Moran R J, Molholm S, Reilly R B, Foxe J J
The School of Electrical, Electronic and Mechanical Engineering, University College Dublin, Dublin, Ireland.
Eur J Neurosci. 2008 May;27(9):2303-12. doi: 10.1111/j.1460-9568.2008.06187.x.
Previous event-related potential (ERP) studies have identified the superior parietal lobule (SPL) as actively multisensory. This study compares effective, or contextually active, connections to this region under unisensory and multisensory conditions. Effective connectivity, the influence of one brain region over another, during unisensory visual, unisensory auditory and multisensory audiovisual stimulation was investigated. ERPs were recorded from subdural electrodes placed over the parietal lobe of three patients while they conducted a rapid reaction-time task. A generative model of interacting neuronal ensembles for ERPs was inverted in a scheme allowing investigation of the connections from and to the SPL, a multisensory processing area. Important features of the ensemble model include inhibitory and excitatory feedback connections to pyramidal cells and extrinsic input to the stellate cell pool, with extrinsic forward and backward connections delineated by laminar connection differences between ensembles. The framework embeds the SPL in a plausible connection of distinct neuronal ensembles mirroring the integrated brain regions involved in the response task. Bayesian model comparison was used to test competing feed-forward and feed-backward models of how the electrophysiological data were generated. Comparisons were performed between multisensory and unisensory data. Findings from three patients show differences in summed unisensory and multisensory ERPs that can be accounted for by a mediation of both forward and backward connections to the SPL. In particular, a negative gain in all forward and backward connections to the SPL from other regions was observed during the period of multisensory integration, while a positive gain was observed for forward projections that arise from the SPL.
以往的事件相关电位（ERP）研究已确定顶上小叶（SPL）具有活跃的多感觉功能。本研究比较了在单感觉和多感觉条件下与该区域的有效连接或情境激活连接。研究了在单感觉视觉、单感觉听觉和多感觉视听刺激过程中，一个脑区对另一个脑区的影响即有效连接性。在三名患者的顶叶上放置硬膜下电极记录ERP，同时他们执行快速反应时间任务。在一个方案中对用于ERP的相互作用神经元集合的生成模型进行了反演，该方案允许研究与多感觉处理区域SPL的双向连接。集合模型的重要特征包括对锥体细胞的抑制性和兴奋性反馈连接以及对星状细胞池的外在输入，外在的前向和后向连接由集合之间的层状连接差异来描绘。该框架将SPL嵌入到一个合理的不同神经元集合的连接中，反映了参与反应任务的整合脑区。使用贝叶斯模型比较来测试关于电生理数据如何产生的相互竞争的前馈和反馈模型。在多感觉和单感觉数据之间进行了比较。三名患者的研究结果表明，单感觉和多感觉ERP总和的差异可以通过与SPL的前向和后向连接的介导来解释。特别是，在多感觉整合期间，观察到从其他区域到SPL的所有前向和后向连接的负增益，而从SPL产生的前向投射则观察到正增益。
