Institute of Psychology, Friedrich-Schiller University of Jena, 07743 Jena, Germany.
J Neurosci. 2013 Jun 5;33(23):9805-12. doi: 10.1523/JNEUROSCI.3423-12.2013.
Previously several functional magnetic resonance imaging (fMRI) studies point toward the role of perceptual expectations in determining adaptation or repetition suppression (RS) in humans. These studies showed that the probability of repetitions of faces within a block influences the magnitude of adaptation in face-related areas of the human brain (Summerfield et al., 2008). However, a current macaque single-cell/local field potential (LFP) recording study using objects as stimuli found no evidence for the modulation of the neural response by the repetition probability in the inferior temporal cortex (Kaliukhovich and Vogels, 2010). Here we examined whether stimulus repetition probability affects fMRI repetition suppression for nonface object stimuli in the human brain. Subjects were exposed to either two identical [repetition trials (RTs)] or two different [alternation trials (ATs)] object stimuli. Both types of trials were presented blocks consisting of either 75% [repetition blocks (RBs)] or 25% [alternation blocks (ABs)] of RTs. We found strong RS, i.e., a lower signal for RTs compared to ATs, in the object sensitive lateral occipital cortex as well as in the face-sensitive occipital and fusiform face areas. More importantly, however, there was no significant difference in the magnitude of RS between RBs and ABs in each of the areas. This is in agreement with the previous monkey single-unit/LFP findings and suggests that RS in the case of nonface visual objects is not modulated by the repetition probability in humans. Our results imply that perceptual expectation effects vary for different visual stimulus categories.
先前的几项功能磁共振成像（fMRI）研究表明，在人类中，知觉预期在确定适应或重复抑制（RS）中起作用。这些研究表明，在一个块内重复出现面孔的概率会影响大脑中与面孔相关区域的适应程度（Summerfield 等人，2008）。然而，一项使用物体作为刺激的当前猕猴单细胞/局部场电位（LFP）记录研究发现，在下颞叶皮层中，没有证据表明重复概率调制神经反应（Kaliukhovich 和 Vogels，2010）。在这里，我们检查了刺激重复概率是否会影响人类大脑中非面孔物体刺激的 fMRI 重复抑制。受试者暴露于两个相同的[重复试验（RTs）]或两个不同的[交替试验（ATs）]物体刺激。这两种类型的试验都呈现出由 75%[重复块（RBs）]或 25%[交替块（ABs）]的 RTs 组成的块。我们在物体敏感的外侧枕叶皮层以及面孔敏感的枕叶和梭状回面孔区发现了强烈的 RS，即 RTs 的信号比 ATs 低。然而，更重要的是，在每个区域中，RB 和 AB 之间的 RS 幅度没有显着差异。这与之前的猴子单细胞/LFP 发现一致，表明在非面孔视觉物体的情况下，RS 不受人类重复概率的调制。我们的结果表明，不同视觉刺激类别之间的知觉预期效应不同。
