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peng zhang, wen wen, xinghuai sun, sheng he; Layer-specific fMRI signals in the human LGN – An investigation of magnocellular and parvocellular pathways in normal subjects and glaucoma patients. Journal of Vision 2014;14(10):395. doi: https://doi.org/10.1167/14.10.395.
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© ARVO (1962-2015); The Authors (2016-present)
The human visual system consists of two functionally and anatomically distinct parallel pathways, namely the magnocellular (M) and parvocellular (P) pathways, which are particularly well represented by the segregated M and P layers of the lateral geniculate nucleus (LGN) of the thalamus. With functional MRI, we were able to reliably localize the M and P layers of the human LGN, using the M and P stimuli designed to preferentially activate the magnocellular or the parvocellular neurons. The topography of the identified M and P layers are in good agreement with the anatomy of the human LGN, and the fMRI measured response properties of the M and P layers are highly consistent with the LGN physiology. Applying this layer-specific fMRI technique, we tested the longstanding yet controversial hypothesis of large cell loss in glaucoma: whether neural damage from early-stage glaucoma is selective to the magnocellular cells. Compared to normal controls, glaucoma patients showed a significant reduction of LGN responses to the M stimulus but not to the P stimulus, and also this selective reduction of response to the M stimulus was found only in the M layers but not in the P layers of the LGN. A selective loss of fMRI response to the M stimulus was also found in the superficial layer of superior colliculus (SC), but not in the cortical visual areas. These results show that fMRI is capable of resolving layer specific signals from subcortical nuclei, and a selective functional loss from early glaucoma can be found in the magnocellular layers. The layer-specific fMRI approach thus proved to be a powerful tool to study the neural mechanisms of parallel pathways in the human visual system.
Meeting abstract presented at VSS 2014
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