Psychophysics describes how variations in stimulus strength lead to changes in perceptual performance. Yet, the contribution of non-sensory information processing to perceptual decision making is still not fully understood. For instance, in two-alternative forced-choice tasks, observers can exhibit tendencies to choose more one alternative over another, with no apparent goal or function. Such choice biases are highly prevalent in mice and, in free-choice tasks, they are insensitive to changes in stimulus discriminability. Thus, a reasonable proposal is that these side-choice biases could derive from functional asymmetries in sensory processing, decision making, or both. Here, we explored how different circuits participate in the production of choice biases in adult mice. We found that the magnitude of the changes in biased choice behavior depended on the inactivated region. Indeed, contralateral, but not ipsilateral, inactivations of the primary visual and posterior parietal cortices reduced the probability of mice choosing their preferred side. In contrast, ipsilateral inactivations of the subtantia nigra pars reticulata and of the frontal orienting fields, reduced and increased the probabilities of mice choosing their preferred side, respectively. These results demonstrate that internal circuit processing contributes to side-choice behavior and illustrates how distinct brain regions could participate in producing normal to aberrant levels of choice variability.

心理物理学描述了刺激强度的变化如何导致知觉表现的变化。然而，非感官信息处理对知觉决策的贡献仍未完全了解。例如，在有两种选择的强制选择任务中，观察者可能表现出倾向于选择更多的一种选择而不是另一种，没有明显的目标或功能。这种选择偏差在小鼠中非常普遍，在自由选择任务中，它们对刺激辨别力的变化不敏感。因此，一个合理的建议是，这些辅助选择偏差可能源于感觉处理、决策制定或两者的功能不对称。在这里，我们探讨了不同的回路如何参与成年小鼠选择偏差的产生。我们发现偏向选择行为的变化幅度取决于失活区域。事实上，对侧而非同侧的初级视觉和后顶叶皮质的失活降低了小鼠选择其首选侧的可能性。相比之下，同侧黑质网状部和额叶定向场的失活分别降低和增加了小鼠选择其首选侧的概率。这些结果表明内部电路处理有助于选择行为，并说明不同的大脑区域如何参与产生正常到异常水平的选择变异性。初级视觉和后顶叶皮质的失活降低了小鼠选择其首选一侧的可能性。相比之下，同侧黑质网状部和额叶定向场的失活分别降低和增加了小鼠选择其首选侧的概率。这些结果表明内部电路处理有助于选择行为，并说明不同的大脑区域如何参与产生正常到异常水平的选择变异性。初级视觉和后顶叶皮质的失活降低了小鼠选择其偏好侧的可能性。相比之下，同侧黑质网状部和额叶定向场的失活分别降低和增加了小鼠选择其首选侧的概率。这些结果表明内部电路处理有助于选择行为，并说明不同的大脑区域如何参与产生正常到异常水平的选择变异性。