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| Author(s): |
Ludmila Brochini Rodrigues
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física (IF/SBI) |
| Defense date: | 2011-09-20 |
| Examining board members: |
Reynaldo Daniel Pinto;
Nestor Felipe Caticha Alfonso;
Leandro Ramos Souza Barbosa;
Antonio Carlos Cassola;
Sidarta Tollendal Gomes Ribeiro
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| Advisor: | Reynaldo Daniel Pinto |
| Abstract | |
Burst firing is ubiquitous in nervous systems. However, the functional role of burst firing in information coding is mostly unknown. Bursting dynamics have been intensively studied in Central Pattern Generators (CPGs), classical examples of autonomous nervous circuits in which the most conspicuous bursting activity is clearly associated to motor function. Recent studies have investigated small perturbations embedded in the otherwise seemingly periodic bursting: the subtle intra-burst spike timing patterns (IBSPs), traditionally neglected for their lack of relation to the CPG motor function. Moreover, IBSPs were found to be cell-type specific and able to reflect changes in CPG connectivity, indicating a potential role in information coding. Here we addressed this matter by investigating how a bursting motor neuron expresses information about other neurons in the network. We performed experiments on the crustacean stomatogastric pyloric CPG, both in control conditions and when interacting in real-time with computer model neurons. The sensitivity of post- to pre-synaptic IBSPs was inferred by computing their average mutual information along each neuron burst. We found that a single motor neuron is able to express, at the beginning of its burst, information about the IBSPs of the beginning of the pre synaptic neuron\'s burst. This phenomenon is observed in different specimens and species, sugesting a genera information coding mechanism. Moreover, this effect was reproduced in a hybrid circuit, in which the presynaptic stimuli are completely controled by the experimenter free of any influence of other elements in the circuit. These results suggest that the presynaptic spiking microstructure are non-linearly and in homogeneously encoded through a single synapse in the post synaptic IBSPs. This way, motor neurons are able to use different time scales to express two types of information simultaneously: muscle contraction (related to bursting rate), and the behavior of other CPG neurons (in a much smaller timescale by using IBSPs as information carriers). Therefore, the coding mechanism described takes part in a previously unsuspected information pathway, providing evidence of the general physiological role of information coding through IBSPs in the regulation of neuronal _ring patterns in remote circuits by the central nervous system. (AU) | |