Peysakhovich Barbara, Tetrick Stephanie M, Silva Alessandra A, Li Sihai, Zhu Ou, Ibos Guilhem, Johnston W Jeffrey, Freedman David J
bioRxiv. 2023 Jan 18:2023.01.17.524416. doi: 10.1101/2023.01.17.524416.
Categorization is a fundamental cognitive process by which the brain assigns stimuli to behaviorally meaningful groups. Investigations of visual categorization in primates have identified a hierarchy of cortical areas that are involved in the transformation of sensory information into abstract category representations. However, categorization behaviors are ubiquitous across diverse animal species, even those without a neocortex, motivating the possibility that subcortical regions may contribute to abstract cognition in primates. One candidate structure is the superior colliculus (SC), an evolutionarily conserved midbrain region that, although traditionally thought to mediate only reflexive spatial orienting, is involved in cognitive tasks that require spatial orienting. Here, we reveal a novel role of the primate SC in abstract, higher-order visual cognition. We compared neural activity in the SC and the posterior parietal cortex (PPC), a region previously shown to causally contribute to category decisions, while monkeys performed a visual categorization task in which they report their decisions with a hand movement. The SC exhibits stronger and shorter-latency category encoding than the PPC, and inactivation of the SC markedly impairs monkeys' category decisions. These results extend SC's established role in spatial orienting to abstract, non-spatial cognition.
分类是一种基本的认知过程，通过该过程大脑将刺激分配到具有行为意义的组中。对灵长类动物视觉分类的研究已经确定了一个皮质区域层次结构，这些区域参与将感觉信息转化为抽象的类别表征。然而，分类行为在各种动物物种中普遍存在，甚至包括那些没有新皮质的物种，这引发了一种可能性，即皮层下区域可能对灵长类动物的抽象认知有贡献。一个候选结构是上丘（SC），这是一个进化上保守的中脑区域，尽管传统上认为它仅介导反射性空间定向，但它参与需要空间定向的认知任务。在这里，我们揭示了灵长类动物上丘在抽象的、高阶视觉认知中的新作用。我们比较了上丘和后顶叶皮层（PPC）中的神经活动，后顶叶皮层是一个先前已被证明对类别决策有因果贡献的区域，同时猴子执行一项视觉分类任务，在该任务中它们通过手部动作报告自己的决策。与后顶叶皮层相比，上丘表现出更强且潜伏期更短的类别编码，并且上丘失活会显著损害猴子的类别决策。这些结果将上丘在空间定向方面已确立的作用扩展到抽象的、非空间认知。
