Functional neuroimaging is the use of

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. Incr ...

technology to measure an aspect of brain function, often with a view to understanding the relationship between activity in certain

brain A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. I ...

areas and specific mental functions. It is primarily used as a research tool in

cognitive neuroscience Cognitive neuroscience is the scientific field that is concerned with the study of the biological processes and aspects that underlie cognition, with a specific focus on the neural connections in the brain which are involved in mental process ...

cognitive psychology Cognitive psychology is the scientific study of mental processes such as attention, language use, memory, perception, problem solving, creativity, and reasoning. Cognitive psychology originated in the 1960s in a break from behaviorism, which ...

neuropsychology Neuropsychology is a branch of psychology concerned with how a person's cognition and behavior are related to the brain and the rest of the nervous system. Professionals in this branch of psychology often focus on how injuries or illnesses of t ...

, and social neuroscience.

Overview

Main brain functional imaging technique resolutions

Common methods of functional neuroimaging include *

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, ...

(PET) *

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) *

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 neocorte ...

(EEG) * Magnetoencephalography (MEG) * Functional near-infrared spectroscopy (fNIRS) *

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) *

Functional ultrasound imaging Functional ultrasound imaging (fUS) is a medical ultrasound imaging technique of detecting or measuring changes in neural activities or metabolism, for example, the loci of brain activity, typically through measuring blood flow or hemodynamic cha ...

(fUS) PET, fMRI, fNIRS and fUS can measure localized changes in cerebral blood flow related to neural activity. These changes are referred to as ''activations''. Regions of the brain which are activated when a subject performs a particular task may play a role in the neural computations which contribute to the behaviour. For instance, widespread activation of the

occipital lobe The occipital lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The name derives from its position at the back of the head, from the Latin ''ob'', "behind", and ''caput'', "head". The occipital lobe is the vi ...

is typically seen in tasks which involve

visual The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight ...

stimulation (compared with tasks that do not). This part of the brain receives signals from the

retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which the ...

and is believed to play a role in

visual perception Visual perception is the ability to interpret the surrounding environment through photopic vision (daytime vision), color vision, scotopic vision (night vision), and mesopic vision (twilight vision), using light in the visible spectrum ref ...

. Other methods of neuroimaging involve recording of electrical currents or magnetic fields, for example EEG and MEG. Different methods have different advantages for research; for instance, MEG measures brain activity with high temporal resolution (down to the millisecond level), but is limited in its ability to localize that activity. fMRI does a much better job of localizing brain activity for spatial resolution, but with a much lower time resolution while functional ultrasound (fUS) can reach an interesting spatio-temporal resolution (down to 100 micrometer, 100 milliseconds, at 15MHz in preclinical models) but is also limited by the neurovascular coupling. Recently, Magnetic particle imaging has been proposed as a new sensitive imaging technique that has sufficient temporal resolution for functional neuroimaging based on the increase of cerebral blood volume. First pre-clinical trials have successfully demonstrated functional imaging in rodents.

Functional neuroimaging topics

The measure used in a particular study is generally related to the particular question being addressed. Measurement limitations vary amongst the techniques. For instance, MEG and EEG record the magnetic or electrical fluctuations that occur when a population of neurons is active. These methods are excellent for measuring the time-course of neural events (on the order of milliseconds,) but generally bad at measuring where those events happen. PET and fMRI measure changes in the composition of blood near a neural event. Because measurable blood changes are slow (on the order of seconds), these methods are much worse at measuring the time-course of neural events, but are generally better at measuring the location. Traditional "activation studies" focus on determining distributed patterns of brain activity associated with specific tasks. However, scientists are able to more thoroughly understand brain function by studying the interaction of distinct brain regions, as a great deal of neural processing is performed by an integrated network of several regions of the brain. An active area of neuroimaging research involves examining the functional connectivity of spatially remote brain regions. Functional connectivity analyses allow the characterization of interregional neural interactions during particular cognitive or motor tasks or merely from spontaneous activity during rest. FMRI and PET enable creation of functional connectivity maps of distinct spatial distributions of temporally correlated brain regions called functional networks. Several studies using neuroimaging techniques have also established that posterior visual areas in blind individuals may be active during the performance of nonvisual tasks such as Braille reading, memory retrieval, and auditory localization as well as other auditory functions. A direct method to measure functional connectivity is to observe how stimulation of one part of the brain will affect other areas. This can be done noninvasively in humans by combining

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 ...

with one of the neuroimaging tools such as PET, fMRI, or EEG. Massimini et al. (''Science'', September 30, 2005) used EEG to record how activity spreads from the stimulated site. They reported that in non-REM sleep, although the brain responds vigorously to stimulation, functional connectivity is much attenuated from its level during wakefulness. Thus, during deep sleep, "brain areas do not talk to each other". Functional neuroimaging draws on data from many areas other than

and social neuroscience, including other biological sciences (such as

neuroanatomy Neuroanatomy is the study of the structure and organization of the nervous system. In contrast to animals with radial symmetry, whose nervous system consists of a distributed network of cells, animals with bilateral symmetry have segregated, defi ...

and

neurophysiology Neurophysiology is a branch of physiology and neuroscience that studies nervous system function rather than nervous system architecture. This area aids in the diagnosis and monitoring of neurological diseases. Historically, it has been dominated ...

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which ...

and maths, to further develop and refine the technology.

Critique and careful interpretation

Functional neuroimaging studies have to be carefully designed and interpreted with care. Statistical analysis (often using a technique called

statistical parametric mapping Statistical parametric mapping (SPM) is a statistical technique for examining differences in brain activity recorded during functional neuroimaging experiments. It was created by Karl Friston. It may alternatively refer to software created by ...

) is often needed so that the different sources of activation within the brain can be distinguished from one another. This can be particularly challenging when considering processes which are difficult to conceptualise or have no easily definable task associated with them (for example

belief A belief is an attitude that something is the case, or that some proposition is true. In epistemology, philosophers use the term "belief" to refer to attitudes about the world which can be either true or false. To believe something is to tak ...

and

consciousness Consciousness, at its simplest, is sentience and awareness of internal and external existence. However, the lack of definitions has led to millennia of analyses, explanations and debates by philosophers, theologians, linguisticians, and scien ...

). Functional neuroimaging of interesting phenomena often gets cited in the press. In one case a group of prominent functional neuroimaging researchers felt compelled to write a letter to

New York Times ''The New York Times'' (''the Times'', ''NYT'', or the Gray Lady) is a daily newspaper based in New York City with a worldwide readership reported in 2020 to comprise a declining 840,000 paid print subscribers, and a growing 6 million paid ...

in response to an

op-ed An op-ed, short for "opposite the editorial page", is a written prose piece, typically published by a North-American newspaper or magazine, which expresses the opinion of an author usually not affiliated with the publication's editorial board. ...

article about a study of so-called neuropolitics. They argued that some of the interpretations of the study were "scientifically unfounded". The Hastings Center issued a report in March 2014 entitled "Interpreting Neuroimages: An Introduction to the Technology and Its Limits",Johnston, J., & Parens, E. (2014
"Interpreting Neuroimages: An Introduction to the Technology and Its Limits", The Hastings Center Report, Volume 44, Issue s2, March-April 2014
with articles by leading neuroscientists and

bioethicists Bioethics is both a field of study and professional practice, interested in ethical issues related to health (primarily focused on the human, but also increasingly includes animal ethics), including those emerging from advances in biology, med ...

. The report briefly explains neuroimaging technologies and mostly critiques, but also somewhat defends, their current state, import and prospects.

References

{{Reflist

External links

The Whole Brain Atlas @ Harvard

The American Society of Neuroimaging (ASN)

UCLA Neuroimaging Training Program

BrainMapping.org, ''a free BrainMapping community information portal''
Neuroimaging Cognitive neuroscience Medical imaging

Overview

Functional neuroimaging topics

Critique and careful interpretation

See also

References

Further reading

External links