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Many times I have been asked about the way in which I processed and graphed the EEG data that I collected for my doctoral studies. For the purpose of my dissertation, I collected the EEG data using the Emotiv neuroheadset and used the EEGLAB open source software to process and graph the EEG data. In this post, I have simplified the steps that I took in order to process my EEG data. Please note that I self-educated myself by reading through tutorials, forum discussions, help pages, and much much more… I am positioning my doctoral work in the field of Neuro Information Science, which is marriage between neuroscience and information science. By no means do I claim to be a neuroscientist or a medical professional. Hope this helps some of you out there. Happy EEGLABing!
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I used the EEGLAB software, an interactive Matlab toolbox that is used for processing continuous and event-related EEG data, among others, in order to analyze the EEG data that I had collected for my research experiment. I used EEGLAB because it has been widely used in academia as well as in professional institutions, helping process complex EEG data while providing solid robust graphic user interface of the processed and the analyzed EEG data. Moreover, EEGLAB provided several data visualization graphs that helped me greatly in my work to find and establish patterns of brainwaves during each phase of the ISP model.
More specifically, I installed the EEGLAB Compiled version for Windows OS. Next, I will list the step-by-step ways in which I used EEGLAB to process my EEG data:
- Open the EEGLAB software.
- Go to the ‘File’ menu and click on ‘Import Data’ from the File menu options. Choose ‘From EDF File’.
- Find and choose the EEG data that is an EDF file saved on the hard drive and hit ‘Open’ in order to import it into EEGLAB.
- The ‘Load Data Using BIOSIG’ will open.
- In the ‘Channel List’ box, type numbers 3 through 16 with one spacebar between each number. This will map the 14 channels of the Emotiv neuroheadset data correctly to the EEGLAB software.
- Clic ‘Ok’
- Name the file in the field ‘Name It’.
- Click ‘Ok’
- Go to the ‘Edit’ menu and click on ‘Channel Location’ from the Edit menu options.
- Go to the Text Editor of the computer and create a file as shown below. Save as a CED file. These numbers will map the 14 sensor channels of the Emotiv neuroheadset channel locations correctly to the EEGLAB software.
- Go back to EEGLAB software and choose the ‘Read Locations’ button. (14location.ced)
- Choose the above CED file from your computer and highlight it.
- Click ‘Open’
- Choose ‘Autodetect’ from the ‘File Format’ menu.
- Click ‘Ok’.
- Click ‘Ok’.
- Go to the ‘Tool’ menu and click on ‘Remove Baseline’ from the Tool menu options.
- Click ‘Ok’.
- Go to the ‘Tool’ menu and click on ‘Run ICA from the Tool menu options.
- Click ‘Ok’.
- At this point, you will see a window like this. Depending on the memory of the computer, this part may be time consuming, if the memory is low.
- Go to the ‘Plot’ menu and click on ‘Channel Data’ from the Plot menu options.
- The brainwaves look like this graph and include outlier data that shows as irregularities in the brainwaves.
- Highlight the outliers of the brainwaves. These outliers show as peaks in the brainwaves.
- Click on the ‘>>’ button in order to move forward on the screen
- Repeat highlighting until the end of the data.
- Click ‘Reject’ in order to delete all the highlighted outlier data.
- Name this new data set in the field ‘Save it as File’.
- Click ‘Ok’.
- Go to the ‘Plot’ menu and click on ‘Channel Spectra and Maps’ from the Plot menu options.
- In the ‘Frequencies to Plot as Scalp Maps (HZ)’ indicate the desired brainwave frequencies to be graphed and plotted
- Click ‘Ok’.
- Depending on the chosen brainwave frequencies, such graph will be displayed.
- Save this plot as JPG file
Nilo Sarraf 