Waveform tuning of electroreceptor cells in the weakly electric fish, Gnathonemus petersii |
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Authors: | G von der Emde H Bleckmann |
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Institution: | Institut für Zoologie, Universit?t Bonn, Poppelsdorfer Schloss, D-53115 Bonn, Germany, Tel.: +49-228 735460; Fax: +49-228 735458 e-mail: Unb308@ibm.rhrz.uni-bonn.de, DE
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Abstract: | Electroreceptive afferents from A- and B-electroreceptor cells of mormyromasts and Knollenorgans were tested for their sensitivity
to different stimulus waveforms in the weakly electric fish Gnathonemus petersii. Both A- and B-mormyromast cells had their lowest sensitivity to a waveform similar to the self-generated electric organ
discharge (EOD) (around 0° phase-shift). Highest sensitivities, i.e. lowest response thresholds, in both A- and B-cells were
measured at phase shifts of +135°. Thus, both cell types were inversely waveform tuned. The sensitivity of B-cells increased
sharply with increasing waveform distortions. Their tuning curves had a sharp minimum of sensitivity at +7° phase shift. A-cells
had a much broader waveform tuning with a plateau level of low sensitivity from +24° to −15°. Across a 360° cycle of phase-shifts,
the range of thresholds was 16 dB for individual B-cells and 4.5 dB for individual A-cells. Knollenorgan afferents were tuned
to 0° phase-shifted EODs and had a dynamic range of 12 dB. Lowest sensitivities were measured at a phase shift of +165°. Experiments
with computer-generated stimuli revealed that the strong sensitivity of mormyromast B-cells of EOD waveform distortions cannot
be attributed to any of the seven waveform parameters tested. In addition, EOD stimuli must have the correct duration for
B-cells to respond to waveform distortions. Thus, waveform tuning appears to be based on the specific combination of several
waveform parameters that occur only with natural EODs.
Accepted: 28 April 1997 |
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Keywords: | Electroreception Mormyromast Knollenorgan Phase-shift Time coding |
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