Sheremata Summer L, Silver Michael A
Department of Psychology, George Washington University, Washington, DC 20052 and
Helen Wills Neuroscience Institute, School of Optometry, and Vision Science Graduate Group, University of California, Berkeley, California 94720.
J Neurosci. 2015 Jan 14;35(2):508-17. doi: 10.1523/JNEUROSCI.2378-14.2015.
Posterior parietal cortex contains several areas defined by topographically organized maps of the contralateral visual field. However, recent studies suggest that ipsilateral stimuli can elicit larger responses in the right than left hemisphere within these areas, depending on task demands. Here we determined the effects of spatial attention on the set of visual field locations (the population receptive field [pRF]) that evoked a response for each voxel in human topographic parietal cortex. A two-dimensional Gaussian was used to model the pRF in each voxel, and we measured the effects of attention on not only the center (preferred visual field location) but also the size (visual field extent) of the pRF. In both hemispheres, larger pRFs were associated with attending to the mapping stimulus compared with attending to a central fixation point. In the left hemisphere, attending to the stimulus also resulted in more peripheral preferred locations of contralateral representations, compared with attending fixation. These effects of attention on both pRF size and preferred location preserved contralateral representations in the left hemisphere. In contrast, attentional modulation of pRF size but not preferred location significantly increased representation of the ipsilateral (right) visual hemifield in right parietal cortex. Thus, attention effects in topographic parietal cortex exhibit hemispheric asymmetries similar to those seen in hemispatial neglect. Our findings suggest potential mechanisms underlying the behavioral deficits associated with this disorder.
顶叶后皮质包含几个由对侧视野的拓扑组织图定义的区域。然而，最近的研究表明，根据任务需求，同侧刺激在这些区域中能在右半球比左半球引发更大的反应。在这里，我们确定了空间注意力对人类地形顶叶皮质中每个体素诱发反应的视野位置集（群体感受野 [pRF]）的影响。使用二维高斯模型来模拟每个体素中的pRF，并且我们不仅测量了注意力对pRF中心（偏好的视野位置）的影响，还测量了对其大小（视野范围）的影响。在两个半球中，与关注中央固定点相比，关注映射刺激与更大的pRF相关。在左半球，与关注固定点相比，关注刺激还导致对侧表征的更外周偏好位置。注意力对pRF大小和偏好位置的这些影响在左半球保留了对侧表征。相比之下，pRF大小而非偏好位置的注意力调制显著增加了右顶叶皮质中同侧（右）视野半野的表征。因此，地形顶叶皮质中的注意力效应表现出与半侧空间忽视中所见类似的半球不对称性。我们的发现提示了与该疾病相关的行为缺陷背后的潜在机制。
