Multiple neural states of representation in short-term memory? It’s a matter of attention

Abstract

Short-term memory (STM) refers to the capacity-limited retention of information over a brief period of time, and working memory (WM) refers to the manipulation and use of that information to guide behavior. In recent years it has become apparent that STM and WM interact and overlap with other cognitive processes, including attention (the selection of a subset of information for further processing) and long-term memory (LTM—the encoding and retention of an effectively unlimited amount of information for a much longer period of time). Broadly speaking, there have been two classes of memory models: systems models, which posit distinct stores for STM and LTM (Atkinson and Shiffrin, 1968; Baddeley and Hitch, 1974); and state-based models, which posit a common store with different activation states corresponding to STM and LTM (Cowan, 1995; McElree, 1996; Oberauer, 2002). In this paper, we will focus on state-based accounts of STM. First, we will consider several theoretical models that postulate, based on considerable behavioral evidence, that information in STM can exist in multiple representational states. We will then consider how neural data from recent studies of STM can inform and constrain these theoretical models. In the process we will highlight the inferential advantage of multivariate, information-based analyses of neuroimaging data (fMRI and electroencephalography (EEG)) over conventional activation-based analysis approaches (Postle, in press). We will conclude by addressing lingering questions regarding the fractionation of STM, highlighting differences between the attention to information vs. the retention of information during brief memory delays.

The reliability of retro-cues determines the fate of noncued visual working memory representations

“…In other words, whether a noncued item is maintained or not may be a separate decision than whether it is attended or not. Such a dissociation is consistent with several models promoting a distinction between memory items that are in the current focus ("template") and other VWM representations that are held prospectively, or "on reserve" (LaRocque, Lewis-Peacock, Drysdale, Oberauer, & Postle, 2013;LaRocque, Lewis-Peacock, & Postle, 2014;Oberauer, 2002;Olivers, Peters, Houtkamp, & Roelfsema, 2011;Rerko & Oberauer, 2013;van Moorselaar, Olivers, et al, 2014;van Moorselaar, Theeuwes, & Olivers, 2014;Zokaei, Manohar, Husain, & Feredoes, 2014). These two types of VWM representations may have different mechanisms of maintenance, which operate more or less independently: (1) Task-relevant (here cued) representations are carried into a prioritized template status (which may also prioritize them for retrieval) regardless of the cue reliability, since there is little to lose by doing so.…”

Feature-based and spatial attentional selection in visual working memory

“…Although a number of state-based models of VWM have posited different activation states of representations that are established by the deployment of attention (LaRocque, Lewis-Peacock, & Postle, 2014), these models differ in their conceptualizations of how many items or elements can be selected. It has been proposed that only one item can be in the focus of attention (Oberauer, 2002;Olivers et al, 2011), thereby ensuring heightened processing efficiency for the selected information (Oberauer & Bialkova, 2009).…”

Does Contralateral Delay Activity Reflect Working Memory Storage or the Current Focus of Spatial Attention within Visual Working Memory?

“…Based on such observations, Drew et al (2011) suggested that these components do not exclusively reflect working memory storage, but also the allocation of focal attention to new target locations. When considered together, the hypothesis that CDA is not exclusively associated with storage but also with spatial attention, and the proposal that spatial attention results in a transient increase in the activation level of a subset of items that are currently held in working memory (e.g., Lewis-Peacock et al, 2012;LaRocque et al, 2014), suggest an alternative to the received storage interpretation of the CDA. Instead of reflecting the sustained maintenance of all visual items that are currently stored, this component may be associated with a relative transient activation of a subset of these items that were entered into working memory during the most recent encoding episode.…”