The cognitive neuroscience of visual short-term memory
Section snippets
Reconsidering the link between delay-period activity and ‘storage’
For decades, a governing assumption in STM research has been that the short-term retention of visual information is supported by regions that show elevated levels of activity during the delay period of STM tasks. Thus, for example, debates over the role of the prefrontal cortex (PFC) in STM and the related construct of working memory were framed in terms of whether or not its delay-period activity showed load-sensitivity — systematic variation of signal intensity as a function of memory set size 1
Event-related potential (ERP) correlates of STM
Another neural effect that has influenced models of visual STM capacity limitation is the contralateral delay activity (CDA), an ERP component that scales monotonically with STM load, but asymptotes at the psychophysically estimated capacity of an individual [34]. The CDA is widely interpreted as an index of the short-term retention of information (e.g., [35]), such that, for example, the presence of a CDA during visual search has been taken as evidence for ‘memory in search’ 36, 37], and the
Do distributed patterns of activity reflect STM or attention?
The multivariate methods reviewed here draw on two longstanding assumptions about STM. First, that stimulus representation is accomplished by anatomically distributed networks. Second, that the short-term retention of these representations is accomplished via elevated activity in these networks. Most often, however, STM tasks confound the focus of attention with the short-term retention, per se, of information. Recent studies have addressed this by first presenting two sample items, then
Conclusion
High-level cognition, including STM, emerges from dynamic, distributed neural interactions that unfold on multiple time scales. The adoption of methods that more closely align with these principles of brain function is leading to discoveries with important implications for cognitive models of STM and working memory (e.g., 51, 52]), and is informing ongoing research into such questions as the factors that underlie capacity limitations of visual STM 27•, 28•], and the relation between STM and
Conflict of interest statement
I declare that I have no conflict of interest.
References and recommended reading
Papers of particular interest, published within the period of review, have been highlighted as:
• of special interest
•• of outstanding interest
Acknowledgments
I thank Nathan Rose for helpful comments on this manuscript, and Adam Riggall for help with figures. The author was supported by National Institutes of Health grants MH064498 and MH095984.
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