Intercostal muscles and purring in the cat: the influence of afferent inputs.

Feline purring has previously been reported as originating in a central oscillator, independent of afferent inputs, and also as not involving expiratory muscles. Here we show, via electromyographic recordings from intercostal muscles, quantified by cross-correlation, that expiratory muscles can be involved and that even if the oscillator is central, reflex components nevertheless play a considerable part in the production of the periodic pattern of muscle activation seen during purring.