13.2: A2.2 Some Basic Solutions
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Resetting and Restarting
If restarting EEGLAB doesn’t work, I try restarting Matlab. Again, this is especially useful when I’m encountering a weird problem. If that doesn’t work, I try resetting ERPLAB’s working memory . This is a file that ERPLAB uses to store your current settings. The problem you’re having might be a side effect of one of your settings, or the settings may have become corrupted, so clearing the settings sometimes helps. To do this, select EEGLAB > ERPLAB > Settings > ERPLAB Memory Settings > Reset ERPLAB’s working memory .
And if restarting Matlab and resetting ERPLAB’s working memory doesn’t work, and the problem is really odd, I try restarting my computer. But that’s very rare. And just like I restart EEGLAB on a regular basis to prevent problems, I recommend restarting your computer once a week or so. If the weird problem persists, you might try moving to a different computer to see if that solves the problem.
Finally, you can try uninstalling and reinstalling EEGLAB and ERPLAB. Although rare, it is possible that the code has been corrupted. I recently encountered a case of a user who reported that one of the ERPLAB dialog boxes was missing some buttons, and she found that reinstalling ERPLAB solved the problem.
Missing Channel Locations or Data Quality Metrics in Datasets or ERPsets
Are your channel locations or data quality metrics missing from a dataset or ERPset? The most common reason for this is that you have applied EEG Channel Operations , ERP Channel Operations , or ERP Bin Operations to your data.
When you apply EEG or ERP Channel Operations, ERPLAB may not be able to figure out the location information for your new channel. For example, when you create a new channel, how can ERPLAB know the 3-D location of this new channel? Indeed, if you create a channel that is the average of several electrode sites, it doesn’t really have a location. There is a box you can check in the GUI labeled Try to preserve location information , and it can preserve the channel locations in many cases (e.g., when you re-reference your data). But it uses a fairly simple algorithm, and it may strip out your previous channel location information if the algorithm can’t figure out a sensible set of locations.
A similar issue arises for the data quality metrics that are computed during averaging. If you modify the channels using ERP Channel Operations or modify the bins using ERP Bin Operations to your data, ERPLAB has no way of knowing whether the data quality metrics are still valid. For example, if you create a new bin with a difference wave or an average of two prior bins, what is the data quality for this new bin? There may be analytic solutions for some cases, but these solutions would require many assumptions. As a result, ERPLAB strips out the data quality information from the ERPset that is created when you run ERP Channel Operations or ERP Bin Operations . Our logic in stripping out the channel location information or data quality metrics in these situations is that we’d rather eliminate the information than provide you with incorrect or misleading information.
Solutions to Miscellaneous Common Problems
- Make sure the MATLAB PATH is set correctly (especially if you’re having problems right after installing a new version). See the section describing the Matlab PATH near the end of Chapter 1 for more details.
- If you don’t see ERPLAB in the EEGLAB GUI, make sure that ERPLAB is installed inside the plugins folder within the EEGLAB folder (e.g., eeglab2020_0 > plugins > ERPLAB8.30). You should see a file named eegplugin_erplab.m inside that folder (and not inside another folder).
- Make sure you’re using the right version of Matlab, EEGLAB, ERPLAB.
- Some ERPLAB functions (e.g., filtering) require the Matlab Signal Processing Toolbox. You may need to install this toolbox. If you purchased Matlab yourself, you may need to buy this toolbox from The Mathworks. If you obtained Matlab through your institution, ask your IT group how to get this toolbox.
- If EEGLAB/ERPLAB/Matlab doesn’t seem to respond to the mouse or keyboard, you may have a window hidden somewhere that’s waiting for input. For example, if you open the GUI for filtering, and then you look at another window, the filtering GUI may be waiting for input, and nothing else will work right until you close the filtering GUI. In general, “figures” can be left open without interfering with other operations, but dialog boxes cannot.
- If you load an EEG dataset and try to view the EEG data with EEGLAB > Plot > Channel data (scroll), but some or all of the channels appear to be missing, the DC offset of the EEG signal is probably shifting the EEG outside of the range that is visible in the plotting window. To solve this, select Display > Remove DC offset in the plotting window.
- If you have trouble plotting ERP waveforms, click the RESET button in the plotting GUI to get rid of custom settings.
- EEGLAB also has a routine for extracting epochs from the continuous EEG ( EEGLAB > Tools > Extract epochs ), but do not use it !!! Instead, use ERPLAB > Extract bin-based epochs .
- Don’t forget to read the Frequently Asked Questions (FAQ) pages for both EEGLAB and ERPLAB .
- Also, EEGLAB and ERPLAB often print information in the command window that can help you figure out why things aren’t working properly.