Coding of Naturalistic Stimuli by Auditory Midbrain Neurons

It is known that humans can make finer discriminations between familiar sounds (e.g. syllables) than between unfamiliar ones (e.g. different noise segments). Here we show that a corresponding enhancement is present in early auditory processing stages. Based on previous work which demonstrated that natural sounds had robust statistical properties that could be quantified, we hypothesize that the auditory system exploits those properties to construct efficient neural codes. To test this hypothesis, we measure the information rate carried by auditory spike trains on narrow-band stimuli whose amplitude modulation has naturalistic characteristics, and compare it to the information rate on stimuli with nonnaturalistic modulation. We find that naturalistic inputs significantly enhance the rate of transmitted information, indicating that auditiory neural responses are matched to characteristics of natural auditory scenes.