Auditory Frequency Perception Adapts Rapidly to the Immediate Past

Frequency modulation is critical to human speech. Evidence from psychophysics, neurophysiology, and neuroimaging suggests that there are neuronal populations tuned to this property of speech. Consistent with this, extended exposure to frequency change produces direction specific aftereffects in frequency change detection. We show that this aftereffect occurs extremely rapidly, requiring only a single trial of just 100-ms duration. We demonstrate this using a long, randomized series of frequency sweeps (both upward and downward, by varying amounts) and analyzing intertrial adaptation effects. We show the point of constant frequency is shifted systematically towards the previous trial's sweep direction (i.e., a frequency sweep aftereffect). Furthermore, the perception of glide direction is also independently influenced by the glide presented two trials previously. The aftereffect is frequency tuned, as exposure to a frequency sweep from a set centered on 1,000 Hz does not influence a subsequent trial drawn from a set centered on 400 Hz. More generally, the rapidity of adaptation suggests the auditory system is constantly adapting and "tuning" itself to the most recent environmental conditions.