title: Electric imaging through active electrolocation: implication for the analysis of complex scenes.
abstract: The electric sense of mormyrids is often regarded as an adaptation to conditions unfavourable for vision and in these fish it has become the dominant sense for active orientation and communication tasks. With this sense, fish can detect and distinguish the electrical properties of the close environment, measure distance, perceive the 3-D shape of objects and discriminate objects according to distance or size and shape, irrespective of conductivity, thus showing a degree of abstraction regarding the interpretation of sensory stimuli. The physical properties of images projected on the sensory surface by the fish's own discharge reveal a "Mexican hat" opposing centre-surround profile. It is likely that computation of the image amplitude to slope ratio is used to measure distance, while peak width and slope give measures of shape and contrast. Modelling has been used to explore how the images of multiple objects superimpose in a complex manner. While electric images are by nature distributed, or 'blurred', behavioural strategies orienting sensory surfaces and the neural architecture of sensory processing networks both contribute to resolving potential ambiguities. Rostral amplification is produced by current funnelling in the head and chin appendage regions, where high density electroreceptor distributions constitute foveal regions. Central magnification of electroreceptive pathways from these regions particularly favours the detection of capacitive properties intrinsic to potential living prey. Swimming movements alter the amplitude and contrast of pre-receptor object-images but image modulation is normalised by central gain-control mechanisms that maintain excitatory and inhibitory balance, removing the contrast-ambiguity introduced by self-motion in much the same way that contrast gain-control is achieved in vision.
authors.affiliation: Neuroethology and Sensory Ecology, Institute of Zoology, University of Bonn, Endenicher Allee 11-13, 43115, Bonn, Germany. Jacob.Engelmann@uni-bonn.de
authors.forename: Jacob
authors.initials: J
authors.lastname: Engelmann
authors.forename: João
authors.initials: J
authors.lastname: Bacelo
authors.forename: Michael
authors.initials: M
authors.lastname: Metzen
authors.forename: Roland
authors.initials: R
authors.lastname: Pusch
authors.forename: Beatrice
authors.initials: B
authors.lastname: Bouton
authors.forename: Adriana
authors.initials: A
authors.lastname: Migliaro
authors.forename: Angel
authors.initials: A
authors.lastname: Caputi
authors.forename: Ruben
authors.initials: R
authors.lastname: Budelli
authors.forename: Kirsty
authors.initials: K
authors.lastname: Grant
authors.forename: Gerhard
authors.initials: G
authors.lastname: von der Emde
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D004555:Electric Fish / Q000502:physiology*; D004557:Electric Organ / Q000502:physiology*; D004574:Electromagnetic Fields; D008954:Models, Biological; D012677:Sensation / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D013037:Spatial Behavior / Q000502:physiology*