PT - JOURNAL ARTICLE AU - Paola Binda AU - Maria Pereverzeva AU - Scott O. Murray TI - Attention to Bright Surfaces Enhances the Pupillary Light Reflex AID - 10.1523/JNEUROSCI.3440-12.2013 DP - 2013 Jan 30 TA - The Journal of Neuroscience PG - 2199--2204 VI - 33 IP - 5 4099 - http://www.jneurosci.org/content/33/5/2199.short 4100 - http://www.jneurosci.org/content/33/5/2199.full SO - J. Neurosci.2013 Jan 30; 33 AB - One longstanding question is how early in the visual system attention exerts its influence. Here we show that an effect of attention can be measured at the earliest possible stage of visual information processing, as a change in the optics of the eye. We tested human subjects and found that covertly attending to bright surfaces results in an enhanced pupillary light reflex (PLR)—the pupillary constriction that occurs in response to light increments. The PLR optimizes the optical quality of the retinal image across illumination conditions, increasing sensitivity by modulating retinal illumination, and improving acuity by reducing spherical aberrations. The attentional modulation of the PLR that we describe constitutes a new mechanism through which vision is affected by attention; we discuss three alternatives for the neural substrates of this effect, including the possibility that attention might act indirectly, via its well established effects in early visual cortex.