Is what goes in what comes out? Encoding and retrieval event-related potentials together determine memory outcome.

Understanding memory function amounts to identifying how events (cognitive and neural) at study eventually influence events at test. Many of the proposed cognitive correlates of memory-related event-related potentials (ERPs) at study resemble proposed cognitive correlates of other memory-related ERPs, recorded at test. We wondered whether a given known ERP feature at study might in fact reflect an effective-encoding process that is, in turn, tapped by another specific ERP feature, recorded at test. To this end, we asked which pairs of known memory-related ERP features explain common variance across a large sample of participants, while they perform a word-recognition task. Two early ERP features, the Late Positive Component (study) and the FN400 (test), covaried significantly. These features also correlated with memory success (d' and response time). Two later ERP features, the Slow Wave (study) and the Late Parietal Positivity (test), also covaried when lures were incorporated into the analysis. Interestingly, these later features were uncorrelated with memory outcome. This novel approach, exploiting naturally occurring subject variability (in strategy and ERP amplitudes), informs our understanding of the memory functions of ERP features in several ways. Specifically, they strengthen the argument that the earlier ERP features may drive old/new recognition (but perhaps not the later features). Our findings suggest the Late Positive Component at study, in some degree, may cause the FN400 to increase at test, together producing effective recognition memory. The Slow Wave at study appears to relate the Left Parietal Positivity at test, but these may play roles in more complex memory judgments and may be less critical for simple old/new recognition.