Differential effects of endogenous and exogenous attention on sensory tuning

Covert spatial attention benefits performance in many visual tasks (e.g. orientation discrimination, visual search). However, in texture segmentation tasks in which increasing spatial resolution can be detrimental, endogenous and exogenous attention have differential effects on performance. Here we tested whether these differences manifest in sensory representations. We used reverse correlation to assess, in a within-subjects design, whether and how endogenous and exogenous attention differentially alter the representation of orientations and spatial frequencies. The same observers detected a vertical grating embedded in noise following central (endogenous attention; Experiment 1) or peripheral (exogenous attention; Experiment 2) pre-cues. We found that both endogenous and exogenous attention similarly improved performance at the attended location by enhancing the gain of all orientations without changing tuning width. Additionally, endogenous attention enhanced the gain of spatial frequencies above and below the target spatial frequency, whereas exogenous attention preferentially enhanced the gain of spatial frequencies higher than the target spatial frequency. We conclude that these changes in sensory tuning may underlie differential effects of endogenous and exogenous attention on performance.