Thut Gregor, Nietzel Annika, Brandt Stephan A, Pascual-Leone Alvaro
Center for Noninvasive Brain Stimulation, Harvard Medical School, and Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA.
J Neurosci. 2006 Sep 13;26(37):9494-502. doi: 10.1523/JNEUROSCI.0875-06.2006.
Covertly directing visual attention toward a spatial location in the absence of visual stimulation enhances future visual processing at the attended position. The neuronal correlates of these attention shifts involve modulation of neuronal "baseline" activity in early visual areas, presumably through top-down control from higher-order attentional systems. We used electroencephalography to study the largely unknown relationship between these neuronal modulations and behavioral outcome in an attention orienting paradigm. Covert visuospatial attention shifts to either a left or right peripheral position in the absence of visual stimulation resulted in differential modulations of oscillatory alpha-band (8-14 Hz) activity over left versus right posterior sites. These changes were driven by varying degrees of alpha-decreases being maximal contralateral to the attended position. When expressed as a lateralization index, these alpha-changes differed significantly between attention conditions, with negative values (alpha_right < alpha_left) indexing leftward and more positive values (alpha_left < or = alpha_right) indexing rightward attention. Moreover, this index appeared deterministic for processing of forthcoming visual targets. Collapsed over trials, there was an advantage for left target processing in accordance with an overall negative bias in alpha-index values. Across trials, left targets were detected most rapidly when preceded by negative index values. Detection of right targets was fastest in trials with most positive values. Our data indicate that collateral modulations of posterior alpha-activity, the momentary bias of visuospatial attention, and imminent visual processing are linked. They suggest that the momentary direction of attention, predicting spatial biases in imminent visual processing, can be estimated from a lateralization index of posterior alpha-activity.
在没有视觉刺激的情况下，将视觉注意力 covertly 引导至某个空间位置，会增强后续对该被关注位置的视觉处理。这些注意力转移的神经关联涉及早期视觉区域神经元“基线”活动的调制，推测是通过来自高阶注意力系统的自上而下的控制。我们使用脑电图来研究在注意力定向范式中这些神经元调制与行为结果之间很大程度上未知的关系。在没有视觉刺激的情况下，将 covert 视觉空间注意力转移到左侧或右侧外周位置，会导致左、右后部位振荡α波段（8 - 14 Hz）活动的差异调制。这些变化是由不同程度的α波减少驱动的，减少最大的部位与被关注位置对侧。当表示为侧化指数时，这些α波变化在不同注意力条件下有显著差异，负值（α右 < α左）表示向左注意力，正值更大（α左 ≤ α右）表示向右注意力。此外，该指数似乎对即将到来的视觉目标的处理具有决定性作用。在各次试验中汇总来看，根据α指数值的总体负偏差，对左侧目标的处理有优势。在各次试验中，当α指数值为负时检测左侧目标最快。在α指数值最正时的试验中检测右侧目标最快。我们的数据表明，后α活动的并行调制、视觉空间注意力的瞬时偏差和即将进行的视觉处理是相关联的。它们表明，可以从后α活动的侧化指数估计出预测即将进行的视觉处理中的空间偏差的注意力瞬时方向。
