Département de Physiologie and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec H3C 3J7, Canada.
J Neurosci. 2011 May 11;31(19):7083-8. doi: 10.1523/JNEUROSCI.5681-10.2011.
It has been proposed that whenever an animal faces several action choices, their neural representations are processed in parallel in frontoparietal cortex and compete in a manner biased by any factor relevant to the decision. We tested this hypothesis by recording single-unit activity in dorsal premotor cortex (PMd) while a monkey performed two delayed center-out reaching tasks. In the one-target task, a single target was presented and its border style indicated its reward value. The two-target task was the same except two targets were presented and the value of each was varied. During the delay period of the one-target task, directionally tuned PMd activity showed no modulation with value. In contrast, during the two-target task, the same neurons showed strong effects of the value associated with their preferred target, always in relation to the value of the other target. Furthermore, the competition between action choices was strongest when targets were furthest apart. This angular distance effect appeared in neural activity as soon as cells became tuned, while modulation by relative value appeared much later. All of these findings can be reproduced by a computational model which suggests that decisions between actions are made through a biased competition taking place within a sensorimotor map of potential actions.
有人提出，每当动物面临多个行动选择时，它们的额顶叶皮层中的神经表示就会并行处理，并以任何与决策相关的因素为偏置进行竞争。我们通过在猴子进行两项延迟中心外伸手任务时记录背侧运动前皮层 (PMd) 的单个单元活动来检验这一假设。在单目标任务中，会呈现一个单一目标，其边界样式表示其奖励价值。两项任务相同，只是呈现了两个目标，并且每个目标的价值都有所不同。在单目标任务的延迟期间，方向调谐的 PMd 活动没有表现出与价值相关的调制。相比之下，在两项任务中，相同的神经元表现出与首选目标相关的强烈价值效应，始终与另一个目标的价值有关。此外，当目标相隔最远时，动作选择之间的竞争最强。这种角距离效应在细胞开始调谐时就会出现在神经活动中，而相对价值的调制则出现得晚得多。所有这些发现都可以通过一个计算模型来再现，该模型表明，通过在潜在动作的感觉运动图中进行有偏差的竞争来做出动作之间的决策。
