Information Rate of Neural Spike Trains in Response to Sinusoidal Electric Stimuli in the Presence of a Pseudo-spontaneous Activity

This article presents an analysis of the information rate of neural spike trains in an auditory nerve fiber (ANF) model stimulated extracellularly by sinusoidal electric stimuli under the case where a high-rate pulsatile waveform is presented as a conditioner for increasing the across-fiber-independency, i.e., desynchronization. In the computer simulation, stimulus current waveforms were presented repeatedly to a stimulating electrode located 1 mm above the 26th node of Ranvier, in an ANF axon model having 50 nodes of Ranvier, each consisting of stochastic sodium and potassium channels. From spike firing times recorded at the 36th node of Ranvier, the inter spike intervals were generated and then "total" and "noise" entropies were estimated to obtain the mutual information and information rate of the spike trains. In the present article, it is shown that at a specific amplitude of sinusoidal waveforms, the possibility to encode the sinusoidal function with various amplitudes became greater (enlarging dynamic range), as well as the information rate was found to be maximized. It was implied that setting the amplitude of sinusoids to the specific values which maximize the information rate might contribute to efficiently encoding information under the high-rate pulsatile stimulation in cochlear prostheses