Effect of sequential comparison on active processing of sound duration.

Previous studies on active duration processing on sounds showed opposing results regarding the predominant involvement of the left or right hemisphere. Duration of an acoustic event is normally judged relative to other sounds. This requires sequential comparison as auditory events unfold over time. We hypothesized that increasing the demand on sequential comparison in a task increases the involvement of the left auditory cortex. With the current fMRI study, we investigated the effect of sequential comparison in active duration discrimination by comparing a categorical with a comparative task. During the categorical task, the participant had to categorize the tones according to their duration (short vs long). During the comparative task, they had to decide for each tone whether its length matched the tone presented before. We used the contralateral noise procedure to reveal the degree of participation of the left and right auditory cortex during these tasks. We found that both tasks more strongly involve the left than the right auditory cortex. Furthermore, the left auditory cortex was more strongly involved during comparison than during categorization. Together with previous studies, this suggests that additional demand for sequential comparison during processing of different basic acoustic parameters leads to an increased recruitment of the left auditory cortex. In addition, the comparison task more strongly involved several brain areas outside the auditory cortex, which may also be related to the demand for additional cognitive resources as compared to the more efficient categorization of sounds. Hum Brain Mapp 38:4459-4469, 2017.