Research Report Auditory enhancement of visual perception at threshold depends on visual abilities Anne Caclin a, b, c , ⁎ , Patrick Bouchet a, b, c , Farida Djoulah a, b, c , Elodie Pirat a, b, c , Jacques Pernier a, b, c , Marie-Hélène Giard a, b, c a INSERM, U1028, Lyon Neuroscience Research Center, Brain Dynamics and Cognition Team, Lyon, F-69000, France b CNRS, UMR5292, Lyon Neuroscience Research Center, Brain Dynamics and Cognition Team, Lyon, F-69000, France c University Lyon 1, Lyon, F-69000, France ARTICLE INFO ABSTRACT Article history: Accepted 9 April 2011 Available online 15 April 2011 Whether or not multisensory interactions can improve detection thresholds, and thus widen the range of perceptible events is a long-standing debate. Here we revisit this question, by testing the influence of auditory stimuli on visual detection threshold, in subjects exhibiting a wide range of visual-only performance. Above the perceptual threshold, crossmodal interactions have indeed been reported to depend on the subject's performance when the modalities are presented in isolation. We thus tested normal-seeing subjects and short-sighted subjects wearing their usual glasses. We used a paradigm limiting potential shortcomings of previous studies: we chose a criterion-free threshold measurement procedure and precluded exogenous cueing effects by systematically presenting a visual cue whenever a visual target (a faint Gabor patch) might occur. Using this carefully controlled procedure, we found that concurrent sounds only improved visual detection thresholds in the sub-group of subjects exhibiting the poorest performance in the visual-only conditions. In these subjects, for oblique orientations of the visual stimuli (but not for vertical or horizontal targets), the auditory improvement was still present when visual detection was already helped with flanking visual stimuli generating a collinear facilitation effect. These findings highlight that crossmodal interactions are most efficient to improve perceptual performance when an isolated modality is deficient. © 2011 Elsevier B.V. All rights reserved. Keywords: Audiovisual interactions Detection threshold Collinear facilitation Inter-individual variability 1. Introduction Whether or not the perceptual threshold in one sensory modality can be improved by concurrent stimulation of another sensory channel is an intriguing question. At a theoretical level, such multisensory interactions would imply that it is possible to push further the limits of the perceptual system and allow to consciously perceive otherwise subliminal stimuli. Multisenso- ry illusions have indeed revealed that, above threshold, stimuli in one modality can modify the perceptual content in another modality, as is for example observed in the McGurk illusion (McGurk and MacDonald, 1976), or in the sound-induced flash illusion (Shams et al., 2000). Pushing further the limits of the perceptual system using multisensory interactions might also be of practical interest to design new perceptual learning or rehabilitation procedures. BRAIN RESEARCH 1396 (2011) 35 – 44 ⁎ Corresponding author at: INSERM U1028, Brain Dynamics and Cognition, 69675 Bron Cedex, France. Fax: +33 4 72 13 89 01. E-mail address: Anne.Caclin@inserm.fr (A. Caclin). 0006-8993/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.brainres.2011.04.016 available at www.sciencedirect.com www.elsevier.com/locate/brainres