in the catfish

Characteristics of responses of the small pit organs of the catfishIctalurus nebulosus to the action of electrical stimuli of varied polarity, intensity, and duration were studied. Single fibers of the lateral nerve innervating these organs possessed regular spontaneous activity with a frequency of 35–45/sec or grouped activity, coinciding with the rhythm of the animal's swimming movements. Threshold current densities varied from 10⁻¹¹ to 10⁻¹⁰ A/mm². Electrical stimuli evoked a phasic-tonic response of the receptor. The latent period was 10–50 msec for on-responses and 10–200 msec for off-responses. In the presence of strong electric fields the receptor responded to a cathodal stimulus by excitation, whereas under ordinary experimental conditions an anodal stimulus is excitatory. The properties of small pit organs are compared with the characteristics of other electroreceptors.     

Effects of temperature on sound production and auditory abilities in the Striped Raphael catfish Platydoras armatulus (Family Doradidae)

Background

Sound production and hearing sensitivity of ectothermic animals are affected by the ambient temperature. This is the first study investigating the influence of temperature on both sound production and on hearing abilities in a fish species, namely the neotropical Striped Raphael catfish Platydoras armatulus.

Methodology/Principal Findings

Doradid catfishes produce stridulation sounds by rubbing the pectoral spines in the shoulder girdle and drumming sounds by an elastic spring mechanism which vibrates the swimbladder. Eight fish were acclimated for at least three weeks to 22°, then to 30° and again to 22°C. Sounds were recorded in distress situations when fish were hand-held. The stridulation sounds became shorter at the higher temperature, whereas pulse number, maximum pulse period and sound pressure level did not change with temperature. The dominant frequency increased when the temperature was raised to 30°C and the minimum pulse period became longer when the temperature decreased again. The fundamental frequency of drumming sounds increased at the higher temperature. Using the auditory evoked potential (AEP) recording technique, the hearing thresholds were tested at six different frequencies from 0.1 to 4 kHz. The temporal resolution was determined by analyzing the minimum resolvable click period (0.3–5 ms). The hearing sensitivity was higher at the higher temperature and differences were more pronounced at higher frequencies. In general, latencies of AEPs in response to single clicks became shorter at the higher temperature, whereas temporal resolution in response to double-clicks did not change.

Conclusions/Significance

These data indicate that sound characteristics as well as hearing abilities are affected by temperatures in fishes. Constraints imposed on hearing sensitivity at different temperatures cannot be compensated even by longer acclimation periods. These changes in sound production and detection suggest that acoustic orientation and communication are affected by temperature changes in the neotropical catfish P. armatulus.