Record based ERP Experiment Analysis

This pipeline allows you to specify markers of interest and generate averaged ERP plots for each sensor, for each record submitted.

Slew limit

You can set a slew rate limit to control the EEG signals between successive samples, up to a maximum value. Large voltage step changes from one sample to the next sometimes occur due to electrostatic discharge from the subject (participant), headset movements, or other artifacts. The effect of voltage step changes on filtered signals, and fast Fourier transform (FFT) epochs can artificially persist for a long time after the event. Setting a maximum slew rate limits the extent of step changes and reduces its impact without significantly affecting the EEG signal components. The default slew rate in Analyzer is 30 microvolts. However, you can enter any positive value here.

Referencing

The data processed by Analyzer can be referenced to an aggregate of all the data selected. The available aggregate functions are:

• Mean

• Median

• Interquartile mean

• None (deactivates re-referencing)

Filter Coefficients

Default values are set for you. However, you can change these values if you want to.

If you do not know what you are doing, please use the default values. The default values are shown below.

Target Markers

For ERP analysis, you can add one or more target markers.

First you must give your target marker(s) a name. Then you must select either Value or Label:

• If you select Value, you must input a numerical value.

• If you select Label, you must input a description, like ‘high’.

The marker label/values can be found in your interval marker file when export a record using EmotivPRO.

By clicking on the + icon you can add more target markers. You can delete a target marker by clicking on the trash bin icon next to it.

Time Before and Time After (Epoch)

Time Before, also known as pre event baseline allows you to input a period before the onset of your event. Time after, indicates the period after the onset of your event that you want to analyze.

Once you’ve input the ranges you need for ERP analysis, click on Start.

Results

While your data is processing, the job management page will open. You can download your results file when the job is complete. This pipeline will output a plot of ERPs for each sensor as below:

The pipeline will also output a .csv file - *subject_id.csv

This file gives your the EEG amplitude in µV for all ERPs used for plotting.

time	eeg.af3_standard	marker_name_standard	marker_value_standard	eeg.af3_deviant	marker_name_deviant	marker_value_deviant
-0.097903013	0.370041117	standard	A	0.664820528	deviant	B
-0.093962908	0.373191418	standard	A	0.687847361	deviant	B
-0.090122938	0.282137158	standard	A	0.828101521	deviant	B

The time column is epoched/event time. Zero indicates the onset of the event/marker specified. Negative(-) values indicate pre-event baseline period and positive (+) values indicate the time after the onset of the event.

On the right end of this .csv file you can find the number of trials/epochs averaged for each channel and marker specified:

channel_names	channel_counts_standard	channel_counts_deviant
eeg.af3	472	124
eeg.f7	427	112
eeg.f3	471	124