fMRI of human LGN: Functional subdivisions and geniculocortical connectivity

描述(申请人提供)：这个项目的目标是研究人类大脑中两个基本的视觉处理流，即大细胞和小细胞通路。这些通路在物理上被分隔在丘脑外侧膝状核(LGN)的细分中，LGN是连接视网膜和视觉皮质的皮质下视觉结构。LGN的大细胞和小细胞亚群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质下位置，在人类中很难研究。更好地了解这些通路的功能专门化对公共卫生很重要，因为特定亚区的缺陷与人类疾病有关，如诵读困难和精神分裂症。此外，有人提出，大细胞和小细胞亚群分别优先为背侧和腹侧皮质的大规模视觉通路提供输入，但人脑皮质下和皮质通路组织之间的确切关系尚不清楚。我们建议使用具有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。通过呈现已知优先驱动单个分区内活动的视觉刺激，我们将根据每个参与者的视觉反应模式来定位LGN内的大细胞和小细胞分区。我们将开发的定位技术可能在未来用于表征健康和疾病大脑中大细胞和小细胞亚群的功能特性。然后，我们将研究大规模视觉皮质网络与大细胞和小细胞LGN亚群之间的功能关系。为此，我们将利用功能磁共振成像技术的最新进展，根据成对大脑区域中相关的功能磁共振活动，获得每个分区与许多客观定义的皮质区域中每个区域之间的连通性测量。这项研究将有助于准确描述皮质下和皮质视觉通路之间的关系，并将评估一个有影响力但未完全验证的关于大细胞和小细胞通路在背侧和腹侧皮质视觉加工中的相对贡献的理论。更全面地了解皮质下和皮质下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.