Electrosensory Research Articles

Sensory coding in oscillatory electroreceptors of paddlefish

Coherence and information theoretic analyses were applied to quantitate the response properties and the encoding of time-varying stimuli in paddlefish electroreceptors (ERs), studied in vivo. External electrical stimuli were Gaussian noise waveforms of varied frequency band and strength, including naturalistic waveforms derived from zooplankton prey. Our coherence analyses elucidated the role of internal oscillations and transduction processes in shaping the 0.5-20 Hz best frequency tuning of these electroreceptors, to match the electrical signals emitted by zooplankton prey. Stimulus-response coherence fell off above approximately 20 Hz, apparently due to intrinsic limits of transduction, but was detectable up to 40-50 Hz. Aligned with this upper fall off was a narrow band of intense internal noise at ∼25 Hz, due to prominent membrane potential oscillations in cells of sensory epithelia, which caused a narrow deadband of external insensitivity. Using coherence analysis, we showed that more than 76% of naturalistic stimuli of weak strength, ∼1 μV∕cm, was linearly encoded into an afferent spike train, which transmitted information at a rate of ∼30 bits∕s. Stimulus transfer to afferent spike timing became essentially nonlinear as the stimulus strength was increased to induce bursting firing. Strong stimuli, as from nearby zooplankton prey, acted to synchronize the bursting responses of afferents, including across populations of electroreceptors, providing a plausible mechanism for reliable information transfer to higher-order neurons through noisy synapses.

Identifying Temporal Codes in Spontaneously Active Sensory Neurons

The manner in which information is encoded in neural signals is a major issue in Neuroscience. A common distinction is between rate codes, where information in neural responses is encoded as the number of spikes within a specified time frame (encoding window), and temporal codes, where the position of spikes within the encoding window carries some or all of the information about the stimulus. One test for the existence of a temporal code in neural responses is to add artificial time jitter to each spike in the response, and then assess whether or not information in the response has been degraded. If so, temporal encoding might be inferred, on the assumption that the jitter is small enough to alter the position, but not the number, of spikes within the encoding window. Here, the effects of artificial jitter on various spike train and information metrics were derived analytically, and this theory was validated using data from afferent neurons of the turtle vestibular and paddlefish electrosensory systems, and from model neurons. We demonstrate that the jitter procedure will degrade information content even when coding is known to be entirely by rate. For this and additional reasons, we conclude that the jitter procedure by itself is not sufficient to establish the presence of a temporal code.

Behavioral responses to weak electric fields and a lanthanide metal in two shark species

The unintentional catch of sharks on hooks intended for other fishes is an economic, environmental and safety concern. Recent research has sought to repel sharks from baited hooks by applying various lanthanide metals and alloys to stimulate the elasmobranch electrosensory system. We present a simplified experimental methodology to test responses of two shark species to a single lanthanide metal. Behavioral responses to prey-simulating, weak electric fields were quantified to establish the sensitivity of the electrosensory system in Squalus acanthias (Linnaeus, 1758) and Mustelus canis (Mitchill, 1815). Both species detected electric fields < 1 nV cm, and responded similarly to other elasmobranchs previously studied. Sharks were then presented with food affixed to treatments of acrylic, stainless steel or neodymium (Nd) metal. S. acanthias only fed in groups and fed from Nd significantly less frequently than from either control. M. canis was tested both individually and in groups and, when alone, fed less from Nd, however, in groups they fed significantly more often from Nd. These results confirm variability in response to a lanthanide metal both across species and within a species in the presence of competition. Since observed differences are not due to differences in sensitivity, other factors appear to influence behavioral responses and may compromise the effectiveness of lanthanide metals for the reduction of shark bycatch.

Two modes of information processing in the electrosensory system of the paddlefish (Polyodon spathula)

Paddlefish are uniquely adapted for the detection of their prey, small water fleas, by primarily using their passive electrosensory system. In a recent anatomical study, we found two populations of secondary neurons in the electrosensory hind brain area (dorsal octavolateral nucleus, DON). Cells in the anterior DON project to the contralateral tectum, whereas cells in the posterior DON project bilaterally to the torus semicircularis and lateral mesencephalic nucleus. In this study, we investigated the properties of both populations and found that they form two physiologically different populations. Cells in the posterior DON are about one order of magnitude more sensitive and respond better to stimuli with lower frequency content than anterior cells. The posterior cells are, therefore, better suited to detect distant prey represented by low-amplitude signals at the receptors, along with a lower frequency spectrum, whereas cells in the anterior DON may only be able to sense nearby prey. This suggests the existence of two distinct channels for electrosensory information processing: one for proximal signals via the anterior DON and one for distant stimuli via the posterior DON with the sensory input fed into the appropriate ascending channels based on the relative sensitivity of both cell populations.

Sparse and dense coding of natural stimuli by distinct midbrain neuron subpopulations in weakly electric fish

While peripheral sensory neurons respond to natural stimuli with a broad range of spatiotemporal frequencies, central neurons instead respond sparsely to specific features in general. The nonlinear transformations leading to this emergent selectivity are not well understood. Here we characterized how the neural representation of stimuli changes across successive brain areas, using the electrosensory system of weakly electric fish as a model system. We found that midbrain torus semicircularis (TS) neurons were on average more selective in their responses than hindbrain electrosensory lateral line lobe (ELL) neurons. Further analysis revealed two categories of TS neurons: dense coding TS neurons that were ELL-like and sparse coding TS neurons that displayed selective responses. These neurons in general responded to preferred stimuli with few spikes and were mostly silent for other stimuli. We further investigated whether information about stimulus attributes was contained in the activities of ELL and TS neurons. To do so, we used a spike train metric to quantify how well stimuli could be discriminated based on spiking responses. We found that sparse coding TS neurons performed poorly even when their activities were combined compared with ELL and dense coding TS neurons. In contrast, combining the activities of as few as 12 dense coding TS neurons could lead to optimal discrimination. On the other hand, sparse coding TS neurons were better detectors of whether their preferred stimulus occurred compared with either dense coding TS or ELL neurons. Our results therefore suggest that the TS implements parallel detection and estimation of sensory input.

Representation of features of electric images caused by objects that are various shapes on electro receptors in electrolocation

Representation of features of electric images caused by objects that are various shapes on electro receptors in electrolocation

Biological smart sensing strategies in weakly electric fish

Biological sensory systems continuously monitor and analyze changes in real-world environments that are relevant to an animal`s specific behavioral needs and goals. Understanding the sensory mechanisms and information processing principles that biological systems utilize for efficient sensory data acquisition may provide useful guidance for the design of smart-sensing systems in engineering applications. Weakly electric fish, which use self-generated electrical energy to actively sense their environment, provide an excellent model system for studying biological principles of sensory data acquisition. The electrosensory system enables these fish to hunt and navigate at night without the use of visual cues. To achieve reliable, real-time task performance, the electrosensory system implements a number of smart sensing strategies, including efficient stimulus encoding, multi-scale virtual sensor arrays, task-dependent filtering and online subtraction of sensory expectation.

Routing the Flow of Sensory Signals Using Plastic Responses to Bursts and Isolated Spikes: Experiment and Theory

Processing complex sensory environments efficiently requires a diverse array of neural coding strategies. Neural codes relying on specific temporal patterning of action potentials may offer advantages over using solely spike rate codes. In particular, stimulus-dependent burst firing may carry additional information that isolated spikes do not. We use the well characterized electrosensory system of weakly electric fish to address how stimulus-dependent burst firing can determine the flow of information in feedforward neural circuits with different forms of short-term synaptic plasticity. Pyramidal cells in the electrosensory lateral line lobe burst in response to low-frequency, local (prey) signals. We show that the ability of pyramidal cells to code for local signals in the presence of additional high-frequency, global (communication) stimuli is uncompromised, while burst firing is reduced. We developed a bursting neuron model to understand how these effects, in particular noise-induced burst suppression, arise from interplay between incoming sensory signals and intrinsic neuronal dynamics. Finally, we examined how postsynaptic target populations preferentially respond to one of the two sensory mixtures (local vs local plus global) depending on whether the populations are in receipt of facilitating or depressing synapses. This form of feedforward neural architecture may allow for efficient information flow in the same neural pathway via either isolated or burst spikes, where the mechanisms by which stimuli are encoded are adaptable and sensitive to a diverse array of stimulus and contextual mixtures.

Coding of electrical signals in different subsystems of the electrosensory system of the weakly electric fish

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Imaging in electrosensory systems

This review addresses the biophysical mechanisms of image formation in electrosensory systems. These electrical images are used for navigation and object detection by many species of fish, some amphibians, and some mammals. In the active electrosensory systems of fish these images are formed by the fish's own electric organ discharge. In the passive electrosensory systems of fish, amphibians and mammals the images are formed by external electrical sources. In this review we describe the biophysics of image formation, the effects of the organism's passive electrical properties, the role of exploration, and the influence of context on electroreception. We suggest that the basic principles established in these specialized systems be useful for understanding other more common sensory systems.

Responses of recurrent nets of asymmetric ON and OFF cells

A neural field model of ON and OFF cells with all-to-all inhibitory feedback is investigated. External spatiotemporal stimuli drive the ON and OFF cells with, respectively, direct and inverted polarity. The dynamic differences between networks built of ON and OFF cells ("ON/OFF") and those having only ON cells ("ON/ON") are described for the general case where ON and OFF cells can have different spontaneous firing rates; this asymmetric case is generic. Neural responses to nonhomogeneous static and time-periodic inputs are analyzed in regimes close to and away from self-oscillation. Static stimuli can cause oscillatory behavior for certain asymmetry levels. Time-periodic stimuli expose dynamical differences between ON/OFF and ON/ON nets. Outside the stimulated region, we show that ON/OFF nets exhibit frequency doubling, while ON/ON nets cannot. On the other hand, ON/ON networks show antiphase responses between stimulated and unstimulated regions, an effect that does not rely on specific receptive field circuitry. An analysis of the resonance properties of both net types reveals that ON/OFF nets exhibit larger response amplitude. Numerical simulations of the neural field models agree with theoretical predictions for localized static and time-periodic forcing. This is also the case for simulations of a network of noisy integrate-and-fire neurons. We finally discuss the application of the model to the electrosensory system and to frequency-doubling effects in retina.

Neural Substrate of an Increase in Sensory Sampling Triggered by a Motor Command in a Gymnotid Fish

Despite recent advances that have elucidated the effects of collateral of motor commands on sensory processing structures, the neural mechanisms underlying the modulation of active sensory systems by internal motor-derived signals remains poorly understood. This study deals with the neural basis of the modulation of the motor component of an active sensory system triggered by a central motor command in a gymnotid fish. In Gymnotus omarorum, activation of Mauthner cells, a pair of reticulospinal neurons responsible for the initiation of escape responses in most teleosts, evokes an abrupt and prolonged increase in the rate of the electric organ discharge (EOD), the output signal of the electrogenic component of the active electrosensory system. We show here that prepacemaker neural structures (PPs) that control the discharge of the command nucleus for EODs are key elements of this modulation. Retrograde labeling combined with injections of glutamate at structures that contain labeled neurons showed that PPs are composed of a bilateral group of dispersed brain stem neurons that extend from the diencephalon to the caudal medulla. Blockade of discrete PPs regions during the Mauthner cell-initiated electrosensory modulation indicate that the long duration of this modulation relied on activation of diencephalic PPs, whereas its peak amplitude depended on the recruitment of medullary PPs. Temporal correlation of motor and sensory consequences of Mauthner cell activation suggests that the Mauthner cell-initiated enhancement of electrosensory sampling is involved in the selection of escape trajectory.

Coding of Stimuli by Ampullary Afferents inGnathonemus petersii

Weakly electric fish use electroreception for both active and passive electrolocation and for electrocommunication. While both active and passive electrolocation systems are prominent in weakly electric Mormyriform fishes, knowledge of their passive electrolocation ability is still scarce. To better estimate the contribution of passive electric sensing to the orientation toward electric stimuli in weakly electric fishes, we investigated frequency tuning applying classical input-output characterization and stimulus reconstruction methods to reveal the encoding capabilities of ampullary receptor afferents. Ampullary receptor afferents were most sensitive (threshold: 40 μV/cm) at low frequencies (<10 Hz) and appear to be tuned to a mix of amplitude and slope of the input signals. The low-frequency tuning was corroborated by behavioral experiments, but behavioral thresholds were one order of magnitude higher. The integration of simultaneously recorded afferents of similar frequency-tuning resulted in strongly enhanced signal-to-noise ratios and increased mutual information rates but did not increase the range of frequencies detectable by the system. Theoretically the neuronal integration of input from receptors experiencing opposite polarities of a stimulus (left and right side of the fish) was shown to enhance encoding of such stimuli, including an increase of bandwidth. Covariance and coherence analysis showed that spiking of ampullary afferents is sufficiently explained by the spike-triggered average, i.e., receptors respond to a single linear feature of the stimulus. Our data support the notion of a division of labor of the active and passive electrosensory systems in weakly electric fishes based on frequency tuning. Future experiments will address the role of central convergence of ampullary input that we expect to lead to higher sensitivity and encoding power of the system.

Spatial stimulation of the electrosensory system of mormyrid electric fish

The long-term goal of this project is to understand adaptive processing in sensory systems. Our work focuses on the electrosensory system of the mormyrid electric fish, a system uniquely suited for the study of adaptive sensory processing. The electrosensory lateral line lobe (ELL) of the mormyrid electric fish presents a special opportunity for examining the influence adaptation on sensory processing because much of the physiology [1] and anatomy [2] has been well characterized. The mormyrid electric fish senses its environment by emitting an electric organ discharge (EOD) and detecting the perturbations that nearby objects cause in the self-generated electric field. Specialized mormyromast electroreceptors sense the self-generated field and its distortions. Afferent fibers from these electroreceptors respond to the fish’s own EOD, and the field strength of the electric field is encoded in the latency of the afferent spike response [3,4]. The electrosensory responses are conveyed with somatotopic precision to the ELL where the fibers terminate [5]. Previous research on electrosensory adaptation has concentrated on point-like electrical fields on the skin. Since the purpose of the electrosensory system is to analyze changes in spatial patterns, we expect that presenting a spatially distributed electrical pattern will lead to a better understanding of adaptive aspects of electrosensory processing in ELL. Thus, we have begun construction of a stimulus device that can present a spatially distributed electrical pattern on the skin of a mormyrid fish. By controlling the patterns that we present, we can simultaneously record from principal cells of ELL to observe changes in responses to spatial patterns. The first phase of our stimulus development program has been to present a low-resolution, 1-dimensional pattern on the fish’s skin. The design was based on an array of vertical rectangles that could be independently controlled to present a spatially varying electrical image along the fish’s skin. We developed electrostatic models to predict fields that would be generated by an array of stimulator pads in water. We have developed an electrical pattern design algorithm that will approximate any given electrical pattern by imposing a set of electrical potentials on the stimulator array. The algorithm will allow flexibility in electrophysiological experimental design to test hypotheses about spatial effects on sensory processing. A cellular modeling component of this study has been developed to predict the responses of individual neurons to stimulation by spatial patterns. Results of our neuronal network models will be compared with experimental measurements of cell responses to the same stimulation to iteratively improve our understanding of mechanisms of electrosensory processing.

Neural Heterogeneities and the coding of contrast envelopes

It is well known that higher order neurons respond to contrast envelopes (second order statistics) present in sensory stimuli. These contrast envelopes can be defined as the curve connecting successive peaks in the stimulus and can only be obtained through a nonlinear transformation of the stimulus such as the Hilbert transform. They contain important information that is decoded by the brain: for example, removal of these envelopes from speech severely reduces its intelligibility. While recent studies have shown potential mechanisms by which higher order neurons can acquire sensitivity to contrast envelopes, it is generally thought that peripheral sensory neurons do not respond to them. Using the electrosensory system of the weakly electric fish as a model we performed extracellular recordings from primary afferents while presenting contrast-modulated random amplitude modulations (AMs) of the fish’s quasi-sinusoidal electric field and found that about 45% of units responded to the time varying contrast envelope. Previous studies have shown that these afferents are spontaneously active and display large heterogeneities in their firing rates and burst firing properties: we therefore investigated whether these heterogeneities are linked to contrast envelope coding. We found that afferents with low spontaneous firing rate responded best to the contrast envelope due to higher levels of rectification. We next investigated the basis of this higher level of rectification using a simple phenomenological model of primary afferent activity. We found that varying levels of intrinsic noise as well as overall bias current in our model could reproduce our experimental results, suggesting that neural heterogeneities can significantly influence contrast envelope coding at the sensory periphery.

Functional origins of the vertebrate cerebellum from a sensory processing antecedent

Abstract The structure of the cerebellar cortex is remarkably similar across vertebrate phylogeny. It is well developed in basal jawed fishes, such as sharks and rays with many of the same cell types and organizational features found in other vertebrate groups, including mammals. In particular, the lattice-like organization of cerebellar cortex (with a molecular layer of parallel fibres, interneurons, spiny Purkinje cell dendrites, and climbing fires) is a common defining characteristic. In addition to the cerebellar cortex, fishes and aquatic amphibians have a variety of cerebellum-like structures in the dorso-lateral wall of the hindbrain. These structures are adjacent to, and in part, contiguous with, the cerebellum. They derive their cerebellum-like name from the presence of a molecular layer of parallel fibers and inhibitory interneurons, which has striking organizational similarities to the molecular layer of the cerebellar cortex. However, these structures also have characteristics which differ from the cerebellum. For example, cerebellum-like structures do not have climbing fibres, and they are clearly sensory. They receive direct afferent input from peripheral sensory receptors and relay their outputs to midbrain sensory areas. As a consequence of this close sensory association, and the ability to characterise their signal processing in a behaviourally relevant context, good progress has been made in determining the fundamental processing algorithm in cerebellar-like structures. In particular, we have come to understand the contribution to signal processing made by the molecular layer, which provides an adaptive filter to cancel self-generated noise in electrosensory and lateral line systems. Given the fundamental similarities of the molecular layer across these structures, coupled with evidence that cerebellum-like structures may have been the evolutionary antecedent of the cerebellum, we address the question: do both share the same functional algorithm?

Freshwater elasmobranchs: a review of their physiology and biochemistry

Only 5% of elasmobranch species live in freshwater (FW) compared to more than 40% of known teleost species. The factors affecting the poor penetration of elasmobranchs into FW environments are currently unknown, however, an important consideration may be the high urea requirement of many proteins in marine elasmobranchs. Urea is an important osmolyte in marine elasmobranchs and must be reduced in dilute environments. There are three identifiable stages in the successful colonization of FW. The euryhaline marine species freely entering and leaving FW represent the initial stage of FW colonization. In this group, there is an apparent inability to eliminate all urea due to protein integrity issues and this results in energy and nitrogen losses that may constrain growth and reproduction. The second stage is represented by those species that live entirely in FW but must also retain some urea. This group also suffers from the same constraints as the first group. These two groups have kidneys and sensory organs that more closely resemble strictly marine forms. The third and final stage is represented by the Potamotrygonid stingrays where the need for urea in FW has been eliminated. Consequently nitrogen and energy losses are reduced and those sections of the kidney needed for urea conservation have been eliminated. The driving force for such modifications is a reduction in urea levels and the concomitant saving of energy needed for urea synthesis. Other physiological adaptations associated with survival in FW include giving birth to live young, the capacity of sperm to be activated in freshwater and modifications of the electrosensory system to function in a low conductivity environment. The need for many anatomical, metabolic and physiological modifications for FW existence may constrain the rapidity and hence the frequency of FW colonization, compared to the situation in the more advanced osmoregulating teleosts. Once optimally adapted to FW, recolonization of sea water by elasmobranchs is problematic due to the loss of urea synthetic capacity and renal structures for urea retention.

Background synaptic activity modulates spike train correlation

Event Abstract Back to Event Background synaptic activity modulates spike train correlation Ashok L. Kumar1*, Maurice J. Chacron2 and Brent Doiron3 1 Carnegie Mellon University, Center for the Neural Basis of Cognition, United States 2 McGill University, Department of Physiology, Canada 3 University of Pittsburgh, Department of Mathematics, United States Sensory neurons have many synaptic inputs, not all of which directly transmit sensory information. Instead, some inputs serve to modulate the neuronal response to relevant stimuli. One example of neural modulation is that the intensity of background synaptic input determines the postsynaptic neuron's leak conductance and membrane potential variability. This in turn controls the gain of its firing rate response to an excitatory stimulus [1]. State dependent gain control in sensory neurons is necessary for proper stimulus processing in low and high contrast environments, and allows attentional state to modulate signal transfer. Most work that characterizes the modulatory influence of background activity has focused on single cell responses, but it is reasonable to expect that such activity may also modulate population responses. We study how background activity shapes correlations between pairs of neurons using simulations, a theory from non-equilibrium statistical mechanics, and data recorded from electrosensory pyramidal neurons in weakly electric fish. We find that increasing background activity can decrease the output spike train correlation of two neurons over long time scales but increase pairwise synchrony on short time scales. We study these effects in simulated integrate-and-fire neurons. Using a linear response theory [2,3], we find that changes in correlation are related to single cell response properties including gain and integration timescale. We first demonstrate these changes in correlation using pairs of model neurons receiving partially correlated conductance-based synaptic activity. The neuron pairs received low or high levels of background activity, and spike train statistics were compared for these two states. We next demonstrate similar state-dependent changes in a recurrent network of neurons in which correlations arise through coupling. Finally, we test our predictions on simultaneously recorded extracellular spike data from primary sensory nucleus in the electrosensory system of weakly electric fish. We induce a state change in the neuronal response properties by driving the animal with stimuli mimicking a prey or a communication signal [4]. Consistent with our theoretical findings, the timescale and correlation of recorded neuron pairs vary depending on these processing states. The findings connect state-dependent changes in single cell response properties, such as firing rate gain, to changes in correlated activity in a neuronal population.

Towards autonomous large scale recordings of natural behavior of weakly electric fish

Event Abstract Back to Event Towards autonomous large scale recordings of natural behavior of weakly electric fish Jörg Henninger1* and Jan Benda1 1 Ludwig-Maximilians-Universität München, Division of Neurobiology, Department Biology II, Germany Weakly electric fish are a well established model system for studying sensory processing in vertebrates, providing great electrophysiological accessibility as well as a concise behavior. These preconditions make it one of the few model systems where electrophysiological data have been successfully discussed in the context of behaviorally relevant stimuli. In order to better understand tuning properties of the electrosensory system, data on the statistical structure that characterizes natural communication signals is needed. However, most behavioral data have been acquired under very restricted lab conditions. We present a novel method that allows to monitor the movement, electric organ discharge (EOD), and communication signals of individual weakly electric fish in their natural habitat. In our proof-of-concept study, we use a setup composed of an evenly spaced grid of 16 electrodes covering up to 9 m2. In a first step, we identify individual fishes by spectral analysis. Fitting a 3D dipole model to the data yields the fishes positions, orientations and EOD strengths. In a second step, the individual fishes EOD is extracted for analysis, e. g. detection of chirps. In a third step, the EOD of all recorded fishes in proximity are integrated at each fish"s position to construct the electric signals each fish receives in context of communication. For the first time, this new method allows to quantitatively analyze the interactions and communication of groups of weakly electric fish in their natural habitat. The method also provides powerful means to cover daily and seasonal changes in communication behavior as well as a novel framework for playback studies. Keywords: computational neuroscience Conference: Bernstein Conference on Computational Neuroscience, Berlin, Germany, 27 Sep - 1 Oct, 2010. Presentation Type: Presentation Topic: Bernstein Conference on Computational Neuroscience Citation: Henninger J and Benda J (2010). Towards autonomous large scale recordings of natural behavior of weakly electric fish. Front. Comput. Neurosci. Conference Abstract: Bernstein Conference on Computational Neuroscience. doi: 10.3389/conf.fncom.2010.51.00005 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 02 Sep 2010; Published Online: 22 Sep 2010. * Correspondence: Dr. Jörg Henninger, Ludwig-Maximilians-Universität München, Division of Neurobiology, Department Biology II, Martinsried, Germany, henninger@bio.lmu.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Jörg Henninger Jan Benda Google Jörg Henninger Jan Benda Google Scholar Jörg Henninger Jan Benda PubMed Jörg Henninger Jan Benda Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Navigation by Induction-Based Magnetoreception in Elasmobranch Fishes

A quantitative frequency-domain model of induction-based magnetoreception is presented for elasmobranch fishes. We show that orientation with respect to the geomagnetic field can be determined by synchronous detection of electrosensory signals at harmonics of the vestibular frequency. The sensitivity required for this compass-sense mechanism is shown to be less than that known from behavioral experiments. Recent attached-magnet experiments have called into doubt the induction-based mechanism for magnetoreception. We show that the use of attached magnets would interfere with an induction-based mechanism unless relative movement between the electrosensory system and the attached magnet is less than 100 μm. This suggests that further experiments may be required to eliminate induction as a basis for magnetoreception.