RESUMO
Due to the Great East Japan Earthquake on 11 March 2011 and the following long-term earthquake swarm, many people living in the earthquake-affected areas have developed mental stress, even though clinically-diagnosable symptoms may not be apparent. Concurrently, many unusual reports have emerged in which persons complain of abnormally increased sensitivity to sudden ambient sounds during their daily lives (e.g., the sound of the washing machine on spin cycle). By recording event-related potentials to various sudden ambient sounds from young adults living in the affected areas, we found that the level of earthquake-induced mental stress, as indexed by the hyperarousal symptoms of posttraumatic stress disorder, was positively related to the magnitude of P3a to sudden ambient sounds. These results reveal a strong relationship between mental stress and enhanced involuntary attentional orienting in a large majority of trauma-exposed people without diagnosable symptoms.