The first
neuroimaging
Neuroimaging is the use of quantitative (computational) techniques to study the structure and function of the central nervous system, developed as an objective way of scientifically studying the healthy human brain in a non-invasive manner. Incre ...
technique ever is the so-called 'human circulation balance' invented by
Angelo Mosso
Angelo Mosso (30 May 1846 – 24 November 1910) is the 19th century Italian physiologist who invented the first neuroimaging technique ever, known as 'human circulation balance'.
Mosso began by recording the pulsation of the human cortex in pati ...
in the 1880s and able to non-invasively measure the redistribution of
blood
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...
during emotional and intellectual activity.
Then, in the early 1900s, a technique called
pneumoencephalography
Pneumoencephalography (sometimes abbreviated PEG; also referred to as an "air study") was a common medical procedure in which most of the cerebrospinal fluid (CSF) was drained from around the brain by means of a lumbar puncture and replaced with ai ...
was set. This process involved draining the
cerebrospinal fluid
Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates.
CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the bra ...
from around the brain and replacing it with air, altering the relative density of the brain and its surroundings, to cause it to show up better on an
x-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
, and it was considered to be incredibly unsafe for patients (Beaumont 8). A form of
magnetic resonance imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wave ...
(MRI) and
computed tomography (CT) were developed in the 1970s and 1980s.
The new MRI and CT technologies were considerably less harmful and are explained in greater detail below. Next came
SPECT
Single-photon emission computed tomography (SPECT, or less commonly, SPET) is a nuclear medicine tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera (that is, ...
and
PET
A pet, or companion animal, is an animal kept primarily for a person's company or entertainment rather than as a working animal, livestock, or a laboratory animal. Popular pets are often considered to have attractive appearances, intelligence, ...
scans, which allowed scientists to map brain function because, unlike MRI and CT, these scans could create more than just static images of the brain's structure. Learning from MRI, PET and SPECT scanning, scientists were able to develop
functional MRI
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) with abilities that opened the door to direct observation of cognitive activities.
Angelo Mosso and his "human circulation balance"
The desire to understand the human
mind
The mind is the set of faculties responsible for all mental phenomena. Often the term is also identified with the phenomena themselves. These faculties include thought, imagination, memory, will, and sensation. They are responsible for various m ...
has been one of the main desires of philosophers throughout the ages. Questions about thoughts, desires, et cetera have drawn
psychologists
A psychologist is a professional who practices psychology and studies mental states, perceptual, cognitive, emotional, and social processes and behavior. Their work often involves the experimentation, observation, and interpretation of how indi ...
,
computer scientists
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to practical disciplines (including th ...
,
philosophers
A philosopher is a person who practices or investigates philosophy. The term ''philosopher'' comes from the grc, φιλόσοφος, , translit=philosophos, meaning 'lover of wisdom'. The coining of the term has been attributed to the Greek th ...
,
sociologists
This is a list of sociologists. It is intended to cover those who have made substantive contributions to social theory and research, including any sociological subfield. Scientists in other fields and philosophers are not included, unless at least ...
and the like together into the new
discipline
Discipline refers to rule following behavior, to regulate, order, control and authority. It may also refer to punishment. Discipline is used to create habits, routines, and automatic mechanisms such as blind obedience. It may be inflicted on ot ...
of
cognitive
Cognition refers to "the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasses all aspects of intellectual functions and processes such as: perception, attention, thought, ...
science.
Non-invasive
A medical procedure is defined as ''non-invasive'' when no break in the skin is created and there is no contact with the mucosa, or skin break, or internal body cavity beyond a natural or artificial body orifice. For example, deep palpation and p ...
imaging of the human brain has proven invaluable in this context.
The very first chapter of the history of neuroimaging traces back to the Italian physiologist
Angelo Mosso
Angelo Mosso (30 May 1846 – 24 November 1910) is the 19th century Italian physiologist who invented the first neuroimaging technique ever, known as 'human circulation balance'.
Mosso began by recording the pulsation of the human cortex in pati ...
who invented the "human circulation balance", which could non-invasively measure the redistribution of
blood
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...
during emotional and intellectual activity.
However, even if only briefly mentioned by
William James
William James (January 11, 1842 – August 26, 1910) was an American philosopher, historian, and psychologist, and the first educator to offer a psychology course in the United States.
James is considered to be a leading thinker of the lat ...
in 1890, the details and precise workings of this balance and the
experiments
An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs when ...
Mosso performed with it have remained largely unknown until the recent discovery of the original instrument as well as of Mosso's reports by
Stefano Sandrone
Stefano Sandrone (1988) is an Italian neuroscientist and a Senior Teaching Fellow at Imperial College London.
Life and works
Stefano Sandrone was born in Canelli, Italy, on the 1st of February 1988, and obtained a Ph.D. in Neuroscience at King†...
and colleagues.
These documents suggest that patients would be placed on a weighted table that would tilt as blood flowed to their head, for instance, while concentrating on reading a philosophy book. Remarkably, Angelo Mosso unearthed and investigated several critical
variables that are still relevant in modern neuroimaging such as the "
signal-to-noise ratio
Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in deci ...
", the appropriate choice of the experimental paradigm and the need for the simultaneous recording of differing physiological
parameters
A parameter (), generally, is any characteristic that can help in defining or classifying a particular system (meaning an event, project, object, situation, etc.). That is, a parameter is an element of a system that is useful, or critical, when ...
.
Early uses of brain imaging
However, Mosso's manuscripts have remained largely unknown for more than a century, and therefore it was the structural
radiographic
Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeut ...
techniques to dominate the field of the imaging of the
human brain
The human brain is the central organ of the human nervous system, and with the spinal cord makes up the central nervous system. The brain consists of the cerebrum, the brainstem and the cerebellum. It controls most of the activities of the ...
. Unfortunately, because the brain is almost entirely composed of soft tissue that is not radio-opaque, it remains essentially invisible to ordinary or plain x-ray examination. This is also true of most brain abnormalities, though there are exceptions such as a calcified tumor (e.g.
meningioma
Meningioma, also known as meningeal tumor, is typically a slow-growing tumor that forms from the meninges, the membranous layers surrounding the brain and spinal cord. Symptoms depend on the location and occur as a result of the tumor pressing o ...
,
craniopharyngioma
A craniopharyngioma is a rare type of brain tumor derived from pituitary gland embryonic tissue that occurs most commonly in children, but also affects adults. It may present at any age, even in the prenatal and neonatal periods, but peak incidence ...
, some types of
glioma
A glioma is a type of tumor that starts in the glial cells of the brain or the spine. Gliomas comprise about 30 percent of all brain tumors and central nervous system tumours, and 80 percent of all malignant brain tumours.
Signs and symptoms
...
); whilst calcification in such normal structures as the pineal body, the choroid plexuses, or large brain arteries may indirectly give important clues to the presence of structural disease in the brain itself.
In 1918 the American neurosurgeon
Walter Dandy
Walter Edward Dandy (April 6, 1886 – April 19, 1946) was an American neurosurgeon and scientist. He is considered one of the founding fathers of neurosurgery, along with Victor Horsley (1857–1916) and Harvey Cushing (1869–1939). Dandy is cr ...
introduced the technique of ventriculography whereby images of the
ventricular system
The ventricular system is a set of four interconnected cavities known as cerebral ventricles in the brain. Within each ventricle is a region of choroid plexus which produces the circulating cerebrospinal fluid (CSF). The ventricular system is con ...
within the brain were obtained by injection of filtered air directly into one or both lateral ventricles of the brain via one or more small trephine holes drilled in the skull under local anaesthesia. Though not usually a painful procedure, ventriculography carried significant risks to the patient under investigation, such as haemorrhage, infection, and dangerous changes in intracranial pressure. Nevertheless, the surgical information given by this method was often remarkably precise and greatly enlarged the capabilities and accuracy of neurosurgical treatment. Dandy also observed that air introduced into the subarachnoid space via lumbar spinal puncture could enter the cerebral ventricles and also demonstrate the cerebrospinal fluid compartments around the base of the brain and over its surface. This technique was called
pneumoencephalography
Pneumoencephalography (sometimes abbreviated PEG; also referred to as an "air study") was a common medical procedure in which most of the cerebrospinal fluid (CSF) was drained from around the brain by means of a lumbar puncture and replaced with ai ...
. It further extended the scope for precise intracranial diagnosis, but at a similar cost of risks to the patient as well as being, in itself, a most unpleasant and often painful ordeal.
Development of modern techniques
In 1927
Egas Moniz, professor of neurology in
Lisbon
Lisbon (; pt, Lisboa ) is the capital and largest city of Portugal, with an estimated population of 544,851 within its administrative limits in an area of 100.05 km2. Grande Lisboa, Lisbon's urban area extends beyond the city's administr ...
and
Nobel Prize in Physiology or Medicine
The Nobel Prize in Physiology or Medicine is awarded yearly by the Nobel Assembly at the Karolinska Institute for outstanding discoveries in physiology or medicine. The Nobel Prize is not a single prize, but five separate prizes that, accord ...
winner in 1949, introduced cerebral
angiography
Angiography or arteriography is a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins, and the heart chambers. Modern angiography is performe ...
, whereby both normal and abnormal
blood vessel
The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...
s in and around the brain could be visualized with great accuracy. In its early days this technique likewise carried both immediate and long-term risks, many of them referable to deleterious effects of the positive-contrast substances that were used for injection into the circulation. Techniques have become very refined in the past few decades, with one in 200 patients or less experiencing ischemic sequelae from the procedure. As a result, cerebral angiography remains an essential part of the neurosurgeon's diagnostic imaging armamentarium and, increasingly, of the therapeutic armamentarium as well, in the neurointerventional management of cerebral
aneurysm
An aneurysm is an outward bulging, likened to a bubble or balloon, caused by a localized, abnormal, weak spot on a blood vessel wall. Aneurysms may be a result of a hereditary condition or an acquired disease. Aneurysms can also be a nidus (s ...
s and other blood-vessel lesions and in some varieties of brain
tumor
A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
.
Computerized tomography
With the advent of
computerized axial tomography (CAT or CT scanning), ever more detailed anatomic images of the brain became available for diagnostic and research purposes. The names of
William H. Oldendorf
William Henry Oldendorf (March 27, 1925 – December 14, 1992) was an American neurologist, physician, researcher, medical pioneer, founding member of the American Society for Neuroimaging (ASN), and originator of the technique of computed tomog ...
(in 1961)
Godfrey Newbold Hounsfield
Sir Godfrey Newbold Hounsfield (28 August 1919 – 12 August 2004) was an England, English electrical engineer who shared the 1979 Nobel Prize for Physiology or Medicine with Allan MacLeod Cormack for his part in developing the diagnostic techn ...
and
Allan McLeod Cormack
Allan MacLeod Cormack (February 23, 1924 – May 7, 1998) was a South African American physicist who won the 1979 Nobel Prize in Physiology or Medicine (along with Godfrey Hounsfield) for his work on X-ray computed tomography (CT).
Early life ...
(in 1973) are associated with this revolutionary innovation, which enabled much easier, safer, non-invasive, painless and (to a reasonable extent) repeatable neuro-investigation. Cormack and Hounsfield won the
Nobel Prize in Physiology or Medicine
The Nobel Prize in Physiology or Medicine is awarded yearly by the Nobel Assembly at the Karolinska Institute for outstanding discoveries in physiology or medicine. The Nobel Prize is not a single prize, but five separate prizes that, accord ...
in 1979 for this work.
Radioactive neuroimaging
Early techniques such as
xenon
Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...
inhalation provided the first blood flow maps of the brain.
Developed in the early 1960s by
Niels A. Lassen,
David H. Ingvar and
Erik Skinhøj in southern
Scandinavia
Scandinavia; Sámi languages: /. ( ) is a subregion#Europe, subregion in Northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. In English usage, ''Scandinavia'' most commonly refers to Denmark, ...
it used the isotope xenon-133. Later versions would have 254
scintillator
A scintillator is a material that exhibits scintillation, the property of luminescence, when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate (i.e. re-emit the absorbed ...
s so a two-dimensional image could be produced on a color monitor. It allowed them to construct images reflecting brain activation from speaking, reading, visual or auditory perception and voluntary movement.
The technique was also used to investigate, e.g., imagined sequential movements, mental calculation and mental spatial navigation.
Soon after the invention of CAT, the development of
radioligand
A radioligand is a radioactive biochemical substance (in particular, a ligand that is radiolabeled) that is used for diagnosis or for research-oriented study of the receptor systems of the body.
In a neuroimaging application the radioligand is inj ...
s started the functional imaging revolution. Radioligands either remain within the blood stream or enter the brain and bind to receptors. Radioligands are either single photon or positron emitters. This is how
single photon emission computed tomography
Single-photon emission computed tomography (SPECT, or less commonly, SPET) is a nuclear medicine tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera (that is, ...
(SPECT) and
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 Metabolism, metabolic processes, and in other physiological activities including bl ...
(PET) got their names. While the first human positron imaging device was developed by Gordon Brownell and William Sweet in the 1950s,
Michel Ter-Pogossian
Michel Matthew Ter-Pogossian (April 21, 1925June 19, 1996) was an American medical physicist. He was professor of radiology at the Washington University School of Medicine for over 30 years. A pioneer in nuclear medicine, he is best known for his ...
,
Edward J. Hoffman
Edward Joseph Hoffman (January 1, 1942 – July 1, 2004) helped invent the first human PET scanner, a commonly used whole-body scanning procedure for detecting diseases like cancer. Hoffman, with Michel Ter-Pogossian and Michael E. Phelps, dev ...
and
Michael Phelps
Michael Fred Phelps II (born June 30, 1985) is an American former competitive swimmer. He is the most successful and most decorated Olympian of all time with a total of 28 medals. Phelps also holds the all-time records for Olympic gold me ...
developed the first human PET scanner in 1973 with hexagonal detectors.
After the work
Marcus Raichle
Marcus E. Raichle (born March 15, 1937) is an American neurologist at the Washington University School of Medicine in Saint Louis, Missouri. He is a professor in the Department of Radiology with joint appointments in Neurology, Neurobiology and B ...
and coworkers, functional imaging took a large step forward with the development of oxygen-15 labelled water (H
215O, or H2O-15) imaging. H2O-15 emits positrons and creates images based on regional blood flow within the brain. Since active neurons recruit a robust blood supply, H2O-15 PET allowed investigators to make regional maps of brain activity during various cognitive tasks. Later, a more common sort of functional imaging based on PET scans used
FDG, a positron-emitting sugar-derivative which is distributed in the brain according to local metabolic activity. Unlike the short half-life of oxygen-15 (2.25 minutes), the 110 minute half-life of FDG allowed PET scans by machines physically distant from the cyclotron producing the isotope (in this case fluorine-18).
Magnetic resonance imaging
Shortly after the initial development of CT,
magnetic resonance imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wave ...
(MRI or MR scanning) was developed. Rather than using ionizing or X-radiation, MRI uses the variation in signals produced by
proton
A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...
s in the body when the head is placed in a strong
magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
. Associated with early application of the basic technique to the human body are the names of Jackson (in 1968),
Damadian (in 1972), and Abe and
Paul Lauterbur
Paul Christian Lauterbur (May 6, 1929 – March 27, 2007) was an American chemist who shared the Nobel Prize in Physiology or Medicine in 2003 with Peter Mansfield for his work which made the development of magnetic resonance imaging (MRI) poss ...
(in 1973). Lauterbur and Sir
Peter Mansfield
Sir Peter Mansfield (9 October 1933 – 8 February 2017) was an English physicist who was awarded the 2003 Nobel Prize in Physiology or Medicine, shared with Paul Lauterbur, for discoveries concerning Magnetic Resonance Imaging (MRI). Mansfie ...
were awarded the 2003
Nobel Prize in Physiology or Medicine
The Nobel Prize in Physiology or Medicine is awarded yearly by the Nobel Assembly at the Karolinska Institute for outstanding discoveries in physiology or medicine. The Nobel Prize is not a single prize, but five separate prizes that, accord ...
for their discoveries concerning MRI. At first, structural imaging benefited more than functional imaging from the introduction of MRI. During the 1980s a veritable explosion of technical refinements and diagnostic MR applications took place, enabling even neurological tyros to diagnose brain pathology that would have been elusive or incapable of demonstration in a living person only a decade or two earlier.
Scientists soon learned that the large blood flow changes measured by H2O-15 PET were also imaged by MRI.
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) was born. Since the 1990s, fMRI has come to dominate the brain mapping field due to its low invasiveness, lack of radiation exposure, and relatively wide availability.
Physicists have also developed other MRI-based techniques such as
arterial spin labeling Arterial spin labeling (ASL), also known as arterial spin tagging, is a magnetic resonance imaging technique used to quantify cerebral blood perfusion by labelling blood water as it flows throughout the brain. ASL specifically refers to magnetic lab ...
(where arterial blood is magnetically tagged before it enters into the tissue of interest and the amount of labeling is measured and compared to a control recording obtained without spin labeling),
magnetic resonance spectroscopy
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic fiel ...
(for measuring some key metabolites such as
N-acetylaspartate
''N''-Acetylaspartic acid, or ''N''-acetylaspartate (NAA), is a derivative of aspartic acid with a formula of C6H9NO5 and a molecular weight of 175.139.
NAA is the second-most-concentrated molecule in the brain after the amino acid glutamate. ...
and lactate within the living brain) and
diffusion tensor imaging
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 in MR images. It ...
(for mapping white matter tracts within the living brain). Whereas structural MRI and CAT scanning have a large place in medicine, fMRI and its brethren techniques are still largely devoted to neuroscience research. However, very recently neurologists have started to use fMRI to begin to answer clinical questions, such as how long after thrombotic stroke is it safe and effective to give clot-dissolving drug like
tissue plasminogen activator
Tissue plasminogen activator (abbreviated tPA or PLAT) is a protein involved in the breakdown of blood clots. It is a serine protease () found on endothelial cells, the cells that line the blood vessels. As an enzyme, it catalyzes the conversion ...
(TPA). Similarly, PET and SPECT have moved out of neuro-research and are increasingly being used clinically to help diagnose and differentiate types of dementing illnesses (
dementia
Dementia is a disorder which manifests as a set of related symptoms, which usually surfaces when the brain is damaged by injury or disease. The symptoms involve progressive impairments in memory, thinking, and behavior, which negatively affe ...
).
Magnetoencephalography
Magnetoencephalography
Magnetoencephalography (MEG) is a functional neuroimaging technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using very sensitive magnetometers. Arrays of SQUIDs (su ...
(MEG) signals were first measured by University of Illinois physicist
David Cohen in 1968,.
He later used one of the first
SQUID
True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...
detectors, to again measure MEG signals.
Multimodal neuroimaging
Multimodal imaging combines existing brain imaging techniques in synergistic ways which facilitate the improved interpretation of data.
Besides fMRI, another example of technology allowing relatively older brain imaging techniques to be even more helpful is the ability to combine different techniques to get one brain map. This happens quite frequently with
MRI
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...
and
EEG
Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex ...
scans. The electrical diagram of the EEG provides split-second timing while the MRI provides high levels of
spatial accuracy.
The combined use of
MEG 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 ...
was first reported in 1999. It combines the spatial resolution of
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 ...
with the temporal resolution of the MEG. Often the non-uniqueness of the MEG source estimation problem (
inverse problem
An inverse problem in science is the process of calculating from a set of observations the causal factors that produced them: for example, calculating an image in X-ray computed tomography, source reconstruction in acoustics, or calculating the ...
) can be alleviated by incorporating information from other imaging modalities as an ''a priori'' constraint.
Anatomically constrained MEG (aMEG) uses anatomical MRI data as a geometrical or location constraint and as a medium for visualization of MEG results. MEG does not provide structural or anatomical information. Therefore, MEG data is often combined with MR data into a composite image whereby functional information is overlaid on the corresponding anatomy to produce an activation map.
Recent breakthroughs
Recent breakthroughs in non-invasive brain imaging have been somewhat limited because most of them have not been completely novel; rather, they are simply refining existing brain imaging techniques.
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 ...
is a perfect example of this from the early 1990s, and it still remains the most popular brain imaging technique available today.
Advances have been made in a number of ways regarding neuroimaging, and this section will cover some of the more prominent improvements including computational advances, transcranial
magnetic
Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particle ...
stimulation, and
nuclear magnetic resonance
Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a ...
.
To begin with, much of the recent progress has had to do not with the actual brain imaging methods themselves but with our ability to utilize computers in analyzing the data. For example, substantial discoveries in the growth of human brains from age three months to the age of fifteen have been made due to the creation of high-resolution brain maps and computer technology to analyze these maps over various periods of time and growth (Thompson,
UCLA
The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California. UCLA's academic roots were established in 1881 as a teachers college then known as the southern branch of the California St ...
). This type of breakthrough represents the nature of most breakthroughs in
neuroscience
Neuroscience is the scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system), its functions and disorders. It is a multidisciplinary science that combines physiology, anatomy, molecular biology, development ...
today. With fMRI technology mapping brains beyond what we are already understanding, most innovators time is being spent trying to make sense of the
data
In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted ...
we already have rather than probing into other realms of brain imaging and
mapping.
This can be seen more clearly in the fact that brain imaging archives are catching on and
neuroinformatics
Neuroinformatics is the field that combines informatics and neuroscience. Neuroinformatics is related with neuroscience data and information processing by artificial neural networks. There are three main directions where neuroinformatics has to be ...
is allowing researchers to examine thousands of brains rather than just a few (Lynch). Also, these archives are universalizing and standardizing formats and descriptions so that they are more searchable for everyone. For the past decade we have been able to get data and now our technology allows us to share findings and research much easier. This has also allowed for "brain atlases" to be made.
Brain maps are simply maps of what normal functioning brains look like (Thompson, Bioinformatics).
Transcranial magnetic stimulation
Transcranial magnetic stimulation (TMS) is a noninvasive form of brain stimulation in which a changing magnetic field is used to induce an electric current at a specific area of the brain through electromagnetic induction. An electric pulse gener ...
(TMS) is a recent innovation in brain imaging. In TMS, a coil is held near a person's head to generate magnetic field impulses that stimulate underlying brain cells to make someone perform a specific action. Using this in combination with MRI, the researcher can generate maps of the brain performing very specific functions. Instead of asking a patient to tap his or her finger, the TMS coil can simply "tell" his or her brain to tap his or her finger. This eliminates many of the
false positives
A false positive is an error in binary classification in which a test result incorrectly indicates the presence of a condition (such as a disease when the disease is not present), while a false negative is the opposite error, where the test result ...
received from traditional MRI and fMRI testing. The images received from this technology are slightly different from the typical MRI results, and they can be used to map any subject's brain by monitoring up to 120 different stimulations. This technology has been used to map both motor processes and visual processes (Potts link at bottom of TMS). In addition to fMRI, the activation of TMS can be measured using
electroencephalography
Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex ...
(EEG)
[Ilmoniemi RJ and Kicic D, Methodology for combined TMS and EEG, Brain Topogr. 22, 233–248 (2010).] or
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 incl ...
(NIRS).
Nuclear magnetic resonance
Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a ...
(NMR) is what MRI and fMRI technologies were derived from, but recent advances have been made by going back to the original NMR technology and revamping some of its aspects. NMR traditionally has two steps, signal encoding and detection, and these steps are normally carried out in the same instrument. The new discovery, however, suggests that using laser-polarized
xenon
Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...
gas for "remembering" encoded information and transporting that information to a remote detection site could prove far more effective (Preuss). Separating the encoding and detection allows researchers to gain data about
chemical
A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., wi ...
,
physical
Physical may refer to:
*Physical examination
In a physical examination, medical examination, or clinical examination, a medical practitioner examines a patient for any possible medical signs or symptoms of a medical condition. It generally co ...
, and
biological
Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary in ...
processes that they have been unable to gain until now. The result allows researchers to map things as big as
geological
Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Eart ...
core samples or as small as single
cell
Cell most often refers to:
* Cell (biology), the functional basic unit of life
Cell may also refer to:
Locations
* Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...
s.
It is interesting to see how advances are split between those seeking a completely mapped brain by utilizing single
neuron
A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. N ...
imaging and those utilizing images of brains as subjects perform various high-level tasks.
Single neuron imaging (SNI) uses a combination of genetic engineering and
optical
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviole ...
imaging techniques to insert tiny
electrodes
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...
into the brain for the purpose of measuring a single neuron's firing. Due to its damaging repercussions, this technique has only been used on animals, but it has shed a lot of light on basic emotional and motivational processes. The goal of studies in higher-level activities is to determine how a network of brain areas collaborates to perform each task. This higher-level imaging is much easier to do because researchers can easily use subjects who have a disease such as
Alzheimer's
Alzheimer's disease (AD) is a neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in remembering recent events. As t ...
. The SNI technology seems to be going after the possibility for AI while the network-probing technology seems to be more for
medical
Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care practic ...
purposes.
References
* Ball, Philip. "Brain Imaging Explained." Online at http://www.nature.com/nsu/010712/010712-13.html
*
* Beaumont, J. Graham. Introduction to Neuropsychology. New York: The Guilford Press, 1983. 314 pages.
* Changeux, Jean-Pierre. Neuronal Man: The Biology of Mind. New York: Oxford University Press, 1985. 348 pages.
* Donoghue, John P. "Connecting Cortex to Machines: Recent Advance in Brain Interfaces." Online at http://www.nature.com/cgi-taf/DynaPage.taf?file=/neuro/journal/v5/n11s/full/nn947.html
* Hook, C. Christopher. "The Techno Sapiens are Coming." Online at www.Christianitytoday.com/ct/2004/001/1.36.html
* Jeeves, Malcolm. Mind Fields: Reflections on the Science of Mind and Brain. Grand Rapids, MI: Baker Books, 1994. 141 pages.
* Johnson, Keith A. "Neuroimaging Primer." Online at http://www.med.harvard.edu/AANLIB/hms1.html
* Leventon, Michael. "Transcranial Magnetic Stimulation." In association with MIT AI Lab. Online at http://www.ai.mit.edu/projects/medical-vision/surgery/tms.html
* Lister, Richard G. and Herbert J. Weingartner. Perspectives on Cognitive Neuroscience. New York: Oxford University Press, 1991. 508 pages.
* Mattson, James and Merrill Simon. The Pioneers of NMR and Magnetic Resonance in Medicine. United States: Dean Books Company, 1996. 838 pages.
* Nilsson, Lars-Goran and
Hans J. Markowitsch. Cognitive Neuroscience of Memory. Seattle: Hogrefe & Huber Publishers, 1999. 307 pages.
* Norman, Donald A. Perspectives on Cognitive Science. New Jersey: Ablex Publishing Corporation, 1981. 303 pages.
*
* Preuss, Paul. "Detection at a Distance for More Sensitive MRI." Online at http://www.lbl.gov/Science-Articles/Archive/MSD-remote-detection-MRI.html
* Rapp, Brenda. The Handbook of Cognitive Neuropsychology. Ann Arbor, MI: Psychology Press, 2001. 652 pages.
* Romain, Gabe. "Brain Imaging Breakthrough for Alzheimer s." Last edited 1/23/2004. Online at https://web.archive.org/web/20041208120231/http://www.betterhumans.com/News/news.aspx?articleID=2004-01-23-4
* Schulder, Michael. "Functional Image-Guided Surgery for Brain Tumors." Online at http://www.virtualtrials.com/Schulder.cfm
* Sheffield Hallam University, School of Science and Mathematics. "Nuclear Magnetic Resonance Spectroscopy." Online at http://www.shu.ac.uk/schools/sci/chem/tutorials/molspec/nmr1.htm
* Shorey, Jamie. "Foundations of fMRI." Online at https://web.archive.org/web/20041209175202/http://www.ee.duke.edu/~jshorey/MRIHomepage/MRImain.html
* Swiercinsky, Dennis P. "Brain Forensics." Last edited 7/11/01. Online at https://web.archive.org/web/20041208062245/http://www.brainsource.com/brainforensics.htm
* Thompson, Paul. "UCLA Researchers Map Brain Growth in Four Dimensions, Revealing Stage-Specific Growth Patterns in Children." Online at https://web.archive.org/web/20041204085436/http://www.loni.ucla.edu/~thompson/MEDIA/press_release.html and https://web.archive.org/web/20041204083259/http://www.loni.ucla.edu/~thompson/JAY/Growth_REVISED.html
* Thompson, Paul M. "Bioinformatics and Brain Imaging: Recent Advances and Neuroscience Applications." Online at https://web.archive.org/web/20050118095748/http://www.loni.ucla.edu/~thompson/SFN2002/SFN2002coursePT_v4.pdf
* Zwillich, Todd. "Brain Scan Technology Poised to Play Policy Roll." Online at https://web.archive.org/web/20041204084542/http://www.loni.ucla.edu/~thompson/MEDIA/RH/rh.html
Notes
{{DEFAULTSORT:History of Neuroimaging
Neuro
Neuroimaging
Neuroimaging is the use of quantitative (computational) techniques to study the structure and function of the central nervous system, developed as an objective way of scientifically studying the healthy human brain in a non-invasive manner. Incre ...
Neuroimaging