Life Sciences Institute and Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.
Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University, Arlington, VA 22203, USA.
Curr Biol. 2020 Dec 21;30(24):4896-4909.e6. doi: 10.1016/j.cub.2020.09.045. Epub 2020 Oct 15.
Sensory stimuli with graded intensities often lead to yes-or-no decisions on whether to respond to the stimuli. How this graded-to-binary conversion is implemented in the central nervous system (CNS) remains poorly understood. Here, we show that graded encodings of noxious stimuli are categorized in a decision-associated CNS region in Drosophila larvae, and then decoded by a group of peptidergic neurons for executing binary escape decisions. GABAergic inhibition gates weak nociceptive encodings from being decoded, whereas escalated amplification through the recruitment of second-order neurons boosts nociceptive encodings at intermediate intensities. These two modulations increase the detection accuracy by reducing responses to negligible stimuli whereas enhancing responses to intense stimuli. Our findings thus unravel a circuit mechanism that underlies accurate detection of harmful stimuli.
具有不同强度的感觉刺激通常会导致人们是否对刺激做出反应的是/否决策。中枢神经系统（CNS）中如何实现这种渐变到二进制的转换仍知之甚少。在这里，我们发现在果蝇幼虫的一个与决策相关的中枢神经系统区域中，对有害刺激的渐变编码被分类，然后由一群肽能神经元对其进行解码，以执行二元逃避决策。GABA 能抑制阻止从弱痛觉编码中进行解码，而通过招募二阶神经元来扩大放大倍数则可以增强中等强度的痛觉编码。这两种调制通过减少对可忽略刺激的反应而增加对强烈刺激的反应，从而提高检测精度。因此，我们的发现揭示了一种电路机制，该机制为准确检测有害刺激提供了基础。
