后顶叶皮质调控视空间注意功能的经颅磁刺激研究

The posterior parietal cortex in visuospatial attention： study with continuous theta burst stimulation

目的探讨后顶叶皮质与视空间注意功能的关联性及其调控机制。方法选取志愿受试者40例参加本实验，所有受试者均按照随机顺序对左、右侧后顶叶进行真、假刺激。于刺激前和每次刺激后（刺激后）对40例受试者进行神经行为学评价和注意网络测试，并对所获得的数据进行分析。结果刺激前、后，受试者各项行为学评价差异均无统计学意义（P〉0．05）。右侧真刺激与假刺激比较，空间提示状态下平均RT明显延长，差异具有统计学意义（t=2．648，P〈0．05）；且右侧真刺激时与左侧真刺激时空间提示状态下的平均RT比较，差异有统计学意义（t=3．689，P〈0．01）。右侧PPC真刺激后，警觉网络效率（t=2．843，P〈0．01）及其比率（t=2．841，P〈0．01）明显降低，而左侧PPC真刺激后，警觉网络效率（t=2．324，P〈0．05）及其比率（t=2．225，P〈0．05）明显增强，且左侧与右侧真刺激后警觉网络效率及其比率比较，差异均也有统计学意义（P〈0．135）；定向网络——右侧PPC真刺激后，定向网络效率（t=5．535，P〈0．01）及其比率（t=5．245，P〈0．01）明显降低，左侧与右侧真刺激后定向网络效率及其比率比较，差异均也有统计学意义（P〈0．05）。结论后顶叶皮质主要与定向和警觉功能有关，具有明显的右侧半球优势。在双侧大脑半球同源脑区间，视空间注意认知过程存在竞争性抑制。

Objective To seek more direct evidence of the role of the posterior parietal cortex （PPC） in controlling visuospatial attention. Methods Forty healthy subjects took the Attention Network Test following con- tinuous theta burst stimulation （cTBS） applied over the left or right PPC or sham stimulation. The Attention Network Test measures the alerting, orienting and executive control components of visual attention separately. Results Subjects responded to spatial cues significantly slower after cTBS. Alerting and orienting showed deficits after cTBS over the right PPC. cTBS over the left PPC resulted in significant improvements in alerting, but not in the orienting. Furthermore, there were significant differences in the alerting and orienting indices between cTBS over the left and right PPC, but not in the executive control index. Conclusions The results suggest that the right PPC is associated with spatial orienting and the alerting function. The findings supported the theory of inter-hemispheric competition for visuospatial attention. Visuospatial attention bias might be selectively modulated through cTBS.