Hemodynamic Response Timing in Human Lateral Geniculate Nucleus & Visual Cortex

Kevin W.-K. Tsai¹, Thomas Witzel², Tommi Raij², Jonathan Polimeni², Jyrki Ahveninen², Wen-Jui Kuo³, John Belliveau², Fa-Hsuan Lin¹

Using magnetic resonance inverse imaging (InI) with 100-ms temporal resolution, whole-brain coverage, and uniform spatial resolution achieved by multiple projections, we recorded BOLD-contrast fMRI responses to visual hemifield stimuli. The lateral geniculate nucleus (LGN) was activated approximately 500 ms before the primary visual cortex (V1). The fact that the LGN->V1 delay is longer in BOLD recordings than in evoked electrophysiological responses may reflect interregional vasculature or neurovascular coupling differences, or relative onsets of evoked/induced neuronal activity.