FasTrak coregistration issue

Bugs
1

Hi,

We are having an issue performing the coregistration of electrodes.

The problems seems to be due to the mounted receiver not being used as a reference. When the subject moves their head, the reference space changes (the stylus does not 'follow' the mounted receiver).

Any ideas if this is a brainstorm issue or something that needs to be solved using PiMng?

We would appreciate any help

2

@Marc.Lalancette

3

Can you check if your digitizer is acquiring two points? [stylus + reference]

Please refer to this discussion and check the output on the terminal:

4

We got the following output from brainstorm:

>> global Digitize
>> Digitize.SerialConnection

   Serial Port Object : Serial-COM4

   Communication Settings 
      Port:               COM4
      BaudRate:           9600
      Terminator:         'LF'

   Communication State 
      Status:             open
      RecordStatus:       off

   Read/Write State  
      TransferStatus:     idle
      BytesAvailable:     0
      ValuesReceived:     0
      ValuesSent:         2

After collecting a data point, we get the output:

>> fprintf(Digitize.SerialConnection,'%s','P')
>> Digitize.SerialConnection

   Serial Port Object : Serial-COM4

   Communication Settings 
      Port:               COM4
      BaudRate:           9600
      Terminator:         'LF'

   Communication State 
      Status:             open
      RecordStatus:       off

   Read/Write State  
      TransferStatus:     idle
      BytesAvailable:     0
      ValuesReceived:     94
      ValuesSent:         3

We noticed that the number of values sent in the beginning is 2. In the discussion you referred to, there should be only 1. Are we missing something?

Thank you,

5

This is difficult to diagnose remotely. But it's very likely a configuration issue with your system. Please double check your system is configured the same way as explained in the tutorial, same number of sensors, plugged in the correct inputs on the digitizer. I just saw it doesn't say where to plug them, but I believe Brainstorm expects the stylus to be in "one" and the other receiver in "two".

If that is correct, my best guess would be the emitter is not oriented correctly with respect to how it is configured. Only half the volume around it will work properly. If you're on the other side, it will "correct" the opposite way when the head moves, which would cause what you're seeing. Please see the last point in the last section in the tutorial (Accuracy).

You can also do some more tests on your side, first to confirm there is no errors with your hardware (in PiMgr), and if you get the same behavior in PiMgr. If the hardware and PiMgr look ok, only then it would possibly be an issue with Braisntorm. Maybe you can also try the new version, which is mostly a change of the GUI, but also uses the newer Matlab interface for serial communication. I doubt that will change anything, but it's an easy thing to try. We've been using this new version for a few months here, the only reason it's not yet released is because I haven't had time to update the tutorial.