Individual Differences in Multisensory Interactions:The Influence of Temporal Phase Coherence and Auditory Salience on Visual Contrast Sensitivity

Audiovisual Interactions Among Near-Threshold Oscillating Stimuli in the Far Periphery Are Phase-Dependent

Recent studies have highlighted the possible contributions of direct connectivity between early sensory cortices to audiovisual integration. Anatomical connections between the early auditory and visual cortices are concentrated in visual sites representing the peripheral field of view. Here, we aimed to engage early sensory interactive pathways with simple, far-peripheral audiovisual stimuli (auditory noise and visual gratings). Using a modulation detection task in one modality performed at an 84% correct threshold level, we investigated multisensory interactions by simultaneously presenting weak stimuli from the other modality in which the temporal modulation was barely-detectable (at 55 and 65% correct detection performance). Furthermore, we manipulated the temporal congruence between the cross-sensory streams. We found evidence for an influence of barely-detectable visual stimuli on the response times for auditory stimuli, but not for the reverse effect. These visual-to-auditory influences only occurred for specific phase-differences (at onset) between the modulated audiovisual stimuli. We discuss our findings in the light of a possible role of direct interactions between early visual and auditory areas, along with contributions from the higher-order association cortex. In sum, our results extend the behavioral evidence of audio-visual processing to the far periphery, and suggest - within this specific experimental setting - an asymmetry between the auditory influence on visual processing and the visual influence on auditory processing.

Rhythmic Modulation of Visual Perception by Continuous Rhythmic Auditory Stimulation

At any given moment our sensory systems receive multiple, often rhythmic, inputs from the environment. Processing of temporally structured events in one sensory modality can guide both behavioral and neural processing of events in other sensory modalities, but whether this occurs remains unclear. Here, we used human electroencephalography (EEG) to test the cross-modal influences of a continuous auditory frequency-modulated (FM) sound on visual perception and visual cortical activity. We report systematic fluctuations in perceptual discrimination of brief visual stimuli in line with the phase of the FM-sound. We further show that this rhythmic modulation in visual perception is related to an accompanying rhythmic modulation of neural activity recorded over visual areas. Importantly, in our task, perceptual and neural visual modulations occurred without any abrupt and salient onsets in the energy of the auditory stimulation and without any rhythmic structure in the visual stimulus. As such, the results provide a critical validation for the existence and functional role of cross-modal entrainment and demonstrates its utility for organizing the perception of multisensory stimulation in the natural environment.SIGNIFICANCE STATEMENT Our sensory environment is filled with rhythmic structures that are often multi-sensory in nature. Here, we show that the alignment of neural activity to the phase of an auditory frequency-modulated (FM) sound has cross-modal consequences for vision: yielding systematic fluctuations in perceptual discrimination of brief visual stimuli that are mediated by accompanying rhythmic modulation of neural activity recorded over visual areas. These cross-modal effects on visual neural activity and perception occurred without any abrupt and salient onsets in the energy of the auditory stimulation and without any rhythmic structure in the visual stimulus. The current work shows that continuous auditory fluctuations in the natural environment can provide a pacing signal for neural activity and perception across the senses.

A crowd of emotional voices influences the perception of emotional faces: Using adaptation, stimulus salience, and attention to probe audio-visual interactions for emotional stimuli

Correctly assessing the emotional state of others is a crucial part of social interaction. While facial expressions provide much information, faces are often not viewed in isolation, but occur with concurrent sounds, usually voices, which also provide information about the emotion being portrayed. Many studies have examined the crossmodal processing of faces and sounds, but results have been mixed, with different paradigms yielding different results. Using a psychophysical adaptation paradigm, we carried out a series of four experiments to determine whether there is a perceptual advantage when faces and voices match in emotion (congruent), versus when they do not match (incongruent). We presented a single face and a crowd of voices, a crowd of faces and a crowd of voices, a single face of reduced salience and a crowd of voices, and tested this last condition with and without attention directed to the emotion in the face. While we observed aftereffects in the hypothesized direction (adaptation to faces conveying positive emotion yielded negative, contrastive, perceptual aftereffects), we only found a congruent advantage (stronger adaptation effects) when faces were attended and of reduced salience, in line with the theory of inverse effectiveness.