Berthold Hedwig, University of Cambridge, Cambridge

Behavioural and neuronal dissection of an auditory pattern recognition network

The acoustic behaviour of field crickets and the “simple” organisation of their central nervous system offer the chance to analyse the neuronal basis of the underlying pattern recognition mechanism and to decipher one of the brain’s codes for sensory processing.

Male crickets attract females by stereotypical calling songs. The tuning of the female phonotactic behaviour in response to different temporal patterns can be characterised with trackball experiments. As tethered female crickets walk and orient towards different auditory patterns they reveal the tuning of their behaviour. By manipulating the duration of individual sound pulses or intervals details of the phonotaxis response can be linked to the underlying neural mechanism.

How is the pattern recognition process organised in the central nervous system? Analysing the response properties of auditory brain neurons supports the concept of a delay-line and coincidence-detector network. Crucial for this mechanism is the activity of a non-spiking brain neuron that generates a post-inhibitory rebound with a delay matching the species-specific pulse interval. Evidence based on response latencies and synaptic activity indicates that the postinhibitory rebound boosts the activity of the coincidence detector neuron, when two pulses with the species-specific pulse interval occur. In this way a circuit of auditory brain neurons is tuned to the temporal characteristics of the male’s calling song.

Behavioural evidence further demonstrates that the temporal tuning of phonotactic behaviour is modulated by the pattern recognition process in a way that is not yet understood. Imaging experiments from auditory brain neurons may help to solve the puzzle.

Organized by

Bernd Ronacher