St John-Saaltink Elexa, Utzerath Christian, Kok Peter, Lau Hakwan C, de Lange Floris P
Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, the Netherlands.
Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, the Netherlands; Department of Psychology, University of California Los Angeles, Los Angeles, California, United States of America.
PLoS One. 2015 Jun 22;10(6):e0131172. doi: 10.1371/journal.pone.0131172. eCollection 2015.
Stimulus expectation can modulate neural responses in early sensory cortical regions, with expected stimuli often leading to a reduced neural response. However, it is unclear whether this expectation suppression is an automatic phenomenon or is instead dependent on the type of task a subject is engaged in. To investigate this, human subjects were presented with visual grating stimuli in the periphery that were either predictable or non-predictable while they performed three tasks that differently engaged cognitive resources. In two of the tasks, the predictable stimulus was task-irrelevant and spatial attention was engaged at fixation, with a high load on either perceptual or working memory resources. In the third task, the predictable stimulus was task-relevant, and therefore spatially attended. We observed that expectation suppression is dependent on the cognitive resources engaged by a subjects' current task. When the grating was task-irrelevant, expectation suppression for predictable items was visible in retinotopically specific areas of early visual cortex (V1-V3) during the perceptual task, but it was abolished when working memory was loaded. When the grating was task-relevant and spatially attended, there was no significant effect of expectation in early visual cortex. These results suggest that expectation suppression is not an automatic phenomenon, but dependent on attentional state and type of available cognitive resources.
刺激预期能够调节早期感觉皮层区域的神经反应，预期刺激通常会导致神经反应减弱。然而，目前尚不清楚这种预期抑制是一种自动现象，还是取决于受试者所从事的任务类型。为了探究这一点，研究人员让人类受试者在执行三项不同程度占用认知资源的任务时，在周边视野中呈现可预测或不可预测的视觉光栅刺激。在其中两项任务中，可预测刺激与任务无关，受试者在注视点处集中空间注意力，这对感知或工作记忆资源造成了较高负荷。在第三项任务中，可预测刺激与任务相关，因此在空间上受到关注。我们观察到，预期抑制取决于受试者当前任务所占用的认知资源。当光栅与任务无关时，在感知任务期间，早期视觉皮层（V1-V3）视网膜拓扑特异性区域中，对可预测项目的预期抑制是可见的，但当工作记忆负荷增加时，这种抑制就会消失。当光栅与任务相关且在空间上受到关注时，早期视觉皮层中预期没有显著影响。这些结果表明，预期抑制不是一种自动现象，而是取决于注意力状态和可用认知资源的类型。
