Full text
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| Author(s): |
Caroline Garcia Forlim
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física (IF/SBI) |
| Defense date: | 2008-08-27 |
| Examining board members: |
Reynaldo Daniel Pinto;
Angel Ariel Caputi Cavalli;
Coraci Pereira Malta
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| Advisor: | Reynaldo Daniel Pinto |
| Abstract | |
We built an experimental apparatus to measure the electric organ discharge times from weakly electric fishes of the Gymnotus carapo species. Such fishes use these pulses to actively locate objects in water as well as in social communication. Our apparatus was designed to allow such measures in the absence of some external perturbations the fishes are sensitive to, such as mechanical vibrations, electric fields and changes in the laboratory luminosity. A set of eight electrods were installed in the corners of the experimental tank and allows to obtain the discharge times without need to restrain the movements of the fish. Actually, from the maximal amplitudes of the discharge in different elecrodes we can infer the position and movements of the fish and relate its electrical dynamics to its behavior. A computer program (C language) was written to use a digital to analog interface to reproduce the time series of a discharge pulse from a real fish (recorded previously) and this electrical signal was used to stimulate the animals. The artificial pulses were applied to an electrical dipole built to mimic the geometry of the electrical organ of a living fish. The intervals between discharges were chosen from sequences obtained from different distributions: random, sequencies from real living fishes, handled sequencies where we repeated some real patterns with random patterns in between, etc. The detection of the stimuli and response pulses were done in another computer with the software Dasylab and the discharge times sequencies were recorded in harddisk for further analysis. Both sequencies were used to compute the average mutual information between the signals and we verified that different fishes recognize and react (changing their pulse interval pattterns) to the same regions of the real stimuli sequence. We also developed another control program (C language) to detect the discharges of a fish in one tank and to stimulate, in real time, a fish in another tank with those pulses, and viceversa, in a bidirectional way. In this way, the only interaction between the fishes is through their electric pulses. The data analysis also consisted in obtaining the average mutual information between the sequencies of the two fishes and we found evidences that the flow of information is higher than that found in unidirectional experiments. Our apparatus allowed us to succesfully apply information theory to study the dynamics of the discharge intervals when the fishes are interacting. In the future we intend to extensivelly use such experiments to relate the electrical patterns to social behavior and to the interaction of these fishes with their environment. (AU) | |
| FAPESP's process: | 06/02118-5 - In vivo study of the electro-location/communication system of the fish Gymnotus carapo by using complex stimuli, non-linear dynamical systems techniques and information theory |
| Grantee: | Caroline Garcia Forlim |
| Support Opportunities: | Scholarships in Brazil - Master |