trigger channels

Forum for discussion on different signal processing algorithms
Locked
emily
Posts: 40
Joined: 24 Mar 2008, 06:13

trigger channels

Post by emily » 07 Apr 2008, 07:53

Hello,
could someone please tell me what the trigger channels are for, is it necessary to have the same amount of trigger channels as you do in the montage? Or point me to where this might be explained in the manual.
thanks very much

mellinger
Posts: 1208
Joined: 12 Feb 2003, 11:06

Post by mellinger » 07 Apr 2008, 08:25

Emily,

BrainVision amplifiers have a trigger input. Signal changes there result in "marker" information being recorded by the Vision Recorder software.
In the BCI2000 RDAClient, these markers are translated into numbers, and written into a "marker channel".
From BCI2000, the marker channel is then treated like an additional EEG channel with a gain setting of 1.

Basically, this channel encodes information present at the amplifier's trigger input, with hardware pins mapped to bits in the marker channel.
"S" triggers are represented in the lower 8 bits of that channel's value, and "R" triggers are represented in the upper 8 bits.
For more details about hardware triggers, you might consult the manual that came with your amplifier.

To use trigger information in BCI2000, you might write a very simple BCI2000 filter that copies the marker channel into a BCI2000 state variable, and place that filter first in the signal processing module (see http://www.bci2000.org/wiki/index.php/P ... ing_Filter for more information about writing a filter).

HTH,
Juergen

emily
Posts: 40
Joined: 24 Mar 2008, 06:13

Post by emily » 07 Apr 2008, 18:44

Thanks Juergen,
I'll read up on them in the Biosemi manual.
cheers,

Locked

Who is online

Users browsing this forum: No registered users and 2 guests