Robustness to real-world background noise increases between primary and non-primary human auditory cortex

Abstract

In everyday listening, the sounds from sources we seek to understand are frequently embedded in background noise, which often profoundly alters auditory nerve spiking. To recognize sources of interest the brain must be somewhat robust to the effects of these background noises. To study the neural basis of listening in real-world background noise, we measured fMRI responses in human auditory cortex to a diverse set of thirty natural sounds, presented in quiet as well as embedded in thirty different everyday background noise textures (e.g., a bustling coffee shop, crickets chirping, etc.). We quantified the noise-robustness of neural responses by correlating each voxel’s response to the natural sounds in quiet with its response to those same sounds superimposed on background noise. Responses in core regions (commonly identified with primary auditory cortex) were substantially affected by background noise. However, noise-robustness increased with distance from primary auditory cortex: nearby non-primary areas were slightly more robust, while more distal areas were hardly affected by the background noises. Our results provide a neural correlate of the noise robustness of real-world listening, and offer evidence of a hierarchical organization in human auditory cortex.