Periodicity of long-term context can influence gap detection

Temporal gap detection in bands of noise is a basic paradigm to investigate auditory temporal resolution. This study further examined the role of the long-term temporal organization for gap detection. Our experiments aimed at determining whether a gap superimposed on an amplitude-modulated noise was easier to detect when the amplitude modulation was regular--or periodic--than when it was not. Care was taken to ensure that the stimulus portion, where the gap was inserted, was exactly the same for both periodic and aperiodic conditions. Results show that gap detection in periodically modulated white noise (125 Hz fundamental frequency, or 8 ms duration from peak to peak) is easier (with a threshold 4.7 ms lower) than in an aperiodically modulated noise (modulation randomly varied from 5 to 18 ms). This effect is observed for variations of the modulation frequency from 125 to 1000 Hz. These results indicate that the regularity of long-term temporal organization of amplitude modulations in noise can improve the detection of a gap.