Auditory cortex responses to sequences of normal and reversed squirrel monkey vocalizations.

Responsiveness of auditory cortex (AC) units of awake squirrel monkeys to a natural sequence of species-specific calls was not significantly different from their responsiveness to a reverse playback of the sequence. No dependency was noted between the percentage of responding units and the average intensity of sounds, their spectral content or their order of presentation. The effectiveness of the sounds in eliciting responses was variable even when the sequence was produced in an unchanging behavioral context. Comparison of these findings with earlier results of individual vocalizations presented normally or backward in an isolated manner suggest that responsiveness of AC neurons to continuous sounds is lower than their responsiveness to isolated sounds, whether natural or artificial.