Lee Stephen M, Peltsch Alicia, Kilmade Maureen, Brien Donald C, Coe Brian C, Johnsrude Ingrid S, Munoz Douglas P
Queen's University, Kingston, Ontario, Canada.
Western University, London, Ontario, Canada.
J Cogn Neurosci. 2016 Aug;28(8):1210-27. doi: 10.1162/jocn_a_00968. Epub 2016 Apr 7.
Every day we generate motor responses that are timed with external cues. This phenomenon of sensorimotor synchronization has been simplified and studied extensively using finger tapping sequences that are executed in synchrony with auditory stimuli. The predictive saccade paradigm closely resembles the finger tapping task. In this paradigm, participants follow a visual target that "steps" between two fixed locations on a visual screen at predictable ISIs. Eventually, the time from target appearance to saccade initiation (i.e., saccadic RT) becomes predictive with values nearing 0 msec. Unlike the finger tapping literature, neural control of predictive behavior described within the eye movement literature has not been well established and is inconsistent, especially between neuroimaging and patient lesion studies. To resolve these discrepancies, we used fMRI to investigate the neural correlates of predictive saccades by contrasting brain areas involved with behavior generated from the predictive saccade task with behavior generated from a reactive saccade task (saccades are generated toward targets that are unpredictably timed). We observed striking differences in neural recruitment between reactive and predictive conditions: Reactive saccades recruited oculomotor structures, as predicted, whereas predictive saccades recruited brain structures that support timing in motor responses, such as the crus I of the cerebellum, and structures commonly associated with the default mode network. Therefore, our results were more consistent with those found in the finger tapping literature.
我们每天都会产生与外部线索同步的运动反应。感觉运动同步这一现象已通过与听觉刺激同步执行的手指敲击序列得到简化并被广泛研究。预测性扫视范式与手指敲击任务极为相似。在该范式中，参与者追踪一个视觉目标，该目标会在视觉屏幕上两个固定位置之间以可预测的间隔时间（ISI）“跳跃”。最终，从目标出现到扫视启动的时间（即扫视反应时间）变得具有预测性，其值接近0毫秒。与手指敲击文献不同，眼动文献中所描述的预测行为的神经控制尚未得到很好的确立，且存在不一致性，尤其是在神经成像和患者病变研究之间。为了解决这些差异，我们使用功能磁共振成像（fMRI）来研究预测性扫视的神经关联，方法是将预测性扫视任务产生的行为与反应性扫视任务（向时间不可预测出现的目标产生扫视）产生的行为所涉及的脑区进行对比。我们观察到反应性和预测性条件下神经募集存在显著差异：如预期的那样，反应性扫视募集了眼球运动结构，而预测性扫视募集了支持运动反应定时的脑结构，如小脑的 Crus I，以及通常与默认模式网络相关的结构。因此，我们的结果与手指敲击文献中的结果更为一致。
