Contributions:CCEPFilter

An example video showing one channel of the CCEP filter.

Introduction

Cortico-cortical evoked potentials (CCEPs) are generated as a response to stimulation within the cortical zone. To best view this response, the CCEP filter time locks the signal to the stimulation and allows the user to view the CCEPS from every recording electrode. There are many adaptable parameters to include flexibility for a variety of experiments.

Location

http://www.bci2000.org/svn/trunk/src/contrib/SignalProcessing/CCEPFilter

Versioning

Authors

• Will Engelhardt (engelhardt@neurotechcenter.org)

Version History

• 05/17/2023 - First working version

Source Code Revisions

• Initial development: 7199
• Tested under: 7303
• Known to compile under: 7364
• Broken since: --

Integration into BCI2000

Confirm your BCI2000 svn is up to date and you have built the most recent version. Insert Start executable CCEPFilter --local as the SignalProcessing filter into the batch file that you want to run.

Parameters

General Configuration

ChannelThreshold

Magnitude threshold which defines a CCEP. Specify the units, such as uV or mV. The surpassing of this threshold is calculated with the CCEPEpochLength data (after the specified TriggerLatencyLength) after being subtracted from the average baseline value (the data during the BaselineEpochLength). If the threshold is surpassed, the channel is yellow. A horizontal bar is also displayed to show where the signal surpasses the threshold. If both the high and low thresholds are surpassed, both bars are displayed. If the signal stays below the threshold, it stays white.

OnsetExpression

Expression that defines the stimulus onset. See the Expression syntax page for more information. This expression should be true when the stimulation is triggered.

Stimulator

An optional setting that configures parameters for a certain device. Currently, only the NeuroOmega is implemented. This setting helps fills in other settings that are "auto" (such as TriggerLatencyLength), and configures the visualization to show which channels are stimulating in light blue. Keep it as auto if the device is not listed.

Duration settings

These parameters all should have units of time (e.g. milliseconds), or auto.

• 
  The three timing sections of the CCEP filter visualization.

BaselineEpochLength

The duration of desired baseline data. This baseline data is helpful for visualizing the data before the stimulation, and is also used to calculate the average signal value from which the threshold is calculated.

TriggerLatencyLength

Approximate latency of the hardware stimulation from the OnsetExpression. The timing should surpass the stimulation artifact of the signal, so the CCEP is accurately calculated. If the length is too small, then the scaling of the visualization will be off, and the calculation of detecting CCEPs will also be inaccurate.

CCEPEpochLength

Duration of time after the baseline and latency. Essentially the amount of time that is needed to view the CCEP.

Counting settings

• 
  The three counting parameters of the CCEP filter visualization. The yellow circles represent counting every third OnsetExpression, then the pink arrows display averaging every 5th number. The original plot is then held because HoldPlots is greater than 1.

These parameters must be integers, they specify a quantity to count.

EpochsToAverage

Number of times the OnsetExpression is met to average together. The resulting average will then be displayed once the number is met. This is helpful if the OnsetExpression is frequently true within a short period of time.

OnsetPeriod

Count every number of times the OnsetExpression is evaluated true. In other words, skip every OnsetPeriod - 1. This is helpful if you want to visualize a time range in which the OnsetExpression is met multiple times. If you are also averaging the plots, it will only average the signals specified by this period.

HoldPlots

The number of plots to hold. If it is 0 or 1, only the most recent signal will be shown. Any number higher, and that amount of signals will be shown. The most recent signal will always be white/yellow, while the others will be darker grey, with the oldest as the darkest.

Visualization

• 
  A demonstration of the three visualization parameters of the CCEP filter. The specific channels are chosen through the Source parameter Online Processing.

VisImageWidth

The total width in pixels that the CCEP visualization will fill. Each sub-window will be adjusted accordingly.

VisImageHeight

The total height in pixels that the CCEP visualization will fill. Each sub-window will fill a portion.

VisMaxWindows

The maximum amount of windows that are desired to be visualized. To choose which windows are visualized, use the parameter in the Source tab, in the Online Processing section, TransmitChList. This lists the channels that are sent to the SignalProcessing filter and on. If VisMaxWindows is less than the number of channels in this list (and non-zero), the first number of windows will be shown.

See also

User Reference:Filters, Contributions:SignalProcessing