A neural mechanism for hyperacuity in jamming avoidance response of electric fish eigenmannia

Eigenmannia can detect the phase difference (Δtxw) of the order of Δ t=1 μsec between a jamming signal and its own signal. We propose that this hyperacuity is accomplished through a combination of two kinds of functional contributions. One comes from a functional structure of the neural unit for coincidence detection, and the other results from a functional structure of a network consisting of the units. The network model is made based on the Jefferess model, but each unit is connected with nearest neighboring units through an excitatory synapse and with the other neighbors through an inhibitory synapse. The network can detect a tenth of the magnitude of the difference which the single unit can do. The unit of coincidence detector consists of a neuron with active dendrites which receives inputs through two excitatory connections and one inhibitory synapse. A single unit can detect the difference of the order of 10 μsec