Magnetoencephalography (MEG)

Magnetoencephalography (MEG) is a non-invasive neuroimaging technique that measures the magnetic fields generated by the electrical activity of neurons in the brain. MEG provides high temporal resolution and is used to study brain function and connectivity.

Principles

MEG is based on the principle of electromagnetic induction, in which changes in magnetic fields induce electrical currents. When neuronal populations in the brain generate electrical activity, they also produce small magnetic fields. These magnetic fields can be detected and measured using highly sensitive sensors called superconducting quantum interference devices (SQUIDs).

Data Acquisition

During a MEG recording session, the subject’s head is placed inside a magnetically shielded room to minimize external interference. The sensors are arranged in a helmet-like device called a sensor array, which is positioned close to the scalp. As the subject performs tasks or rests, the MEG system continuously records the magnetic fields produced by the brain activity.

Data Analysis

MEG data analysis involves processing the recorded magnetic signals to extract meaningful information about brain activity. This typically includes preprocessing steps such as noise removal, spike detection, and filtering. Advanced analysis techniques, such as source localization and functional connectivity analysis, are then applied to identify the brain regions involved in specific tasks or cognitive processes.

Applications

MEG has diverse applications in neuroscience and clinical research. It is used to study brain dynamics, investigate sensory and cognitive processes, map functional brain networks, and understand the neural basis of various neurological disorders. MEG is particularly valuable in capturing the rapid temporal dynamics of brain activity, complementing other imaging techniques such as functional magnetic resonance imaging (fMRI) that offer higher spatial resolution but lower temporal resolution.