Jan Benda: Beat encoding at mistuned octaves within single sensory neurons

Universität Tübingen

The perception of beats has been extensively studied by Georg Simon Ohm, Hermann Helmholtz, and others already in the 19th century. They described beat-like perceptions not only for two spectrally close tones, but also for tones close to multiple octaves of a reference tone. However, the underlying mechanisms of this prominent percept are still unknown. We studied the encoding of superimposed periodic signals in electric fish, where such signals play a central role in social interactions including courtship. Our data show that slow amplitude modulations periodically occur at octaves of the reference signal. Electrosensory neurons indeed encode these reoccuring slow amplitude modulations. With simulations and mathematics we demonstrate that a threshold raised to a power of three preceding the spike generator is required to extract these slow amplitude modulations. The synapse of the receptor cell onto its afferent is a potential substrate for such a smooth threshold operation. Similarly, the hair cell synapse in mammalian auditory systems might also give rise to slow firing rate modulations in auditory fibers in response to mistuned octaves. I conclude the talk with some aspects of the encoding of three-wave interactions in the context of an electrosensory cocktail-party problem.

 

Organized by

Benjamin Lindner / Margret Franke