Task-Load-Dependent Activation of Dopaminergic Midbrain Areas in the Absence of Reward
Task-Load-Dependent Activation of Dopaminergic Midbrain Areas in the Absence of Reward
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DOI：
10.1523/jneurosci.4845-10.2011
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发表时间：
2011-03-30
影响因子：
5.3
通讯作者：
Noesselt, Toemme
中科院分区：
文献类型：
--
作者：
Boehler, Carsten N.;Hopf, Jens-Max;Noesselt, Toemme
皮质和皮质下结构中的多巴胺释放在奖励相关的神经过程中起着核心作用。在这种情况下，多巴胺能输入通常被认为发挥激活作用，促进获得预期奖励所需的行为和认知操作。在这里，我们提供了来自人类功能磁共振成像的证据，表明这种激活作用也可以通过任务需求相关过程介导，从而超越仅涉及外在激励因素的情况。使用预先预测不同水平的任务需求的视觉辨别任务，我们发现在没有奖励或类似的外在激励因素的情况下，黑质（SN）的血流动力学活动增强，以满足高任务需求。因此，这一观察结果表明 SN 也可以通过内源方式被激活。与奖励相关过程中的作用并行，与奖励无关的激活可能有助于招募满足增强的任务需求所需的处理资源。同时，为了应对高任务要求，皮层和皮层下控制区域的广泛网络的活动得到增强，而默认模式网络的区域则被更强烈地停用。目前的观察结果表明，SN 代表了更广泛的神经网络中的核心节点，它根据不断变化的情境机会和任务要求调整可用神经和行为资源的数量，这通常由外在因素驱动，但也可以进行内源控制。
Dopamine release in cortical and subcortical structures plays a central role in reward-related neural processes. Within this context, dopaminergic inputs are commonly assumed to play an activating role, facilitating behavioral and cognitive operations necessary to obtain a prospective reward. Here, we provide evidence from human fMRI that this activating role can also be mediated by task-demand-related processes and thus extendsbeyondsituationsthatonlyentailextrinsicmotivatingfactors. Using a visual discrimination task in which varying levels of task demands were precued, we found enhanced hemodynamic activity in the substantia nigra (SN) for high task demands in the absence of reward or similar extrinsic motivating factors. This observation thus indicates that the SN can also be activated in an endogenous fashion. In parallel to its role in reward-related processes, reward-independent activation likely serves to recruit the processing resources needed to meet enhanced task demands. Simultaneously, activity in a wide network of cortical and subcortical control regions was enhanced in response to high task demands, whereas areas of the default-mode network were deactivated more strongly. The present observations suggest that the SN represents a core node within a broader neural network that adjusts the amount of available neural and behavioral resources to changing situational opportunities and task requirements, which is often driven by extrinsic factors but can also be controlled endogenously.