Introduction

Although the magnetic fields produced by peripheral nerve action potentials were recorded as early as 1960, the first noninvasive magnetic recordings from the human central nervous system were not performed until late in that decade. David Cohen recorded the first magnetoencephalogram (MEG) in 1968 at the Massachusetts Institute of Technology. Using a one-million turn copper coil in a magnetically shielded room and averaging 2500 samples triggered by a simultaneous electroencephalography (EEG) recording, Cohen (1968) was able to demonstrate evidence of magnetic oscillatory activity in the alpha band in four subjects. Subsequent work in the field of MEG was aided tremendously by the application of superconducting technology, which allowed the recording of spontaneous alpha activity without the use of signal averaging (Cohen, 1972).

From those first years of single-channel, homemade MEG instruments, the field of neuromagnetism has evolved into one of the multichannel recording devices with whole-head sensor coverage. This fact, combined with a larger installed base of MEG systems and increasing sophistication in data analysis techniques, has allowed MEG to take its place in the modern functional neuroimaging community as a technology that has enormous potential for application to psychiatric and neurologic illnesses. In the first 10 years after the seminal Cohen paper, fewer than 25 papers were published on the topic of MEG, but over 800 articles have been published in the last 10 years alone, testament to the rapid growth of the field in the three decades since its inception.