Oculomotor Distraction by Signals Invisible to the Retinotectal and Magnocellular Pathways

Abstract

Irrelevant stimulus onsets interfere with saccade planning to other stimuli, prolonging saccadic latency (the oculomotor distractor effect) or eliciting directional errors (saccadic capture). Such stimulus-driven interference has been associated with the retinotectal pathway, the direct pathway from retina to superior colliculus. Consistent with this theory, the distractor effect has not been found for stimuli visible only to the short-wave cones in the retina (S cones), which are thought not to contribute to the retinotectal pathway. However, S-cone signals are generally slower than luminance signals and such differences in temporal dynamics have not been taken into account when investigating the saccadic distractor effect. Here, by varying the delay between target and distractor, we found that S-cone stimuli do in fact produce a distractor effect, but the optimal delay is generally different from that for luminance distractors. The temporal dynamics of the distractor effect conform to a general framework of saccadic competition that takes sensory transmission time into account. Additionally, we observe that S-cone stimuli are able to produce saccadic capture in our paradigm. We conclude that stimulus-driven oculomotor interference does not rely on the retinotectal pathway, or indeed the magnocellular pathway, which is also blind to our S-cone stimuli.

Oculomotor inhibition covaries with conscious detection

“…Previous studies have used purely chromatic stimuli to argue that the retinotectal pathway, being insensitive to chromatic contrast (Marrocco and Li 1977;Perry and Cowey 1984), is not necessary for oculomotor freezing (Bompas and Sumner 2009;Rolfs et al 2008;Sumner et al 2006;. Our study goes an important step further by demonstrating that the retinotectal pathway is not sufficient for oculomotor freezing, even for luminance contrast.…”

“…The particular timing and magnitude of these microsaccade rate changes depend on stimulus parameters (Bonneh et al 2015;Rolfs et al 2008). Similarly, irrelevant stimulus onsets delay the execution of large voluntary eye movements (Bompas and Sumner 2009;Reingold and Stampe 2002;Sumner et al 2006;Walker et al 1997). We refer to these rapid inhibitory reflexes collectively as "oculomotor freezing.…”

Saccadic Inhibition Reveals the Timing of Automatic and Voluntary Signals in the Human Brain

“…7). In agreement with this, by reanalyzing data from Bompas and Sumner (2009a), we observe that stimuli restricted to a chromatic pathway produce dips that occur later in time (T 0 ϭ 95 ms, T M ϭ 126 ms) than those for salience-matched achromatic distractors (T 0 ϭ 70 ms, T M ϭ 116 ms) but with no evidence for reduced amplitude (53 vs 56%; Fig. 7).…”

“…The interpolation had the consequence of systematically anticipating the beginning of dips by 4 ms. Because this was the case similarly for all conditions and in our analysis of simulated data, we did not correct for this. Bompas and Sumner, 2009a). The material and procedure was the same as for experiment 1, except in the details below.…”

“…Note that S-cone stimuli presented on a background of luminance noise are thought to be invisible to the retinotectal pathway. The dip for S-cone distractors (purple) is plotted on a distractor-to-saccade distribution (average of all late distractor SOAs and all five observers from Bompas and Sumner, 2009a), and the gray line illustrates the no-distractor condition. Right, The effect of chromaticity is simulated in the DINASAUR model by increasing the delay of exogenous signals.…”