Modelling Realistic Generator Circuits of Spontaneous Activity of the Mouse Spinal Cord

Collective spontaneous activity is a commonly reported phenomenon in electrophysiological studies of many areas of the central nervous system; however, the mechanisms underlying the emergence of such activity have received little attention. Recent studies in the spinal cord dorsal horn report collective events in which groups of neurons fire action potentials in a quasi-synchronic way producing population bursts. We proposed that this coordinated activity should originate at neurons with the intrinsic capacity of firing action potentials. Neurons of this kind are found in the dorsal horn, but they tend to produce action potential at regular intervals and high frequency whereas collective events occur at irregular intervals and lower frequencies. The goal of the present research was to test the hypothesis that irregular collective events could be generated by synaptic interactions between neurons with intrinsic firing properties. To this end, we used popular modeling tools to create in silico neurons with similar electrophysiological behavior to that reported in the dorsal horn. Then we formed circuits with these elements and tested the ability of such circuits to produce collective events. Results obtained show that only a few circuits can produce such events. Many of these circuits share common structural and functional elements. These circuits showed a robust behavior which was not affected by external inputs or by changing the number of neurons of the ensemble. The present work supports the hypothesis that collective events as those recorded in the dorsal horn, emerge from neuronal generators formed by neurons with intrinsic firing capacity.