Equipment

Here a list of the cutting-edge instrumentation and technology the MEG Facility is equippded with.instrumentation:

Main Lab Components

 

• Magnetically Shielded Room
• Projector VPixx Propixx
• MEG console workstation for acquisition (in the scanner room)
• MEG remote console for preparation (in the preparation room)
• Stimulation station >>> visual, tactile, auditory stimulations
• EYE tracker

 

Meg Elekta Neuromag MEG device

The MEG lab is equipped with an Elekta Neuromag system, which allows to record the extremely small magnetic field generated by (mostly) neurons post-synaptic activity in the brain. The extreme sensitivity of the instrument can be exploited only in a Magnetically Shielded Room, shielding from external magnetic interferences. The sensor array of the Elekta Neuromag system is equipped with 102 triple-sensor elements (two planar gradiometers one magnetometer at each position) for combining the focal sensitivity of a pair of planar gradiometers with the deep source detection capability of a magnetometer. In our lab the level of noise (sensitivity) is, for both gradiometers and magnetometers, below 2.5 fT at 10 Hz. The sensors are SQUIDs (Superconducting Quantum Interference Devices) that operate at a temperature of 3 °K (-273 C°). Cooling down of the system is then required and is done using liquid helium, that is refilled once a week by MEG operators (usally on Monday morning). The sampling rate can be up to 5 kHz but 1 kHz is apropriate for the majority of the experiments. The helmet array is configured with 306 independently sampled sensors, evenly distributed over the surface of the head. Head coverage is from eyebrows to cerebellum with excellent coverage of temporal lobes. MEG measurements can be done in supine and seated position.

MEG and EEG integration

EEG and MEG originate from the same neurophysiological processes (currents of ions trigered by post-synaptic activity), but with some important differences.
The MEG records the magnetic fields which are less distorted than electric fields by the tissues between the originating neural population and the sensors. Since MEG recordings are less distorted on the different head tissues they allow for a better spatial resolution than EEG. Planning an EEG/MEG study it should be taken into account that MEG detects mostly tangential components of superficial brain currents while EEG instead is sensitive to both tangential and radial components, depending on the distortion of the field. EEG can be measured simultaneously to MEG at up to 128 channels. Be aware that preparing the EEG needs additional time for subject preparation. Contact the MEG staff for further advice on this topic.

GO EEG preparation.

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