Department of Physiology and Pharmacology, Sapienza University of Rome, Rome, 00185, Italy.
Department of Physiology and Pharmacology, Sapienza University of Rome, Rome, 00185, Italy
J Neurosci. 2021 Sep 8;41(36):7591-7606. doi: 10.1523/JNEUROSCI.0641-20.2021. Epub 2021 Jul 30.
Reward prospect weighs on motor decision processes, enhancing the selection of appropriate actions and the inhibition of others. While many studies have investigated the neuronal basis of reward representations and of cortical control of actions, the neuronal correlates of the influences of reward prospect on motor decisions are less clear. We recorded from the dorsal premotor cortex (PMd) of 2 male macaque monkeys performing a modified version of the Stop-signal (countermanding) task. This task challenges motor decisions by requiring responding to a frequent Go stimulus, but to suppress this response when a rare Stop signal is presented during the reaction time. We unbalanced the motivation to respond or to suppress the response by presenting a cue informing on three different rewards schedules: in one case, Go trials were rewarded more than Stop trials; in another case, Stop trials were rewarded more than Go trials; in the last case, both types of trials were rewarded equally. Monkeys adopted different strategies according to reward information provided by the cue: the higher the reward for Stop trials, the higher their ability to suppress the response and the slower their response to Go stimuli. PMd neuronal activity evolved in time and correlated with the behavior: PMd signaled first the cue salience, representing the chance to earn the highest reward at stake, then reflected the shaping of the motor choice by the motivation to move or to stop. These findings represent a neuronal correlate of the influence of reward information on motor decision. The motivation to obtain rewards drives how animals act over their environment. To explore the involvement of motor cortices in motivated behaviors, we recorded high-resolution neuronal activity in the premotor cortex of monkeys performing a task that manipulated the motivation to generate/withhold a movement through different cued reward probabilities. Our results show the presence of neuronal signals dynamically reflecting the salience of the cue, in the time immediately following its presentation, and a motivation-related activity in performing (or cancelling) a motor program, while the behavioral response approached. The encoding of multiple reward-related signals in this region leads to consider an important role of premotor areas in the reward circuitry supporting action.
奖励预期会影响运动决策过程，增强对适当行为的选择和对其他行为的抑制。虽然许多研究已经调查了奖励表示和皮质控制动作的神经元基础，但奖励预期对运动决策的影响的神经元相关性还不太清楚。我们从两只雄性猕猴的背侧运动前皮层 (PMd) 记录了修改后的停止信号 (取消) 任务。在这个任务中，需要对频繁的 Go 刺激做出反应，但当在反应时间内出现罕见的停止信号时，需要抑制这种反应。我们通过呈现一个提示来平衡反应或抑制反应的动机，提示告知三种不同的奖励计划：在一种情况下，Go 试验的奖励比停止试验多；在另一种情况下，停止试验的奖励比 Go 试验多；在最后一种情况下，两种类型的试验都有同等的奖励。猴子根据提示提供的奖励信息采取了不同的策略：停止试验的奖励越高，它们抑制反应的能力就越高，对 Go 刺激的反应就越慢。PMd 神经元活动随时间演变并与行为相关：PMd 首先提示信号的显著性，代表有机会获得最高奖励，然后反映了通过移动或停止的动机来塑造运动选择。这些发现代表了奖励信息对运动决策影响的神经元相关性。获得奖励的动机驱使动物在环境中行动。为了探索运动皮层在动机行为中的作用，我们在执行任务的猴子的前运动皮层中记录了高分辨率的神经元活动，该任务通过不同提示奖励概率来操纵产生/抑制运动的动机。我们的结果表明，在提示呈现后的立即时间内，存在动态反映提示显著性的神经元信号，以及在执行 (或取消) 运动程序时与动机相关的活动，而行为反应则接近。该区域中多个与奖励相关的信号的编码导致考虑前运动区域在支持动作的奖励回路中的重要作用。
