. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 196 REPORTS FROM THE MBL GENERAL SCIENTIFIC MEETINGS we have evaluated the sensitivity of the auditory midbrain (torus semicircularis, TS) to sound pulses produced at several periodic rates. The stimuli for our previous experiments have been various frequencies of sinusoidal particle motion (described in 3). Here. we have used sound pulses to determine whether cells in the TS are selective for IPI or pulse rate. Fish were anesthetized with 3 uminobenzoic acid (1:1000. Sigma), immobilized with an injection of pancuronium brom
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 196 REPORTS FROM THE MBL GENERAL SCIENTIFIC MEETINGS we have evaluated the sensitivity of the auditory midbrain (torus semicircularis, TS) to sound pulses produced at several periodic rates. The stimuli for our previous experiments have been various frequencies of sinusoidal particle motion (described in 3). Here. we have used sound pulses to determine whether cells in the TS are selective for IPI or pulse rate. Fish were anesthetized with 3 uminobenzoic acid (1:1000. Sigma), immobilized with an injection of pancuronium bromide ( mg/kg); and lidocaine was applied to the skin prior to surgery. After its left midbrain region was exposed, the fish was secured to a seawater-filled dish in the stimulus shaker system (3). Glass micropipettes were broken to obtain low impedance elec- trodes (5-20 megohms) when filled with 4% neurobiotin in 2 M NaCl for determining electrode tip locations. All recordings were made in the left torus semicircularis. The stimulus pulse was a 150-Hz sinusoid multiplied by the first half-cycle (10 ms duration) of a 50-Hz cosine. This produced a pulse as brief as possible, but still having frequency components low enough to stimulate the toadfish auditory system. Pulse trains were produced at 13 repetition rates between 10 and 83 pulses/s, or IPIs of 12-100 ms. The shortest IPI was dictated by the pulse duration (10 ms), because higher rates would have resulted in pulse coincidence. The pulse trains (500-ms duration) were presented 8 times each, in random order, at several levels (peak-peak displace- ment in dB with respect to 1 nm) within a cell's dynamic range. The total number of spikes produced for each set of 8 pulse-train repetitions was measured at each level. Responses were classified as selective or nonselective. A selec- tive unit was defined as one for which the number of spikes evoked by the most effective IPI was at least standard deviation units above the
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
