Multivoxel Pattern Analysis Reveals Increased Memory Targeting and Reduced Use of Retrieved Details during Single-Agenda Source Monitoring

Abstract

We used multivoxel pattern analysis (MVPA) of functional MRI (fMRI) data to gain insight into how subjects' retrieval agendas influence source memory judgments (was item X studied using source Y?). In Experiment 1, we used a single-agenda test where subjects judged whether items were studied with the targeted source or not. In Experiment 2, we used a multiagenda test where subjects judged whether items were studied using the targeted source, studied using a different source, or nonstudied. To evaluate the differences between singleand multiagenda source monitoring, we trained a classifier to detect source-specific fMRI activity at study, and then we applied the classifier to data from the test phase. We focused on trials where the targeted source and the actual source differed, so we could use MVPA to track neural activity associated with both the targeted source and the actual source. Our results indicate that single-agenda monitoring was associated with increased focus on the targeted source (as evidenced by increased targeted-source activity, relative to baseline) and reduced use of information relating to the actual, nontarget source. In the multiagenda experiment, high levels of actual-source activity were associated with increased correct rejections, suggesting that subjects were using recollection of actual-source information to avoid source memory errors. In the single-agenda experiment, there were comparable levels of actual-source activity (suggesting that recollection was taking place), but the relationship between actual-source activity and behavior was absent (suggesting that subjects were failing to make proper use of this information).

Distributed Patterns of Reactivation Predict Vividness of Recollection

“…A few studies have reported a link between MVPA measures of cortical reinstatement and the subjective experience of recollection (Gordon, Rissman, Kiani, & Wagner, 2013;Ritchey, Wing, Labar, & Cabeza, 2013;Staresina, Henson, Kriegeskorte, & Alink, 2012;Kuhl, Rissman, Chun, & Wagner, 2011;Johnson et al, 2009;McDuff, Frankel, & Norman, 2009). However, most of these studies have assessed recollection as an all-or-none phenomenon that is either present or absent (e.g., with a remember/know paradigm; Tulving, 1985).…”

Reinstatement of distributed cortical oscillations occurs with precise spatiotemporal dynamics during successful memory retrieval

“…MVPA relies on classifying neural activity during retrieval to dissociate broad manipulations such as category or task that are present during encoding (13)(14)(15)(16). MVPA, however, is unable to directly examine whether successful retrieval reinstates the neural representations of individual items.…”

Fidelity of neural reactivation reveals competition between memories

“…During the critical retrieval phase, subjects were presented with word cues and attempted to covertly recall target associates, indicating by button press whether they were able to recall the specific image vs. a more general memory for the category of the image (face/scene). The scanned encoding and retrieval rounds were followed by a behavioral posttest that reassessed memory for AB and DE pairs, allowing for measurement of the impact that AC learning had on memory for previously learned AB pairs.Reactivation was assessed via multivoxel pattern analysis (MVPA)-a technique well-suited to measuring reactivation (20)(21)(22). Accordingly, we first trained a pattern classifier to discriminate patterns of activity within the VOTC that were associated with the encoding of words paired with faces vs. scenes; we then applied the classifier to retrieval trials to estimate the degree to which VOTC responses reflected face vs. scene reactivation-that is, the fidelity with which target memories were retrieved.…”

“…Reactivation was assessed via multivoxel pattern analysis (MVPA)-a technique well-suited to measuring reactivation (20)(21)(22). Accordingly, we first trained a pattern classifier to discriminate patterns of activity within the VOTC that were associated with the encoding of words paired with faces vs. scenes; we then applied the classifier to retrieval trials to estimate the degree to which VOTC responses reflected face vs. scene reactivation-that is, the fidelity with which target memories were retrieved.…”