Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
J Cogn Neurosci. 2011 Nov;23(11):3355-65. doi: 10.1162/jocn_a_00032. Epub 2011 Mar 31.
Previous work has shown that neurons in the PFC show selectivity for learned categorical groupings. In contrast, brain regions lower in the visual hierarchy, such as inferior temporal cortex, do not seem to favor category information over information about physical appearance. However, the role of premotor cortex (PMC) in categorization has not been studied, despite evidence that PMC is strongly engaged by well-learned tasks and reflects learned rules. Here, we directly compare PFC neurons with PMC neurons during visual categorization. Unlike PFC neurons, relatively few PMC neurons distinguished between categories of visual images during a delayed match-to-category task. However, despite the lack of category information in the PMC, more than half of the neurons in both PFC and PMC reflected whether the category of a test image did or did not match the category of a sample image (i.e., had match information). Thus, PFC neurons represented all variables required to solve the cognitive problem, whereas PMC neurons instead represented only the final decision variable that drove the appropriate motor action required to obtain a reward. This dichotomy fits well with PFC's hypothesized role in learning arbitrary information and directing behavior as well as the PMC's role in motor planning.
先前的工作表明，前额叶皮层（PFC）中的神经元对经过学习的分类群体表现出选择性。相比之下，视觉层次结构较低的脑区，如颞下回，似乎并不倾向于将类别信息置于物理外观信息之上。然而，尽管有证据表明运动前皮层（PMC）强烈参与了熟练的任务并反映了学习的规则，但 PMC 在分类中的作用尚未得到研究。在这里，我们在视觉分类过程中直接比较了 PFC 神经元和 PMC 神经元。与 PFC 神经元不同，在延迟匹配到类别任务中，相对较少的 PMC 神经元区分视觉图像的类别。然而，尽管 PMC 中没有类别信息，但 PFC 和 PMC 中的一半以上的神经元反映了测试图像的类别是否与样本图像的类别匹配（即，具有匹配信息）。因此，PFC 神经元表示解决认知问题所需的所有变量，而 PMC 神经元则表示驱动获得奖励所需的适当运动动作的最终决策变量。这种二分法很好地符合了 PFC 假设的在学习任意信息和指导行为中的作用，以及 PMC 在运动规划中的作用。
