ELECTROPHYSIOLOGY OF THE CEPHALIC LATERAL-LINE OF THE SURFACE-FEEDINGFISH APLOCHEILUS-LINEATUS

We investigated the responses of primary afferents innervating the cep halic lateral line of the surface-feeding fish Aplocheilus lineatus to sinusoidal surface wave stimuli. All afferents showed ongoing activit y. The degree of spike synchronization with the excitatory phase of a wave cycle and/or the firing rate encoded stimulus amplitude. Modulati on of the fiber's discharge rate usually reflected the waves' frequenc y and thus may be used by the fish to determine stimulus frequency. Di fferent primary afferents may show differences in vibration threshold, frequency sensitivity, phase coupling and dynamic amplitude range. Fi bers innervating different head neuromasts were, however, not consiste ntly different in their average response properties. Therefore, we con clude that the arrangement of the cephalic lateral line of A. lineatus separates the relevant stimulus parameters into distinct channels to only a limited extent, leaving most of the stimulus analysis for centr al processing, and that surface feeding does not involve obvious speci alizations of the peripheral lateral line, compared with midwater fish and surface-feeding amphibians. (C) 1998 Elsevier Science Inc.