Abstract
Introduction: The magnocellular stream throughout the sensory systems in the brain is specialized for encoding temporal information. However, it is difficult to study in isolation because it is intermixed with other streams in cortex. Here we report the quantitative T1 (qT1) mapping that can be used to anatomically segregate the streams in vivo in the lateral (LGN) and medial geniculate nuclei (MGN) in the thalamus, where the magnocellular stream remains disjoint. Methods: We acquired quantitative MRI data on a Siemens Prisma 3T MRI using an MP2RAGE sequence with two inversion times, to calculate the qT1 parameter for each voxel. The magnocellular portions of the LGN and MGN can be structurally segregated based on myelination. Three subjects participated in four sessions, each lasting maximum 90 minutes. We collected 16 scans from each subject to determine the number of scans necessary for a good segregation performance with qT1 maps. Results: Using 2-component mixture Gaussian model fitting, we identified the magnocellular divisions in both nuclei. Random subsampling of scans further revealed that similar segregation could be found using only 2 to 4 scans which take approximately 1 hour to acquire. Conclusion: It is possible to use the quantitative MRI technique at 3T to segment the magnocellular regions of the LGN and MGN. This enables the magnocellular stream to be studied independently to determine its role in perception in normal and clinical populations.