A neural circuit for song pattern recognition in the cricket brain

Abstract

Acoustic communication is based on amplitude and frequency modulation of sound signals. Temporal features of the signal require processing by central auditory neurons, the brain circuits, however that detect temporal features are poorly understood. We show how five neurons in the brain of female field crickets form an auditory feature-detector circuit for the pulse pattern of the male calling song, and exhibit properties of a delay-line and coincidence-detection mechanism. The network receives its direct input from a single ascending auditory interneuron. An internal delay that matches the pulse period of the calling song is established by a non-spiking brain neuron. In response to a sound pulse, it generates a transient inhibition that triggers a delayed rebound depolarization. The direct input and the delayed responses converge in a coincidence detector neuron, which responds best to the pulse pattern of the species-specific calling song as the rebound activation of the non-spiking neuron coincides with the response of the ascending interneuron to the subsequent sound pulse. The output of the coincidence detector neuron is further processed by a feature detector neuron to suppress unselective responses and background activity. The circuit reveals principal mechanisms of sensory processing underlying the perception of temporal auditory patterns.