A universal model of single-unit sensory receptor action

We present a model governing the operation of all “isolated” sensory receptors with their primary afferent neurons. The input to the system is the intensity of a sensory signal, be it chemical, optical etc., and the output is the rate of neural impulse transmission in the afferent neuron. The model is based on the premise that information is conserved when transmitted by an efficient sensory channel. Earlier studies on this informational or entropic model of receptor function were constrained to the cases where the sensory stimulus assumed the form of an infinite step function. The theory was quite successful in treating mathematically all responses to such elementary sensory stimuli—both neural, and by extension, psychophysical. For example, the theory unified the logarithmic and power laws of sensation. However, the earlier model was incapable of predicting responses to time-varying stimuli. The generalized model, which we present here, accounts for both steady and time-varying signals. We show that more intense stimuli are remembered by sensory receptors for longer periods of time than are less intense stimuli.