Parsing pathways of visual perception

视觉引导的行为在整个感觉和运动回路中引起了广泛的尖峰活动变化。确定这些复杂的神经元尖峰模式是如何被读出（即解码）以产生感知和指导行为的，对于理解我们如何与世界互动至关重要，但关于大脑如何完成这一过程的因果证据却很少。视觉皮层（V1）的输出神经元表现出不同的动态，这取决于它们是投射到皮层、皮层下还是后脑目标，最近的研究表明，简单的视觉行为可能更强烈地依赖于某些V1输出。这表明V1可能代表多个不同的信息流。然而，不同V1输出产生的活动差异对视觉引导行为的影响程度值得进一步探索。在这里，我们试图解决两个基本问题，即V1的尖峰是如何引起感知和行动的：1)在某些V1投射中产生的活动与感知的联系是否比其他的更紧密？2)同样的V1输出是否会因感觉输入和运动输出之间的偶然性而对行为产生不同的影响？我的学员和我将重点研究V1神经元，它们投射上丘（SC）或纹状体（Str），因为这两个结构都接受直接的V1输入，并执行对感知决策至关重要的感觉运动功能。小鼠将被训练来执行具有挑战性的感知任务，并在心理物理阈值下可靠地工作。我们将通过光遗传学调节投射到SC或Str的V1神经元不同亚群的活性。在第一个实验中（目的1），小鼠将报告V1投射神经元的直接光遗传学激活。在这里，行为报告提供了明确的证据，表明实验者控制的活动模式可以被解码来指导行为，这与神经假肢装置有着巨大的相关性。第二组小鼠（目标2）将接受训练，报告在两种不同的视觉任务（检测与区分视觉运动）中视觉运动的变化。我们将在不同时间选择性地抑制V1对SC或Str的投射，以评估它们对行为的贡献时间以及这些贡献是否依赖于任务。在实验中，行为过程中的体内电生理记录将帮助我们将感觉输入和任务表现与V1、SC和Str的种群峰值联系起来（目标3）。这一研究项目将深入了解不同V1输出通道中产生的神经元信号是如何产生感知和行为的。此外，开展这项工作的HQP将培养强大的技能，为他们在学术界或新兴的神经技术部门等私营企业的职业生涯做好准备。

Visually-guided behaviours evoke widespread changes in spiking activity throughout sensory and motor circuits. Determining how these complex patterns of neuronal spiking are read out (i.e., decoded) to generate perception and guide behavior is of central importance for understanding how we interact with the world, yet there is very little causal evidence for how the brain accomplishes this. Output neurons from visual cortex (V1) exhibit distinct dynamics depending on whether they project to cortical, subcortical, or hindbrain targets and recent work shows that simple visual behaviours may depend more strongly on some V1 outputs than others. This suggests that V1 may represent multiple, distinct streams of information. However, the degree to which activity arising in distinct V1 outputs differentially impacts visually-guided behaviours warrants further exploration. Here, we seek to address two fundamental questions regarding how spiking in V1 gives rise to perception and action: 1) Is activity arising in some V1 projections more closely linked to perception than others? and 2) Does the same V1 output differentially affect behaviour depending on contingencies between sensory input and motor output? My trainees and I will focus on V1 neurons that project either the superior colliculus (SC) or the Striatum (Str) as both structures receive direct V1 input and perform sensorimotor functions that are critical for perceptual decision-making. Mice will be trained to perform challenging perceptual tasks and work reliably at psychophysical threshold. We will optogenetically modulate activity in distinct subpopulations of V1 neurons that project either to the SC or Str. In the first experiment (Objective 1), mice will report direct optogenetic activation of V1 projection neurons. Here, behavioral reports provide unequivocal evidence that the experimenter-controlled patterns of activity can be decoded to guide behavior, which has immense relevance for neuroprosthetic devices. A second set of mice (Objective 2) will be trained to report changes in visual motion in two different visual tasks (detect versus discriminate visual motion). We will selectively inhibit V1 projections to the SC or Str at different times to assess the timing of their contributions to behaviour and whether those contributions are task-dependent. Across experiments, in vivo electrophysiological recordings during behaviour will helps us link sensory input and task performance with population spiking in V1, SC, and the Str (Objective 3). This program of research will yield much needed insight into how neuronal signals in arising in different V1 output channels give rise to perception and behaviour. Furthermore, the HQP conducting this work will develop a strong skillset that will prepare them for careers in academia or private industries such as the emerging neurotechnology sector.