Filmer Hannah L, Dux Paul E, Mattingley Jason B
School of Psychology, The University of Queensland, McElwain Building, St Lucia, QLD 4072, Australia.
School of Psychology, The University of Queensland, McElwain Building, St Lucia, QLD 4072, Australia.
Neuropsychologia. 2015 Jul;74:120-6. doi: 10.1016/j.neuropsychologia.2015.01.038. Epub 2015 Jan 28.
Spatial attention can be used to direct neural processing resources to a subset of task-relevant or otherwise salient items within the environment. Such selective processes are particularly important for resolving competition between multiple stimuli. Deficits in processing single stimuli can arise after damage to parietal, frontal and temporal brain regions, as is typical in patients with contralesional spatial neglect. By contrast, deficits in processing multiple competing stimuli may arise specifically following lesions of the posterior parietal cortex (PPC), as occurs in the disorder of spatial extinction. It remains unclear, however, whether mechanisms involved in selecting single and competing stimuli reflect the same or dissociable neural operations within the PPC. To address this issue, in separate sessions, we applied transcranial direct current stimulation (tDCS) to the left or right PPC and measured the effect on detecting and discriminating single and competing visual stimulus events. Our results revealed reliable tDCS modulations of stimulus processing, specific to the right PPC, as well as a dissociation in the detection of single and competing stimuli. For the right PPC only, single stimuli presented to the left (contralateral) visual field were affected selectively by anodal tDCS, whereas competing stimuli across the two visual fields were affected by both anodal and cathodal tDCS. These contrasting effects of anodal and cathodal tDCS on perception of single and competing stimuli suggest dissociable neural coding properties within the right PPC.
空间注意力可用于将神经处理资源导向环境中与任务相关或其他显著项目的一个子集。这种选择性过程对于解决多个刺激之间的竞争尤为重要。在顶叶、额叶和颞叶脑区受损后，处理单个刺激时可能会出现缺陷，这在对侧空间忽视患者中很常见。相比之下，处理多个竞争性刺激时的缺陷可能特别发生在顶叶后皮质（PPC）受损后，就像在空间消退障碍中那样。然而，尚不清楚在PPC内选择单个和竞争性刺激所涉及的机制是否反映相同或可分离的神经操作。为了解决这个问题，在不同的实验环节中，我们将经颅直流电刺激（tDCS）应用于左侧或右侧PPC，并测量其对检测和区分单个及竞争性视觉刺激事件的影响。我们的结果揭示了tDCS对刺激处理的可靠调制，这对右侧PPC具有特异性，同时也揭示了在检测单个和竞争性刺激方面的分离。仅对于右侧PPC，呈现给左侧（对侧）视野的单个刺激受阳极tDCS的选择性影响，而两个视野中的竞争性刺激则受阳极和阴极tDCS的影响。阳极和阴极tDCS对单个和竞争性刺激感知的这些对比效应表明右侧PPC内具有可分离的神经编码特性。
