Lower Parietal Encoding Activation Is Associated with Sharper Information and Better Memory

Abstract

Mean fMRI activation in ventral posterior parietal cortex (vPPC) during memory encoding often negatively predicts successful remembering. A popular interpretation of this phenomenon is that vPPC reflects "off-task" processing. However, recent fMRI studies considering distributed patterns of activity suggest that vPPC actively represents encoded material. Here, we assessed the relationships between pattern-based content representations in vPPC, mean activation in vPPC, and subsequent remembering. We analyzed data from two fMRI experiments where subjects studied then recalled word-face or word-scene associations. For each encoding trial, we measured 1) mean univariate activation within vPPC and 2) the strength of face/scene information as indexed by pattern analysis. Mean activation in vPPC negatively predicted subsequent remembering, but the strength of pattern-based information in the same vPPC voxels positively predicted later memory. Indeed, univariate amplitude averaged across vPPC voxels negatively correlated with pattern-based information strength. This dissociation reflected a tendency for univariate reductions to maximally occur in voxels that were not strongly tuned for the category of encoded stimuli. These results indicate that vPPC activity patterns reflect the content and quality of memory encoding and constitute a striking example of lower univariate activity corresponding to stronger pattern-based information.

Multimodal integration and vividness in the angular gyrus during episodic encoding and retrieval

“…We show further here that the linear pattern associated with vivid remembering in the AnG also occurs at encoding, suggesting that it is also involved in the construction of representations that enable vivid subsequent memories. We note that this pattern of encoding-related activity, i.e., greater AnG activation for subsequently remembered vs. forgotten memories, is inconsistent with some previous studies (e.g., Daselaar et al, 2009;Lee et al, 2017), which reported negative subsequent memory effects in the AnG (that is, greater activation for subsequently forgotten vs. remembered memories).…”

“…First, Uncapher and Wagner (2009) suggest that retention interval is a crucial predictor of the directionality of subsequent memory effects in the vPPC, whereby positive effects are more often associated with relatively short retention times (< 45 minutes), which is consistent with our present findings. Second, Lee et al (2017) speculate that positive subsequent memory effects would be observed in situations where the encoding of an item might benefit from retrieval and/or integration of related information (for example, when memory is measured via free recall, encoding an item as part of a broader context of temporally adjacent experiences would benefit subsequent retrieval). In the current study, participants were required to generate associations during encoding, thereby encoding the items into broader context, which might account for the positive subsequent memory effect that we have observed.…”

Discovering Event Structure in Continuous Narrative Perception and Memory

“…Changes in cortical activity patterns may drive encoding through a comparator operation in the hippocampus (Lisman & Grace, 2005; Vinogradova, 2001), or the prediction error associated with event boundaries may potentiate the dopamine pathway (Zacks, Kurby, Eisenberg, & Haroutunian, 2011), thereby leading to improved hippocampal encoding (Kempadoo, Mosharov, Choi, Sulzer, & Kandel, 2016; Takeuchi et al, 2016). Notably, the positive relationship between hippocampal activity and subsequent cortical reinstatement was specific to hippocampal activity at the end of an event; there was no significant relationship between hippocampal activity at the start of an event and subsequent reinstatement, and higher hippocampal activity during an event was associated with worse reinstatement (a similar relationship was observed in parietal cortex by Lee, Chun, & Kuhl, 2016). In this respect, our results differ from other results showing that the hippocampal response to novel events drives memory for the novel events themselves (for a review, see Ranganath & Rainer, 2003) – here, we show that the hippocampal response to a new event is linked to subsequent memory for the previous event.…”

Visual and semantic representations predict subsequent memory in perceptual and conceptual memory tests

“…The domains of object vision and semantic cognition have been getting closer, both by the fact that semantic cognition researchers often examine the nature of natural object representations at both visual and semantic levels Martin et al 2018), and also that both domains are relying increasingly on the use of advanced neural network models to reveal statistical regularities in object representation (Jozwik et al 2017;Devereux et al 2018). However, the episodic memory domain has been somehow disconnected from the other two, partly because it has tended to focus on broad categorical distinctions (e.g., faces vs. scenes) rather than in the component visual or semantic features (Lee et al 2016). The current study strengthens the links between the three domains by examining how the representations of the visual and semantic features of object pictures predict subsequent performance in episodic perceptual and conceptual memory tasks.…”