Dissecting cholinergic modulation of interneurons underlying state-dependent processing in mouse visual cortex

项目总结 视皮层可以根据环境以不同方式处理相同的刺激；行为状态，如 运动或唤醒可以改变视觉反应的大小和特异性。神经调节剂 乙酰胆碱(ACh)参与状态依赖性加工，并作用于不同的抑制性中间神经元。 大脑皮层回路，但仍不确定中间神经元类别如何促进状态依赖。特例 围绕生长抑素阳性(SOM)细胞的作用存在争议，生长抑素阳性细胞直接通过 抑制锥体细胞。一种模型表明，ACh对上游中间神经元的作用触发了抑制 通过释放抑制性神经递质γ-氨基丁酸(GABA)。这解除了对金字塔的抑制 细胞在运动和潜在的其他状态时增加视觉回路的增益。然而，矛盾的是 研究结果表明，ACh通过M受体直接促进的SOM细胞实际上是 在移动过程中更加活跃，这表明去抑制模型不足以解释语境依赖。 这一建议验证了毒鼠碱和GABA能作用于SOM细胞的假设 视觉辨别中调节视皮层回路和整形的互补效应。我假设 对SOM细胞的毒鼠碱作用有助于调节锥体细胞群，而GABA能作用 在SOM细胞上有助于锥体细胞的增加。我将利用史无前例的交叉控制来剖析这一点 通过药物急性限制性栓系(DART)方法对特定细胞类型上的特定受体进行研究 再加上小鼠初级视皮层的双光子钙成像。 目的1：选择性拮抗SOM细胞上的M受体，记录SOM细胞的活性 以及附近的锥体细胞，因为小鼠被动地观看视觉刺激。我将评估视觉反应以及如何 通过运动和唤醒改变反应，以揭示ACh对基础视觉中SOM细胞的直接影响 通过行为状态进行加工和调制。在目标2中，我将选择性地阻断SOM细胞上的GABA受体， 再次记录被动观看期间的SOM和锥体细胞活动。这将使我能够澄清抑制是如何 在运动和觉醒过程中，SOM细胞参与了基本的视觉过程和电路调制。如果，如 假设，毒鼠碱和GABA能控制会影响锥体细胞的调谐和增益，这可能 有意义地影响视觉辨别力。来评估这两条通路如何影响动物的感知能力 并利用视觉信息，在目标3中，我将选择性地拮抗SOM上的M受体或GABA能受体 并记录SOM和锥体细胞的活动，而小鼠则执行取向改变检测任务。 结合这些数据，将解决围绕神经调节剂如何向视觉回路灌输的长期问题 上下文专用性。

PROJECT SUMMARY The visual cortex can process identical stimuli differently depending on context; behavioral states such as locomotion or arousal can alter the magnitude and the specificity of visual responses. The neuromodulator acetylcholine (ACh) is implicated in state-dependent processing and acts on diverse inhibitory interneurons in cortical circuits, but it remains uncertain how interneuron classes contribute to state-dependence. Particular controversy surrounds the role of the somatostatin-positive (SOM) cells, which shape circuit output by directly inhibiting pyramidal cells. One model suggests that ACh action on upstream interneurons triggers suppression of SOM cells via release of the inhibitory neurotransmitter γ-Aminobutyric acid (GABA). This disinhibits pyramidal cells to increase gain in visual circuits during locomotion and potentially other states. However, contradictory findings reveal that SOM cells, which can be directly facilitated by ACh through muscarinic receptors, are actually more active during locomotion, indicating the disinhibitory model is not sufficient to explain context dependence. This proposal tests the hypothesis that muscarinic and GABAergic action on SOM cells have complementary effects on modulating visual cortex circuits and shaping in visual discrimination. I hypothesize that muscarinic action on SOM cells contributes to tuning of the pyramidal population, while GABAergic action on SOM cells contributes to pyramidal cell gain. I will dissect this utilizing unprecedented intersectional control of specific receptors on specific cell types via the Drugs Acutely Restricted by Tethering (DART) methodology coupled with 2-photon calcium imaging of mouse primary visual cortex. In Aim 1, I will selectively antagonize muscarinic receptors on SOM cells and record activity of SOM cells and nearby pyramidal cells as mice passively view visual stimuli. I will assess visual responses and how responses are altered by locomotion and arousal, to reveal the direct impact of ACh on SOM cells in basal visual processing and modulation by behavioral state. In Aim 2, I will selectively block GABA receptors on SOM cells, again recording SOM and pyramidal cell activity during passive viewing. This will allow me to clarify how inhibition onto SOM cells contributes to basal visual process and circuit modulation during locomotion and arousal. If, as hypothesized, muscarinic and GABAergic control impact tuning and gain of pyramidal cells, this could meaningfully impact visual discrimination. To assess how these two pathways act on animals' ability to perceive and use visual information, in Aim 3 I will selectively antagonize muscarinic or GABAergic receptors on SOM cells, and record activity of SOM and pyramidal cells, while mice perform an orientation change detection task. Together these data will resolve longstanding questions around how neuromodulators imbue visual circuits with context specificity.