fMRI of human LGN: Functional subdivisions and geniculocortical connectivity

描述（由申请人提供）：本项目的目标是研究人脑中两种基本的视觉处理流，即大细胞通路和旁细胞通路。这些通路在物理上分离于丘脑外侧膝状核（LGN）的分支中，外侧膝状核是连接视网膜和视觉皮层的皮质下视觉结构。LGN的大细胞和小细胞分支具有不同和互补的视觉功能，但由于其体积小且位于大脑深处的皮层下，因此难以在人类中进行研究。更好地了解这些通路的功能专门化对公共卫生很重要，因为特定细分的缺陷与阅读障碍和精神分裂症等人类疾病有关。此外，有人提出，大细胞和小细胞细分分别优先为背侧和腹侧皮层的大规模视觉通路提供输入，但人类大脑皮层下和皮层通路组织之间的确切关系尚不清楚。我们建议使用高空间和时间分辨率的功能磁共振成像（fMRI）来非侵入性地表征人类LGN对视觉刺激的反应。通过呈现已知的优先驱动单个细分内活动的视觉刺激，我们将根据每个参与者的视觉反应模式定位LGN内的大细胞和微粒细胞细分。我们将开发的定位技术可能在未来用于表征健康和患病大脑中大细胞和细小细胞细分的功能特性。然后，我们将研究大尺度视觉皮质网络与大细胞和小细胞LGN细分之间的功能关系。为了做到这一点，我们将采用fMRI成像技术的最新进展，以获得每个细分和许多客观定义的皮层区域之间的连通性的测量，基于成对大脑区域的相关fMRI活动。这项研究将有助于准确地描述皮层下和皮层视觉通路之间的关系，并将评估一个有影响力但尚未完全验证的理论，即大细胞和旁细胞通路对背侧和腹侧皮层视觉处理的相对贡献。更全面地了解皮层下和皮层视觉通路的正常功能组织，对于开发影响大脑视觉区域的多种疾病、障碍和损伤的治疗方法至关重要。

DESCRIPTION (provided by applicant): The goal of this project is to investigate two fundamental visual processing streams in the human brain, the magnocellular and parvocellular pathways. These pathways are physically segregated in subdivisions of the lateral geniculate nucleus (LGN) of the thalamus, a subcortical visual structure that connects the retina to the visual cortex. The magnocellular and parvocellular subdivisions of the LGN have different and complementary visual functions but have been difficult to study in humans due to their small size and subcortical location deep within the brain. A better understanding of the functional specialization of these pathways is important for public health, because deficits in specific subdivisions have been associated with human disorders such as dyslexia and schizophrenia. Further, it has been proposed that the magnocellular and parvocellular subdivisions preferentially provide input to large-scale visual pathways in dorsal and ventral cortex, respectively, but the precise relationships between subcortical and cortical pathway organization in the human brain remain unknown. We propose to use functional magnetic resonance imaging (fMRI) with high spatial and temporal resolution to noninvasively characterize responses to visual stimulation in human LGN. By presenting visual stimuli known to preferentially drive activity within a single subdivision, we will localize the magnocellular and parvocellular subdivisions within the LGN in each participant based on their patterns of visual responses. The localization technique we will develop may be used in the future to characterize the functional properties of the magnocellular and parvocellular subdivisions in both healthy and diseased brains. We will then investigate the functional relationships among large-scale visual cortical networks and the magnocellular and parvocellular LGN subdivisions. To do this, we will employ recent advances in imaging technology for fMRI to obtain measures of connectivity between each subdivision and each of many objectively defined cortical areas, based on correlated fMRI activity in pairs of brain regions. This investigation will help to precisely characterize relationships between subcortical and cortical visual pathways and will assess an influential but incompletely tested theory about the relative contributions of magnocellular and parvocellular pathways to visual processing in dorsal and ventral cortex. A more complete understanding of the normal functional organization of subcortical and cortical visual pathways is critical for developing treatments for multiple diseases, disorders, and injuries that affect visual areas of the brain.