Responses of the goldfish head lateral line to moving objects

We investigated how fibers in the anterior lateral line nerve of goldfish, Carassius auratus, respond to water motions generated by an object that was moved alongside the fish. Motion direction was from anterior to posterior or opposite, object diameter was between 0.1 and 4 cm and the distance between object and fish varied between 1 and 6 cm. Fibers exhibited monophasic responses characterized by a transient increase in discharge rate, biphasic responses consisting of an increase followed by a decrease in discharge rate or vice versa, or triphasic responses characterized by a rate increase followed by a decrease and again an increase or by the inverse pattern. In two-thirds of the fibers response patterns depended on object motion direction. Of these, about 60% responded to a reversal of motion direction with an inversion of the response pattern. Our results differ from previous data obtained from posterior lateral line nerve fibers in the relative proportions of the observed response patterns, and by a much smaller proportion of fibers that exhibited a direction-dependent response. These differences can be explained by the fact that the spatial orientations of the neuromasts on the head are more heterogenuous than on the trunk.