3.12: Review of Processing Steps

To review, here are the steps we carried out in this chapter:

• Loaded the single-participant ERPsets for each of our 10 participants
  • I provided a script that makes this faster
• Examined the number of accepted and rejected trials, ERP waveforms, and data quality measures for each participant to check for problems
• Made a grand average from our 10 participants
• Applied a low-pass filter to the ERPsets to attenuate the high-frequency noise
  • We did this first for the grand average, and then for the single-participant waveforms
• Obtained N400 amplitude “scores” (mean voltage from 300-500 ms) for the related and unrelated targets in each participant’s averaged ERP waveforms
  • We used the Preview window to verify that the scoring process was working correctly
• Performed a simple statistical analysis with the data from a single channel and a more complex analysis with the data from multiple channels
  • The N400 amplitude scores were exported into a text file and then imported into a statistical package
  • ERPLAB does not perform statistical analyses—we did not want to “reinvent the wheel,” and it is difficult to anticipate every possible statistical analysis someone would want to perform
  • We also compared the table of means from the statistical analyses with our grand average ERP waveforms to make sure that the analysis was performed correctly
• Used Channel Operations to create a new “cluster” channel that was an average of three of the original channels
• Used Bin Operations to create a difference wave by subtracting one bin from another

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