Shore S E
Department of Otolaryngology, Medical College of Ohio, Toledo, USA.
J Acoust Soc Am. 1998 Jul;104(1):378-89. doi: 10.1121/1.423294.
When responses to one part of a sequence of auditory signals reduce the responses to a subsequent portion of the signal, "forward masking" results. Although forward masking occurs in the auditory nerve, that observed in the ventral cochlear nucleus (VCN) more closely resembles psychophysical forward masking. In contrast to the auditory nerve in which the amount of forward masking is proportional to the amount of excitation produced by the masker, most VCN neurons show a poor correlation between forward masking and excitation produced by the masker, indicating a more complex interaction between responses to adjacent signals. This study tested the hypothesis that one component of forward masking is produced by inputs from centrifugal neural connections to the VCN. The centrifugal pathways were interrupted with knife-cut lesions medial to the CN. Responses of single units obtained 60 minutes after the lesions were compared to those obtained before the lesions. In primarylike, sustained chopper and on units the lesions resulted in a reduction in forward masking and enhanced recovery. In contrast, lesions resulted in increased masking in primarylike-notch and low-intensity chopper units. The relationship between masker-elicited excitation and forward masking became more monotonic for transient choppers and on units, approaching that observed for auditory nerve fibers. These effects are probably the result of removal of both inhibitory and excitatory inputs, ultimately reflecting a balance of excitation and inhibition to each neural population in the VCN.
当对一系列听觉信号的某一部分的反应减少了对该信号后续部分的反应时，就会产生“前掩蔽”。虽然前掩蔽发生在听神经中，但在腹侧耳蜗核（VCN）中观察到的前掩蔽更类似于心理物理学上的前掩蔽。与听神经中前掩蔽的量与掩蔽声产生的兴奋量成正比不同，大多数VCN神经元在前掩蔽与掩蔽声产生的兴奋之间显示出较差的相关性，这表明对相邻信号的反应之间存在更复杂的相互作用。本研究检验了一个假设，即前掩蔽的一个组成部分是由离心神经连接到VCN的输入产生的。通过在耳蜗核内侧进行刀切损伤来中断离心通路。将损伤后60分钟获得的单个神经元的反应与损伤前获得的反应进行比较。在初级样、持续斩波和开启型神经元中，损伤导致前掩蔽减少和恢复增强。相反，损伤导致初级样陷波和低强度斩波神经元的掩蔽增加。对于瞬态斩波和开启型神经元，掩蔽声诱发的兴奋与前掩蔽之间的关系变得更加单调，接近在听神经纤维中观察到的情况。这些效应可能是去除抑制性和兴奋性输入的结果，最终反映了VCN中每个神经群体的兴奋与抑制的平衡。
