Kuhn Taylor, Gullett Joseph M, Boutzoukas Angelique E, Bohsali Anastasia, Mareci Thomas H, FitzGerald David B, Carney Paul R, Bauer Russell M
Department of Clinical and Health Psychology, University of Florida, Gainesville, FL, United States of America; Department of Physical Therapy, University of Florida, Gainesville, FL, United States of America.
Department of Clinical and Health Psychology, University of Florida, Gainesville, FL, United States of America; Department of VA Brain Rehabilitation Research Center, Malcolm Randall VA Center Gainesville, FL, United States of America.
Epilepsy Behav. 2018 Nov;88:87-95. doi: 10.1016/j.yebeh.2018.06.038. Epub 2018 Sep 20.
Evidence for structural connectivity patterns within the medial temporal lobe derives primarily from postmortem histological studies. In humans and nonhuman primates, the parahippocampal gyrus (PHg) is subdivided into parahippocampal (PHc) and perirhinal (PRc) cortices, which receive input from distinct cortical networks. Likewise, their efferent projections to the entorhinal cortex (ERc) are distinct. The PHc projects primarily to the medial ERc (M-ERc). The PRc projects primarily to the lateral portion of the ERc (L-ERc). Both M-ERc and L-ERc, via the perforant pathway, project to the dentate gyrus and hippocampal (HC) subfields. Until recently, these neural circuits could not be visualized in vivo. Diffusion tensor imaging algorithms have been developed to segment gray matter structures based on probabilistic connectivity patterns. However, these algorithms have not yet been applied to investigate connectivity in the temporal lobe or changes in connectivity architecture related to disease processes. In this study, this segmentation procedure was used to classify ERc gray matter based on PRc, ERc, and HC connectivity patterns in 7 patients with temporal lobe epilepsy (TLE) without hippocampal sclerosis (mean age, 14.86 ± 3.34 years) and 7 healthy controls (mean age, 23.86 ± 2.97 years). Within samples paired t-tests allowed for comparison of ERc connectivity between epileptogenic and contralateral hemispheres. In healthy controls, there were no significant within-group differences in surface area, volume, or cluster number of ERc connectivity-defined regions (CDR). Likewise, in line with histology results, ERc CDR in the control group were well-organized, uniform, and segregated via PRc/PHc afferent and HC efferent connections. Conversely, in TLE, there were significantly more PRc and HC CDR clusters in the epileptogenic than the contralateral hemisphere. The surface area of the PRc CDR was greater, and that of the HC CDRs was smaller, in the epileptogenic hemisphere as well. Further, there was no clear delineation between M-ERc and L-ERc connectivity with PRc, PHc or HC in TLE. These results suggest a breakdown of the spatial organization of PHg-ERc-HC connectivity in TLE. Whether this breakdown is the cause or result of epileptic activity remains an exciting research question.
内侧颞叶内结构连接模式的证据主要来自死后组织学研究。在人类和非人类灵长类动物中，海马旁回（PHg）可细分为海马旁皮质（PHc）和内嗅周皮质（PRc），它们接收来自不同皮质网络的输入。同样，它们向内嗅皮质（ERc）的传出投射也各不相同。PHc主要投射到内侧内嗅皮质（M-ERc）。PRc主要投射到内嗅皮质的外侧部分（L-ERc）。M-ERc和L-ERc都通过穿通通路投射到齿状回和海马（HC）亚区。直到最近，这些神经回路在体内还无法可视化。已开发出扩散张量成像算法，以基于概率连接模式对灰质结构进行分割。然而，这些算法尚未应用于研究颞叶的连接性或与疾病过程相关的连接结构变化。在本研究中，这种分割程序被用于根据PRc、ERc和HC连接模式，对7例无海马硬化的颞叶癫痫（TLE）患者（平均年龄14.86±3.34岁）和7名健康对照者（平均年龄23.86±2.97岁）的ERc灰质进行分类。在样本内，配对t检验用于比较致痫半球和对侧半球之间的ERc连接性。在健康对照者中，ERc连接性定义区域（CDR）的表面积、体积或簇数在组内无显著差异。同样，与组织学结果一致，对照组的ERc CDR组织良好、均匀，并通过PRc/PHc传入和HC传出连接分开。相反，在TLE中，致痫半球的PRc和HC CDR簇明显多于对侧半球。致痫半球的PRc CDR表面积也更大，而HC CDR的表面积更小。此外，在TLE中，M-ERc和L-ERc与PRc、PHc或HC之间的连接没有明显的界限。这些结果表明，TLE中PHg-ERc-HC连接的空间组织遭到破坏。这种破坏是癫痫活动的原因还是结果，仍然是一个令人兴奋的研究问题。
