J Neurophysiol (March 1, 2003). 10.1152/jn.00732.2002
Submitted on Submitted 27 August 2002; accepted in final form 28 October 2002

Synaptic Modulation of the Interspike Interval Signatures of Bursting Pyloric Neurons

Attila Szcs,^1,3 Reynaldo D. Pinto,^1,4 Michail I. Rabinovich,¹ Henry D. I. Abarbanel,^1,2 and Allen I. Selverston¹

 ¹Institute for Nonlinear Science and  ²Department of Physics and Marine Research Laboratory, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0402;  ³Balaton Limnological Research Institute of the Hungarian Academy of Sciences, H-8237 Tihany, Hungary; and  ⁴Instituto de Fisica da Universidade de Sao Paulo, 05315-970, Sao Paulo, Brazil

Szcs, Attila, Reynaldo D. Pinto, Michail I. Rabinovich, Henry D. I. Abarbanel, and Allen I. Selverston. Synaptic Modulation of the Interspike Interval Signatures of Bursting Pyloric Neurons. J. Neurophysiol. 89: 1363-1377, 2003. The pyloric network of the lobster stomatogastric nervous system is one of the best described assemblies of oscillatory neurons producing bursts of action potentials. While the temporal patterns of bursts have been investigated in detail, those of spikes have received less attention. Here we analyze the intraburst firing patterns of pyloric neurons and the synaptic interactions shaping their dynamics in millisecond time scales not performed before. We find that different pyloric neurons express characteristic, cell-specific firing patterns in their bursts. Nonlinear analysis of the interspike intervals (ISIs) reveals distinctive temporal structures (`interspike interval signatures'), which are found to depend on the synaptic connectivity of the network. We compare ISI patterns of the pyloric dilator (PD), lateral pyloric (LP), and ventricular dilator (VD) neurons in 1) normal conditions, 2) after blocking glutamatergic synaptic connections, and 3) in various functional configurations of the three neurons. Manipulation of the synaptic connectivity results in characteristic changes in the ISI signatures of the postsynaptic neurons. The intraburst firing pattern of the PD neuron is regularized by the inhibitory synaptic connection from the LP neuron as revealed in current-clamp experiments and also as reconstructed with a dynamic clamp. On the other hand, mutual inhibition between the LP and VD neurons tend to produce more irregular bursts with increased spike jitter. The results show that synaptic interactions fine-tune the output of pyloric neurons. The present data also suggest a way of processing of synaptic information: bursting neurons are capable of encoding incoming signals by altering the fine structure of their intraburst spike patterns.