Complexity in Neuronal Networks

The brain can be thought of as a collective ensemble ranging in the spatial domain from microscopic elements (molecules, receptors, ionic channels, synapses) to macroscopic entities (layers, nuclei, cortical areas, neural networks) (Figure 1). The same multi-scale analysis can be replicated in the temporal domain, when decomposing brain activity in a multitude of dynamic processes with time constants ranging from microseconds (molecule transconformation, channel opening) to years (postnatal cell replacement, for example in the bird song system; long-term memories, for example in vertebrate hippocampus). A tantalising challenge to the field of system and computational neuroscience is to bind in a coherent way these different hierarchies of organisation on the basis of experimentally defined descriptors, each of which is endowed with a specific spatio-temporal domain and measurement precision.