Department of Psychology, Institute of Neuroscience, 1254 University of Oregon, Eugene, OR 97403, USA.
Cereb Cortex. 2020 May 18;30(6):3590-3607. doi: 10.1093/cercor/bhz328.
Auditory cortex (AC) is necessary for the detection of brief gaps in ongoing sounds, but not for the detection of longer gaps or other stimuli such as tones or noise. It remains unclear why this is so, and what is special about brief gaps in particular. Here, we used both optogenetic suppression and conventional lesions to show that the cortical dependence of brief gap detection hinges specifically on gap termination. We then identified a cortico-collicular gap detection circuit that amplifies cortical gap termination responses before projecting to inferior colliculus (IC) to impact behavior. We found that gaps evoked off-responses and on-responses in cortical neurons, which temporally overlapped for brief gaps, but not long gaps. This overlap specifically enhanced cortical responses to brief gaps, whereas IC neurons preferred longer gaps. Optogenetic suppression of AC reduced collicular responses specifically to brief gaps, indicating that under normal conditions, the enhanced cortical representation of brief gaps amplifies collicular gap responses. Together these mechanisms explain how and why AC contributes to the behavioral detection of brief gaps, which are critical cues for speech perception, perceptual grouping, and auditory scene analysis.
听觉皮层（AC）对于检测持续声音中的短暂间隙是必要的，但对于检测较长的间隙或其他刺激，如音调或噪声则不是必需的。目前尚不清楚为什么会这样，以及特别是什么使得短暂间隙如此特殊。在这里，我们使用光遗传学抑制和常规损伤来表明，短暂间隙检测的皮层依赖性特别取决于间隙的终止。然后，我们确定了一个皮质-丘系间隙检测电路，该电路在投射到下丘（IC）以影响行为之前，放大皮质间隙终止反应。我们发现，皮质神经元中引发了间隙诱发的 OFF 反应和 ON 反应，对于短暂的间隙，它们在时间上重叠，但对于长间隙则不重叠。这种重叠特别增强了皮质对短暂间隙的反应，而 IC 神经元则更喜欢长间隙。AC 的光遗传学抑制特异性地减少了丘脑中对短暂间隙的反应，表明在正常情况下，短暂间隙的皮质增强表示会放大丘脑中的间隙反应。这些机制共同解释了 AC 如何以及为什么有助于对短暂间隙的行为检测，这些间隙是言语感知、知觉分组和听觉场景分析的关键线索。
