The present two studies looked for measurable differences between correct recognition of targets and false recognition of critical lures in a DRM like task.   

Past Research
Previous research is mixed as to whether or not there are measurable differences between the appropriate recognition of target items and the false recognition of critical lures on old/new recognition memory tests. Researchers have demonstrated that participants will report differences in the subjective experience of correctly accepting targets and falsely accepting critical lures on such measures as the MCQ, but these differences are not always found. Likewise Miller et al. review research that had found measurable differences in the amount of brain activity associated with the correct acceptance of targets and the false recognition of critical lures, but also review other research that has not observed these differences. 

Present Study
Using ERPs these researchers recorded electrical conductance on the surface of participants’ scalps (as indicated in figure 1) as they were completing a memory test. 

Logic Behind ERP
These researchers were interested in measuring P300 waves. P300s occur when information presented to subjects is rare and meaningful.  On memory tests items gain meaningfulness by being old.  So the question is whether false memories will produce P300s and whether they will be similar to the P300s produced by memories for targets.

In particular, these researchers looked for differences in the amplitude of the P300 waves. Larger waves (waves higher in amplitude) are thought to be associated with increased brain activity. Also, differences in the latency of the P300 waves were measured. Laency simply refers to how long a P300 wave lasted. Finally, these researchers looked for differences in the distribution of activation across the scalp. As can be seen in figure 1 of their paper, there are several different areas of the brain where activity is being measured. Johnson’s triacrchic model claims that the task or characteristic of the stimuli will determine the amplitude of the P300, which also may result in different readings across the scalp. These different areas of the scalp are thought to be associated with different neural generators. The activation across the scalp can give a gross approximation of the underling regions of the brain that are contributing to an observed behavior. 

Procedure
Participants viewed 25 lists of 14 words presented visually to participants. The 14 words on a list were all strong associates of a critical non-presented word. In addition to this critical lure the first or second strongest associate of the critical lure was used as an additional critical lure. After, viewing the words at study participants completed a 333-item recognition test. Of these 333-items, 50 were targets, 50 were critical lures, and 233 were unrelated lures. The presentation of the different types of items was randomized so that there would be several unrelated lures presented between targets and critical lure, allowing for the oddball effect to be measured. This simply means that the pattern of activity on the scalp is pretty similar across unrelated lures and will spike when a target or critical lure is presented.

Analysis of the data
Two different corrections were used to calculate P300 waves. The baseline to peak P300 index is the most common correction used, but these researchers make an argument that a different correction, the peak-to-peak index is actually better suited for these data. The peak-to-peak method takes the amount of activity while the word is being presented and subtracts out the lowest point of activity from the time after the maximum P300.

Results
Participants correctly recognized 89% of the targets, and falsely recognized 51% of the critical lures. Again these researchers were interested in testing for differences between ERP activity for the correct recognition of targets and the inappropriate recognition of distractor items. There was one difference found between these types of recognition judgments. P300 waves lasted longer for the correct acceptance of targets than for the false recognition of critical lures, although there was no difference between the amplitude of the P300 waves associated with each of these.

Discussion
Several different explanations are provided for the differences in latency between correct recognition of targets and false recognition of critical lures. First, the researchers suggest that these patterns may reflect an unconscious knowledge that the critical lure was not actually presented. Second, these differences could be similar to the finding that participants experience less sensory detail when falsely recognizing a critical lure than when correctly recognizing a target.