Department of Speech, Language, & Hearing Sciences, Sargent College of Health and Rehabilitation Sciences, Boston University, 635 Commonwealth Avenue, Room 326, Boston, MA 02215, United States of America.
Department of Speech, Language, & Hearing Sciences, Sargent College of Health and Rehabilitation Sciences, Boston University, 635 Commonwealth Avenue, Room 326, Boston, MA 02215, United States of America.
Neuroimage Clin. 2019;23:101919. doi: 10.1016/j.nicl.2019.101919. Epub 2019 Jul 2.
Traditional models of left hemisphere stroke recovery propose that reactivation of remaining ipsilesional tissue is optimal for language processing whereas reliance on contralesional right hemisphere homologues is less beneficial or possibly maladaptive in the chronic recovery stage. However, neuroimaging evidence for this proposal is mixed. This study aimed to elucidate patterns of effective connectivity in patients with chronic aphasia in light of healthy control connectivity patterns and in relation to damaged tissue within left hemisphere regions of interest and according to performance on a semantic decision task. Using fMRI and dynamic causal modeling, biologically-plausible models within four model families were created to correspond to potential neural recovery patterns, including Family A: Left-lateralized connectivity (i.e., no/minimal damage), Family B: Bilateral anterior-weighted connectivity (i.e., posterior damage), Family C: Bilateral posterior-weighted connectivity (i.e., anterior damage) and Family D: Right-lateralized connectivity (i.e., extensive damage). Controls exhibited a strong preference for left-lateralized network models (Family A) whereas patients demonstrated a split preference for Families A and C. At the level of connections, controls exhibited stronger left intrahemispheric task-modulated connections than did patients. Within the patient group, damage to left superior frontal structures resulted in greater right intrahemispheric connectivity whereas damage to left ventral structures resulted in heightened modulation of left frontal regions. Lesion metrics best predicted accuracy on the fMRI task and aphasia severity whereas left intrahemispheric connectivity predicted fMRI task reaction times. These results are discussed within the context of the hierarchical recovery model of chronic aphasia.
传统的左半球卒中恢复模型提出，剩余同侧组织的再激活对于语言处理是最佳的，而依赖对侧右半球同功是在慢性恢复阶段不太有益或可能适应不良的。然而，对于这一建议的神经影像学证据是混杂的。本研究旨在阐明慢性失语症患者的有效连接模式，根据健康对照组的连接模式，并根据左半球感兴趣区域内受损组织和语义决策任务的表现，阐明有效连接模式。使用 fMRI 和动态因果建模，在四个模型家族中创建了符合潜在神经恢复模式的生物合理模型，包括家族 A：左侧连接（即，无/最小损伤）、家族 B：双侧前加权连接（即，后损伤）、家族 C：双侧后加权连接（即，前损伤）和家族 D：右侧连接（即，广泛损伤）。对照组表现出对左侧网络模型（家族 A）的强烈偏好，而患者则表现出对家族 A 和 C 的偏好。在连接水平上，对照组表现出比患者更强的左侧半球内任务调节连接。在患者组中，左侧额上结构的损伤导致右侧半球内连接增强，而左侧腹侧结构的损伤导致左侧额叶区域的调节增强。损伤指标最好预测 fMRI 任务和失语症严重程度的准确性，而左侧半球内连接预测 fMRI 任务反应时间。这些结果在慢性失语症的层次恢复模型的背景下进行了讨论。
