Poster #: 63
Topic: Memory and perception
Friday, Sep 11, 2015
Discrimination of auditory motion velocities: difference thresholds and mismatch negativity
1Group of Auditory Physiology, I.P.Pavlov Institute of Physiology, St.Petersburg, Russia
The sensitivity of the auditory system to the sound motion velocity is known to be a complex phenomenon which can be influenced by associated cues, such as distance and duration. The ability to discriminate the velocity of moving sounds was examined using psychophysical and electrophysiological methods. White noise bursts (100 - 1300 Hz, 200 ms duration) were dichotically presented to 11 human subjects. Abrupt displacement of the sound from the head midline to the left or right ear or gradual motion to the same distance at different velocities were simulated manipulating interaural time difference. Stimulus design minimized the impact of additional cues on the discrimination of the velocity per se.
Difference threshold for gradual motion velocity measured using the standard 2AFC procedure combined with adaptive staircase method exceeded relative velocity increase of 50%. Such a high threshold value could result from distance and duration cues being out of listeners’ perception. Significant mismatch negativity (MMN) was elicited by the relative velocity increase of 38%. The result suggested that MMN was more sensitive to velocity difference than the psychophysical measuring and less dependent on the additional cues. Abrupt displacement of the sound elicited stronger MMNs than gradual motion. Discrimination of abrupt and gradual motion estimated using 2AFC procedure hardly reached the 75% threshold level. At the individual level MMN amplitudes did not correlate with any of the psychophysical measures obtained.