From Cajal to Connectome and Beyond

Annu Rev Neurosci. 2016 Jul 8;39:197-216. doi: 10.1146/annurev-neuro-071714-033954.


One goal of systems neuroscience is a structure-function model of nervous system organization that would allow mechanistic linking of mind, brain, and behavior. A necessary but not sufficient foundation is a connectome, a complete matrix of structural connections between the nodes of a nervous system. Connections between two nodes can be described at four nested levels of analysis: macroconnections between gray matter regions, mesoconnections between neuron types, microconnections between individual neurons, and nanoconnections at synapses. A long history of attempts to understand how the brain operates as a system began at the macrolevel in the fifth century, was revolutionized at the meso- and microlevels by Cajal and others in the late nineteenth century, and reached the nanolevel in the mid-twentieth century with the advent of electron microscopy. The greatest challenge today is extracting knowledge and understanding of nervous system structure-function architecture from vast amounts of data.

Keywords: big data; nervous system; network analysis; neural connections.

Publication types

  • Review

MeSH terms

  • Animals
  • Brain / physiology*
  • Connectome* / methods
  • Humans
  • Models, Neurological
  • Neural Pathways / physiology*
  • Neurons / physiology*
  • Synapses / physiology*