Galazyuk A V, Voytenko S V, Longenecker R J
Department of Anatomy and Neurobiology, Northeast Ohio Medical University, 4209 State Route 44, Rootstown, OH, 44272, USA.
Department of Neuronal Networks Physiology, Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Kiev, Ukraine.
J Assoc Res Otolaryngol. 2017 Apr;18(2):343-353. doi: 10.1007/s10162-016-0601-9. Epub 2016 Nov 10.
Tinnitus is the perception of a sound that has no external source. Sound stimuli can suppress spontaneous firing in auditory neurons long after stimulus offset. It is unknown how changes in sound stimulus parameters affect this forward suppression. Using in vivo extracellular recording in awake mice, we found that about 40 % of spontaneously active inferior colliculus (IC) neurons exhibited forward suppression of spontaneous activity after sound offset. The duration of this suppression increased with sound duration and lasted about 40 s following a 30-s stimulus offset. Pure tones presented at the neuron's characteristic frequency (CF) were more effective in triggering suppression compared to non-CF or wideband noise stimuli. In contrast, non-CF stimuli often induced forward facilitation. About one third of IC neurons exhibited shorter suppression durations with each subsequent sound presentation. These characteristics of forward suppression are similar to the psychoacoustic properties of residual inhibition of tinnitus: a phenomenon of brief (about 30 s) suppression of tinnitus observed in tinnitus patients after sound presentations. Because elevated spontaneous firing in central auditory neurons has been linked to tinnitus, forward suppression of this firing with sound might be an underlying mechanism of residual inhibition.
耳鸣是对一种没有外部声源的声音的感知。声音刺激在刺激停止后很长时间仍能抑制听觉神经元的自发放电。声音刺激参数的变化如何影响这种前向抑制尚不清楚。通过对清醒小鼠进行体内细胞外记录，我们发现约40%的自发放电的下丘（IC）神经元在声音停止后表现出自发活动的前向抑制。这种抑制的持续时间随声音持续时间增加，在30秒的刺激停止后持续约40秒。与非特征频率（CF）或宽带噪声刺激相比，以神经元特征频率（CF）呈现的纯音在触发抑制方面更有效。相反，非CF刺激常常诱发前向易化。约三分之一的IC神经元在随后的每次声音呈现时表现出较短的抑制持续时间。前向抑制的这些特征类似于耳鸣残余抑制的心理声学特性：耳鸣患者在声音呈现后观察到的短暂（约30秒）耳鸣抑制现象。由于中枢听觉神经元自发放电增加与耳鸣有关，用声音对这种放电进行前向抑制可能是残余抑制的潜在机制。
