Radboudumc, Donders Institute for Brain, Cognition, and Behaviour, Department of Cognitive Neuroscience, Geert Groteplein-Noord 21, 6525 EZ, Nijmegen, The Netherlands.
Radboud University, Donders Institute for Brain, Cognition and Behaviour, Kapittelweg 29, 6525 EN, Nijmegen, The Netherlands.
Sci Rep. 2017 Aug 18;7(1):8781. doi: 10.1038/s41598-017-09374-z.
Repeated exposure to the same stimulus results in an attenuated brain response in cortical regions that are activated during the processing of that stimulus. This phenomenon, called repetition suppression (RS), has been shown to be modulated by expectation. Typically, this is achieved by varying the probability of stimulus repetitions (P) between blocks of an experiment, generating an abstract expectation that 'things will repeat'. Here, we examined whether stimulus-specific expectations also modulate RS. We designed a task where expectation and repetition are manipulated independently, using stimulus-specific expectations. We investigated to which extent such stimulus-specific expectations modulated the visual evoked response to objects in lateral occipital cortex (LOC) and primary visual cortex (V1), using functional magnetic resonance imaging (fMRI). In LOC, we found that RS interacted with expectation, such that repetition suppression was more pronounced for unexpected relative to expected stimuli. Additionally, we found that the response of stimulus-preferring voxels in V1 was generally decreased when stimuli were expected. These results suggest that stimulus-specific expectations about objects modulate LOC and propagate back to the earliest cortical station processing visual input.
重复暴露于相同刺激会导致在处理该刺激时被激活的皮质区域的大脑反应减弱。这种现象称为重复抑制（RS），已被证明可以通过期望进行调节。通常，这是通过在实验的块之间改变刺激重复的概率（P）来实现的，从而产生“事情会重复”的抽象期望。在这里，我们研究了特定于刺激的期望是否也会调节 RS。我们设计了一个任务，其中使用特定于刺激的期望来独立地操纵期望和重复。我们使用功能磁共振成像（fMRI）研究了这种特定于刺激的期望在多大程度上调节了外侧枕叶皮层（LOC）和初级视觉皮层（V1）中对物体的视觉诱发电位。在 LOC 中，我们发现 RS 与期望相互作用，使得相对于预期刺激，意外刺激的抑制更为明显。此外，我们发现当预期刺激时，V1 中对刺激有偏好的体素的反应通常会降低。这些结果表明，关于物体的特定于刺激的期望会调节 LOC，并向处理视觉输入的最早皮质站传播。
