Hsing-Hao Lee¹ (), Marisa Carrasco¹; ¹New York University

[Background] Visual adaptation and covert spatial attention help manage bioenergetic resources. Adaptation decreases contrast sensitivity toward repeated features; covert attention increases it at the attended location but decreases it at the unattended location. Visual performance is better along the horizontal than vertical meridian (horizontal-vertical anisotropy, HVA), and better along the lower than upper vertical meridian (vertical meridian asymmetry, VMA). Adaptation reduces contrast sensitivity more at the horizontal than vertical meridian; covert endogenous attention enhances contrast sensitivity similarly around polar angle. Here we investigated whether endogenous (voluntary) attention enhances contrast sensitivity after adaptation and how this relation varies across meridians. [Methods] To equate discriminability across the four cardinal locations, we titrated contrast threshold while observers performed an orientation discrimination task (±2.5° off the vertical axis, 5 cpd) in the neutral condition, with and without adaptation to 100%-contrast vertical Gabor adaptors. We then tested the effect of endogenous attention along the horizontal and vertical meridians (blocked), using a pre-cue indicating the target location (valid cue), a distractor location (invalid cue), or all locations (neutral cue), with and without adaptation. [Results] (1) Titration yielded lower thresholds at the horizontal than vertical meridian (HVA) and at the lower than upper vertical meridian (VMA) in non-adapted trials; (2) With equated discriminability, adaptation effects were stronger at the horizontal than vertical meridian; (3) Attention improved performance (d′) at validly-cued locations and reduced it at invalidly-cued locations in both adapted and non-adapted conditions, and the extent of the attentional effect was similar across meridians. [Conclusion] This study confirmed visual field asymmetries and a stronger adaptation effect at the horizontal than vertical meridian (Lee & Carrasco, VSS 2024). Critically, it revealed that, despite this differential adaptation effect, endogenous attention enhances contrast sensitivity, with comparable efficacy across the visual field.

Acknowledgements: This study was supported by the Ministry of Education in Taiwan to HHL and NIH NEI R01-EY027401 to MC