Department of Psychology, Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London, WC1N 3AR, UK.
Exp Brain Res. 2010 Jul;204(3):465-73. doi: 10.1007/s00221-010-2181-y. Epub 2010 Feb 18.
When a weak shock is delivered to the finger immediately before a voluntary movement, or during a delay interval where subjects are prepared to make the movement, shock detection rates worsen progressively as the movement approaches. Further, we previously showed that shock detection improves again if a NoGo signal produces inhibition of a prepared response. Here, we used a somatosensory version of the stop-signal paradigm to investigate inhibitory processing during the 'horserace' period when motor excitation and inhibition processes may be simultaneously active. When subjects made a rapid keypress response to a go-signal, shock detection deteriorated in a time-dependent manner, replicating sensory suppression. However, when go-signals were followed by adaptively delayed stop-signals so that subjects could not inhibit the prepared movement, and made errors of commission, we found a paradoxical brief increase in shock detection performance just after the stop-signal, as if in a NoGo trial. During this brief window, the somatosensory system showed a pattern consistent with motor inhibition, even though the motor system itself was too far advanced in movement execution for action to be inhibited. Most models of stop-signal processing propose a two-horse race between excitation and inhibition, with a winner-takes-all solution. We show that there may be distinct motor and somatosensory races. Moreover, inhibitory processes may lead in the somatosensory race, at least briefly, even when excitatory processes win the motor race.
当在自愿运动之前立即向手指施加弱电击，或者在受试者准备进行运动的延迟间隔期间施加电击时，随着运动的临近，电击检测率会逐渐恶化。此外，我们之前曾表明，如果 NoGo 信号产生对准备好的反应的抑制，那么电击检测会再次改善。在这里，我们使用停止信号范式的体感版本来研究在“赛马”期间（此时运动兴奋和抑制过程可能同时活跃）的抑制处理。当受试者对 Go 信号做出快速按键反应时，电击检测会以时间依赖的方式恶化，从而复制了感觉抑制。然而，当 Go 信号之后是自适应延迟的停止信号，使得受试者无法抑制准备好的运动并产生冲动性错误时，我们发现就在停止信号之后出现了一个矛盾的短暂电击检测性能的增加，就好像在 NoGo 试验中一样。在这个短暂的窗口中，体感系统表现出与运动抑制一致的模式，即使运动系统本身在运动执行中已经过于先进，以至于无法进行抑制。停止信号处理的大多数模型都提出了兴奋和抑制之间的双马赛跑，并有一个赢家通吃的解决方案。我们表明，可能存在明显的运动和体感竞赛。此外，即使在运动竞赛中兴奋过程获胜，抑制过程也可能在体感竞赛中至少短暂地领先。
