From the Single Synapse to the Neuronal activity: Experimental and Modeling approaches

Synapses are the way neurons share and transmit information among each other. On their activity depends the single neuron code formation. Although very simple in principle, the single synaptic activity is finely regulated by very complex mechanisms both at the pre- and post-synaptic side. The pre-synaptic spike activity, the probability of a single spike to produce the vesicle release, the number of neurotransmitter molecules in the vesicle and its position respect to the centre of the synapse (eccentricity), the pre-synaptic metabotropic receptors and Ca2+ activity are among the pre-synaptic factors. The post-synaptic ones include the number of receptors, their affinity for the neurotransmitter, the synergy of different neurotransmitters, the input resistance of the post synaptic membrane, the Ca2+ channel density and the effects of the retrograde spike diffusion. Some of these factors are strongly activity-dependent. The number of post-synaptic receptors, in fact, change as a function of the synaptic activity producing phenomena like Long Term Potentiation (LTP) and Long Term Depression (LTD) which are the basic mechanisms of memory formation and learning. Other factors are essentially of stochastic nature as, for example, the eccentricity of the vesicle. By the above considerations, it is not surprising that the Post Synaptic Response can have a large variability in its amplitude and duration even in the case of repeated stimulations of the single synapse. The activity of the single neuron depends on the integration of its synaptic inputs in a given time window. The number of Excitatory and Inhibitory synapses and their EPSP (IPSP) frequency, determine the neuronal coding activity. A great challenge of the modern computational neurobiology is the understanding of the correlation between the synaptic inputs (stimuli) and the code formation (neuronal spike sequence). The main focus of the present Special Issue is to collect papers, both of experimental and computational nature, with the most recent achievements related to synaptic transmission, synaptic integration, single neuron activity and neural coding. For this goal, articles related (but not restricted) to the following topics will be welcome.