Phase and amplitude maps of the electric organ discharge of the weakly electric fish, Apteronotus leptorhynchus

Rasnow, Brian; Assad, Christopher; Bower, James M.

doi:10.1007/bf00213530

Cited by 44 publications

(44 citation statements)

References 28 publications

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“…In fact, we have seen that this region had the lowest exterior energy value (see Fig.·4A, green curve; energy rostral of vertical red line is minimal). The importance of skin and body tissues for filtering purposes had been suggested in the past; for example, Rasnow et al hypothesized that this was the reason why the fish's EOD propagates less in the trunk (Rasnow et al, 1993). Our geometrically simple models have allowed us to study conductivity and body shape independently and to verify, for the first time, such hypotheses.…”

Section: Electric Field Characterizationmentioning

confidence: 62%

“…Previous studies have noted that the electric field in the head region of A. leptorhynchus is relatively uniform along the body (Rasnow et al, 1993;Nelson, 2005), but have not investigated its possible origin. In this section, we quantitatively analyze the degree of electric field uniformity and its possible origin for the first time.…”

Section: Electric Field Characterization Filteringmentioning

confidence: 99%

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Modeling the electric field of weakly electric fish

Babineau¹,

Longtin²,

Lewis

2006

Journal of Experimental Biology

104

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SUMMARY Weakly electric fish characterize the environment in which they live by sensing distortions in their self-generated electric field. These distortions result in electric images forming across their skin. In order to better understand electric field generation and image formation in one particular species of electric fish, Apteronotus leptorhynchus, we have developed three different numerical models of a two-dimensional cross-section of the fish's body and its surroundings. One of these models mimics the real contour of the fish; two other geometrically simple models allow for an independent study of the effects of the fish's body geometry and conductivity on electric field and image formation. Using these models, we show that the fish's tapered body shape is mainly responsible for the smooth, uniform field in the rostral region, where most electroreceptors are located. The fish's narrowing body geometry is also responsible for the relatively large electric potential in the caudal region. Numerical tests also confirm the previous hypothesis that the electric fish body acts approximately like an ideal voltage divider; this is true especially for the tail region. Next, we calculate electric images produced by simple objects and find they vary according to the current density profile assigned to the fish's electric organ. This explains some of the qualitative differences previously reported for different modeling approaches. The variation of the electric image's shape as a function of different object locations is explained in terms of the fish's geometrical and electrical parameters. Lastly, we discuss novel cues for determining an object's rostro-caudal location and lateral distance using these electric images.

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Section: Electric Field Characterizationmentioning

confidence: 62%

Section: Electric Field Characterization Filteringmentioning

confidence: 99%

Modeling the electric field of weakly electric fish

Babineau¹,

Longtin²,

Lewis

2006

Journal of Experimental Biology

104

View full text Add to dashboard Cite

show abstract

“…the value obtained in the absence of stimulation). The dipole was located approximately at the center of the animal were the isopotential lines of the electric field are approximately parallel to the skin surface (Rasnow et al, 1993). The stimuli were calibrated to obtain contrasts of 15%, 30%, and 45%.…”

Section: Stimulationmentioning

confidence: 99%

Neural heterogeneities influence envelope and temporal coding at the sensory periphery

Savard¹,

Krahe²,

Chacron³

2011

Neuroscience

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Peripheral sensory neurons respond to stimuli containing a wide range of spatio-temporal frequencies. We investigated electroreceptor neuron coding in the gymnotiform wave-type weakly electric fish Apteronotus leptorhynchus. Previous studies used low to mid temporal frequencies (<256 Hz) and showed that electroreceptor neuron responses to sensory stimuli could be almost exclusively accounted for by linear models, thereby implying a rate code. We instead used temporal frequencies up to 425 Hz, which is in the upper behaviorally relevant range for this species. We show that electroreceptors can: (A) respond up to the highest frequencies tested and (B) display strong nonlinearities in their responses to such stimuli. These nonlinearities were manifested by the fact that the responses to repeated presentations of the same stimulus were coherent at temporal frequencies outside of those contained in the stimulus waveform. Specifically, these consisted of low frequencies corresponding to the time varying contrast or envelope of the stimulus as well as higher harmonics of the frequencies contained in the stimulus. Heterogeneities in the afferent population influenced nonlinear coding as afferents with the lowest baseline firing rates tended to display the strongest nonlinear responses. To understand the link between afferent heterogeneity and nonlinear responsiveness, we used a phenomenological mathematical model of electrosensory afferents. Varying a single parameter in the model was sufficient to account for the variability seen in our experimental data and yielded a prediction: nonlinear responses to the envelope and at higher harmonics are both due to afferents with lower baseline firing rates displaying greater degrees of rectification in their responses. This prediction was verified experimentally as we found that the coherence between the half-wave rectified stimulus and the response resembled the coherence between the responses to repeated presentations of the stimulus in our dataset. This result shows that rectification cannot only give rise to responses to low frequency envelopes but also at frequencies that are higher than those contained in the stimulus. The latter result implies that information is contained in the fine temporal structure of electroreceptor afferent spike trains. Our results show that heterogeneities in peripheral neuronal populations can have dramatic consequences on the nature of the neural code.

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“…These axons have both rostraland caudal-running segments in the electric organ of A. albifrons, which produces a biphasic EOD waveform, but they run only caudally in Sternarchorhamphus, which has a monophasic waveform (Bennett, 1970). Rostro-caudal asynchrony of electric organ firing occurs in some apteronotids and may also influence waveform as it does in some species that produce pulse-type EODs (Caputi, 1999;Rasnow et al, 1993). Studying electric organ morphology and physiology in species with complex EOD waveforms (e.g.…”

Section: Evolution Of Signal Production Mechanismsmentioning

confidence: 99%

Phylogenetic comparative analysis of electric communication signals in ghost knifefishes (Gymnotiformes: Apteronotidae)

Turner

Derylo

Santana

et al. 2007

Journal of Experimental Biology

116

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The evolution of communication behavior, like that of all traits, is shaped both by external forces of natural and sexual selection and by internal forces of development and physiology. Complexity in both the function and production mechanisms of communication signals makes them a powerful model for understanding evolutionary interactions within and across levels of biological organization (Ryan, 2005).Electrocommunication in weakly electric fish is an outstanding model for integrating mechanistic and historical biology (sensu Autumn et al., 2002) because these behaviors are diverse across species, are easily recorded and analyzed, and are controlled by a well-characterized neural circuit. The family Apteronotidae is particularly well-suited for a comparative approach because it has the highest species diversity among Neotropical electric fish (Crampton and Albert, 2006). Apteronotids continuously emit a quasi-sinusoidal voltage signal or electric organ discharge (EOD) that has two functions. Nearby objects locally distort the electric field generated by the EOD, and by detecting these distortions with their electroreceptors, fish can electrolocate. The fish can also use their EODs to communicate by detecting the interactions of their own EOD with those of other fish. Individual apteronotid fish maintain an extremely stable EOD frequency (EODf) (Bullock, 1970;Moortgat et al., 1998) and waveform (Rasnow and Bower, 1996). In addition to using the baseline EOD frequency and waveform as communication signals, fish also modulate the frequency and amplitude of the EOD during social interactions Electrocommunication signals in electric fish are diverse, easily recorded and have well-characterized neural control. Two signal features, the frequency and waveform of the electric organ discharge (EOD), vary widely across species. Modulations of the EOD (i.e. chirps and gradual frequency rises) also function as active communication signals during social interactions, but they have been studied in relatively few species. We compared the electrocommunication signals of 13 species in the largest gymnotiform family, Apteronotidae. Playback stimuli were used to elicit chirps and rises. We analyzed EOD frequency and waveform and the production and structure of chirps and rises. Species diversity in these signals was characterized with discriminant function analyses, and correlations between signal parameters were tested with phylogenetic comparative methods. Signals varied markedly across species and even between congeners and populations of the same species. Chirps and EODs were particularly evolutionarily labile, whereas rises differed little across species. Although all chirp parameters contributed to species differences in these signals, chirp amplitude modulation, frequency modulation (FM) and duration were particularly diverse. Within this diversity, however, interspecific correlations between chirp parameters suggest that mechanistic trade-offs may shape some aspects of signal evolution. In particular, a consistent trade-of...

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Phase and amplitude maps of the electric organ discharge of the weakly electric fish, Apteronotus leptorhynchus

Cited by 44 publications

References 28 publications

Modeling the electric field of weakly electric fish

Modeling the electric field of weakly electric fish

Neural heterogeneities influence envelope and temporal coding at the sensory periphery

Phylogenetic comparative analysis of electric communication signals in ghost knifefishes (Gymnotiformes: Apteronotidae)

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