Xu Benjamin, Levy Sarah, Butman John, Pham Dzung, Cohen Leonardo G, Sandrini Marco
Human Cortical Physiology and Neurorehabilitation Section, The National Institute of Neurological Disorders and Stroke, The National Institutes of Health Bethesda, MD, USA ; Center for Neuroscience and Regenerative Medicine Bethesda, MD, USA.
Clinical Center, Department of Radiology, National Institutes of Health Bethesda, MD, USA.
Front Hum Neurosci. 2015 Feb 4;9:34. doi: 10.3389/fnhum.2015.00034. eCollection 2015.
Being able to stop (or inhibit) an action rapidly as in a stop-signal task (SST) is an essential human ability. Previous studies showed that when a pre-stimulus cue warned of the possible need to stop a response in an upcoming trial, participants' response time (RT) increased if the subsequent trial required a "go" response (i.e., "go" RT cost) relative to a trial where this uncertainty was not present. This increase of the "go" RT correlated with more efficient response stopping. However, it remains a question whether foreknowledge of upcoming inhibition trials given prior to the task is sufficient to modulate neural activity associated with the primary "go" responses irrespective of whether stopping an overt response is required. We presented three task conditions with identical primary (i.e., "go") response trials but without pre-stimulus cues. Participants were informed that Condition 1 had only "go" trials (All-go condition), Condition 2 required a "stop" response for some trials (Stop condition), and Condition 3 required a response incongruent with the primary response (i.e., Switch response) for some trials (Switch condition). Participants performed the tasks during functional magnetic resonance imaging (fMRI) scans. Results showed a significant increase in the "go" RT (cost) in the Stop and Switch conditions relative to the All-go condition. The "go" RT cost was correlated with decreased inhibition time. fMRI activation in the frontal-basal-ganglia regions during the "go" responses in the Stop and Switch conditions was also correlated with the efficiency of Stop and Switch responses. These results suggest that foreknowledge prior to the task is sufficient to influence neural activity associated with the primary response and modulate inhibition efficiency, irrespective of whether stopping an overt response is required.
能够像在停止信号任务（SST）中那样迅速停止（或抑制）一个动作是人类的一项基本能力。先前的研究表明，当一个刺激前提示警告即将到来的试验中可能需要停止反应时，如果随后的试验需要“执行”反应（即“执行”反应成本），相对于不存在这种不确定性的试验，参与者的反应时间（RT）会增加。这种“执行”RT的增加与更有效的反应停止相关。然而，在任务之前给出即将到来的抑制试验的预知信息是否足以调节与主要“执行”反应相关的神经活动，而不管是否需要停止明显的反应，这仍然是一个问题。我们呈现了三种任务条件，它们具有相同的主要（即“执行”）反应试验，但没有刺激前提示。参与者被告知，条件1只有“执行”试验（全执行条件），条件2在某些试验中需要“停止”反应（停止条件），条件3在某些试验中需要与主要反应不一致的反应（即切换反应）（切换条件）。参与者在功能磁共振成像（fMRI）扫描期间执行任务。结果显示，与全执行条件相比，停止和切换条件下的“执行”RT（成本）显著增加。“执行”RT成本与抑制时间的减少相关。在停止和切换条件下“执行”反应期间额叶 - 基底神经节区域的fMRI激活也与停止和切换反应的效率相关。这些结果表明，任务之前的预知信息足以影响与主要反应相关的神经活动并调节抑制效率，而不管是否需要停止明显的反应。
