Abstract
The retinal projection to the superior colliculus is thought to be important both for stimulus-driven eye movements and for the involuntary capture of attention. It has further been argued that eye-movement planning and attentional orienting share common neural mechanisms. The superior colliculus is thought to receive no direct projections from short-wave sensitive cones (S cones), and consistent with this, we show that irrelevant peripheral stimuli visible only to S cones do not produce the saccadic distractor effect produced by luminance stimuli. However, we show that the same S-cone stimuli do have normal involuntary attentional effects on responses to subsequent targets. We conclude that involuntary attentional shifts do not require signals in the direct collicular pathway, or indeed the magnocellular pathway as our S cone stimuli were invisible to this channel also, and that while some attentional effects may share mechanisms with eye-movement control, others do not. A third experiment, in which the previously irrelevant stimuli became targets for pro-saccades and anti-saccades, indicated that the luminance stimuli were much harder to detect than the S cone stimuli. This double dissociation with the results of experiment 1 suggests that perceptual awareness and saccade distraction are mediated by different pathways.