Auditory responses in a vocal nucleus of the leopard frog Rana pipiens: Characterization and effects of hormones

Abstract

Auditory-evoked responses of single neurons were studied in the pretrigeminal nucleus of leopard frogs; this nucleus is involved in the control of vocal output [R. S. Schmidt, J. Comp. Physiol. 108, 99–113 (1976)]. Frogs receiving hormone treatment (human chorionic gonadotropin, 25 u subcutaneously daily for 5 to 14 days) and untreated frogs were used. There was a significantly greater probability (chi-squared = 9.66, df = 1, p < 0.01) of encountering auditory activity in this nucleus in hormone-treated frogs, but there was no apparent difference between the groups in the characteristics of the evoked activity. Most units showed V-shaped tuning curves with best excitatory frequencies ranging from 350–1100 Hz, thresholds from 31–87 dB SPL, and Q(10 dB) from 1.2–5.1. Response latencies varied from 10–50 ms and dynamic ranges from 20–40 dB. Both phasic and tonic response patterns were seen. Approximately 10% of the units would not respond to pure tones except at intensities above 100 dB; these units would respond to white noise, with thresholds between 50 and 70 dB SPL. This auditory input to the vocal system may play a role in acoustically evoked mate calling. [Supported by N.I.H.]