Dear Colleagues: The following paper was just published in JEB: http://jeb.biologists.org/cgi/content/abstract/215/17/3055 Evoked-potential audiogram of an Indo-Pacific humpback dolphin (Sousa chinensis). Songhai Li, Ding Wang, Kexiong Wang, Elizabeth A. Taylor, Emilie Cros, Wenjing Shi, Zhitao Wang, Liang Fang, Yuefei Chen, and Fanming Kong. J Exp Biol 2012;215 3055-3063 SUMMARY An evoked-potential audiogram was measured for an Indo-Pacific humpback dolphin (Sousa chinensis) living in the dolphinarium of Nanning Zoo, China. Rhythmic 20 ms pip trains composed of cosine-enveloped 0.25 ms tone pips at a pip rate of 1 kHz were presented as sound stimuli. The dolphin was trained to remain still at the water surface and to wear soft latex suction-cup EEG electrodes used to measure the animal's envelope-following evoked potentials to the sound stimuli. Responses to 1000 rhythmic 20 ms pip trains for each amplitude/frequency combination were averaged and analysed using a fast Fourier transform to obtain an evoked auditory response. The hearing threshold was defined as the zero crossing point of the response input�output function using linear regression. Fourteen frequencies ranging from 5.6 to 152 kHz were studied. The results showed that most of the thresholds were lower than 90 dB re. 1 �Pa (r.m.s.), covering a frequency range from 11.2 to 128 kHz, and the lowest threshold of 47 dB was measured at 45 kHz. The audiogram, which is a function of hearing threshold versus stimulus carrier frequency, presented a U-shape with a region of high hearing sensitivity (within 20 dB of the lowest threshold) between approximately 20 and 120 kHz. At frequencies lower than this high-sensitivity region, thresholds increased at a rate of approximately 11 dB octave�1 up to 93 dB at 5.6 kHz. The thresholds at high frequencies above 108 kHz increased steeply at a rate of 130 dB octave�1 up to 127 dB at 152 kHz. If you are interested in a pdf copy, please send an email to lish@ihb.ac.cn or tmsshl@nus.edu.sg Best Regards Songhai Li Ph.D 2012-08-09