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Working memory (WM) is critical to many aspects of cognition, but it frequently fails. Much WM research has focused on capacity limits, but even for single, simple features, the fidelity of individual representations is limited. Why is this? One possibility is that, because of neural noise and interference, neural representations do not remain stable across a WM delay, nor do they simply decay, but instead, they may “drift” over time to a new, less accurate state. We tested this hypothesis in a functional magnetic resonance imaging study of a match/nonmatch WM recognition task for a single item with a single critical feature: orientation. We developed a novel pattern-based index of “representational drift” to characterize ongoing changes in brain activity patterns throughout the WM maintenance period, and we were successfully able to predict performance on the match/nonmatch recognition task using this representational drift index. Specifically, in trials where the target and probe stimuli matched, participants incorrectly reported more nonmatches when their activity patterns drifted away from the target. In trials where the target and probe did not match, participants incorrectly reported more matches when their activity patterns drifted toward the probe. On the basis of these results, we contend that neural noise does not cause WM errors merely by degrading representations and increasing random guessing; instead, one means by which noise introduces errors is by pushing WM representations away from the target and toward other meaningful (yet incorrect) configurations. Thus, we demonstrate that behaviorally meaningful drift within representation space can be indexed by neuroimaging.
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Noun phrase representational complexity reduces maintenance cost in working memory by increasing distinctiveness between referents
Previous studies have shown that representationally complex referents are encoded slower into working memory (WM) but are retrieved faster (Hofmeister, 2011; Karimi & Ferreira, 2016). However, the cost of maintaining complex representations is still not well understood. Through two self-paced reading experiments, we investigated the cost of encoding, maintaining and retrieving complex representations in WM. While we replicated the facilitatory effect during retrieval, the slowdown during encoding was not consistent across our experiments. More critically, for the first time, our experiments demonstrated that maintaining complex representations in WM is less costly than maintaining their simple counterparts. Furthermore, we found that WM maintenance cost is reduced because complex target noun phrases are more distinct from other competing referents in WM than simple ones. Overall, our results showed that the semantic elaboration of complex representations can reduce maintenance cost and provided new perspectives into this understudied WM process.
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- Award ID(s):
- 2116952
- PAR ID:
- 10432471
- Editor(s):
- Culbertson J; Perfors A; Rabagliati H; Ramenzoni V
- Date Published:
- Journal Name:
- Proceedings of the Annual Conference of the Cognitive Science Society
- Volume:
- 44
- ISSN:
- 1069-7977
- Page Range / eLocation ID:
- 1298-1305
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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