Event-related potential (ERP) correlates of memory blocking and priming during a word fragment test

Exposure to orthographically similar words impairs the ability to complete word fragments (e.g., Smith and Tindell, 1997), providing evidence that retrieval has been blocked (the Memory Block Effect or MBE). Two studies measured event-related potentials (ERPs) to explore the neural correlates of priming and blocking. The behavioral data in both experiments revealed that exposure to blocking words decreased fragment completions, increased intrusions (i.e., attempts to complete fragments using a blocking word), and slowed response times relative to control fragments. The ERPs in Experiment 1 indicate that priming and blocking begin during the early stages of lexical processing because lexical-related ERP amplitudes (N200) were larger than the control condition. A negative, frontal ERP emerged approximately 500 ms after fragment onset and was attenuated for blocking and primed fragments, which suggests that it reflects executive processes that govern solving fragments. Experiment 2 replicated these effects and revealed that both N200 and the late, negative ERP amplitudes varied according to whether or not the fragments were completed, which indicates that these ERPs reflect lexical activation and blocking processes. Collectively, the data suggest that blocking and priming begin to influence word fragment completion during early lexical processing and blocking impedes a normal memory search.