TY - JOUR T1 - Neural Representation of Concurrent Vowels in Macaque Primary Auditory Cortex JF - eneuro JO - eneuro DO - 10.1523/ENEURO.0071-16.2016 SP - ENEURO.0071-16.2016 AU - Yonatan I. Fishman AU - Christophe Micheyl AU - Mitchell Steinschneider Y1 - 2016/06/06 UR - http://www.eneuro.org/content/early/2016/06/05/ENEURO.0071-16.2016.abstract N2 - Successful speech perception in real-world environments requires that the auditory system segregate competing voices which overlap in frequency and time into separate streams. Vowels are major constituents of speech and are comprised of frequencies (harmonics) that are integer multiples of a common fundamental frequency (F0). The pitch and identity of a vowel are determined by its F0 and spectral envelope (formant structure), respectively. When two spectrally-overlapping vowels differing in F0 are presented concurrently, they can be readily perceived as two separate ‘auditory objects’ with pitches at their respective F0s. A difference in pitch between two simultaneous vowels provides a powerful cue for their segregation which, in turn, facilitates their individual identification. The neural mechanisms underlying the segregation of concurrent vowels based on pitch differences are poorly understood. Here, we examine neural population responses in macaque primary auditory cortex (A1) to single and double concurrent vowels (/a/and/i/) that differ in F0 such that they are heard as two separate ‘auditory objects’ with distinct pitches. We find that neural population responses in A1 can resolve, via a rate-place code, lower harmonics of both single and double concurrent vowels. Furthermore, we show that the formant structures, and hence the identities, of single vowels can be reliably recovered from the neural representation of double concurrent vowels. We conclude that A1 contains sufficient spectral information to enable concurrent vowel segregation and identification by downstream cortical areas.Significance Statement: The ability to attend to a particular voice among competing voices is crucial for speech perception in complex acoustic environments. This ability requires that listeners perceptually segregate sounds into discrete auditory streams which correspond to their sources. Vowels are major constituents of speech. The pitch and identity of a vowel are determined by its fundamental frequency and spectral envelope (formant structure), respectively. A difference in pitch between two simultaneous vowels provides a powerful cue for their segregation which, in turn, facilitates their individual identification. Here, we show that primary auditory cortex contains sufficient spectral information to enable concurrent vowel segregation and identification based on differences in pitch by downstream cortical areas, consistent with its role in auditory scene analysis. ER -