Reyes-Puerta Vicente, Philipp Roland, Lindner Werner, Lünenburger Lars, Hoffmann Klaus-Peter
Department of General Zoology and Neurobiology, Ruhr University Bochum, D-44780 Bochum, Germany.
J Neurophysiol. 2009 Jun;101(6):3199-211. doi: 10.1152/jn.90983.2008. Epub 2009 Apr 1.
Target probability has been shown to modulate motor preparatory activity of neurons in the caudal superior colliculus (SC) of the primate. Here we tested whether top-down processes, such as task predictability, influence the activity of neurons also at the rostral pole of the SC (rSC), classically related to fixation. To investigate this, double-step saccade tasks were embedded in two different paradigms, one containing unpredictable and another containing predictable tasks. During predictable tasks the animals could develop some expectation about the forthcoming second target jump, i.e., anticipate when and where to make the second saccade. Neuronal responses were recorded during both paradigms and compared, revealing the influence of task predictability on the activity of rSC neurons during specific periods of fixation. In particular, neuronal activity stayed significantly lower during the fixation period between two successive saccades in predictable than in unpredictable tasks. In addition there was a learning effect within a session during predictable conditions, i.e., the intersaccadic activity was higher in the early than in the late trials. Further, reaction times for the second saccade were shorter in predictable than in unpredictable tasks. However, we demonstrated that this difference in reaction times cannot be solely accounted for by the reported difference in neural activity, which was mainly influenced by the predictability of the tasks. With these results we show that top-down processes such as predictability are imposed on the activity of neurons in the rostral pole of the primate SC.
研究表明，目标概率可调节灵长类动物尾侧上丘（SC）中神经元的运动准备活动。在此，我们测试了自上而下的过程，如任务可预测性，是否也会影响经典上与注视相关的上丘头端（rSC）神经元的活动。为了研究这一点，双步扫视任务被嵌入到两种不同的范式中，一种包含不可预测的任务，另一种包含可预测的任务。在可预测任务期间，动物可以对即将到来的第二个目标跳跃产生一些预期，即预测何时以及何处进行第二次扫视。在两种范式中都记录了神经元反应并进行比较，揭示了任务可预测性在特定注视期对rSC神经元活动的影响。特别是，在可预测任务中，两个连续扫视之间的注视期内，神经元活动显著低于不可预测任务。此外，在可预测条件下的一个实验过程中存在学习效应，即早期试验中的扫视间期活动高于晚期试验。此外，可预测任务中第二次扫视的反应时间比不可预测任务中的短。然而，我们证明，反应时间的这种差异不能仅仅由所报道的神经活动差异来解释，神经活动差异主要受任务可预测性的影响。通过这些结果，我们表明，诸如可预测性等自上而下的过程会施加于灵长类动物SC头端神经元的活动上。
