Neural coding of timbre in birdsong

SANTIAGO BOARI; ANA AMADOR

Mar del Plata, Buenos Aires, Argentina

Congreso; XXX Congreso Anual de la Sociedad Argentina de Investigación en Neurociencias (SAN); 2015

Sociedad Argentina de Investigación en Neurociencias

Given two sounds of same pitch, loudness and duration, timbre is the acoustical property responsible for the identity of the sound source. Timbre is a multidimensional attribute that is most elusive to describe. Some of these dimensions have been identified and explored in psychoacoustics experiments conducted on human subjects, but an objective way to measure timbre is yet to be determined.In this work, we studied the contribution of attack time to the sound identity. Attack time is a well-established dimension of timbre: it is the time it takes for the sound envelope to reach its first maximum.Zebra finches (Taeniopygia guttata) present a remarkable opportunity to study timbre in complex vocalizations as they present a wide syllable repertoire that contains a large number of syllables with a rapid attack time and a slower decaying envelope. In addition, previous experimental evidence showed that telencephalic neurons in HVC respond in a highly selective fashion to auditory presentations of the Bird?s Own Song (BOS) while not responding to the reversed song. Therefore, we used HVC neural activity as a measure of BOS recognition. We generated a modified BOS in which the sound envelope of each syllable was reversed (MOD). This effectively switches the attack and decay times of each syllable while maintaining the rest of the acoustical properties intact. We have found that these changes in the attack time lead to a decrease in the neural response of HVC units, unveiling a neural representation of timbre in HVC.