Values for intercept and slope of horizontal/vertical moveme

[tanten]

As a BCI2000 starter, we recently managed to keep a system up and running. Among the different parameters, the values for intercept and slope of horizontal/vertical movement (LR_A, LR_B, UD_A, UD_B) puzzles me most.
The description provided by the manual is not really clear to me.
Further, it seems that the BCI2000 software sometimes automatically changes these values, which rarely results in 'division by zero' errors.

Could someone explain to me how these parameters influence the performance of the filtering or visualisation? Are the values independent of the User Application?

Thanking you in advance,

Tim

[gschalk]

Hi Tim,

The basic idea behind these variables is quite simple. These define the offset (e.g., UD_A) and gain (e.g., UD_B) for the two control signals for x and y movement. In other words, there are two control signal resulting from application of the MUD and MLR matrices. From these numbers, an offset is subtracted (e.g., UD_A) and the resulting number is multiplied with a gain (e.g., UD_B).

The purpose of this procedure is that the output control signal that is communicated to the User Application is always in a certain value range, so that User App does not have to be changed if SigProc changes.

If InterceptControl in Filtering is set to 0, these values are not changed adaptively. If it's set to 1, they are changed.

I hope this helps,
Gerv