Musical expertise induces audiovisual integration of abstract congruency rules

Abstract

Perception of everyday life events relies mostly on multisensory integration. Hence, studying the neural correlates of the integration of multiple senses constitutes an important tool in understanding perception within an ecologically valid framework. The present study used magnetoencephalography in human subjects to identify the neural correlates of an audiovisual incongruency response, which is not generated due to incongruency of the unisensory physical characteristics of the stimulation but from the violation of an abstract congruency rule. The chosen rule-"the higher the pitch of the tone, the higher the position of the circle"-was comparable to musical reading. In parallel, plasticity effects due to long-term musical training on this response were investigated by comparing musicians to non-musicians. The applied paradigm was based on an appropriate modification of the multifeatured oddball paradigm incorporating, within one run, deviants based on a multisensory audiovisual incongruent condition and two unisensory mismatch conditions: an auditory and a visual one. Results indicated the presence of an audiovisual incongruency response, generated mainly in frontal regions, an auditory mismatch negativity, and a visual mismatch response. Moreover, results revealed that long-term musical training generates plastic changes in frontal, temporal, and occipital areas that affect this multisensory incongruency response as well as the unisensory auditory and visual mismatch responses.

Figures

Figure 1.

Examples of audiovisual congruent and incongruent trials. A, Congruent trial (that also served as auditory and visual standard). B, Incongruent trial. The line “Time” represents the duration of the presentation of the auditory and visual part of the stimulus. The last picture of each trial represents the intertrial stimulus in which subjects had to answer if the trail was congruent or incongruent.

Figure 2.

Distribution of the magnetic field of the audiovisual incongruency response in sensor space. The stars indicate clusters of sensors where the difference between the congruent and the incongruent condition is significant according to the permutation tests. The three red or three blue stars indicate significance of p = 0.000; while the two green or two violet stars indicate significance of p = 0.001.

Figure 3.

Right, Statistical parametric maps of the audiovisual incongruency response and the musicians to non-musicians comparison, as revealed by the flexible factorial model. Threshold: AlphaSim corrected at p < 0.001 by taking into account peak voxel significance (threshold p < 0.001 uncorrected) and cluster size (threshold size, >172 voxels). Left, Grand average global field power for congruent (black lines) and incongruent (gray lines) response for musicians (continuous lines) and non-musicians (dashed lines). Gray bar, Time interval where the analysis was performed.

Figure 4.

Right, Statistical parametric maps of the auditory MMN response and the musicians to non-musicians comparison as revealed by the flexible factorial model. Threshold: AlphaSim corrected at p < 0.001 by taking into account peak voxel significance (threshold p < 0.001 uncorrected) and cluster size (threshold size, >172 voxels). Left, Grand average global field power for standard (black lines) and deviant (gray lines) response for musicians (continuous lines) and non-musicians (dashed lines). Gray bar, Time interval where the analysis was performed.

Figure 5.

Right, Statistical parametric maps of the visual mismatch response and the musicians to non-musicians comparison as revealed by the flexible factorial model. Threshold: AlphaSim corrected at p < 0.001 by taking into account peak voxel significance (threshold p < 0.001 uncorrected) and cluster size (threshold size, >172 voxels). Left, Grand average global field power for standard (black lines) and deviant (gray lines) response for musicians (continuous lines) and non-musicians (dashed lines). Gray bar, Time interval where the analysis was performed.