Peripheral lateral line responses to amplitude-modulated sinusoidal wave stimuli

This report describes the responses of single afferent fibers in the poster ior lateral line nerve of the goldfish, Carassius auratus, to pure tone and to amplitude-modulated sinusoidal wave stimuli generated by a dipole sourc e (stationary vibrating sphere). Responses were characterized in terms of o utput-input functions relating responses to vibration amplitude, peri-stimu lus time histograms relating responses to stimulus duration, and the degree of phase-locking to both the carrier frequency and the modulation frequenc y of the amplitude-modulated stimulus. All posterior lateral line nerve fib ers responded to a pure sine wave with sustained and strongly phase-locked discharges. When stimulated with amplitude-modulated sine waves, fibers res ponded with strong phase-locking to the carrier frequency and, in addition, discharge rates were modulated according to the amplitude modulation frequ ency. However, phase-locking to the amplitude modulation frequency was weak er than phase-locking to the carrier frequency. The data indicate that the discharges of primary lateral line afferents encode both the carrier freque ncy and the modulation frequency of an amplitude-modulated wave stimulus.