title: The variability of multisensory processes of natural stimuli in human and non-human primates in a detection task.
abstract: BACKGROUND
  Behavioral studies in both human and animals generally converge to the dogma that multisensory integration improves reaction times (RTs) in comparison to unimodal stimulation. These multisensory effects depend on diverse conditions among which the most studied were the spatial and temporal congruences. Further, most of the studies are using relatively simple stimuli while in everyday life, we are confronted to a large variety of complex stimulations constantly changing our attentional focus over time, a modality switch that can impact on stimuli detection. In the present study, we examined the potential sources of the variability in reaction times and multisensory gains with respect to the intrinsic features of a large set of natural stimuli.
  
  
  RESULTS
  Rhesus macaque monkeys and human subjects performed a simple audio-visual stimulus detection task in which a large collection of unimodal and bimodal natural stimuli with semantic specificities was presented at different saliencies. Although we were able to reproduce the well-established redundant signal effect, we failed to reveal a systematic violation of the race model which is considered to demonstrate multisensory integration. In both monkeys and human species, our study revealed a large range of multisensory gains, with negative and positive values. While modality switch has clear effects on reaction times, one of the main causes of the variability of multisensory gains appeared to be linked to the intrinsic physical parameters of the stimuli.
  
  
  CONCLUSIONS
  Based on the variability of multisensory benefits, our results suggest that the neuronal mechanisms responsible of the redundant effect (interactions vs. integration) are highly dependent on the stimulus complexity suggesting different implications of uni- and multisensory brain regions. Further, in a simple detection task, the semantic values of individual stimuli tend to have no significant impact on task performances, an effect which is probably present in more cognitive tasks.
authors.affiliation: Cerco, CNRS UMR 5549, Toulouse, France.|Université de Toulouse, UPS, Centre de Recherche Cerveau et Cognition, Toulouse, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Juan
authors.affiliation: Cerco, CNRS UMR 5549, Toulouse, France.|Université de Toulouse, UPS, Centre de Recherche Cerveau et Cognition, Toulouse, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Cappe
authors.affiliation: Cerco, CNRS UMR 5549, Toulouse, France.|Université de Toulouse, UPS, Centre de Recherche Cerveau et Cognition, Toulouse, France.
authors.forename: Baptiste
authors.initials: B
authors.lastname: Alric
authors.affiliation: Cerco, CNRS UMR 5549, Toulouse, France.|Université de Toulouse, UPS, Centre de Recherche Cerveau et Cognition, Toulouse, France.
authors.forename: Benoit
authors.initials: B
authors.lastname: Roby
authors.affiliation: Cerco, CNRS UMR 5549, Toulouse, France.|Université de Toulouse, UPS, Centre de Recherche Cerveau et Cognition, Toulouse, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Gilardeau
authors.affiliation: Cerco, CNRS UMR 5549, Toulouse, France.|Université de Toulouse, UPS, Centre de Recherche Cerveau et Cognition, Toulouse, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Barone
authors.affiliation: Cerco, CNRS UMR 5549, Toulouse, France.|Université de Toulouse, UPS, Centre de Recherche Cerveau et Cognition, Toulouse, France.|INSERM, Toulouse, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Girard
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods*; D000328:Adult; D000818:Animals; D001522:Behavior, Animal; D005260:Female; D006801:Humans; D008253:Macaca mulatta; D008297:Male; D033281:Nontherapeutic Human Experimentation; D010775:Photic Stimulation / Q000379:methods*; D011930:Reaction Time / Q000502:physiology*