Kaia L. Vilberg

In two earlier experiments, we reported that left parietal cortex activity covaried with the amount of pictorial information recollected. The present experiment addressed the question whether our earlier results would generalize to verbal materials. Participants studied a series of word pairs and were then tested on individual old and new words in a modified remember/know task. In this task, participants were required to indicate whether recollection was accompanied by retrieval of study pairmates or not. As before, we operationally defined ‘amount recollected’ as the contrast between these two types of remember response. We found that the same left parietal region previously identified as sensitive to amount of recollected pictorial information is also sensitive to amount of recollected verbal information.

The present study addressed the question whether neural activity in left lateral parietal cortex is modulated by amount of information recollected. In two experiments (one using fMRI and the other ERPs), subjects first studied pairs of pictures presented for either 1 or 6 s. They then performed a standard “Remember/Know” recognition memory test in which the old items comprised one of the pictures from each studied pair. In both experiments, a surprise posttest indicated that subjects recollected more details about the study presentation of the items presented for the longer duration. In the fMRI experiment, recollection‐ and familiarity‐based recognition elicited activity in distinct cortical networks. Additionally, recollection‐related activity in left inferior parietal cortex was of greater magnitude for test items presented for 6 s than for 1 s. In the ERP study the “left‐parietal old/new effect”—a putative correlate of successful recollection—was likewise modulated by amount of information retrieved. Together, these findings provide further support for dual‐process models of recognition memory and add weight to the proposal that retrieval‐related activity in left inferior parietal cortex reflects processes supporting the online representation of retrieved episodic information. Hum Brain Mapp 2009.