Neural correlates of frog calling

Summary

Neural activity correlated with electrically-evoked, mating calling movements of the larynx was recorded from the region of the main sensory nucleus of the trigeminal in the northern leopard frog (Figs. 1, 3–5). The probable importance of this area for calling was shown further by the facts that stimulation through an electrode from which correlates had been recorded evoked release calling activity (Fig. 6) and that bilateral, electrolytic lesions through such electrodes abolished electrically-evoked, mating calling movements of the larynx (Fig. 3). The neural correlates survived complete denervation of the brain stem and their patterns were independent of the pattern of the evoking stimulus (Fig. 4). Therefore, the patterns of these correlates were generated within the brain stem. Neural correlates and laryngeal electromyograms typical of mating calling could be recorded after removal of the preoptic area, showing that that structure was not necessary for generation of mating calling patterns (Fig. 5). A revised model of the neural mechanisms of calling is presented (Fig. 8). This model postulates a vocal-phase pulse generator in the region of the main sensory nuclei V. This generator, once triggered, then activates more posterior breathing circuits and modifies their activity to produce calling, rather than breathing movements.