Neural Communication II: Firing Rate and Information Encoding

Abstract

Neural information is a frequency encoded in the rate of action potentials. Neuronal postsynaptic potentials determine the action potential firing rate, and conversely, the action potential rate of input neurons determines the magnitude of the postsynaptic potentials or the magnitude of the response of an end organ. This is a complementary pair of modulation and demodulation processes. By demodulating the recorded firing of a sensory nerve, we can determine the sensory input that generated the action potential sequence. This is particularly interesting when demodulation of the firing rate leads to studying the dynamics of sensory receptors, muscle units, and even autonomic function. Therefore, the physiological study of neural interaction requires the calculation of instantaneous firing rate thereby deducing the stimulus to the primary process generating the action potential sequence. In order to do this, we need to understand the modulation process and then apply the appropriate demodulation process. In this chapter, frequency modulation and pulse modulation techniques are discussed with reference to action potential sequences. One interesting application of such demodulation is in the study of heart rate variability.

Information is the resolution of uncertainty.

– Claude Shannon