Binaural coincidence detection is essential for the localization of external sounds and requires auditory signal processing with high temporal precision. We present an integrate-and-fire model of spike processing in the third order nucleus laminaris of the auditory pathway of the barn owl. Each input spike generates an excitatory postsynaptic potential with a width of 250 fjs. Output spikes occur with a tenfold enhanced temporal precision. This is possible since neuronal connections are fine tuned during a critical period of development as has been suggested by recent experiments. This rule does not only explain the temporal presicion in the output, but causes also a tuning to interaural time difference. The learning rule is of the Hebbian type: A synaptic weight is increased if a presynaptic spike arrives at about the same time as or slightly before postsynaptic firing. A presynaptic spike arriving after postsynaptic firing leads to a decrease of the synaptic efficacy.
展开▼
