Department of Psychology, University of Pennsylvania, Philadelphia, PA 19104, USA.
Department of Psychology, University of Pennsylvania, Philadelphia, PA 19104, USA; Carney Institute for Brain Science, Brown University, Providence, RI 02912, USA.
Neuroimage. 2021 Aug 15;237:118159. doi: 10.1016/j.neuroimage.2021.118159. Epub 2021 May 12.
Across many studies, ventromedial prefrontal cortex (vmPFC) activity has been found to correlate with subjective value during value-based decision-making. Recently, however, vmPFC has also been shown to reflect a hexagonal gridlike code during navigation through physical and conceptual space, and such gridlike codes have been proposed to enable value-based choices between novel options. Here, we first show that, in theory, a hexagonal gridlike code can in some cases mimic vmPFC activity previously attributed to subjective value, raising the possibility that the subjective value correlates previously observed in vmPFC may have actually been a misconstrued gridlike signal. We then compare the two accounts empirically, using fMRI data from a large number of subjects performing an intertemporal choice task. We find clear and unambiguous evidence that subjective value is a better description of vmPFC activity in this task than a hexagonal gridlike code. In fact, we find no significant evidence at all for a hexagonal gridlike code in vmPFC activity during intertemporal choice. This result limits the generality of gridlike modulation as description of vmPFC activity. We suggest that vmPFC may flexibly switch representational schemes so as to encode the most relevant information for the current task.
在许多研究中，腹内侧前额叶皮层（vmPFC）的活动与基于价值的决策过程中的主观价值相关。然而，最近vmPFC 也被证明在物理和概念空间的导航过程中反映出六边形网格状的代码，并且这种网格状的代码被提出可以在新颖选项之间进行基于价值的选择。在这里，我们首先表明，在某些情况下，六边形网格状的代码可以模拟先前归因于主观价值的 vmPFC 活动，这增加了先前在 vmPFC 中观察到的主观价值相关信号实际上可能是误解的网格信号的可能性。然后，我们使用大量进行跨期选择任务的受试者的 fMRI 数据，从经验上比较了这两种解释。我们发现明确且毫不含糊的证据表明，在该任务中，主观价值是对 vmPFC 活动的更好描述，而不是六边形网格状代码。实际上，我们在 vmPFC 活动中进行跨期选择时根本没有发现六边形网格状代码的显著证据。这个结果限制了网格状调制作为 vmPFC 活动描述的普遍性。我们认为，vmPFC 可能会灵活地切换表示方案，以便为当前任务编码最相关的信息。
