bci2000.org BBS

Hello,

We recently installed the latest BCI2000 upgrade. When doing a 1D task with the cursor starting on the left side of the screen and moving towards the target on the right, we were able to easily adjust the speed of the cursor by changing either LR_B or the horizontal pixel rate (on the old BCI2000 version). However, in this new version the cursor moves incredibly slow (or not at all) in the L - R direction regardless of changes made to XPixelsPerSec or any of the related settings under the Statistics Tab.

Do you have any suggestions for increasing the cursor speed or what could be causing it move so slow (almost 2 minutes to get across the screen when it moves, other times it doesn't move at all).

Thanks,
Elizabeth Felton
UW-Madison

Elisabeth,

Please increase either Statistics->XGain or Statistics->XMean. They correspond to LR_B and LR_A in the old version, respectively. This should be described in the newest version of the UserManual.

Gerv

Hello,

Thanks for responding to my questions so quickly.

I have already tried changing the Xmean and Xintercept values, but neither seems to have an impact on the cursor speed. I change the values in Config, hit Set Config, the press Start. The cursor will be just as slow and then at the end of the set of trials I will go back into Config and they will have reverted back to the default values. I can understand if adaptation has taken place, but I'm not convinced that's what's happening (plus, the cursor never increases in speed).

I was able to get the cursor to move faster by increasing the sampling frequency and decreasing the sample block size. However, it went quickly across the screen once and then wouldn't move it all for the next trial. I stopped the set and found that the Stats values had changed drastically (XGain - 30000 (5 previously), XMean = 0 (-5 previously), etc.) This has also happened when I make changes to XPixelsPerSecond (although the cursor sometimes doesn't even move across the screen... the values seem to change immediately).


Thanks,
Elizabeth

Hi,

I highly suspect you have adaptation turned on for x. (XTrendControl > 0). However, if you want the cursor to always go across the screen by itself, you just have to give it a constant bias/offset in XMean/Offset and set XTrendControl to 0.

Let me know if this helps.

Gerv

Yes, that was the problem. Thank you!