Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1010, USA.
J Neurosci. 2011 Jun 8;31(23):8406-21. doi: 10.1523/JNEUROSCI.1419-11.2011.
Choice behavior and its neural correlates have been intensely studied with tasks in which a subject makes a perceptual judgment and indicates the result with a motor action. Yet a question crucial for relating behavior to neural activity remains unresolved: what fraction of a subject's reaction time (RT) is devoted to the perceptual evaluation step, as opposed to executing the motor report? Making such timing measurements accurately is complicated because RTs reflect both sensory and motor processing, and because speed and accuracy may be traded. To overcome these problems, we designed the compelled-saccade task, a two-alternative forced-choice task in which the instruction to initiate a saccade precedes the appearance of the relevant sensory information. With this paradigm, it is possible to track perceptual performance as a function of the amount of time during which sensory information is available to influence a subject's choice. The result-the tachometric curve-directly reveals a subject's perceptual processing capacity independently of motor demands. Psychophysical data, together with modeling and computer-simulation results, reveal that task performance depends on three separable components: the timing of the motor responses, the speed of the perceptual evaluation, and additional cognitive factors. Each can vary quickly, from one trial to the next, or can show stable, longer-term changes. This novel dissociation between sensory and motor processes yields a precise metric of how perceptual capacity varies under various experimental conditions and serves to interpret choice-related neuronal activity as perceptual, motor, or both.
选择行为及其神经相关已经在各种任务中进行了深入研究，这些任务要求主体进行感知判断，并通过运动动作来指示结果。然而，一个与神经活动相关的关键问题仍然没有得到解决：主体的反应时间（RT）中有多少部分用于感知评估步骤，而不是执行运动报告？要准确进行这种定时测量是复杂的，因为 RT 反映了感觉和运动处理，并且速度和准确性可能会相互交换。为了克服这些问题，我们设计了强迫性眼球运动任务，这是一种双选择强制选择任务，其中启动眼球运动的指令先于相关感觉信息的出现。通过这个范式，可以跟踪感知性能作为可用的感觉信息量的函数，以影响主体的选择。结果——计时曲线——直接揭示了主体的感知处理能力，而不受运动需求的影响。心理物理学数据，以及建模和计算机模拟结果，揭示了任务表现取决于三个可分离的成分：运动反应的定时、感知评估的速度以及额外的认知因素。每个因素都可以在每次试验之间快速变化，或者可以显示稳定的、长期的变化。这种感觉和运动过程之间的新颖分离提供了一个精确的度量标准，用于衡量在各种实验条件下感知能力如何变化，并有助于将与选择相关的神经元活动解释为感知、运动或两者兼而有之。
