Is periodicity detection central?
What periodicity is perceived when two different segments of noise, E and F, are alternated dichotically between the ears (Left: EFEFE..; Right FEFEF..)? Earlier work has suggested that for nonfusible signals, preliminary auditory processing is performed separately for the two ears before the results are combined. If so, the perceived period should correspond to the combined lengths of the two segments, since this is the signal that iterates in one ear EF. But if periodicity is detected centrally, the perceived period should be equal to the length of one of the alternated segments (E, F), since each segment presented to one ear is immediately repeated in the other. Subjects compared an alternated sequence with two dichotic iterated sequences. (Left: CCC...; Right: DDD...) in an AXB paradigm, and segment duration was varied between 25 and 400 ms. In one comparison sequence, the iterated segments were equal in duration to the alternated segments (C = D = E = F), and in the other they were twice as long (C = D = E + F). The results show that periodicity is detected separately for the two ears at the shorter durations (nonfusible signals), but becomes central when the segments become long enough for structure to be heard within each segment (i.e, longer than 140-200 ms).
D001307:Auditory Perception; D006801:Humans; D008570:Memory, Short-Term; D010507:Periodicity; D011571:Psychoacoustics