EEG

A Brain Vision (Morrisville, NC) system is used for the monitoring/recording of spontaneous EEG signal from ocular sites (used in the artifact rejection process) and for the recording of electric evoked potentials (eEPs) simultaneously with the magnetic evoked potentials (mEPs) that form the basis of the lab’s research capabilities.

BRAIN VISION SYSTEM

We have a DC 32-channel system with a DC-capable 32-channel digital EEG amplifier with a USB interface. The BrainAmp DC Amplifier and the PowerPack are set up inside the MSR during recording. These two devices (which are near the subject’s feet, as far from the dewar as the cable from the EEG cap will allow) are connected to the BrainAmp USB2 Adapter via a fiber optic cable. This USB2 Adapter is outside the MSR and connected, via a USB cable, to the PC used for the EEG signal acquisition.

ELECTRODES/ELECTRODE CAPS

For both spontaneous and evoked potentials, we use electrode systems from EASYCAP GmbH (Herrsching, Germany). All electrodes are sintered Ag/AgCl Multitrode flat disks. For evoked studies, we use custom-fabricated caps. These caps are standard in that they contain 29 Multitrode B18-LU-150-MEG compatible electrodes in a standard 10-20 system array, as well as 3 Multitrode B18-HU-200-MEG electrodes for monitoring ocular signals, one Multitrode B18-LU-150-MEG ground electrode, and one Multitrode B18-LU-150-MEG Ref electrode.

RECORDING NOTES

For both artifact monitoring and full cap evoked recording, we use two references, located on the left and right mastoid. The right mastoid is typically the site used as reference during data acquisition; electrode signals are then re-referenced to the left mastoid site during offline averaging.

Electrode impedances are kept below 6kΩ. To assess impedance, we use the EIM-107 Prep-Check Plus multi-lead impedance meter from General Devices (Ridgefield, NJ). We have found this to be a very handy device, being easily programmable to test at various thresholds and in various sequences.

Another helpful tool has been ASP (Irvine, CA) CIDEX OPA, which we use for disinfecting electrodes and caps. This solution is much less volatile and corrosive than other disinfecting agents, and does not require a specially vented fume hood for use.

BIOAMPLIFIER SYSTEM FOR EOG RECORDINGS

A bioamplifier system is used for the monitoring/recording of EOG signals (from ocular sites, used in the artifact rejection process) simultaneously with magnetic evoked potentials (mEPs).

BIOAMPLIFIER HEADBOX

Our 24-channel bioelectric amplifier and headbox are products of SA Instrumentation Co. (Encinitas, CA). The amplifier is electrically and magnetically isolated, and run from a DC power source. The headbox accepts loose-lead electrodes. We can also utilize electrode caps for this system inside the MSR.