Neuromagnetic

Neuromagnetic refers to the magnetic fields generated by neural activity in the brain and to the study and measurement of those fields. These magnetic signals arise primarily from synchronized currents in the apical dendrites of cortical pyramidal neurons, producing very weak fields that pass through the skull with limited distortion.

Measurement of neuromagnetic activity is accomplished with sensitive detectors such as superconducting quantum interference devices (SQUIDs) or, more recently, optically pumped magnetometers. Measurements are conducted in magnetically shielded rooms to reduce ambient interference, enabling the capture of millisecond-scale dynamics that reflect rapid neural processing.

The analysis of neuromagnetic data involves forward modeling and inverse problem techniques. A forward model estimates the magnetic field produced by hypothesized neural sources, while inverse methods aim to localize actual sources from sensor data. Common approaches include equivalent current dipole modeling, minimum norm estimates, and beamformers, often incorporating realistic head models derived from anatomical MRI.

Applications of neuromagnetic measurements are broad. In clinical settings, magnetoencephalography (MEG) is used for functional brain mapping, presurgical localization of epileptogenic zones, and assessment of sensory and cognitive function. In research, neuromagnetic methods investigate perception, language, attention, motor control, and sleep. Compared with electroencephalography (EEG), neuromagnetic signals are less distorted by skull and scalp, though MEG is more sensitive to activity in superficial cortical regions and less capable of detecting deep sources.

Historically, pioneering work in the 1960s and 1970s established neuromagnetism as a noninvasive window into brain dynamics, with MEG becoming a mainstream research and clinical tool in subsequent decades. Advances in sensor technology and computational methods continue to expand its capabilities.