Abstract
The lateral geniculate nucleus (LGN) of the thalamus is an important subcortical structurerelaying visual information from retina to the primary visual cortex, but the function of the human LGNs is not well understood. Theprimate LGNs consist of six main layers of neurons with distinct functions and anatomies.The ability to resolve layer-specific activities of the LGN non-invasively in the human brainhas important implications. In this study, we tested whether ultrahigh field fMRI at 7T coulddistinguish eye-specific activities and revealocular dominance layers of the human LGN.Achromatic checkerboard patterns werepresented monocularly at full contrast and counterphase flickering at 7.5Hz. BOLD signals in the LGNs were acquired with gradient Echo EPI at 1.2mm isotropic voxels, and balanced-SSFP sequence with 1x1x2mm voxels. Results showed a highly reliable eye-dominance pattern for each LGN of three subjects, which is a sandwiched organizationof three layered sections, arranged in the medial-ventral to dorsal-lateral direction. Themiddle section showed greater response to the ipsilateral eye, while the surrounding two hada response bias to the contralateral eye. This pattern is consistent with the fact that layer 2, 3 and 5 of the LGN receive visual input from the ipsilateral eye, while layer 1, 4 and 6 receive information from the contralateral eye.The pattern was highly consistent between odd and even runs within each scanning session, as well as across different sessions. To further confirm this finding, we ran a simulation test based on Nissl stained images of the human LGN at 20μm resolution, with the BOLD point-spread function taken into account. The simulation results showedidentical patterns as found with fMRI. We conclude that BOLD fMRI at 7T is capable toresolve layer-specific activities in the human LGN, which has important implications to understand its function in visual perceptionand cognition.
Meeting abstract presented at VSS 2018