Department Overview:

This Department studies the information processing ability of the nervous system using a variety of experimental techniques and formal theoretical synthesis.
The main activity of the department is scientific research. Our present goal is to find laws describing how the nervous system represents the world and recognizes itself and the bodies under its control as part of an evolving scenario. Our plan is to contribute to the discovery of these laws using the comparative analysis of concrete biological examples and abstracting our findings in formal general theories. The scope of the lab is multidisciplinary, integrating functional and dynamic approaches. We plan to team up a staff able to manage a diversity of techniques from various disciplines. Present research programs and scientific achievements are listed below.
In parallel with research activity, our lab is a workshop for the experimental and theoretical formation of young researchers at the graduate and post-graduate levels. In this aspect we participate in the postgraduate national program PEDECIBA and maintain formal relationships with different Faculties of the Universidad de la República. On November 2004 the Institute of Electrical Engineering of the Universidad de la República and our department international Symposium on Representation of reality by brain and machines.

Present research problem:

The nervous system must solve the so called “inverse problem” to achieve the appropriate motor control, to generate a coherent description of the environment and to make decisions based on the estimated probability of the progress of environmental changes generated by external or self-generated actions. A single scene stimulating the sensory systems of the individual could generate many patterns of neural activity and a single pattern can correspond to different scenarios. Because the finitude of computational resources exhibited by any physical device there are multiple solutions to the inverse problem. However, even the less evolved animals are extremely successful for representing their environment and based on such representations, controlling their movements or generating complex behaviors.
Animals use different strategies for reducing the number of solutions to the inverse problem. Firstly, there is an active control of the flow of sensory images adding self- generated components to the externally generated images or “exafferences”. The sensory input resulting from the combined self- and externally- generated actions is called “reafference”. Secondly, the nervous system extracts the externally generated signals from the whole sensory input subtracting internal predictions of the sensory consequences of the self generated motor acts. The implementation of this task involves center surround interactions, feed forward and feed back loops and long and short term plastic phenomena. Finally, the nervous system organizes behavior based on the opportune and appropriate prediction of the consequence of the self-generated acts in a particular contextual environment. The animal’s perceptual world and ability for transforming it are inextricable and there is not perception without action or appropriate action without perception. Our goal is to find general rules used by different nervous systems to organize the action-perception cycle.

Present experimental model.
The active electrosensory system of electric fish shows the following conditions that make of it an excellent example for studying the action-perception cycle: a) it is accessible at different levels from psychophysics studies to molecular analyses b) it is widely represented among fish and shows an evolutive richness facilitating the identification of common traits and peculiar expressions of single groups. c) it shares with other sensory systems basic principles of brain organization and information processing. An analysis of the contribution of electric fish to the understanding of reafferent system may be found in a recent theoretical article (Caputi, 2004).

Waveform constancy of the emitted carrier makes possible that carrier-tuned cutaneous electroreceptors (Castelló et al, 2000). sense consistently the changes imprinted by the surrounding impedance distribution. Information obtained by electroreceptors is used, among other purposes, to identify the self generated discharge (Castelló et al 1998), to control the intervals interdischarge (time resolution, Caputi et al 2003) and the relative position of the fish and surrounding objects (point of view).

Present research programs:

1) running at the lab are:

a) in vivo study of the action perception cycle including i) the correlation of the experimental changes to the local electric image with changes in the electromotor activity and with the unitary and field potential response responses in the electrosensory lobe in freely moving and curarized fish ii) the generation of dynamic models of the action perception cycle.
b) the anatomical and histochemical study of gymnotus brain using classic techniques, retrograde and intracellular labeling and immunohistochemistry (Funded by PDT, CONICYT, Uruguay to Dr. M. Castelló)
c) the study of the electrosensory lobe cells and their circuitry assemblage using in vitro brain slices preparations (Funded by NIH, USA, through a FIRCA project, in cooperation with Dr. C. Bell).

2) multilateral programs with other labs:

a) modeling of the electric image (long term cooperation with with R. Budelli).
b) integration of motor and electromotor behaviours during electrolocation (with L. Gómez, R. Budelli, R. Canetti, and K. Grant, Funded by PDT, Conicyt, Uruguay and ECOS progran French-Uruguayan agreement),
c) comparative study of the electrosensory lateral line lobe in electric fish (long term cooperation with with C. Bell, K. Grant and O. Trujillo-Cenóz).
d) comparative analysis of the EO and the EOD of the different species of the genus Gymnotus (with O. Trujillo-Cenóz and J. Albert, application pending to NSF)

Scientific production (ask for a reprint):

1. Caputi, A. A Aprendiendo neurobiologia con los peces electricos. Actas de Fisiologia. 5: 109-157.

2. Caputi, A. A The electric organ discharge of pulse gymnotiforms. From a single impulse to a complex electromotor pattern 202: 1229-1241

3. R Budelli and AA Caputi The electric image in weakly electric fish: perception of objects of complex impedance J. Exp. Biol. 203: 481-492.

4. Sicardi, E.A., Caputi, A.A., Budelli, R., Physical basis of distance discrimination in weakly electric fish Physica A, 283, 86-93

5. ME Castello, PA Aguilera, O Trujillo-Cenoz, and AA Caputi. Electroreception in Gymnotus carapo: pre-receptor processing and the distribution of electroreceptor types J. Exp. Biol. 203: 3279-3287.

6. PA Aguilera, ME Castello, and AA Caputi. Electroreception in Gymnotus carapo: differences between self-generated and conspecific-generated signal carriers J. Exp. Biol 204: 185-198.

7. A.A. Caputi M.E.Castelló, P. Aguilera, and O.Trujillo-Cenóz, Peripheral aspects of electrolocation and electrocommunication in G. Carapo. Journal of Physiology - Paris 96: 493–505.

8. R. Budelli, A.A. Caputi, L. Gomez, D. Rother and K. Grant, The electric image in G. Petersii. J. Physiol. (Paris) 96: 421–29

9. A.A. Caputi, P. A. Aguilera, M.E. Castelló, Probability and amplitude of the novelty response as a function of the change in contrast of the reafferent image in Gymnotus carapo. J.Exp Biol. 206: 999-1010.

10. P.A. Aguilera, A. A. Caputi. Electroreception in Gymnotus Carapo: detection of changes in reafferent electrosensory signal waveform J.Exp Biol, 206: 989-998

11. D. Rother, A. Migliaro, R. Canetti, L. Gómez, A. Caputi, R. Budelli. Electric images of two low resistance objects in weakly electric fish. Biosystems 71: 171-179

12. A. A. Caputi. Contribution of electric fish to the understanding of reafferent sensory systems. J. Physiol. (in press).

Book Chapters

1. Lorenzo D, Silva A., Caputi A., Borde M., Macadar O. Electrogeneration in weakly electric fish. In: Sensory biology of jawed fishes. New insights. Oxford & IBH Publishing
Co. Pvt. Ltd.

2. Caputi A.A, Carlson B., Macadar, O. Electric organs and their control In: Electroreception Ed. By T.H.Bullock, C. Hopkins, A.N. Popper and R.R. Fay. Springer
Verlag. (in edition to appear in 2004).

Divulgation

El mundo eléctrico, una invitación a pensar