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Abstract #3803

Heterogeneity of hemodynamic response dynamics across the subcortical-cortical visual pathway

Laura Lewis1,2, Kawin Setsompop2,3, Bruce R Rosen2,3, and Jonathan R Polimeni2,3

1Society of Fellows, Harvard University, Cambridge, MA, United States, 2Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States, 3Department of Radiology, Harvard Medical School, Boston, MA, United States

The hemodynamic response is nonlinear in response to short duration stimuli, and this nonlinearity varies across cortex. To study the nonlinearities in subcortical vs. cortical structures, we performed high-resolution fMRI at 7 Tesla to characterize responses to short visual stimuli in superior colliculus (SC), lateral geniculate nucleus (LGN) and primary visual cortex (V1). Response nonlinearity was increased in SC, and response timecourses were consistently narrower in LGN than in V1. We conclude that analysis of subcortical activations using fMRI will require flexible models of the hemodynamic response, and suggest future studies to identify the neural and vascular factors contributing to these nonlinearities.

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