Humans are able to discriminate sounds that only slightly differ from each other. For example, the range of human hearing is generally considered to span from 20 Hz to 20.000 Hz tones, and difference of as small as 10-15 Hz between two pip tones can be readily distinguished.
The present study further examines this phenomenon by analyzing the malleability of auditory discrimination. While it has been long known that active/conscious training can improve auditory discrimination, recent studies have demonstrated that also unsupervised perceptual learning using passive stimulation can improve auditory discrimination abilities. One particular type of perceptual learning protocol consists of exposing the subject passively to rapidly presented series of stimulations (10 to 20 presentations per second).
In the present article, it was shown that such rapid auditory stimulation (lasting for 2 min) with a sinusoidal tone leads to increased discriminability of the stimulated tone from a standard tone, while the response to an untrained tone was unaltered in a pre- vs. post-training comparison. This effect was assessed using electroencephalography (EEG) and indexed by a significant increase in amplitude of the so-called mismatch negativity (MMN) brain potential.
Thus, the employed brief passive discrimination training led to improvement in auditory sensitivity for subtle differences in sounds.