Neuromagnetic correlates of the vocal characteristics of vowels in auditory cortex Free

As a child grows up the formants of their vowels move down in frequency and the spacing of the harmonics that determines voice pitch decreases. Perceptually, these variables determine who listeners hear speaking (child, woman or man). In a logarithmic-frequency spectrum, the envelope with its formant peaks, moves toward the origin as a unit, without changing shape as a child grows up. Similarly, the harmonics, which constitute the fine structure of the spectrum, move toward the origin as a unit without changing shape, but at a different rate. This paper describes neuromagnetic studies which show that the generator associated with voice pitch is in Heschl's gyrus just lateral to primary auditory cortex, while the generator associated spectral envelope position is in planum temporale, some distance behind the pitch activity generator. The posterior generator is close to the location of the large N1m that typically accompanies the onset of acoustic energy of any sort. The pitch processing component of the N1m was isolated from the energy-onset component by presenting sequences of vowels with minimal inter-vowel intervals; it appears isolated in the responses to the second and succeeding vowels.