ABSTRACT
Transduction, the process by which environmental stimuli are converted into neural signals, is a multistage process with important steps occurring at both the macroscopic and cellular levels. Before the actual conversion of energies (and energy conversion is the essential feature of transduction), each of the receptor organs carries out some nonneural or preneural modification of the incoming stimulus. The eye, for example, modulates the intensity of a photic stimulus by varying the pupil size. It also filters the light, since some wavelengths are selectively absorbed by the ocular media. Preneural modifications also occur in the mechanical receptors. The ear modulates auditory stimulus intensity by means of a system of membranes, muscles, and levers. Far more important, however, is the preneural conversion of the temporal patterns of acoustic energy to mechanical spatial patterns as a function of the hydrodynamics of the cochlea. This important alteration of dimensions is carried out on an entirely mechanical and totally nonneural basis.
