Summary
Gnathonemus petersii discriminates between ohmic and capacitive objects. To investigate the sensory basis of this discrimination we recorded from primary afférents that innervate either A or B mormyromast sensory cells. Modified and natural electric organ discharges were used as stimuli. In both A and B fibres frequencies below the peak-power frequency (3.8 to 4.5 kHz) of the electric organ discharge caused minimal first-spike latencies and a maximum number of spikes. A fibres did not discriminate phase-shifted stimuli, whereas B fibres responded significantly with a decrease in first-spike latency if the phase shift was only — 1°. In both A and B fibres an amplitude increase caused a decrease in spike latency and an increase in spike number; an amplitude decrease had the reverse effect. If stimulated with quasi-natural electric organ discharges distorted by capacitive objects, the responses of A fibres decreased with increasing signal distortion. In contrast, the responses of B fibres increased until amplitude effects began to dominate. Gnathonemus may use the physiological differences between A and B fibres to detect and discriminate between capacitive and purely ohmic objects.
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Abbreviations
- ELL:
-
electrosensory lateral line lobe
- EOD:
-
electric organ discharge
- LFS:
-
local filtered signal
- p-p:
-
peak-to-peak
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von der Emde, G., Bleckmann, H. Differential responses of two types of electroreceptive afferents to signal distortions may permit capacitance measurement in a weakly electric fish, Gnathonemus petersii . J Comp Physiol A 171, 683–694 (1992). https://doi.org/10.1007/BF00194116
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DOI: https://doi.org/10.1007/BF00194116