Retrospective auditory cues can improve detection of near-threshold visual targets

www.nature.com/scientificreports OPEN Retrospective auditory cues can improve detection of nearthreshold visual targets Daphné Rimsky-Robert 1* , Viola Störmer2, Jérôme Sackur 3 & Claire Sergent1 Recent studies have demonstrated that visually cueing attention towards a stimulus location after its disappearance can facilitate visual processing of the target and increase task performance. Here, we tested whether such retro-cueing effects can also occur across different sensory modalities, as cross-modal facilitation has been shown in pre-cueing studies using auditory stimuli prior to the onset of a visual target. In the present study, participants detected low-contrast Gabor patches in a speeded response task. These patches were presented in the left or right visual periphery, preceded or followed by a lateralized and task-irrelevant sound at 4 stimulus-onset asynchronies (SOA; −600 ms, −150 ms, +150 ms, +450 ms). We found that pre-cueing at the −150 ms SOA led to a general increase in detection performance irrespective of the sound’s location relative to the target. On top of this temporal effect, sound-cues also had a spatially specific effect, with further improvement when cue and target originated from the same location. Critically, the temporal effect was absent, but the spatial effect was present in the short-SOA retro-cueing condition (+150 ms). Drift-diffusion analysis of the response time distributions allowed us to better characterize the evidenced effects. Overall, our results show that sounds can facilitate visual processing, both pre- and retro-actively, indicative of a flexible and multisensory attentional system that underlies our conscious visual experience. What mechanisms lay the ground for conscious experience? As this question remains debated to this day, two radically different accounts aim at solving the issue. On the one hand it is argued that consciousness arises from local recurrent loops of information in the sensory cortices, and that top-down selection processes such as attention gate reportability of that information, rather than perceptual awareness itself1–3. On the other hand, other researchers argue that perceptual awareness is the result of information transfer across domains, and that a broad network of regions beyond the sensory cortices is involved4,5. A key difference between these two theories is that, in the first case, the conscious or non-conscious fate of a sensory input is decided within sensory areas before any involvement of supra-modal areas. This means that whether a stimulus becomes conscious or not is determined within the first 100–150 ms following its presentation6. In the latter case, supra-modal or other sensory cortices are pivotal for conscious experience, and perceptual awareness is not dependent only on local recurrent information transfer within a single sensory modality. Recent studies7,8 used an attentional spatial cueing paradigm9 in which a cue could appear before or after the appearance of a target event to test the broadcasting vs. local feedback account of conscious perception: indeed, if conscious perception correlates with the broadcast of sensory information via top-down attention across the brain, then retrospectively orienting attention towards the sensory trace of a target could potentially promote initially unseen stimuli into consciousness. In contrast, if conscious perception is decided during the initial sensory processing steps, as assumed by the local feedback account, a retro-cue that directs attention to the target retroactively should not influence whether the stimulus is consciously perceived or not. Previous research tested these two predictions by asking participants to judge the orientation of low-contrast Gabor patches while spatial visual retro-cues attracted attention either to the target’s past location or to the opposite location. These studies showed that such retrospective cueing of exogenous spatial attention facilitated conscious perception of the past target – similar to previously observed pre-cueing effects where the cue is presented at the target location prior to its onset9. This effect was called “retro-perception”10, and highlighted the existence of temporal flexibility in the processes allowing for conscious access, while providing evidence for the importance of attention as a gating 1 Integrative Neuroscience and Cognition Center - UMR 8002 CNRS/Université Paris Descartes, Paris, France. Department of Psychology & Neuroscience Graduate Program, University of California, San Diego, USA. 3LSCP, École des Hautes Études en Sciences Sociales, Paris, France. *email: 2 Scientific Reports | (2019) 9:18966 | https://doi.org/10.1038/s41598-019-55261-0 1 www.nature.com/scientificreports/ www.nature.com/scientificreports mechanism for conscious experience. However, since these studies used spatial cues within the same modality as the target, it cannot be excluded that this retro-perception effect was at least partly due to a low-level, visual interaction between the retrospective cue and the visual trace of the target, rather than to top-down attentional involvement11. In order to address this question we devised an experiment in which the target and the retrospective cues where presented in different sensory modalities, in order to minimize direct local interactions between experimental stimuli within the sensory cortex. In particular, we used auditory cues and visual targets because they are initially processed in distinct cerebral regions. While there exists evidence that these could interact through rapid direct pathways between the sensory cortices with no involvement of supra-modal structures12, this can be avoided by using stimulus-onset asynchronies (SOAs) above 100 ms13. Many previous studies have shown that hearing a salient sound can facilitate processing of subsequently presented visual stimuli at the same location14. These cross-modal effects of attention have been shown to not only speed response times, but also increase visual sensitivity15,16. For example, pre-cueing the occurrence of a visual target with a peripheral sound has been shown to increase participants’ detection rate of visual stimuli near the perceptual threshold15, facilitate the discrimination of visual targets17, enhance perceived contrast of the target18, or accelerate the perceived timing of a visual event19. These behavioral effects are accompanied by an increase in early neural responses to the visual target over the occipital cortex contralateral to the side of presentation20. These results suggest that cross-modal orienting of attention can alter sensory processing in the visual cortex. However, in all these studies, the auditory cue preceded the target. Here we wanted to test whether auditory retro-cues could also affect perception of near-threshold visual stimuli– similar to what has been shown for visual retro-cues7. While retro-cueing studies exist on cross-modal perceptio (...truncated)