SQUIDs Scan the Magnetic Brain
Did you know that your brain produced magnetic fields? Neither did I until I found myself at the Oxford Centre for Human Brain Activity (OHBA). There a large magnetoencephalograph (MEG) scanner detects the position and strength of these very weak magnetic fields to help investigate neurological disorders such as epilepsy. Research into ADHD and other childhood disorders as well as Alzheimer’s and other memory-related disorders of ageing are also be studied using this technique.
Scanning for these magnetic fields, which are generated by the minute electric currents in the active neurones of the brain, only became possible by using superconductor technology cooled to a temperature of -269°C and most of the high superstructure of the scanner is taken up with a large internal tank of liquid helium . The MEG scanner uses an array of 306 highly sensitive SQUIDs (Superconducting Quantum Interference Devices) which detect the extremely weak fields and associated gradients generated by neural activity in different parts of the brain.
In practice, once the subject has been fitted with some electrodes to detect any eye or body movement during the scan, they sit or lie with part of the scanner, containing the detectors, forming a ‘helmet’ and they are then presented with sound through earphones and/or visual images on a screen. This stimulates electrical activity in different areas of the brain and the SQUIDs detect and map the resulting magnetic fields.
A feature of a MEG scanner is that as no radiation is produced subjects can be accompanied for the entire scan – children can have parents present and older people can have researchers or carers with them.
Although the scanner is non-invasive and does not emit radiation its sensitivity makes interference from external magnetic fields a major factor so it is housed in a small heavily shielded room which doesn’t allow a lot of space for photographic lights and cameras. On my pictures most of the lighting is by studio and portable flash balanced, where necessary, to the much lower brightness of the visual stimulus screen images and the images of the full height of the scanner use an ultra-wide angle lens
You can see the Gallery with more images of this fascinating bit of kit here.
I must thank OHBA for kindly arranging the excellent models who helped with this shoot, and whose patience I feel I must have tested!