Studio Tutorial: Design of the Example Experiment

This tutorial uses data from 6 subjects from the N400 paradigm in the ERP CORE dataset. To make this tutorial simpler, we've done some minor preprocessing to the data. We will explain how to download the preprocessed data on the next page. This section will provide a brief overview of the experimental paradigm and event codes.

Experimental Design and Results

The figure below (from Advanced ERP Data Analysis) shows the design of the N400 experiment and the grand average ERP waveforms from the CPz electrode site. The experiment involved a sequence of trials, each of which consisted of a prime word followed by a target word. The participants’ task was to press one of two buttons on each trial to indicate whether the target was semantically related or semantically unrelated to the preceding prime word. For example, they would press the related button for CHAIR preceded by TABLE and the unrelated button for SPIDER preceded by RAKE. Additional methodological details can be found in the original ERP CORE journal article.

Many studies have shown that a word will elicit a larger N400 component if it is semantically unrelated to the preceding word. This is exactly what was found in the present experiment. Panel B of the figure above shows that the ERP waveform for target words that were related or unrelated to the preceding prime word. As in previous research, the voltage was more negative from ~200-600 ms for the unrelated targets than for the related targets (but the overall waveform was positive because of other ERP components during that time period). This can also be visualized in Panel C, which shows the unrelated-minus-related difference wave. Note that the shaded area around the waveform shows the standard error of the mean at each time point.

Event Codes

The table below lists the event codes for the N400 experiment. An event code was produced for each prime word and each target word, and different codes were used depending on whether the target was semantically related or unrelated to the prime on that trial. Note that we used two different lists of words (for counterbalancing purposes), and that was also indicated by the event codes. An event code was also generated for each buttonpress response, with a code of 201 for correct responses and 202 for incorrect responses. Thus, a sequence of three event codes occurred on each trial (prime, target, and response).

	Word Type	Relatedness	Word List	Event Code	Occurrences
Stimuli	Prime	Related	List 1	111	30
	Prime	Related	List 2	112	30
	Prime	Unrelated	List 1	121	30
	Prime	Unrelated	List 2	122	30
	Target	Related	List 1	211	30
	Target	Related	List 2	212	30
	Target	Unrelated	List 1	221	30
	Target	Unrelated	List 2	222	30
	Accuracy			Event Code
Responses	correct			201	Variable
	incorrect			202	Variable

You can see these event codes in the screenshot below, which shows a 5-second period of EEG data. Event code 121 (a prime from list 1 that will be followed by an unrelated target) is followed by event code 221 (a target from list 2 that was preceded by an unrelated prime) and then by event code 201 (a correct response).

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Part 1	Part 2	Part 3	Part 4
General Overview	Filtering EEG	Plotting ERPs	Shifting Event Codes
Importing EEG Data	The EventList	ERP Information	Epoch Continuous EEG
➡️ Example Experiment	BINLISTER	Grand Average	Spectral Data Quality
Load and View Data	Epoch and Baseline	Bin Operations	Channels and Locations
	Artifact Detection	Filtering ERPs	Re-Sampling; Re-Epoching
	Averaging (ERPs)	Averaging (Channels)	Converting to CSD
	Artifact Correction	Channel Operations
	Interpolation	Measurement Tool