Depicting Brain'S Activity With An Atomic Magnetometer
Andrei Ben-amar Baranga
Electrical and Computer Eng. Dept., Ben Gurion University, and Physics Dept., Nuclear Research Center – Negev, Beer Sheva, Israel
26/2/2015 ore 11:00
Extensive scientific effort is underway worldwide towards the understanding of one of the most intriguing human attributes, the mind. The past decade has seen fascinating developments in human brain activity imaging that have enabled researchers and clinicians to specify which brain systems take part in generating thoughts, emotions and actions. Yet, despite the progress to date, the complexity of brain functioning require huge scientific and technical efforts still to be done for brain imaging. CT and MRI provide outstanding anatomical brain imaging. PET, SPECT and fMRI provide partial information on brain activity with low spatial and temporal resolution and require injection of radioactive elements or the application of very high magnetic fields.
Stimulation of a neuron involves ion flux across the cytoplasmic membrane, followed by a rapid change in membrane potential and propagation of an electric pulse along the neuronal cell. The resulting electric potential may be measured on the scalp by electroencephalography (EEG), and the resulting magnetic field, by magnetoencephalography (MEG). These two totally non-invasive techniques, which provide complementary information, are sufficiently fast to study the temporal aspect of the mental operations. Magnetic fields, unlike electric potentials, are not affected by surrounding conducting tissues (like the extra-cranial tissue) and thus may reflect more accurately their source. In contrast to fMRI, both technologies measure directly fast electrophysiological events on a millisecond scale. However the brain magnetic field monitored outside the scalp is very weak, a milliard times weaker than earth magnetic field, and ultra high sensitive magnetometers are required. MEG systems based on liquid-He Superconducting Quantum Interference Device (SQUID) are commercially available today. A pioneering technology for MEG based on a Spin-Exchange Relaxation Free (SERF) atomic magnetometer was developed and published lately. The atomic magnetometer does not require cryogenic cooling and is therefore more reliable and substantially less expensive than the SQUIDs, opening the way to lower cost machines.