Brain simulation is the concept of creating a functioning computer model of a brain or part of a brain. Brain simulation projects intend to contribute to a complete understanding of the brain, and eventually also assist the process of treating and diagnosing

brain disease Central nervous system diseases, also known as central nervous system disorders, are a group of neurological disorders that affect the structure or function of the brain or spinal cord, which collectively form the central nervous system (CNS). Th ...

s. Various simulations from around the world have been fully or partially released as open source software, such as C. elegans,C. Elegans simulation
Open source software project at Github and the Blue Brain Project Showcase. In 2013 the Human Brain Project, which has utilized techniques used by the Blue Brain Project and built upon them,Human Brain Project, Framework Partnership Agreement https://www.humanbrainproject.eu/documents/10180/538356/FPA++Annex+1+Part+B/41c4da2e-0e69-4295-8e98-3484677d661f created a Brain Simulation Platform (BSP), an internet-accessible collaborative platform designed for the simulation of brain models.

Methods

Modelling a brain (or brain subsystem) involves modelling neurons' electrical and bulk chemical properties (e.g. extracellular

serotonin Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter. Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and vas ...

gradients). A model of the neural connectome of the target organism is also required. The connectome is extremely complex, and its detailed wiring is not yet understood; thus it is presently being modeled empirically in smaller mammals by projects like the Blue Brain Project. The Blue Brain Project intends to create a computer simulation of a mammalian

cortical column A cortical column is a group of neurons forming a cylindrical structure through the cerebral cortex of the brain perpendicular to the cortical surface. The structure was first identified by Mountcastle in 1957. He later identified cortical minicolu ...

down to the molecular level. By one estimate, a full reconstruction of the human connectome using the methodology of the Blue Brain Project would require a zettabyte of data storage.

Examples

Caenorhabditis elegans (roundworm)

The connectivity of the neural circuit for touch sensitivity of the simple C. elegans nematode (roundworm) was mapped in 1985 and partly simulated in 1993. Since 2004, many software simulations of the complete neural and muscular system have been developed, including simulation of the worm's physical environment. Some of these models including source code have been made available for download. However, there is still a lack of understanding of how the neurons and the connections between them generate the surprisingly complex range of behaviors that are observed in the relatively simple organism. This contrast between the apparent simplicity of how the mapped neurons interact with their neighbours, and exceeding complexity of the overall brain function, is an example of an emergent property. This kind of emergent property is paralleled within

artificial neural networks Artificial neural networks (ANNs), usually simply called neural networks (NNs) or neural nets, are computing systems inspired by the biological neural networks that constitute animal brains. An ANN is based on a collection of connected unit ...

, the neurons of which are exceedingly simple compared to their often complex, abstract outputs.

Drosophila neural system

The brain of the fruit fly, Drosophila, has also been thoroughly studied. A simulated model of the fruit fly's brain offers a unique model of sibling neurons. Like the roundworm, this has been made available as open-source software.
Neurokernel open-source fruit fly brain simulation

Mouse brain mapping and simulation

Henry Markram Henry John Markram (born 28 March 1962) is a South African-born Israeli neuroscientist, professor at the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland and director of the Blue Brain Project and founder of the Human Brain Proj ...

mapped the types of neurons within the mouse brain and their connections between 1995 and 2005. In December 2006, the

Blue Brain The Blue Brain Project is a Swiss brain research initiative that aims to create a digital reconstruction of the mouse brain. The project was founded in May 2005 by the Brain and Mind Institute of ''École Polytechnique Fédérale de Lausanne'' (EP ...

project completed a simulation of a rat's neocortical column. The neocortical column is considered the smallest functional unit of the

neocortex The neocortex, also called the neopallium, isocortex, or the six-layered cortex, is a set of layers of the mammalian cerebral cortex involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, sp ...

. The neocortex is the part of the brain thought to be responsible for higher-order functions like conscious thought, and contains 10,000 neurons in the rat brain (and 10⁸

synapse In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell. Synapses are essential to the transmission of nervous impulses from ...

s). In November 2007, the project reported the end of its first phase, delivering a data-driven process for creating, validating, and researching the neocortical column. An artificial neural network described as being "as big and as complex as half of a mouse brain" was run on an IBM Blue Gene supercomputer by the University of Nevada's research team in 2007. Each second of simulated time took ten seconds of computer time. The researchers claimed to observe "biologically consistent" nerve impulses that flowed through the virtual cortex. However, the simulation lacked the structures seen in real mice brains, and they intend to improve the accuracy of the neuron and synapse models. In 2019, Idan Segev, one of the computational neuroscientists working on the Blue Brain Project, gave a talk titled: "Brain in the computer: what did I learn from simulating the brain." In his talk, he mentioned that the whole cortex for the mouse brain was complete and virtual EEG experiments would begin soon. He also mentioned that the model had become too heavy on the supercomputers they were using at the time, and that they were consequently exploring methods in which every neuron could be represented as a neural network (see citation for details).

Blue Brain and the rat

is a project that was launched in May 2005 by IBM and the

Swiss Federal Institute of Technology The Swiss Federal Institutes of Technology are two institutes of higher education in Switzerland (part of the ETH Domain): * Swiss Federal Institute of Technology in Lausanne Swiss may refer to: * the adjectival form of Switzerland *Swiss people ...

in Lausanne. The intention of the project was to create a

computer simulation Computer simulation is the process of mathematical modelling, performed on a computer, which is designed to predict the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be dete ...

of a mammalian cortical column down to the molecular level. The project uses a

supercomputer A supercomputer is a computer with a high level of performance as compared to a general-purpose computer. The performance of a supercomputer is commonly measured in floating-point operations per second ( FLOPS) instead of million instructions ...

based on IBM's Blue Gene design to simulate the electrical behavior of neurons based upon their synaptic connectivity and ion permeability. The project seeks to eventually reveal insights into human cognition and various psychiatric disorders caused by malfunctioning neurons, such as

autism The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental condition (or conditions) characterized by difficulti ...

, and to understand how pharmacological agents affect network behavior.

K computer and human brain

In late 2013, researchers in Japan and Germany used the K computer, then 4th fastest supercomputer, and the simulation software NEST to simulate 1% of the human brain. The simulation modeled a network consisting of 1.73 billion nerve cells connected by 10.4 trillion synapses. To realize this feat, the program recruited 82,944 processors of the K Computer. The process took 40 minutes, to complete the simulation of 1 second of neuronal network activity in real, biological, time.

Human Brain Project

The Human Brain Project (HBP) is a 10-year program of research funded by the European Union. It began in 2013 and employs around 500 scientists across Europe. It includes 6 platforms: * Neuroinformatics (shared databases), *Brain Simulation *High-Performance Analytics and Computing * Medical informatics (patient database) *

Neuromorphic computing Neuromorphic engineering, also known as neuromorphic computing, is the use of electronic circuits to mimic neuro-biological architectures present in the nervous system. A neuromorphic computer/chip is any device that uses physical artificial ne ...

(brain-inspired computing) * Neurorobotics (robotic simulations). The Brain Simulation Platform (BSP) is a device for internet-accessible tools, which allows investigations that are not possible in the laboratory. They are applying Blue Brain techniques to other brain regions, such as the

cerebellum The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebel ...

, hippocampus, and the basal ganglia.

Open source brain simulation

Various models of the brain have been released as open-source software (OSS) and are available on sites such as GitHub, including the C. elegans roundworm, the Drosophila fruit fly, and the human brain models Elysia and Spaun,
spaun2.0 brain simulation which is the world's largest functional brain model and is based on the Neural Engineering Object, NENGO software architecture.Eliasmith, C., Stewart T. C., Choo X., Bekolay T., DeWolf T., Tang Y., Rasmussen, D. (2012). A large-scale model of the functioning brain. Science. Vol. 338 no. 6111 pp. 1202-1205. DOI: 10.1126/science.1225266. The Blue Brain Project Showcase likewise illustrates how models and data from the Blue Brain Project can be converted to

NeuroML NeuroML is an XML (Extensible Markup Language) based model description language that aims to provide a common data format for defining and exchanging models in computational neuroscience. The focus of NeuroML is on models which are based on the bio ...

and PyNN ( Python neuronal network models). The Brain Simulation Platform (BSP) is an internet-accessible

open collaboration Open collaboration is any "system of innovation or production that relies on goal-oriented yet loosely coordinated participants who interact to create a product (or service) of economic value, which is made available to contributors and noncontribu ...

platform for brain simulation, created by the Human Brain Project.

References

{{reflist Computational neuroscience Brain