Department of Psychology, The University of Edinburgh, 7 George Square, Edinburgh EH8 9JZ, UK.
Neuropsychologia. 2012 Jul;50(9):2303-16. doi: 10.1016/j.neuropsychologia.2012.05.034. Epub 2012 Jun 7.
During covert shifts of tactile spatial attention both somatotopic and external reference frames are employed to encode hand location. When participants cross their hands these frames of references produce conflicting spatial codes which disrupt tactile attentional selectivity. Because attentional shifts are triggered not only in Attention tasks but also during covert movement preparation, the present study aimed at investigating the reference frame employed during such 'motor shifts of attention'. Event related brain potentials (ERPs) were recorded during a Motor task where a visual cue (S1) indicated the relevant hand for a manual movement prior to a tactile Go/Nogo stimulus (S2). For comparison, we ran a tactile Attention task where the same cue (S1) now indicated the relevant hand for a tactile discrimination (S2). Both tasks were performed under uncrossed and crossed hands conditions. In both Attention and Motor tasks similar lateralized components were observed following S1 presentation. Anterior and posterior ERP components indicative of covert attention shifts were exclusively guided by an external reference frame, while a later central negativity operated according to a somatotopic reference frame in both tasks. In the Motor task, this negativity reflected selective activation of the motor cortex in preparation for movement execution. In the Attention task, this component might reflect activity in the somatosensory cortex in preparation for the subsequent tactile discrimination. The presence of multiple and conflicting spatial codes resulted in disruption of tactile attentional selection in the Attention task where attentional modulations of tactile processing were delayed and attenuated with crossed hands as indicated by the analysis of ERPs elicited by S2. In contrast, attentional modulations of S2 processing in the Motor task were largely unaffected by the hand posture manipulation, suggesting that motor attention employs primarily one spatial coordinate system.
在触觉空间注意的隐蔽转移过程中，躯体定位和外部参照系都被用于对手部位置进行编码。当参与者双手交叉时，这些参照系会产生相互冲突的空间编码，从而破坏触觉注意力的选择性。由于注意力的转移不仅在注意任务中触发，也在隐蔽的运动准备过程中触发，本研究旨在调查在这种“注意力的运动转移”中使用的参照系。在一个运动任务中记录了事件相关脑电位 (ERPs)，在该任务中，一个视觉提示 (S1) 在触觉 Go/Nogo 刺激 (S2) 之前指示用于手动运动的相关手。为了进行比较，我们进行了一个触觉注意任务，其中相同的提示 (S1) 现在指示用于触觉辨别 (S2) 的相关手。在未交叉和交叉手的情况下进行了这两个任务。在注意力和运动任务中，在 S1 呈现后都观察到类似的偏侧化成分。表明隐蔽注意力转移的额前和额后 ERP 成分仅受外部参照系的指导，而一个较晚的中央负性成分在两个任务中都根据躯体定位参照系运作。在运动任务中，这种负性反映了运动皮层在准备执行运动时的选择性激活。在注意任务中，该成分可能反映了为随后的触觉辨别做准备时躯体感觉皮层的活动。在注意任务中，由于存在多个相互冲突的空间代码，导致触觉注意力选择受到干扰，在交叉手时，触觉处理的注意力调节被延迟和减弱，这可以通过对 S2 引发的 ERPs 的分析来表明。相比之下，运动任务中 S2 处理的注意力调节在很大程度上不受手部姿势操作的影响，这表明运动注意力主要使用一个空间坐标系。
