Individual Band-Power Reports

This pipeline allows you to specify markers of interest and generate averaged Band Power plots 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.

Epoch

In order to calculate the power in each frequency band (see below), the data is divided into ‘Epochs’. A Fourier transform is applied to each Epoch to calculate the power at each frequency. You can change the length of the Epoch window (in samples where the number of samples must be a power of 2) and the sliding window step size (the number of samples the data window is moved to form each successive Epoch).

Band frequencies

You can add as many frequency bands to your Analyzer as you want. You can also remove frequency bands that you do not need.

The limits of the frequency bands must be between 0 (lowest) and 64 (highest) Hz.

Report Specification

1. Element of Phase Name

First you can choose whether you want to select Phase Names or Element Names. If you built your experiment using EmotivPRO Builder, then you will have the option of generating reports for either the entire Phase or individual Elements. If you built your experiment using any other software (e.g. PsychoPy) select Elements here.

2. Parameters / Markers

Specify the marker labels here. The element name must match the marker label (in "type" column) found in your interval marker file. You can obtain the interval marker file when you export a record using EmotivPRO.

3. Channels

Specify any specific channels of interest. You can clear all the values here to generate a report for all the channels. Remember to specify channels that are available in your headset.

Finally click start to run the job.

Results

While your data is processing, the job management page will open. You can download your results file when the job is complete.

To understand details of the FFT implemented in EmotivPRO Analyzer please view the Band Power calculation section and for details of the fields in your .csv outputs please see the csv outputs section.

This pipeline will generate a plot with bandpower in decibels(dB) on the y-axis as below:

The above plot shows average bandpower in dB for each channel (O1 and O2), for the frequency band specified (8 to 12 Hz band). Sub plots orange and blue are the specified markers eyes closed and eyes opened respectively.