In addition, neural structures within the same individual vary across time, as a result of experiential and developmental processes of growth, plasticity and repair. Variability may be measured between corresponding structures in brains of individuals of the same species. Variability is found in the shape of individual neurons and their processes, as well as in the size, placement and interconnection of large-scale structures.
Specificity is found in the arrangement of individual synaptic connections between morphologically and physiologically distinct neuronal types, in the spatial extent and branching pattern of axonal arborizations, and in long-range connectivity between neural structures such as cell nuclei or brain regions. At the macroscale, very large numbers of neurons and neuronal populations forming distinct brain regions are interconnected by inter-regional pathways, forming large-scale patterns of anatomical connectivity.Īnatomical connections at all levels of scale are both specific and variable. At the mesoscale, they are arranged into networks of columns and minicolumns. At the microscale, detailed anatomical and physiological studies have revealed many of the basic components and interconnections of microcircuits in the mammalian cerebral cortex. These levels include individual synaptic connections that link individual neurons at the microscale, networks connecting neuronal populations at the mesoscale, as well as brain regions linked by fiber pathways at the macroscale. In more highly evolved nervous systems, brain connectivity can be described at several levels of scale.
Neural connectivity patterns have long attracted the attention of neuroanatomists ( Cajal, 1909 Brodmann, 1909 Swanson, 2003) and play crucial roles in determining the functional properties of neurons and neuronal systems.
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