LEARNING AND GENERALIZATION OF AUDITORY TEMPORAL-INTERVAL DISCRIMINATION IN HUMANS

The sensory encoding of the duration, interval, and order of different stimulus features provides vital information to the nervous system, T he present study focuses on the influence of practice on auditory temp oral-interval discrimination. The goals of the experiment were to dete rmine (1) whether practice improved the ability to discriminate a stan dard interval of 100 msec bounded by brief 1 kHz tones from longer int ervals, and, if so, (2) whether this improvement generalized to differ ent tonal frequencies or temporal intervals. Learning was examined in 14 human subjects using an adaptive, two-alternative, forced-choice pr ocedure. One hour of training per day for 10 d led to marked improveme nts in the ability to discriminate between the standard and longer int ervals. The generalization of learning was evaluated by independently varying the spectral (tonal frequency) and temporal (interval) compone nts of the stimuli in four conditions tested both before and after the training phase. Remarkably, there was complete generalization to the trained interval of 100 msec bounded by tones at the untrained frequen cy of 4 kHz, but no generalization to the untrained intervals of 50, 2 00, or 500 msec bounded by tones at the trained frequency of 1 kHz. Th us, these data show that (1) temporal-interval discrimination using a 100-msec standard undergoes perceptual learning, and (2) the neural me chanisms underlying this learning are temporally, but not spectrally, specific. These results are compared with those from previous investig ations of learning in visual spatial tasks, and are discussed in relat ion to biologically plausible models of temporal processing.