MEG-EGI Integration Setup
Figure 1 shows the hardware setup available in the MEG lab allowing synchronous EEG (EGI system) and MEG recording. The EEG recording should be started before the MEG acquisition. In this setup, the MEG 1-kHz clock will trigger a TR event which indicates the beginning of the MEG acquisition to the EGI. The MEG 1-kHz clock should be physically connected to “MRI TR Pulse IN” on the Net Amps 300 Clock Synch I/O box using a BNC connector (see Figure 1).
Figure 1: MEG-EGI integration setup. For details, see GES Hardware Technical Manual (chapter GES 300 MR), June 2010, Electrical Geodesics, Inc.
The EGI acquisition software setting (Net Station on the MAC laptop) should be as follows:
- In “Digital Inputs Control panel>Source”, choose “TTL”
- In “Digital Inputs Control panel> Events”, choose “MR channels”
- In “Digital Inputs Control panel> Events> Advanced Event Setup”, make sure that the TR event (ex. value 128, if “MRI TR Pulse OUT” on the Net Amps 300 Clock Synch I/O box is connected to “IN 8” on the Trigger Unit box) is defined as “Track: MR Pulse” and Edge is activated.
The first pulse of 1-kHz clock from MEG triggers this TR event. “MRI TR Pulse OUT” remains 1 during the MEG acquisition. Therefore, check your STI-DINs correspondence according to the IN on the Trigger Unit box connected to the MRI TR Pulse OUT on the Net Amps 300 Clock Synch I/O box.