connectome
In plain wordsA full chart of how a nervous system is wired: which nerve cells, or which brain regions, are linked to which others.
A complete record of which parts of a nervous system are wired to which — individual neurons and their synapses at the microscale, or brain regions and the fiber tracts joining them at the macroscale; connectomics is the field that produces and analyzes such maps. Microscale connectomes are reconstructed from serial-section electron microscopy, today largely by machine learningmachine learning, n.: A way of building software that learns from examples instead of following rules written by a programmer. Shown thousands of labeled photos, for instance, a program can learn to recognize cats. segmentation, since a cubic millimeter of tissue yields petabytes of images. Complete connectomes exist for the nematode worm C. elegans (302 neurons, 1986) and for the adult fruit-fly brain (about 140,000 neurons, 2024), and synapse-level maps cover about a cubic millimeter each of human and mouse cortex. Connectomes inform AI as inspiration for artificial neural networkneural network, n.: A kind of computer program that learns a task from examples by tuning thousands to billions of connections between simple number-crunching units, an arrangement loosely inspired by nerve cells in the brain. architectures, as constraints on models that predict neural activity, and as the proposed starting point for whole brain emulationwhole brain emulation, n.: Copying a particular person's brain into a computer in such detail, down to individual neurons and their connections, that the simulation would think and behave like that person.. A wiring diagram alone does not fix behavior: synaptic strengths, neuromodulators and dynamics also matter.
Wiring the model to match the fly connectome let it predict which visual neurons respond to motion.
Origin
Coined independently in 2005 by Olaf Sporns, Giulio Tononi and Rolf Kötter, in a PLoS Computational Biology paper calling for a map of the human connectome, and by Patric Hagmann in his doctoral thesis, by analogy with 'genome'. Sebastian Seung's book Connectome (2012) popularized the slogan 'you are your connectome'.
Usage note
A connectome is a biological map, not an artificial neural networkneural network, n.: A kind of computer program that learns a task from examples by tuning thousands to billions of connections between simple number-crunching units, an arrangement loosely inspired by nerve cells in the brain., although the two share the vocabulary of neurons and connections. Even the complete C. elegans connectome has not yielded a full simulation of the worm's behavior.
Related
- whole brain emulationwhole brain emulation, n.: Copying a particular person's brain into a computer in such detail, down to individual neurons and their connections, that the simulation would think and behave like that person.
- neural networkneural network, n.: A kind of computer program that learns a task from examples by tuning thousands to billions of connections between simple number-crunching units, an arrangement loosely inspired by nerve cells in the brain.
- mind uploadingmind uploading, n.: The idea of moving a person's mind out of their biological brain and into a computer, so that they could go on living as software.
- neuromorphic computingneuromorphic computing, n.: Computer chips designed to work more like brains, with artificial neurons that send brief spikes only when needed, aiming to do AI tasks with far less energy.
- connectionismconnectionism, n.: The view that minds and intelligent machines are best built from huge networks of simple, neuron-like units whose connection strengths are learned, rather than from explicit rules and symbols.
- artificial neuronartificial neuron, n.: The basic building block of a neural network: a tiny calculator that multiplies each incoming number by a weight, adds them up, and passes the total through a simple function to decide its output.
Sources
- Sporns, O., Tononi, G. & Kötter, R. (2005). The Human Connectome: A Structural Description of the Human Brain. PLoS Computational Biology 1(4).
- White, J. G., Southgate, E., Thomson, J. N. & Brenner, S. (1986). The Structure of the Nervous System of the Nematode Caenorhabditis elegans. Philosophical Transactions of the Royal Society B 314.
- Dorkenwald, S. et al. (2024). Neuronal wiring diagram of an adult brain. Nature 634.