Tobias Sommer

If two associations share an item, one may be remembered at the expense of the other (BC recalled but not AB). Here, we identify the neural processes by which this competition materializes and is resolved. We analyzed fMRI signal while participants studied sets of pairs that reliably induced pair-to-pair associative interference, but which participants could not fully resolve. Precuneus activity tracked retrieval of previous pairs during study of later overlapping pairs. This retrieval apparently produced interference by diverting study resources from the currently displayed pair. However, when activity in ventromedial prefrontal cortex, as well as anterior subregions of the hippocampus, was present while the earlier pair had been studied, interference was reversed, and both pairs were likely to be recalled. Angular gyrus and mid-frontal activity were related to interference resolution once the participant had seen both pairs. Taken together, associations compete via precuneus-mediated competitive retrieval, but ventromedial prefrontal cortex may neutralize this by ensuring that when the earlier association is remembered while studying the later pair, memories of the two pairs can overcome interference likely via activity in mid-frontal cortex and angular gyrus.