Effects of perturbation magnitude and voice F0 level on the pitch-shift reflex.

The purpose of the present study was to investigate the responsiveness of the pitch-shift reflex to small magnitude stimuli and voice fundamental frequency (F(0)) level. English speakers received pitch-shifted voice feedback (+/-10, 20, 30, 40, and 50 cents, 200 ms duration) during vowel phonations at a high and a low F(0) level. Mean pitch-shift response magnitude increased as a function of pitch-shift stimulus magnitude, but when expressed as a percent of stimulus magnitude, declined from 100% with +/-10 cents to 37% with +/-50 cents stimuli. Response magnitudes were larger and latencies were shorter with a high F(0) level (16 cents;130 ms) compared to a low F(0) level (13 cents;152 ms). Data from the present study demonstrate that vocal response magnitudes are equal to small perturbation magnitudes, and they are larger and faster with a high F(0) voice. These results suggest that the audio-vocal system is optimally suited for compensating for small pitch rather than larger perturbations. Data also suggest the sensitivity of the audio-vocal system to voice perturbation may vary with F(0) level.