Responses of the goldfish trunk lateral line to moving objects

We recorded the responses of single afferent fibers in the posterior lateral-line nerve of the goldfish, Carassius auratus, to a small object moving in the water. Responses consisted of a dominant and reproducible pattern of discharge which was characterized by excitation followed by inhibition or vice versa. The pattern depended on the direction in which the object moved and was inverse when the direction was reversed. About half of the fibers continued to discharge bursts of spikes for a long time after the object had passed the fish. These spike bursts were not reproducible from one stimulus presentation to the next. In many fibers, the pattern of the response changed with speed and lateral distance of the moving object. Response strength increased with increasing object speed and decreasing lateral distance. Measurements of water motions revealed that the object generated complex water movements, aspects of which were reflected in the discharges of primary lateral-line afferents. The observed uniformity of the responses in the periphery suggests that many, but not all, of the response patterns of central lateral-line units to moving objects are due to additional information processing by the central nervous system and not to peripheral hydrodynamic effects.