Differential effects of the temporal and spatial distribution of audiovisual stimuli on cross‐modal spatial recalibration

• Published in: The European journal of neuroscience Vol. 52; no. 7; pp. 3763 - 3775
• Main Authors: Bruns, Patrick, Dinse, Hubert R., Röder, Brigitte
• Format: Journal Article
• Language: English
• Published: France Wiley Subscription Services, Inc 01.10.2020
• Subjects: Auditory discrimination learning; Between-subjects design; Hearing; Localization; Long-term potentiation; multisensory; recalibration; Sensory integration; Spatial discrimination; Spatial distribution; spatial hearing; ventriloquism; spatial hearing; recalibration; multisensory; ventriloquism; long-term potentiation
• ISSN: 0953-816X; 1460-9568; 1460-9568
• DOI: 10.1111/ejn.14779

Visual input constantly recalibrates auditory spatial representations. Exposure to isochronous audiovisual stimuli with a fixed spatial disparity typically results in a subsequent auditory localization bias (ventriloquism aftereffect, VAE), whereas exposure to spatially congruent audiovisual stimuli improves subsequent auditory localization (multisensory enhancement, ME). Here, we tested whether cross‐modal recalibration is affected by the stimulation rate and/or the distribution of audiovisual spatial disparities during training. Auditory localization was tested before and after participants were exposed either to audiovisual stimuli with a constant spatial disparity of 13.5° (VAE) or to spatially congruent audiovisual stimulation (ME). In a between‐subjects design, audiovisual stimuli were presented either at a low frequency of 2 Hz, as used in previous studies of VAE and ME, or intermittently at a high frequency of 10 Hz, which mimics long‐term potentiation (LTP) protocols and which was found superior in eliciting unisensory perceptual learning. Compared to low‐frequency stimulation, VAE was reduced after high‐frequency stimulation, whereas ME occurred regardless of the stimulation protocol. In two additional groups, we manipulated the spatial distribution of audiovisual stimuli in the low‐frequency condition. Stimuli were presented with varying audiovisual disparities centered around 13.5° (VAE) or 0° (ME). Both VAE and ME were equally strong compared to a fixed spatial relationship of 13.5° or 0°, respectively. Taken together, our results suggest (a) that VAE and ME represent partly dissociable forms of learning and (b) that auditory representations adjust to the overall stimulus statistics rather than to a specific audiovisual spatial relationship. The temporal pattern of audiovisual stimulation (low‐ vs. high‐frequency) modulated the strength of cross‐modal recalibration to spatially incongruent stimuli although it did not affect multisensory enhancement with spatially congruent stimulation. This suggests that recalibration and enhancement represent partly dissociable forms of cross‐modal learning. Both forms of cross‐modal learning depended on the overall stimulus statistics rather than on a specific audiovisual spatial relationship.