Modeling the electric field of weakly electric fish

Summary Natural sensory stimuli have a rich spatiotemporal structure and can often be characterized as a high frequency signal that is independently modulated at lower frequencies. This lower frequency modulation is known as the envelope. Envelopes are commonly found in a variety of sensory signals, such as contrast modulations of visual stimuli and amplitude modulations of auditory stimuli. While psychophysical studies have shown that envelopes can carry information that is essential for perception, how envelope information is processed in the brain is poorly understood. Here we review the behavioral salience and neural mechanisms for the processing of envelopes in the electrosensory system of wave-type gymnotiform weakly electric fishes. These fish can generate envelope signals through movement, interactions of their electric fields in social groups or communication signals. The envelopes that result from the first two behavioral contexts differ in their frequency content, with movement envelopes typically being of lower frequency. Recent behavioral evidence has shown that weakly electric fish respond in robust and stereotypical ways to social envelopes to increase the envelope frequency. Finally, neurophysiological results show how envelopes are processed by peripheral and central electrosensory neurons. Peripheral electrosensory neurons respond to both stimulus and envelope signals. Neurons in the primary hindbrain recipient of these afferents, the electrosensory lateral line lobe (ELL), exhibit heterogeneities in their responses to stimulus and envelope signals. Complete segregation of stimulus and envelope information is achieved in neurons in the target of ELL efferents, the midbrain torus semicircularis (Ts).

Section: Introductionmentioning

confidence: 99%

Perception and coding of envelopes in weakly electric fishes

Stamper

Fortune

Chacron

2013

“…Second, the attenuation of the perturbing field with distance means that the electric image is blurred as the distance from the object to the fish increases (Bastian, 1986;Rasnow and Bower, 1996;Rasnow, 1996;Caputi et al, 1998;Budelli and Caputi, 2000;Sicardi et al, 2000;Chen et al, 2005;Gómez et al, 2004;Snyder et al, 2007;Babineau et al, 2006;Pereira and Caputi, 2010). This predicts a reduction of the spatial resolution.…”

Section: Introductionmentioning

confidence: 99%

The active electrosensory range ofGymnotus omarorum

Pereira

Aguilera

Caputi

2012

SUMMARYThis article reports a biophysical and behavioral assessment of the active electrolocation range of Gymnotus omarorum. Physical measurements show that the stimulus field of a point on the sensory mosaic (i.e. the potential positions in which an object may cause a significant departure of the transcutaneous field from basal in the absence of an object) consists of relatively extended volumes surrounding this point. The shape of this stimulus field is dependent on the position of the point on the receptive mosaic and the size of the object. Although the limit of stimulus fields is difficult to assess (it depends on receptor threshold), departure from the basal field decays rapidly, vanishing at about 1.5 diameters for conductive spheres. This short range was predictable from earlier theoretical constructs and experimental data. Here, we addressed the contribution of three different but synergetic mechanisms by which electrosensory signals attenuate with object distance. Using novelty responses as an indicator of object detection we confirmed that the active electrosensory detection range is very short. Behavioral data also indicate that the ability to precisely locate a small object of edible size decays even more rapidly than the ability to detect it. The role of active electroreception is discussed in the context of the fishʼs habitat.

“…These neurons form a gap junction-coupled network and fire synchronous action potentials that propagate via the R axons The voltage map for the fish is based on the model described previously (Babineau et al, 2006;Babineau et al, 2007) for Apteronotus leptorhynchus. Energetic cost of EOD generation to drive the EOD in a one-to-one manner.…”

Section: Electromotor Network: Pacemaker Nucleusmentioning

confidence: 99%

The energetics of electric organ discharge generation in gymnotiform weakly electric fish

Salazar

Krahe

Lewis

2013

Self Cite

SummaryGymnotiform weakly electric fish produce an electric signal to sense their environment and communicate with conspecifics. Although the generation of such relatively large electric signals over an entire lifetime is expected to be energetically costly, supporting evidence to date is equivocal. In this article, we first provide a theoretical analysis of the energy budget underlying signal production. Our analysis suggests that wave-type and pulse-type species invest a similar fraction of metabolic resources into electric signal generation, supporting previous evidence of a trade-off between signal amplitude and frequency. We then consider a comparative and evolutionary framework in which to interpret and guide future studies. We suggest that species differences in signal generation and plasticity, when considered in an energetics context, will not only help to evaluate the role of energetic constraints in the evolution of signal diversity but also lead to important general insights into the energetics of bioelectric signal generation.