Sustained Splits of Attention within versus across Visual Hemifields Produce Distinct Spatial Gain Profiles
Sustained Splits of Attention within versus across Visual Hemifields Produce Distinct Spatial Gain Profiles
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DOI：
10.1162/jocn_a_00883
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发表时间：
2016
影响因子：
3.2
通讯作者：
S. Walter;C. Keitel;Matthias M. Müller
中科院分区：
文献类型：
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作者：
S. Walter;C. Keitel;Matthias M. Müller
视觉注意可以同时集中在不连续位置的两个刺激上，而忽略中间刺激。然而，在多焦点注意任务中，当注意到的刺激落在一个视觉半视野内时，行为表现会动摇，而不是当它们分布在左右两个半球时。这种“不同半视野优势”被归因于早期视觉皮质中每个大脑半球在很大程度上独立的处理能力。在这里，我们调查了这种优势如何影响空间注意力的持续分配。我们在下视野中展示了六个等偏心发光二极管(LED)，每个LED以不同的频率闪烁。参与者关注空间上由中间LED隔开的两个LED，并对将要参加的LED上的同步事件做出响应。与任务相关的LED对要么位于同一半视野内(“半视野内”条件)，要么被垂直子午线隔开(“跨半视野”条件)。闪光驱动的大脑振荡，即稳态视觉诱发电位(SSVEP)，将注意力分配给单个LED。行为表现和SSVEP均表明，在“跨半视野”条件下，与“半视野内”条件相比，“跨半视野”条件下对被关注的LED对的处理能力增强。此外，SSVEP仅在“跨半视野”条件下表现出对中间刺激的有效过滤。因此，尽管参与实验的发光二极管之间的物理距离相同，但在“跨半场”和“半场内”条件下，增益效应的空间分布却截然不同。这些发现证实了早期大脑皮层视觉加工阶段依赖于大脑半球特定的加工能力，并强调了它们在视觉注意力同时分配到多个位置的限制作用。
Visual attention can be focused concurrently on two stimuli at noncontiguous locations while intermediate stimuli remain ignored. Nevertheless, behavioral performance in multifocal attention tasks falters when attended stimuli fall within one visual hemifield as opposed to when they are distributed across left and right hemifields. This “different-hemifield advantage” has been ascribed to largely independent processing capacities of each cerebral hemisphere in early visual cortices. Here, we investigated how this advantage influences the sustained division of spatial attention. We presented six isoeccentric light-emitting diodes (LEDs) in the lower visual field, each flickering at a different frequency. Participants attended to two LEDs that were spatially separated by an intermediate LED and responded to synchronous events at to-be-attended LEDs. Task-relevant pairs of LEDs were either located in the same hemifield (“within-hemifield” conditions) or separated by the vertical meridian (“across-hemifield” conditions). Flicker-driven brain oscillations, steady-state visual evoked potentials (SSVEPs), indexed the allocation of attention to individual LEDs. Both behavioral performance and SSVEPs indicated enhanced processing of attended LED pairs during “across-hemifield” relative to “within-hemifield” conditions. Moreover, SSVEPs demonstrated effective filtering of intermediate stimuli in “across-hemifield” condition only. Thus, despite identical physical distances between LEDs of attended pairs, the spatial profiles of gain effects differed profoundly between “across-hemifield” and “within-hemifield” conditions. These findings corroborate that early cortical visual processing stages rely on hemisphere-specific processing capacities and highlight their limiting role in the concurrent allocation of visual attention to multiple locations.