The steady increase in urbanization presents several challenges for humans, as they are forced to adapt to an environment that differs from the natural habitats in which they evolved. Consequently, studying the effects of this environmental shift on psychological well-being has become increasingly important. Especially the influences of environmental sounds seem understudied. Previous research has demonstrated that exposure to natural sounds can improve cognitive performance and positive affect while exposure to urban sounds was found to be detrimental. In order to facilitate the benefits of natural sound exposure, a deeper understanding of the underlying psychological and neural mechanisms is essential. The current dissertation sought to provide insights into these mechanisms by investigating the brain’s response to environmental sounds via magnetic resonance imaging (MRI) and sub-clinical assessment of mental well-being. In Paper I (Stobbe et al., 2023), the impact of exposure to natural versus urban soundscapes on brain activity during cognitive performance was assessed. It was found that performance gains in a working memory task were associated with a reduction of activity in the medial prefrontal cortex (mPFC) proposing facilitated information processing in a subregion of the frontal executive network following exposure to a natural soundscape. Moreover, the reduction of negative emotions was linked to reduced activity in the inferior parietal lobule (IPL), a region that is part of the cognitive control network, suggesting that cognitive processes required less effort and elicited fewer negative emotions following the exposure to the natural soundscape condition. In Paper II (Stobbe et al., 2024), the effects of natural versus urban sounds on brain entropy (BEN) and functional connectivity (FC) during the sound exposure was examined. It was demonstrated, that the brain’s signal complexity, or BEN, in the posterior cingulate cortex (PCC) was significantly higher while participants listened to the urban soundscape. The increased BEN was found to be associated with a reduction of positive emotions in the urban soundscape condition, suggesting that the dislike of urban sounds might be represented by high signal complexity within the PCC. Additionally, it was discovered that FC in the auditory brain network was greater during exposure to natural soundscape compared to urban soundscape. This increment of FC was found to be associated with a performance gain on two working memory tasks, indicating that exposure to natural sounds could facilitate the brain’s processing efficiency via increased FC within a task relevant network. xii In Paper III (Stobbe et al., 2022), the influence of birdsongs versus traffic noise on depressive, anxious and paranoid states was investigated. It was found that while traffic noise exposure heightened the depressive states of healthy participants, exposure to birdsongs alleviated anxious and paranoid states in the same sample. These results suggest a possible explanation for the high prevalence of mental illness in urban areas while they simultaneously provide insights into how natural sounds such as birdsong could potentially be utilized to prevent the emergence mental illness. In conclusion, the present dissertation complements the debate on whether exposure to natural sounds can lead to improvements with respect to cognition and mental well-being and provides insights into possible mechanisms that underlie these benefits. These insights could contribute to more effective natural sound interventions and highlight the potential hazards of urban noise pollution.
