![]() Whether the neurons in VC that give rise to these cortico-fugal pathways play a role in simple goal-directed behavior remains poorly understood. At least in mammals, both structures receive two main sources of visual information: one ascending from the periphery ( Klaus et al., 2019 Krauzlis et al., 2013) and the other, descending from visual cortex (VC) via its prominent cortico-fugal pathways ( Feinberg and Mallatt, 2019 Smeets et al., 2000 Suryanarayana et al., 2020). The striatum is fundamental for reinforcement learning ( Cox and Witten, 2019) and action initiation ( Klaus et al., 2019) and the optic tectum (called the superior colliculus in mammals) plays an important role in the detection of salient visual stimuli that trigger innate behaviors ( Feinberg and Mallatt, 2019 Grillner and El Manira, 2020). The striatum and the optic tectum are two evolutionary conserved subcortical structures involved in the learning and performance of simple goal-directed behavior in many vertebrates. A major challenge to our understanding of the neuronal basis of this elemental form of sensory-based and goal-directed behavior is that any visual stimulus evokes neuronal activity across multiple brain structures ( Macé et al., 2018 Seabrook et al., 2017) and, within each structure, across diverse types of neurons ( Harris and Mrsic-Flogel, 2013 Harris and Shepherd, 2015 Reinhard et al., 2019). For example, many vertebrates can learn to alter their behavior in response to the detection of arbitrary visual stimuli in order to obtain a reward or avoid punishment ( Llinás, 1976 Prusky and Douglas, 2004 Skinner, 1963 Valente, 2012). ![]() While the detection of ethologically relevant visual stimuli can elicit innate behavior, often visual stimuli become relevant through learning, leading to goal-directed behavior upon stimulus detection ( Morris et al., 2018 Schultz, 2006). ![]() Visual stimuli guide the behavior of many animals. This functional dissociation between distinct cortico-fugal neurons in controlling learning speed and detection sensitivity suggests an adaptive contribution of cortico-fugal pathways even in simple goal-directed behavior. We show that the ablation of striatal projecting neurons reduces learning speed, whereas the ablation of superior colliculus projecting neurons does not impact learning but reduces detection sensitivity. Here, we address the impact of two populations of cortico-fugal neurons in mouse VC in the learning and performance of a visual detection task. The function of cortico-fugal neurons in visually guided, goal-directed behavior remains unclear. In mammals, however, these structures also receive descending visual input from visual cortex (VC), via neurons that give rise to cortico-fugal projections. Such goal-directed behavior involves evolutionary conserved brain structures like the striatum and optic tectum, which receive ascending visual input from the periphery. Vertebrates can change their behavior upon detection of visual stimuli according to the outcome their actions produce.
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