Noto M, Nishikawa J, Tateno T
Bioengineering and Bioinformatics, Graduate School of Information Science and Technology, Hokkaido University, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan.
Bioengineering and Bioinformatics, Graduate School of Information Science and Technology, Hokkaido University, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan; Special Research Promotion Group, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, Japan.
Neuroscience. 2016 Mar 24;318:58-83. doi: 10.1016/j.neuroscience.2015.12.060. Epub 2016 Jan 7.
A sound interrupted by silence is perceived as discontinuous. However, when high-intensity noise is inserted during the silence, the missing sound may be perceptually restored and be heard as uninterrupted. This illusory phenomenon is called auditory induction. Recent electrophysiological studies have revealed that auditory induction is associated with the primary auditory cortex (A1). Although experimental evidence has been accumulating, the neural mechanisms underlying auditory induction in A1 neurons are poorly understood. To elucidate this, we used both experimental and computational approaches. First, using an optical imaging method, we characterized population responses across auditory cortical fields to sound and identified five subfields in rats. Next, we examined neural population activity related to auditory induction with high temporal and spatial resolution in the rat auditory cortex (AC), including the A1 and several other AC subfields. Our imaging results showed that tone-burst stimuli interrupted by a silent gap elicited early phasic responses to the first tone and similar or smaller responses to the second tone following the gap. In contrast, tone stimuli interrupted by broadband noise (BN), considered to cause auditory induction, considerably suppressed or eliminated responses to the tone following the noise. Additionally, tone-burst stimuli that were interrupted by notched noise centered at the tone frequency, which is considered to decrease the strength of auditory induction, partially restored the second responses from the suppression caused by BN. To phenomenologically mimic the neural population activity in the A1 and thus investigate the mechanisms underlying auditory induction, we constructed a computational model from the periphery through the AC, including a nonlinear dynamical system. The computational model successively reproduced some of the above-mentioned experimental results. Therefore, our results suggest that a nonlinear, self-exciting system is a key element for qualitatively reproducing A1 population activity and to understand the underlying mechanisms.
被沉默打断的声音会被感知为不连续的。然而，当在沉默期间插入高强度噪声时，缺失的声音可能会在感知上被恢复并被听成是连续的。这种虚幻现象被称为听觉诱导。最近的电生理研究表明，听觉诱导与初级听觉皮层（A1）有关。尽管实验证据不断积累，但A1神经元中听觉诱导的神经机制仍知之甚少。为了阐明这一点，我们同时使用了实验和计算方法。首先，我们使用光学成像方法，对整个听觉皮层区域对声音的群体反应进行了表征，并在大鼠中识别出五个子区域。接下来，我们在大鼠听觉皮层（AC），包括A1和其他几个AC子区域，以高时间和空间分辨率研究了与听觉诱导相关的神经群体活动。我们的成像结果表明，被无声间隙打断的短音刺激对第一个音引发了早期的相位反应，而对间隙后的第二个音的反应相似或更小。相比之下，被宽带噪声（BN）打断的音调刺激，被认为会引起听觉诱导，大大抑制或消除了对噪声后音调的反应。此外，被以音调频率为中心的带阻噪声打断的短音刺激，被认为会降低听觉诱导的强度，部分恢复了因BN引起的抑制后的第二个反应。为了从现象学上模拟A1中的神经群体活动，从而研究听觉诱导的潜在机制，我们构建了一个从外周到AC的计算模型，包括一个非线性动力系统。该计算模型相继重现了上述一些实验结果。因此，我们的结果表明，一个非线性的自激系统是定性重现A1群体活动并理解其潜在机制的关键要素。
