TY - JOUR T1 - Endogenous and exogenous attention distinctly modulate fMRI activity in visual cortex JF - bioRxiv DO - 10.1101/414508 SP - 414508 AU - Laura Dugué AU - Elisha P. Merriam AU - David J. Heeger AU - Marisa Carrasco Y1 - 2018/01/01 UR - http://biorxiv.org/content/early/2018/09/11/414508.abstract N2 - It is considered that endogenous (voluntary) attention acts via top-down, and exogenous (involuntary) attention via bottom-up mechanisms, and that both affect visual areas similarly. Using an fMRI ROI-based analysis for occipital areas, we measured average fMRI activity for valid (target at cued location) and invalid (target at un-cued location) trials, for pre- or post-cueing in the endogenous and exogenous conditions independently, with same observers and task. The results show: (1) stronger effect for both types of attention in contralateral than ipsilateral regions to the attended hemifield; (2) higher fMRI activity at the valid-than invalid-cued locations; (3) increasing modulation of fMRI activity along the visual hierarchy for endogenous, but constant modulation for exogenous, pre-cueing; (4) constant modulation of endogenous along the visual area hierarchy, but no modulation for exogenous, postcueing. Endogenous and exogenous attention distinctly modulate activity in visual areas due to their differential engagement of top-down and bottom-up processes. ER -