Acoustic Behavior and Reproduction in Five Species of Corydoras Catfishes (Callichthyidae).

determine with certainty whether these recordings were made from For this cell, hypothetical excitatory and inhibitory magnitudes are primary afferent axons or from cells of the DON, response patterns approximately equal at all levels, with the excitatory cosine oriclassified as very sharpened or moderately sharpened (40%) were ented at about 36” to the left front, and the inhibitory cosine never observed in over 400 recordings from saccular afferents (2). oriented at about 34” to the right front. The origin of the putative Further work using intracellular recording and neurobiotin injecinhibition remains to be determined, but could arise from the tion will help resolve this ambiguity. contralateral ear via commissural DON connections (6). Figure 1A illustrates directional response patterns of a representative sharpened DON cell in the horizontal plane. Sharpening is level-independent for this cell and results in a responsiveness maximum oriented about 30” to the left front. Idealized cosine responsiveness functions are illustrated in Figure 1B. Clearly, the directional response of the DON cell is not well modeled by a single cosine function. The directional responses of most sharpened cells in the DON are well modeled by a combination of excitation and inhibition from at least two inputs with cosinusoidal directional response patterns. Fitting excitatory and inhibitory cosinusoidal influences to a cell’s directional response function gives the relative magnitudes and orientations of the hypothetical inputs. Research funded by a National Institutes of Health ROl grant to the Parmly Hearing Institute.