Saturating level-response functions

37 3.3 Level response functions of medullary units to pure sine wave stimuli and to amplitude modulated water motions. 3.3.1 Input-output functions to pure sine wave stimuli Extracellular recordings were made from 42 single units in 19 goldfish. As already mentioned (see above), many MON units stimulated with pure sine wave water motions phase locked to the CF of the stimulus. In general, in many units discharge rates and the degree of phase-locking increased with increasing displacement amplitudes of the sphere (Figs. 16-19). In many units, however, discharge rates reached a plateau at stimulus levels above 160 µm (Fig. 17A, 19A) (for an exception see Fig. 16). In most units the degree of phase-locking also reached a plateau at stimulus levels greater than 160 µm (Figs. 17 B, C and 19 B, C). In general, threshold amplitudes of the units varied between 25 µm and 100 µm p-p sphere displacement (Figs. 16-19). In some units level response functions were steep, i.e., in these units discharge rates increased over a narrow range of displacements (50 µm to 160 µm) (c.f. Fig. 17A).