知觉空间分离和恐惧条件化对清醒大鼠的下丘频率跟随反应的调节作用
首发时间:2013-03-14
摘要:在混响环境中,人类被试和实验大鼠都能够整合来自声源的直达声和反射声,只感知到一个声源附近的融合的声像,这种现象叫做听觉优先效应。这种知觉整合现象产生的声源间的主观空间分离可以增强听者对目标声源的选择性注意并提高其识别率。然而,知觉空间分离去掩蔽的神经相关物目前尚无文献报道。另一方面,听觉恐惧条件化被证实可以增强条件化刺激的中枢神经表征。本实验旨在考察恐惧条件化以及条件化后的目标声刺激与掩蔽噪音间的知觉空间分离是否能够选择性增强目标声刺激在清醒大鼠的听觉中脑下丘引发的神经反应。结果显示,大鼠下丘对噪音掩蔽下的复合纯音的频率跟随反应(神经元群对周期性声音信号的持续性锁相反应形成的场电位)在复合纯音被恐惧条件化后显著提高。更重要的是,当条件化后的复合纯音(而非条件化控制操作后的复合纯音)与掩蔽噪音处于知觉空间分离条件下比在知觉空间重合条件下引发的下丘频率跟随反应更强。这提示,在清醒大鼠中,恐惧条件化以及条件化目标刺激与掩蔽噪音间的知觉空间分离引发的空间选择性注意能以一种刺激特异性的方式增强下丘神经元对条件化目标刺激神经发放的同步性进而增强该刺激的中枢神经表征。
关键词: 生理心理学 知觉空间分离 恐惧条件化 频率追随反应 下丘
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Perceived Spatial Separation and Fear Conditioning Unmasks Frequency-following Responses of Inferior Colliculus in Awake Rats
Abstract:In a (simulated) reverberant environment, both human listeners and laboratory rats are able to perceptually integrate the direct wave of a sound source with the reflections of the source, leading to a fused image as coming from the location around the source (the precedence effect). This perceptual grouping effect produces perceived spatial separation between sound sources and facilitates selective attention to the target source. However, the neural correlates of the unmasking effects of perceived spatial separation have not been reported in the literature. On the other side, it is known that auditory fear conditioning can improve the central neural representation of the conditioned stimulus. This study investigated whether in awake rats fear conditioning and the perceptual fusion-induced separation between a fear-conditioned target sound and a noise masker selectivelyenhancesthe responses to the target in the auditory midbrain, inferior colliculus (IC). The results show that frequency-following responses (FFRs, i.e., sustained potentials based on phase-locked firing of neuron populations to periodical sound waveforms) recorded in the IC to a tone-complex, which was masked by a wideband noise, were enhanced following the tone-complex became fear conditioned. More importantly, the fear-conditioned tone-complex, but not the pseudo-conditioned tone-complex, elicited further larger IC FFRs when it was perceived as separated from the masker than when it was perceived as co-located with the masker. The results suggest that in awake ratsfear conditioning and perceived spatial separation-induced selective spatial attention can enhance the synchronization of firing of IC neuronsto emotionally salienttarget sound and its correlated neural representationwith a high degree of stimulus specificity.
Keywords: physiopsychology perceived spatial separation fear conditioning frequency-following responses inferior colliculus
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知觉空间分离和恐惧条件化对清醒大鼠的下丘频率跟随反应的调节作用
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