Hearing emotional sounds: category representation in the human amygdala

Previous studies have shown that the amygdala is more involved in processing animate categories, such as humans and animals, than inanimate objects, but little is known regarding whether this animate advantage applies to auditory stimuli. To address this issue, we performed a functional Magnetic Resonance Imaging (fMRI) study with emotion and category as factors, in which subjects heard sounds from different categories (i.e., humans, animals, and objects) in negative and neutral dimensions. Emotional levels and semantic familiarity were matched across categories. The results showed that the amygdala responded more to human vocalization than to animal vocalization and sounds of inanimate objects in both negative and neutral valences, and more to animal sounds than to objects in neural condition. In addition, the amygdala, together with the insula and the right superior temporal sulcus, further distinguished human voices from animal sounds. These data indicated that the amygdala is prepared to respond to animate sources, especially human vocalizations in auditory modality.