Auditory neuronal responses are modified by background noise. Inferior colliculus (IC) neuronal responses adapt to the most frequent sound level within an acoustic scene (adaptation to stimulus statistics), a mechanism that may preserve neuronal and behavioral thresholds for signal detection. However, it is still unclear if the presence of foreground stimuli and/or task involvement can modify neuronal adaptation. To investigate how task-engagement interacts with this mechanism, we compared the response of IC neurons to background noise, which caused adaptation to stimulus statistics, while macaque monkeys performed a masked tone detection task (task-driven condition) with responses recorded when the same background noise was presented alone (passive listening condition). In the task-dependent condition, monkeys performed a Go/No-Go task while 50 ms tones were embedded within an adaptation-inducing continuous background noise, whose level changed every 50 ms and were drawn from a probability distribution. The adaptation to noise stimulus statistics in IC neuronal responses was significantly enhanced in the task-driven condition compared to the passive listening condition, showing that foreground stimuli and/or task-engagement can modify IC neuronal responses. Additionally, the response of IC neurons to noise was significantly affected by the preceding sensory information (history effect) regardless of task involvement. These studies show that dynamic range adaptation in IC preserves behavioral and neurometric thresholds irrespective of noise type, and a dependence of neuronal activity on task-related factors at subcortical levels of processing.

中文翻译：

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前景刺激和任务参与增强了猕猴下丘神经元对背景噪声的适应。

听觉神经元反应受背景噪音影响。下丘 (IC) 神经元反应适应声学场景中最常见的声级（适应刺激统计），这是一种可以保留用于信号检测的神经元和行为阈值的机制。然而，目前尚不清楚前景刺激和/或任务参与的存在是否可以改变神经元适应。为了研究任务参与如何与这种机制相互作用，我们比较了 IC 神经元对背景噪声的反应，这导致了对刺激统计的适应，而猕猴则执行了掩蔽音检测任务（任务驱动条件），当相同时记录响应背景噪音单独呈现（被动聆听条件）。在任务依赖条件下，猴子执行 Go/No-Go 任务，而 50 ms 音调嵌入在诱导适应的连续背景噪声中，其水平每 50 ms 改变一次，并从概率分布中提取。与被动聆听条件相比，任务驱动条件下对 IC 神经元反应中噪声刺激统计的适应性显着增强，表明前景刺激和/或任务参与可以改变 IC 神经元反应。此外，无论任务是否参与，IC 神经元对噪声的反应都受到先前感官信息（历史效应）的显着影响。这些研究表明，无论噪声类型如何，IC 中的动态范围适应都保留了行为和神经测量阈值，以及神经元活动对皮质下处理水平的任务相关因素的依赖性。