fMRI of human LGN: Functional subdivisions and geniculocortical connectivity

描述（由申请人提供）：该项目的目标是研究人类大脑中的两个基本视觉处理流，即大细胞和小细胞通路。这些通路在丘脑的外侧膝状体核（LGN）的细分中物理隔离，外侧膝状体核是连接视网膜和视觉皮层的皮层下视觉结构。LGN的大细胞和小细胞亚群具有不同的和互补的视觉功能，但由于它们的小尺寸和大脑深处的皮质下位置，很难在人类中进行研究。更好地了解这些途径的功能专业化对公共卫生很重要，因为特定细分的缺陷与人类疾病如阅读障碍和精神分裂症有关。此外，有人提出，大细胞和小细胞的细分优先提供输入到大规模的视觉通路在背侧和腹侧皮层，分别，但皮质下和皮质通路组织在人脑之间的精确关系仍然未知。 我们建议使用功能磁共振成像（fMRI）与高空间和时间分辨率的非侵入性表征人类LGN的视觉刺激的反应。通过呈现已知优先驱动单个细分内的活动的视觉刺激，我们将根据每个参与者的视觉反应模式定位LGN内的大细胞和小细胞细分。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的大细胞和小细胞亚群的功能特性。 然后，我们将研究大规模的视觉皮层网络和大细胞和小细胞LGN细分之间的功能关系。为了做到这一点，我们将采用最新的fMRI成像技术的进步，以获得每个细分和许多客观定义的皮层区域之间的连接措施，根据相关的fMRI活动对大脑区域。这项调查将有助于精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的，但不完全测试的理论，大细胞和小细胞通路的相对贡献，在背侧和腹侧皮层的视觉处理。更全面地了解皮质下和皮质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.