Brain mapping is a set of

neuroscience Neuroscience is the scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system), its functions, and its disorders. It is a multidisciplinary science that combines physiology, anatomy, molecular biology, ...

techniques predicated on the mapping of (biological) quantities or properties onto spatial representations of the (human or non-human)

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

resulting in

map A map is a symbolic depiction of interrelationships, commonly spatial, between things within a space. A map may be annotated with text and graphics. Like any graphic, a map may be fixed to paper or other durable media, or may be displayed on ...

s. According to the definition established in 2013 by

Society for Brain Mapping and Therapeutics The International Brain Mapping and Intraoperative Surgical Planning Society (IBMISPS-Tax ID 20-2793206) DBA The Society for Brain Mapping and Therapeutics (SBMT) is a non-profit biomedical association (501c6) principally concerned with Brain Map ...

(SBMT), brain mapping is specifically defined, in summary, as the study of the

anatomy Anatomy () is the branch of morphology concerned with the study of the internal structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old scien ...

and function of the brain and

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

through the use of

imaging Imaging is the representation or reproduction of an object's form; especially a visual representation (i.e., the formation of an image). Imaging technology is the application of materials and methods to create, preserve, or duplicate images. ...

immunohistochemistry Immunohistochemistry is a form of immunostaining. It involves the process of selectively identifying antigens in cells and tissue, by exploiting the principle of Antibody, antibodies binding specifically to antigens in biological tissues. Alber ...

molecular A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry, ...

optogenetics Optogenetics is a biological technique to control the activity of neurons or other cell types with light. This is achieved by Gene expression, expression of Channelrhodopsin, light-sensitive ion channels, Halorhodopsin, pumps or Photoactivated ade ...

stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell ...

and

cellular biology Cell biology (also cellular biology or cytology) is a branch of biology that studies the Anatomy, structure, Physiology, function, and behavior of cell (biology), cells. All living organisms are made of cells. A cell is the basic unit of life th ...

engineering Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, s ...

neurophysiology Neurophysiology is a branch of physiology and neuroscience concerned with the functions of the nervous system and their mechanisms. The term ''neurophysiology'' originates from the Greek word ''νεῦρον'' ("nerve") and ''physiology'' (whic ...

and

nanotechnology Nanotechnology is the manipulation of matter with at least one dimension sized from 1 to 100 nanometers (nm). At this scale, commonly known as the nanoscale, surface area and quantum mechanical effects become important in describing propertie ...

. In 2024, a team of 287 researchers completed a full brain mapping of an adult animal (a ''

Drosophila melanogaster ''Drosophila melanogaster'' is a species of fly (an insect of the Order (biology), order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly", "pomace fly" ...

'', or fruit fly) and published their results in ''Nature''.

Overview

All

neuroimaging Neuroimaging is the use of quantitative (computational) techniques to study the neuroanatomy, structure and function of the central nervous system, developed as an objective way of scientifically studying the healthy human brain in a non-invasive ...

is considered part of brain mapping. Brain mapping can be conceived as a higher form of neuroimaging, producing brain images supplemented by the result of additional (imaging or non-imaging) data processing or analysis, such as maps projecting (measures of) behavior onto brain regions (see

fMRI Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area o ...

). One such map, called a

connectogram Connectograms are graphical representations of connectomics, the field of study dedicated to mapping and interpreting all of the white matter fiber connections in the human brain. These circular graphs based on diffusion MRI data utilize graph theo ...

, depicts cortical regions around a circle, organized by lobes. Concentric circles within the ring represent various common neurological measurements, such as cortical thickness or curvature. In the center of the circles, lines representing white matter fibers illustrate the connections between cortical regions, weighted by

fractional anisotropy Fractional anisotropy (FA) is a scalar (mathematics), scalar value between zero and one that describes the degree of anisotropy of a diffusion process. A value of zero means that diffusion is isotropic, i.e. it is unrestricted (or equally restricted ...

and strength of connection. At higher resolutions brain maps are called connectomes. These maps incorporate individual neural connections in the brain and are often presented as wiring diagrams. Brain mapping techniques are constantly evolving, and rely on the development and refinement of image acquisition, representation, analysis, visualization and interpretation techniques. Functional and structural neuroimaging are at the core of the mapping aspect of brain mapping. Some scientists have criticized the brain image-based claims made in

scientific journals Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. Modern science is typically divided into twoor threemajor branches: the natural sciences, which stu ...

and the popular press, like the discovery of "the part of the brain responsible" things like love or musical abilities or a specific memory. Many mapping techniques have a relatively low resolution, including hundreds of thousands of neurons in a single

voxel In computing, a voxel is a representation of a value on a three-dimensional regular grid, akin to the two-dimensional pixel. Voxels are frequently used in the Data visualization, visualization and analysis of medical imaging, medical and scient ...

. Many functions also involve multiple parts of the brain, meaning that this type of claim is probably both unverifiable with the equipment used, and generally based on an incorrect assumption about how brain functions are divided. It may be that most brain functions will only be described correctly after being measured with much more fine-grained measurements that look not at large regions but instead at a very large number of tiny individual brain circuits. Many of these studies also have technical problems like small sample size or poor equipment calibration which means they cannot be reproduced - considerations which are sometimes ignored to produce a sensational journal article or news headline. In some cases the brain mapping techniques are used for commercial purposes,

lie detection Lie detection is an assessment of a verbal statement with the goal to reveal a possible intentional deceit. Lie detection may refer to a cognitive process of detecting deception by evaluating message content as well as non-verbal cues. It also may r ...

, or medical diagnosis in ways which have not been scientifically validated.

History

In the late 1980s in the United States, the Institute of Medicine of the National Academy of Science was commissioned to establish a panel to investigate the value of integrating neuroscientific information across a variety of techniques. Of specific interest is using structural and

functional magnetic resonance imaging Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area o ...

(fMRI),

diffusion MRI Diffusion-weighted magnetic resonance imaging (DWI or DW-MRI) is the use of specific MRI sequences as well as software that generates images from the resulting data that uses the diffusion of water molecules to generate contrast (vision), contrast ...

(dMRI),

magnetoencephalography Magnetoencephalography (MEG) is a functional neuroimaging technique for mapping brain activity by recording magnetic fields produced by electric current, electrical currents occurring naturally in the human brain, brain, using very sensitive magn ...

(MEG), electroencephalography ( EEG),

positron emission tomography Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, r ...

(PET),

Near-infrared spectroscopy Near-infrared spectroscopy (NIRS) is a spectroscopic method that uses the near-infrared region of the electromagnetic spectrum (from 780 nm to 2500 nm). Typical applications include medical and physiological diagnostics and research inc ...

(NIRS) and other non-invasive scanning techniques to map

physiology Physiology (; ) is the science, scientific study of function (biology), functions and mechanism (biology), mechanisms in a life, living system. As a branches of science, subdiscipline of biology, physiology focuses on how organisms, organ syst ...

perfusion Perfusion is the passage of fluid through the circulatory system or lymphatic system to an organ (anatomy), organ or a tissue (biology), tissue, usually referring to the delivery of blood to a capillary bed in tissue. Perfusion may also refer t ...

, function and

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...

s of the human brain. Both healthy and

disease A disease is a particular abnormal condition that adversely affects the structure or function (biology), function of all or part of an organism and is not immediately due to any external injury. Diseases are often known to be medical condi ...

d brains may be mapped to study

memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembe ...

learning Learning is the process of acquiring new understanding, knowledge, behaviors, skills, value (personal and cultural), values, Attitude (psychology), attitudes, and preferences. The ability to learn is possessed by humans, non-human animals, and ...

aging Ageing (or aging in American English) is the process of becoming Old age, older until death. The term refers mainly to humans, many other animals, and fungi; whereas for example, bacteria, perennial plants and some simple animals are potentiall ...

, and

drug A drug is any chemical substance other than a nutrient or an essential dietary ingredient, which, when administered to a living organism, produces a biological effect. Consumption of drugs can be via insufflation (medicine), inhalation, drug i ...

effects in various populations such as people with

schizophrenia Schizophrenia () is a mental disorder characterized variously by hallucinations (typically, Auditory hallucination#Schizophrenia, hearing voices), delusions, thought disorder, disorganized thinking and behavior, and Reduced affect display, f ...

autism Autism, also known as autism spectrum disorder (ASD), is a neurodevelopmental disorder characterized by differences or difficulties in social communication and interaction, a preference for predictability and routine, sensory processing d ...

, and

clinical depression Major depressive disorder (MDD), also known as clinical depression, is a mental disorder characterized by at least two weeks of pervasive low mood, low self-esteem, and loss of interest or pleasure in normally enjoyable activities. Intro ...

. This led to the establishment of the Human Brain Project. It may also be crucial to understanding traumatic brain injuries (as in the case of Phineas Gage) and improving brain injury treatment. Following a series of meetings, the International Consortium for Brain Mapping (ICBM) evolved. The ultimate goal is to develop flexible computational brain atlases.

Achievements

The interactive and citizen science website Eyewire maps mices' retinal cells and was launched in 2012. In 2021, the most comprehensive 3D map of the human brain was published by researchers at

Google Google LLC (, ) is an American multinational corporation and technology company focusing on online advertising, search engine technology, cloud computing, computer software, quantum computing, e-commerce, consumer electronics, and artificial ...

. It shows neurons and their connections along with blood vessels and other components of a millionth of a brain. For the map, the 1 mm³ sized fragment was sliced into about 5,300 pieces of about 30

nanometer 330px, Different lengths as in respect to the Molecule">molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm), or nanometer (American spelling Despite the va ...

thickness which were then each scanned with an

electron microscope An electron microscope is a microscope that uses a beam of electrons as a source of illumination. It uses electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing it ...

. The interactive map required 1.4

petabyte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable un ...

s of storage-space. About two months later, scientists reported that they created the first complete neuron-level-resolution 3D map of a monkey brain which they scanned via a new method within 100 hours. They made only a fraction of the 3D map publicly available as the entire map takes more than 1 petabyte of storage space even when compressed. In October 2021, the BRAIN Initiative Cell Census Network concluded the first phase of a long-term project to generate an atlas of the entire mouse (mammalian) brain with 17 studies, including an atlas and census of cell types in the

primary motor cortex The primary motor cortex ( Brodmann area 4) is a brain region that in humans is located in the dorsal portion of the frontal lobe. It is the primary region of the motor system and works in association with other motor areas including premotor c ...

. In 2024, FlyWire, a team of 287 researchers spanning 76 institutions completed a brain mapping, or connectome, of an adult animal (a ''

'', or fruit fly) and published their results in ''

Nature Nature is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...

''. Prior to this, the only adult animal to have its brain entirely reconstructed was the nematode ''

Caenorhabditis elegans ''Caenorhabditis elegans'' () is a free-living transparent nematode about 1 mm in length that lives in temperate soil environments. It is the type species of its genus. The name is a Hybrid word, blend of the Greek ''caeno-'' (recent), ''r ...

'', but the fruit fly brain map is the first "complete map of any complex brain", according to Murthy, one of the researchers involved. Primary mapping data was collected through

electron microscopy An electron microscope is a microscope that uses a beam of electrons as a source of illumination. It uses electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing i ...

, assisted by

artificial intelligence Artificial intelligence (AI) is the capability of computer, computational systems to perform tasks typically associated with human intelligence, such as learning, reasoning, problem-solving, perception, and decision-making. It is a field of re ...

and citizen scientists, who corrected errors that artificial intelligence made. The resulting model had more than 140,000 neurons with over 50 million synapses. From the model, research expect to identify how the brain creates new connections for functions such as vision, creating

digital twin A digital twin is a digital model of an intended or actual real-world physical product, system, or process (a ''physical twin'') that serves as a digital counterpart of it for purposes such as simulation, integration, testing, monitoring, and m ...

equivalents to track how segments of the neuron connection map interact to external signals, including the nervous system.

Brain development

In 2021, the first connectome that shows how an animal's brain changes throughout its lifetime was reported. Scientists mapped and compared the whole brains of eight isogenic '' C. elegans'' worms, each at a different stage of development. Later that year, scientists combined electron microscopy and brainbow imaging to show for the first time the development of a mammalian neural circuit. They reported the complete wiring diagrams between the CNS and muscles of ten individual mice.

Vision

In August 2021, scientists of the

MICrONS The micrometre (English in the Commonwealth of Nations, Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a uni ...

program, launched in 2016, published a functional connectomics dataset that "contains calcium imaging of an estimated 75,000 neurons from primary visual cortex (VISp) and three higher visual areas (VISrl, VISal and VISlm), that were recorded while a mouse viewed natural movies and parametric stimuli". Based on this data they also published "interactive visualizations of anatomical and functional data that span all 6 layers of mouse primary visual cortex and 3 higher visual areas (LM, AL, RL) within a cubic millimeter volume" – the ''MICrONS Explorer''.

Brain regeneration

In 2022, a first spatiotemporal cellular atlas of the

axolotl The axolotl (; from ) (''Ambystoma mexicanum'') is a neoteny, paedomorphic salamander, one that Sexual maturity, matures without undergoing metamorphosis into the terrestrial adult form; adults remain Aquatic animal, fully aquatic with obvio ...

brain development and regeneration, the interactive ''Axolotl Regenerative Telencephalon Interpretation via Spatiotemporal Transcriptomic Atlas '', revealed key insights about axolotl brain regeneration.

Current atlas tools

* Talairach Atlas, 1988 * Harvard Whole Brain Atlas, 1995 * MNI Template, 1998 (the standard template of SPM and International Consortium for Brain Mapping) * Atlas of the Developing Human Brain, 2012
Infant Brain Atlas
2023