Qingyuan Chen¹ (), Hsing-Hao Lee¹, Klara Hoxha², Antonio Fernández¹, Nina M. Hanning^1,3, Marisa Carrasco¹; ¹New York University, ²University of Bologna, ³Humboldt-Universität zu Berlin

[BACKGROUND] Both endogenous and exogenous covert spatial attention improve visual sensitivity. Neurostimulation studies using transcranial magnetic stimulation (TMS) have shown that (i) early visual areas (V1/V2) are critical for exogenous but not endogenous attention, and (ii) the human homologue of the right frontal eye field (rFEF+) plays a central role for endogenous attention. It is unknown whether rFEF+ also plays a critical role for exogenous attention. Here, we used the same psychophysics-TMS protocol as in the previous studies to manipulate cortical activity in rFEF+ and measured its effects on the benefits and costs of exogenous attention. [METHODS] Observers performed an orientation discrimination task. Two oriented Gabor patches were preceded by an exogenous cue that was either valid, invalid, or neutral. We applied MRI-guided double-pulse TMS to the observers’ rFEF+ during stimulus presentation. To measure contrast response functions (CRF), we varied stimulus contrast and analyzed sensitivity (d′) in the target-stimulated and distractor-stimulated hemifields, contralateral and ipsilateral to the rFEF+ stimulation, respectively. [RESULTS] When TMS was applied to rFEF+, we found both benefits at the attended location and costs at the unattended locations at the high contrast levels, consistent with response gain, in both target- or distractor-stimulated hemifields. In contrast, when TMS was applied to V1/V2 in our previous study, the effects of exogenous attention remained at the distractor-stimulated location but were eliminated at the target-stimulated location. [CONCLUSION] This study reveals distinct roles of rFEF+ and V1/V2 in exogenous attention, emphasizing the critical involvement of rFEF+ in endogenous, but not exogenous attention. Together, our TMS findings establish a double dissociation between the two types of covert spatial attention and two critical cortical regions.

Acknowledgements: The Ministry of Education in Taiwan to HHL, Marie Skłodowska-Curie individual fellowship (MSCA-IF 898520) by the European Commission to NMH and NIH R01-EY019693 to MC