Ashbridge E, Walsh V, Cowey A
Department of Experimental Psychology, Oxford University, UK.
Neuropsychologia. 1997 Aug;35(8):1121-31. doi: 10.1016/s0028-3932(97)00003-1.
Transcranial magnetic stimulation was applied over the parietal visual cortex of subjects while they were performing 'pop-out' or conjunction visual search tasks in arrays containing eight distractors. Magnetic stimulation had no detrimental effect on the performance of pop-out search, but did significantly increase reaction times on conjunction search when stimulation was applied over the right parietal cortex 100 msec after the onset of the visual display for trials when the target was present. Target absent reaction times were elevated when stimulation was applied 160 msec after array onset. Stimulation had no effect on the number of errors made. The results suggest that a sub-region of the right parietal lobe is important for conjunction search but not for pre-attentive pop-out. The result from target present trials is consistent with timing data from studies of single cells in monkeys and the hypothesis that parietal areas generate a signal that projects back to extrastriate visual areas to enhance the processing of features in a restricted part of the visual field. The timing of the effect indicates that transcranial stimulation disrupts the mechanisms underlying the focal attention necessary for feature binding in conjunction search. The effects of TMS on target absent trials are interpreted in terms of fronto-parietal connections and the role of frontal cortex in decision-making. The results also highlight the efficacy of transcranial magnetic stimulation as a complement to other spatial and temporal imaging techniques.
在受试者执行“凸显”或联合视觉搜索任务时，对其顶叶视觉皮层施加经颅磁刺激，任务阵列中包含八个干扰项。磁刺激对凸显搜索的表现没有不利影响，但在视觉显示开始100毫秒后，当在右侧顶叶皮层施加刺激时，联合搜索的反应时间显著增加，此时目标存在。当在阵列开始160毫秒后施加刺激时，无目标反应时间延长。刺激对错误数量没有影响。结果表明，右侧顶叶的一个子区域对联合搜索很重要，但对前注意凸显搜索不重要。目标存在试验的结果与猴子单细胞研究的时间数据一致，也与顶叶区域产生信号并投射回纹外视觉区域以增强视野受限部分特征处理的假设一致。这种效应的时间表明，经颅刺激破坏了联合搜索中特征绑定所需的焦点注意力的潜在机制。经颅磁刺激对无目标试验的影响是根据额顶叶连接以及额叶皮层在决策中的作用来解释的。结果还突出了经颅磁刺激作为其他空间和时间成像技术补充的有效性。
