Towards an alphabet of motor patterns in active electrolocation behavior of Gnathonemus petersii
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1
University of Bielefeld, Faculty of Biology, Germany
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2
Universidad de la Republica, Facultad de Ciencias, Uruguay
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3
Georg-August-Universität Göttingen, Schwann-Schleiden Research Center, Germany
Weakly electric fish, in our study the Mormyrid Gnathonemus petersii, build up an electric field surrounding their body by emitting pulse like discharges with an electric organ located in their tail. The local amplitude of this dipole field varies, resulting in a basal intensity distribution over the body of the fish. This is perceived by an array of electroreceptors in the skin. Objects within the dipole field alter the field locally. By analyzing these modulations of the basal intensity distribution (termed electric image), Gnathonemus analyses objects in the environment during navigational or prey capture behavior.
In natural electrolocation behavior electric images are subjected to contextual changes when the relative spatial configuration between a fish and an object changes. In contrast to this, measurements of electric images were mostly restricted to static configurations since fish had to be immobilized for recordings. How spatiotemporal changes in electric images affect the information available for electrolocation is therefore elusive for Mormyrids. To overcome these limitations, we here apply 2D video-tracking with a theoretical model previously verified to produce reliable estimations of electric images. We filmed unrestrained Gnathonemus during object exploration (metal cubes of 1, 8 and 27 cm3) in an IR-illuminated tank, triggering the video acquisition by the animals own electric organ discharges. Thereby we gather detailed spatial and temporal information linked to the pace of the animals sensing interval.
2D-body kinematics (thrust, slip and yaw velocities) as well as the spatial relationship between the fish and the object (distance, angle, body posture, etc.) were extracted from the videos (custom written Matlab routines). To identify behavioral prototypes and to describe the sequence of behaviors during natural object exploration, body kinetics were subjected to a k-means clustering. Using the resulting behavioral alphabet we can reconstruct motor patterns that build up object exploration behavior, e.g. chin probing or va-et-vient movements (see figure). In conjunction with the electric images modeled at the instance of each EOD we can examine the impact of specific movements during behavioral sequences on the sensory input. This will allow a quantitative approach to understand how ego-motion affects or might be used to optimize sensory input with respect to behavioral tasks. Thus this is the first study considering the impact of electrolocation behavior on sensory information in a temporal and context-dependent manner.
Keywords:
behavioral clustering,
electric image,
electrolocation,
object exploration,
spatiotemporal analysis
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster (but consider for student poster award)
Topic:
Sensory: Electrosensory
Citation:
Hofmann
V,
Sanguinetti-Scheck
JI,
Geurten
BR,
Gómez-Sena
L and
Engelmann
J
(2012). Towards an alphabet of motor patterns in active electrolocation behavior of Gnathonemus petersii.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00301
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Received:
30 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Mr. Volker Hofmann, University of Bielefeld, Faculty of Biology, Bielefeld, 33501, Germany, volker.hofmann@mail.mcgill.ca