Birdsong sounds are often used to inform visually-challenged people about the presence of basic infrastructures, and therefore need to be salient in noisy urban environments. How salient sounds are processed in the brain could inform us about the optimal birdsong in such environments. However, brain activity related to birdsong salience is not yet known.
Oscillatory magnetoencephalographic (MEG) activities and subjective salience induced by six birdsongs under three background noise conditions were measured. Thirteen participants completed the MEG measurements and 11 participants took part in the paired-comparison tests. We estimated the power of induced oscillatory activities, and explored the relationship between subjective salience of birdsongs and the power of induced activities using sparse regression analysis.
According to sparse regression analysis, the subjective salience was explained by the power of induced alpha (8–13 Hz) in the frontal region, induced beta (13–30 Hz) in the occipital region, and induced gamma (30–50 Hz) in the parietal region. The power of the frontal alpha and parietal gamma activities significantly varied across both birds and noise conditions.
These results indicate that frontal alpha activity is related to the salience of birdsong and that parietal gamma activity is related to differences in salience across noisy environments. These results suggest that salient birdsong under a noisy environment activates the bottom-up attention network.