THIS IS AN AUTHOR-GENERATED PREPRINT OF A MANUSCRIPT IN-PRESS IN CURRENT BIOLOGY Correspondence

The dimmer a stimulus is, the more time it takes the neural signal from the retina to reach visual cortex [1]. Presumably because of this variation in latency, a dim moving object appears to lag behind where it would appear if it were bright [2,3]. To investigate whether this flaw in perception afflicts our ability to interact with moving objects, we asked subjects to press a button at the moment a rotating bar became aligned with a stationary reference: over a 15-fold range of luminance, they did not respond later when the moving bar was dimmer. This result suggests that the visuomotor system compensates for the changes in visual latency caused by luminance variation, despite uncorrected lags in conscious perception. To successfully interact with the environment, we must move our limbs at specific moments relative to external events. To do so accurately, we must compensate for the neural delays between sensory stimulation and cognitive processing, and between executive commands and muscle contraction [4]. It is not known, however, whether visuomotor timing corrects for the variation in neural latencies resulting from the large differences in light levels encountered in the natural environment. Eight subjects fixated the center of a rotating bar and attempted to synchronize