A Linear Transfer Function underlying Impulse Frequency Modulation in a Cockroach Mechanoreceptor

Abstract

Pringle and Wilson¹ have indicated the potential usefulness in neurophysiology of the linear transfer function concept of the engineering sciences², in their investigation of the dynamic behaviour of the mechano-receptor of the large tactile spine on the femur of the cockroach Periplaneta americana. They have pointed out in particular that adaptation of impulse frequency following a step function stimulus (the step function transient response) and the responses to be expected from stimulation with sinusoidal forcing functions (the steady-state frequency response) are related through the transfer function, and that independent observations made with these two stimulus forms can therefore be compared to test the validity of proposed models of dynamic behaviour. In their work¹, these authors proposed that the present receptor adapts according to a time function containing three exponential terms. However, only a small range of forcing frequencies was available for their frequency response study, and their conclusion was based largely on an interpretation of the adaptation curve. Moreover, the close agreement of their sinusoidal data with this model is evidently due to a miscalculation of three coefficients in their equation (2).