Abstract
This paper presents the effects of spontaneous random activity on information transmission in an auditory brain stem neuron model. In computer simulations, the supra-threshold synaptic current stimuli ascending from auditory nerve fibers (ANFs) were modeled by a filtered inhomogeneous Poisson process modulated by sinusoidal functions at a frequency of 220–3520 Hz with regard to the human speech spectrum. The stochastic sodium and stochastic high- and low-threshold potassium channels were incorporated into a single compartment model of the soma in spherical bushy neurons, so as to realize threshold fluctuations or a variation of spike firing times. The results show that the information rates estimated from the entropy of inter-spike intervals of spike trains tend toward a convex function of the spontaneous rates when the intensity of sinusoidal functions decreases. Furthermore, the results show that a convex function of the spontaneous rates tends to disappear as the frequency of the sinusoidal function increases, such that the phase-locked response can be unobserved. It is concluded that this sort of stochastic resonance (SR) phenomenon, which depends on the spontaneous rates with supra-threshold stimuli, can better enhance information transmission in a smaller intensity of sinusoidal functions within the human speech spectrum, like the situation in which the regular SR can enhance weak signals.
Highlights
Determining the location of a sound source from subtle differences in intensity and/or temporal information, i.e., sound localization, is crucial to the survival of many species and in human communication
Phenomenon, which depends on the spontaneous rates with supra-threshold stimuli, can better enhance information transmission in a smaller intensity of sinusoidal functions within the human speech spectrum, like the situation in which the regular stochastic resonance (SR) can enhance weak signals
The transmembrane potential, the conductance of the excitatory synapse and the intensity function of an inhomogeneous Poisson process are depicted as a function of time in Figure 2, when the synaptic conductance is set such that the synaptic current can become the supra-threshold stimulus, at λc = 200 s−1 and f = 220 Hz
Summary
Determining the location of a sound source from subtle differences in intensity and/or temporal information, i.e., sound localization, is crucial to the survival of many species and in human communication. The superior olive complex (SOC) in mammals is a center for sound localization and includes the medial superior olive (MSO) for interaural time difference (ITD) and the lateral superior olive (LSO) for interaural level difference (ILD) [2]. This means that the SOC receives information from both ears. One group of nerve fibers innervating SOC comes from the spherical bushy neuron of the anteroventral cochlear nucleus (AVCN), preserving fine temporal information for ITD detection. The spherical bushy neurons have high-threshold potassium channels, but a different kind of potassium channel, i.e., low-threshold potassium channels, to sharpen the waveform of action potentials [5]
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