Abstracts

Rationale: Cortico-cortical evoked potential(CCEP) has been used as a novel powerful tool to verify the electrophysiology of white matter fibers in the last decade. Recently, DT-MRI investigations of the arcuate fasciculus has divided this tract into three segments, anterior, posterior and long segment, so we investigate the electrophysiological connectivity by the method of CCEP for these three segments. Methods: The researching subjects include 7 patients who suffered from medically intractable epilepsy and underwent chronic intracranial electrode placement. According to the recent DTI researches, Three areas has been defined as the terminates of the white matter fibers. Broca’s territory (BT) including BA44/45 and part of the middle frontal gyrus and inferior precentral gyrus, Wernicke’s territory (WT) including the posterior part of both the superior and middle temporal gyrus, and Geschwind’s territory (GT) which refer to the the inferior parietal lobe including the supramarginal and angular gyrus. Single pulses stimulation was performed on each pair of adjacent electrodes, and the potential was recorded at other brain region. CCEPs were analyzed with 3D reconstruction and then a pattern of the wave distribution was produced to analysis the electrophysiological connectivity between different cortex.  Results: Typical CCEP waveforms were detected in those patients, most of the electrophysiological connectivity is consonance with the anatomy connectivity. When stimulated at the BT in patients 1-5, CCEPs can be obtained at the GT in patients 1-4(latency of N1=30.8ms n=10), and at the WT in patients 1,5(latency of N1=31.5ms n=4). When stimulated at the GT in patients 1,2,4,7, CCEPs were obtained at BT in patents 1,2,4(latency of N1=34.8ms n=8), and WT in patients 1,2,4,7(latency of N1=37.2ms n=19). When stimulated the WT in patients 1,2,4-7, CCEPs were obtained at BT in patients 1,2,5,6 (latency of N1=42.6ms n=6), and GT in patients 4,6,7(latency of N1=42.1ms n=10). The distribution suggests that these three regions are connecting with each other by the three segments, but which we noted that the CCEPs recorded at temporal lobe is mainly located at the middle and inferior temporal gyrus, which is different from the DTI research but consonant with a recent postmortem result. Conclusions: CCEP is an efficient technique in mapping the functional connectivity in human brain. The subdural electrodes have a good property in covering the convex surface of the brain, and also applicable for analysis the distribution of CCEPs. the distribution suggests that the perisylvian language network is consist of three nodes which respectively is frontal, parietal and temporal part, and three links which are the three segments of the arcuate fasciculus, these links connect each node, makes them contact to each other reciprocally. These results provide an effective supplementary in learning the connectivity in our brain. Funding: This work was supported by a Research Grant from Beijing Municipal Commission of Science and Technology and National Natural Science Foundation of Chinareferences:Matsumoto R, Nair D R, Lapresto E, et al. Functional connectivity in the human language system: a cortico-cortical evoked potential study. Brain: a journal of neurology, 2004, 127(Pt 10): 2316-30.Catani M, Jones D K, Ffytche D H. Perisylvian language networks of the human brain. Annals of neurology, 2005, 57(1): 8-16.Martino J, De Witt Hamer P C, Berger M S, et al. Analysis of the subcomponents and cortical terminations of the perisylvian superior longitudinal fasciculus: a fiber dissection and DTI tractography study. Brain structure & function, 2013, 218(1): 105-21.