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后掩蔽效应对大棕蝠下丘神经元声反应的影响

栾瑞红, 吴飞健, Jen P H S, 孙心德　

华东师范大学生命科学学院.上海 200062；华中师范大学生命科学学院.湖北,武汉 430079；密苏里大学生物科学系,密苏里州 65211,美国

摘要

以回声定位蝙蝠为模式动物,采用在体动物细胞外单位记录法,研究了后掩蔽效应对下丘神经元声反应的影响。结果显示,部分神经元(38%,12/31)对测试声刺激的反应明显受到掩蔽声的抑制,其后掩蔽效应强弱与掩蔽声和测试声的相对强度差(inter--stimulus level difference,SLD),以及测试声与掩蔽声之间的间隔时间(inter--stimulus onset asynchrony,SOA)有关:当掩蔽声强度升高或测试声强度降低时,后掩蔽效应增强;而SOA的缩短,亦可见后掩蔽效应增强。另外,相当数量的神经元(52%,16/31)对测试声刺激的反应并不受掩蔽声的影响,其中有的神经元只有在特定SLD和SOA时,才表现出后掩蔽效应。而少数下丘神经元(10%,3/31)在特定SLD和SOA时,掩蔽声对测试声反应有易化作用。上述结果表明,部分下丘神经元参与了声认知活动中的后掩蔽形成过程,推测下丘神经元在定型声反应特性中,对掩蔽声诱导的兴奋前抑制性输入与测试声诱导的兴奋性输入之间的时相性动态整合起关键作用。

关键词： 后掩蔽效应; 掩蔽声; 测试声; 蝙蝠; 下丘; 回声定位

Effects of backward masking on the responses of the inferior collicular neurons in the big brown bat, Eptesicus fuscus

Luan Ruihong, Wu Feijian, Jen P H S, Sun Xinde

College of Life Sciences,East China Normal University.Shanghai 200062；China；Division of Biological Sciences,University of Missouri-Columbia,MO 65211

Abstract

Temporal features of sound convey information vital for behaviors as diverse as speech recognition by human and echolocation by bats. However, auditory stimuli presented in temporal proximity might interfere with each other. Although much progress has been made in the description of this phenomenon from psychophysical studies, the neural mechanism responsible for its formation at central auditory structures especially at the inferior colliculus (IC), a midbrain auditory nucleus which practically receives massive bilateral projections from all the major auditory structures in the brainstem, remains unclear. This study was designed to investigate it in vivo by using electrophysiological recording from the inferior collicular neurons of the big brown bat, Eptesicus fuscus. In our results,the responses of 12 (38%, n= 31) neurons to the test sound (leading sound) were obviously inhibited by the masker (lagging sound). The inhibitory effects in these neurons were correlated with the inter-stimulus level difference (SLD) and the inter-stimulus onset asynchrony (SOA) interval. The strength of backward masking increased with the masker intensity increasing, the test sound intensity decreasing and the SOA interval shortening. There were no obvious effects of backward masking on the responses of many other neurons (52%,16/31), and yet in a part of these neurons, the neural inhibition of responses to the test sound was observed at the special SLD and the special SOA intervals. Moreover, few of the 31 sampled IC neurons (10%, 3/31) displayed facilitating responses to the test sound at the special SLD and the special SOA intervals. These data demonstrate that a lot of IC neurons are involved in the generation of the backward masking of acoustical perception. It is conjectured that the temporal dynamic integration between the leading inhibitory inputs evoked by the masker sound and the excitatory inputs evoked by the test sound might play a key role in shaping the acoustical response characteristics of the IC neurons.

Key words: backward masking;masker;test sound;bat;inferior colliculus;echolocation

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引用本文：

栾瑞红, 吴飞健, Jen P H S, 孙心德　 . 后掩蔽效应对大棕蝠下丘神经元声反应的影响[J]. 生理学报 2005; 57 (2): .

Luan Ruihong, Wu Feijian, Jen P H S, Sun Xinde. Effects of backward masking on the responses of the inferior collicular neurons in the big brown bat, Eptesicus fuscus. Acta Physiol Sin 2005; 57 (2): (in Chinese with English abstract).