The electric image in weakly electric fish: physical images of resistive objects in Gnathonemus petersii.

1998 ◽  
Vol 201 (14) ◽  
pp. 2115-2128 ◽  
Author(s):  
A A Caputi ◽  
R Budelli ◽  
K Grant ◽  
C C Bell
Keyword(s):  
Electric Organ Discharge ◽  
Signal To Noise Ratio ◽  
Electric Organ ◽  
Weakly Electric Fish ◽  
Skin Impedance ◽  
Equivalent Model ◽  
Voltage Profile ◽  
Electric Image ◽  
Weakly Electric ◽  
Gnathonemus Petersii

The present study describes a measurement-based model of electric image generation in the weakly electric mormyrid fish Gnathonemus petersii. Measurements of skin impedance, internal resistivity and fish body dimensions have been used to generate an electrical-equivalent model of the fish and to calculate electrical images and equivalent dipole sources for elementary resistive objects. These calculations allow us to understand how exafferent and reafferent signals are sensed by electroreceptors. An object's electric image consists of the modulation of the transcutaneous voltage profile generated by the fish's own discharge. The results suggest a set of rules for electrolocation: (1) the side of the fish where modulation is larger indicates the side on which the object is situated; (2) the object's position in the electroreceptive field is indicated by the point of maximum modulation of the transcutaneous voltage; (3) the degree of focus of the image indicates the distance to the object. In addition, center-surround opposition originating at pre-receptor level is proposed. Both experimental measurements and modeling indicate that fish skin impedance is relatively low (400-11 000 <IMG src="/images/symbols/capomega.gif" WIDTH="13" HEIGHT="13" ALIGN="BOTTOM" NATURALSIZEFLAG="3">cm<SUP>2</SUP>) and mainly resistive. This low skin impedance appears to enhance the local electric organ discharge modulation, the center-surround effect, the signal-to-noise ratio for electrolocation and the active space for electrocommunication.

The electric image in weakly electric fish: perception of objects of complex impedance

2000 ◽  
Vol 203 (3) ◽  
pp. 481-492 ◽  
Author(s):  
R. Budelli ◽  
A.A. Caputi
Keyword(s):  
Linear Function ◽  
Electric Organ Discharge ◽  
Amplitude Ratio ◽  
Complex Impedance ◽  
Electric Organ ◽  
Weakly Electric Fish ◽  
Peak Amplitude ◽  
Electrical Characteristics ◽  
Electric Image ◽  
Weakly Electric

Weakly electric fish explore the environment using electrolocation. They produce an electric field that is detected by cutaneous electroreceptors; external objects distort the field, thus generating an electric image. The electric image of objects of complex impedance was investigated using a realistic model, which was able to reproduce previous experimental data. The transcutaneous voltage in the presence of an elementary object is modulated in amplitude and waveform on the skin. Amplitude modulation (measured as the relative change in the local peak-to-peak amplitude) consists of a ‘Mexican hat’ profile whose maximum relative slope depends on the distance of the fish from the object. Waveform modulation depends on both the distance and the electrical characteristics of the object. Changes in waveform are indicated by the amplitude ratio of the larger positive and negative phases of the local electric organ discharge on the skin. Using the peak-to-peak amplitude and the positive-to-negative amplitude ratio of this discharge, a perceptual space can be defined and correlated with the capacitance and resistance of the object. When the object is moved away, the perceptual space is reduced but keeps the same proportions (homothetically): for a given object, the positive-to-negative amplitude ratio is a linear function of the peak-to-peak amplitude. This linear function depends on the electrical characteristics of the object. However, there are ‘families’ of objects with different electrical characteristics that produce changes in the parameters of the local electric organ discharge that are related by the same linear function. We propose that these functions code the perceptual properties of an object related to its impedance.

Bio-Inspired Active Electrolocation Sensors for Inspection of Tube Systems

2012 ◽  
Vol 84 ◽  
pp. 45-50 ◽  
Author(s):  
Martin Gottwald ◽  
Gerhard von der Emde
Keyword(s):  
Blood Vessels ◽  
Electric Fields ◽  
Skin Surface ◽  
Ring Electrode ◽  
Weakly Electric Fish ◽  
Atherosclerotic Lesions ◽  
Electric Image ◽  
Coronary Blood Vessels ◽  
Weakly Electric ◽  
Gnathonemus Petersii

At night, weakly electric fish Gnathonemus petersii use active electrolocation to scan their environment with self generated electric fields. Nearby objects distort the electric fields and are recognized as electric images on the electroreceptive skin surface of the animal. By analyzing the electric image, G. petersii can sense an object’s distance, dimensions and electrical properties. The principles and algorithms of active electrolocation can be applied to catheter-based sensor systems for analysing wall changes in fluid filled tube systems, for example atherosclerotic plaques of the coronary blood vessels. We used a basic atherosclerosis model of synthetic blood vessels and plaques, which were scanned with a ring electrode catheter applying active electrolocation. Based on the electric images of the plaques and the evaluation of bio-inspired image parameters, the plaque’s fine-structure could be assessed. Our results show that imaging through active electrolocation principally has the potential to detect and characterize atherosclerotic lesions.

Evoked chirping in the weakly electric fish Apteronotus leptorhynchus: a quantitative biophysical analysis

1993 ◽  
Vol 71 (11) ◽  
pp. 2301-2310 ◽  
Author(s):  
Günther K. H. Zupanc ◽  
Leonard Maler
Keyword(s):  
Electric Organ Discharge ◽  
Electric Organ ◽  
Stimulus Onset ◽  
Weakly Electric Fish ◽  
Apteronotus Leptorhynchus ◽  
Biophysical Analysis ◽  
Absolute Amplitude ◽  
Electric Organ Discharges ◽  
Gymnotiform Fish ◽  
Weakly Electric

Apteronotus leptorhynchus, a gymnotiform fish, produces highly regular electric organ discharges of 600–1000 Hz. Short-term modulations of the electric organ discharge ("chirps") were elicited by imitating the discharges of neighboring fish. Chirps displayed an increase in frequency of approximately 100 Hz, a duration of about 15 ms, and an absolute amplitude of 0.5–2 mV. Since, similar to natural conditions, chirps summated with the beat caused by interference of the fish's own electric organ discharge and the imitating discharge, the size and shape of the chirp's amplitude envelope varied greatly according to its phase relative to the beat cycle; however, the frequency of the chirp amplitude modulation was always 50–100 Hz. All 21 males examined chirped, but their rate of chirping varied considerably (range 2–59 chirps/30 s; mean 22 chirps/30 s). In contrast, only one out of nine females chirped (mean 0.25 chirps/30 s). The latency between stimulus onset and first chirp was variable and often long (range 1.0–25.0 s; median 3.3 s). We propose that chirps are not a sensory reflex but a communicatory behavior regulated by hypothalamic peptidergic input.

scholarly journals Electrical signalling of dominance in a wild population of electric fish

2010 ◽  
Vol 7 (2) ◽  
pp. 197-200 ◽  
Author(s):  
Vincent Fugère ◽  
Hernán Ortega ◽  
Rüdiger Krahe
Keyword(s):  
High Frequency ◽  
Electric Fish ◽  
Electric Organ Discharge ◽  
Low Frequency ◽  
Electric Organ ◽  
Weakly Electric Fish ◽  
Dominance Status ◽  
Strong Positive Relationship ◽  
Electrical Signalling ◽  
Weakly Electric

Animals often use signals to communicate their dominance status and avoid the costs of combat. We investigated whether the frequency of the electric organ discharge (EOD) of the weakly electric fish, Sternarchorhynchus sp., signals the dominance status of individuals. We correlated EOD frequency with body size and found a strong positive relationship. We then performed a competition experiment in which we found that higher frequency individuals were dominant over lower frequency ones. Finally, we conducted an electrical playback experiment and found that subjects more readily approached and attacked the stimulus electrodes when they played low-frequency signals than high-frequency ones. We propose that EOD frequency communicates dominance status in this gymnotiform species.

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