Institute of Neuroscience and Medicine (INM-3), Research Centre Jülich, Jülich, Germany.
J Cogn Neurosci. 2011 Feb;23(2):414-24. doi: 10.1162/jocn.2010.21441. Epub 2010 Feb 10.
Besides the fact that RTs in cognitive tasks are affected by the specific demands of a trial, the context in which this trial occurs codetermines the speed of the response. For instance, invalid spatial cues generally prolong RTs to targets in the location-cueing paradigm, whereas the magnitude of these RT costs additionally varies as a function of the preceding trial types so that RTs for invalid trials may be increased when preceded by valid rather than invalid trials. In the present fMRI study, we investigated trial sequence effects in a combined oddball and location-cueing paradigm. In particular, we tested whether RTs and neural activity to infrequent invalid or deviant targets varied as a function of the number of preceding valid standard trials. As expected, RTs in invalid and deviant trials were significantly slower when more valid standard trials had been presented beforehand. This behavioral effect was reflected in the neural activity of the right inferior/middle frontal gyrus where the amplitude of the hemodynamic response in invalid and deviant trials was positively related to the number of preceding valid standard trials. In contrast, decreased activity (i.e., a negative parametric modulation effect) was observed when more valid standard trials were successively presented. Further positive parametric effects for the number of preceding valid standard trials were observed in the left caudate nucleus and lingual gyrus. The data suggest that inferior frontal cortex extracts both event regularities and irregularities in event streams.
除了认知任务中的 RT 受到特定试验要求的影响外，试验发生的上下文也决定了反应的速度。例如，无效的空间线索通常会延长位置提示范式中目标的 RT，但这些 RT 成本的大小还会根据前面的试验类型而变化，因此无效试验的 RT 可能会增加，而不是无效试验的 RT 增加。在本 fMRI 研究中，我们在一个结合了Oddball 和位置提示范式的实验中研究了试验序列效应。特别是，我们测试了在前面呈现了更多有效标准试验的情况下，罕见的无效或偏差目标的 RT 和神经活动是否会发生变化。正如预期的那样，当前面呈现了更多的有效标准试验时，无效和偏差试验的 RT 明显变慢。这种行为效应反映在右额下回/中回的神经活动中，无效和偏差试验的血流动力学反应幅度与前面呈现的有效标准试验的数量呈正相关。相比之下，当连续呈现更多的有效标准试验时，观察到活动减少（即负的参数调制效应）。当前面呈现更多的有效标准试验时，左侧尾状核和舌回也观察到正的参数效应。数据表明，下额叶皮层提取了事件流中的事件规则和不规则性。
