Role of acoustic striae in hearing: mechanism for enhancement of sound detection in cats.

We report the results of behavioral studies in cats conducted first, to demonstrate the presence of a monaural mechanism for the enhancement of signal to noise; and then to examine the necessity or sufficiency of the acoustic striae for this mechanism. The results show that cats do indeed have a monaural mechanism for enhancing the detection of tones in co-located background noise for noise levels at least as high as 60 dB SPL. The ablation-behavior results show that surgical section of the dorsal (DAS) and most of the intermediate (IAS) striae has no measurable effect on this mechanism. In sharp contrast, even partial section of the trapezoid body results in a profound and permanent deficit and this deficit is not accounted for by hearing loss alone. It is concluded that the ascending and descending fibers in the dorsal and intermediate acoustic striae are neither necessary nor sufficient for enhancing the detection of salient sounds in a noisy environment while the ascending or descending fibers in the ventral acoustic stria are sufficient and probably necessary.