Magnetoencephalography---theory, instrumentation, and applications to noninvasive studies of the working human brain

Journal Article · Thu Apr 01 04:00:00 EST 1993 · Reviews of Modern Physics; (United States)

DOI:https://doi.org/10.1103/RevModPhys.65.413· OSTI ID:6619337

Haemaelaeinen, M; Hari, R; Ilmoniemi, R J; Knuutila, J; Lounasmaa, O V ^[1]

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1. Low Temperature Laboratory, Helsinki University of Technology, 02150 Espoo (Finland)

Magnetoencephalography (MEG) is a noninvasive technique for investigating neuronal activity in the living human brain. The time resolution of the method is better than 1 ms and the spatial discrimination is, under favorable circumstances, 2--3 mm for sources in the cerebral cortex. In MEG studies, the weak 10 fT--1 pT magnetic fields produced by electric currents flowing in neurons are measured with multichannel SQUID (superconducting quantum interference device) gradiometers. The sites in the cerebral cortex that are activated by a stimulus can be found from the detected magnetic-field distribution, provided that appropriate assumptions about the source render the solution of the inverse problem unique. Many interesting properties of the working human brain can be studied, including spontaneous activity and signal processing following external stimuli. For clinical purposes, determination of the locations of epileptic foci is of interest. The authors begin with a general introduction and a short discussion of the neural basis of MEG. The mathematical theory of the method is then explained in detail, followed by a thorough description of MEG instrumentation, data analysis, and practical construction of multi-SQUID devices. Finally, several MEG experiments performed in the authors' laboratory are described, covering studies of evoked responses and of spontaneous activity in both healthy and diseased brains. Many MEG studies by other groups are discussed briefly as well.

• OSTI ID: 6619337
• Journal Information: Reviews of Modern Physics; (United States), Journal Name: Reviews of Modern Physics; (United States) Vol. 65:2; ISSN 0034-6861; ISSN RMPHAT
• Country of Publication: United States
• Language: English

Related Subjects

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62 RADIOLOGY AND NUCLEAR MEDICINE
665412 -- Superconducting Devices-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANIMAL CELLS
BIOELECTRICITY
BODY
BRAIN
CARBONIC ACID DERIVATIVES
CENTRAL NERVOUS SYSTEM
CEREBRAL CORTEX
CEREBRUM
DATA ANALYSIS
DIPOLES
DRUGS
ELECTRICITY
ELECTRONIC EQUIPMENT
EQUIPMENT
FLUXMETERS
MAGNETIC FIELDS
MEASURING INSTRUMENTS
MEG
MICROWAVE EQUIPMENT
MULTIPOLES
NERVE CELLS
NERVOUS SYSTEM
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANS
RADIOPROTECTIVE SUBSTANCES
RESOLUTION
SOMATIC CELLS
SPATIAL RESOLUTION
SQUID DEVICES
SUPERCONDUCTING DEVICES
THIOLS
TIME RESOLUTION
TIMING PROPERTIES