Dynamic Updating of Working Memory Resources for Visual Objects

Abstract

Recent neurophysiological and imaging studies have investigated how neural representations underlying working memory (WM) are dynamically updated for objects presented sequentially. Although such studies implicate information encoded in oscillatory activity across distributed brain networks, interpretation of findings depends crucially on the underlying conceptual model of how memory resources are distributed.Here, we quantify the fidelity of human memory for sequences of colored stimuli of different orientation. The precision with which each orientation was recalled declined with increases in total memory load, but also depended on when in the sequence it appeared. When one item was prioritized, its recall was enhanced, but with corresponding decrements in precision for other objects. Comparison with the same number of items presented simultaneously revealed an additional performance cost for sequential display that could not be explained by temporal decay. Memory precision was lower for sequential compared with simultaneous presentation, even when each item in the sequence was presented at a different location.Importantly, stochastic modeling established this cost for sequential display was due to misbinding object features (color and orientation). These results support the view that WM resources can be dynamically and flexibly updated as new items have to be stored, but redistribution of resources with the addition of new items is associated with misbinding object features, providing important constraints and a framework for interpreting neural data.

Human short-term spatial memory: Precision predicts capacity

“…Our experimental results do not support the idea of a fixed, upper limit of 4 or 7 for short-term allocentric spatial memory capacity in humans. Our findings are also inconsistent with the proposal that working memory consists of a pool of resources that can be allocated flexibly to provide either a small number of high-resolution representations or a large number of low-resolution representations (Bays & Husain, 2008;Gorgoraptis et al, 2011;van den Berg et al, 2012). Instead, we determined that the number of locations held in short-term allocentric spatial memory can be predicted based on memory performance for individual locations.…”

“…The ''slot model'' is consistent with classical views of working memory in which a limited number of items or chunks of information can be temporarily held in memory, and both Cowan's (Cowan, 2001) and Miller's (Miller, 1956) conceptions of working memory capacity fall into this category, with capacities limited to 4 and 7, respectively. On the other hand, ''resource models'' propose that working memory comprises a pool of resources that can be allocated flexibly to provide either a small number of high-resolution representations or a large number of low-resolution representations (Bays & Husain, 2008;Gorgoraptis, Catalao, Bays, & Husain, 2011;van den Berg, Shin, Chou, George, & Ma, 2012). These opposing theories have led researchers to conduct a myriad of studies on human visual working memory capacity, the results of which favor either the ''slot model'' or the ''resource model'', depending on the specifics of the experiment (Ma, Husain, & Bays, 2014).…”

In search of the focus of attention in working memory: 13 years of the retro-cue effect

“…These findings converge with other studies that have observed that one item can be retained in a privileged state (of heightened accessibility) even when other items are cued between the initial cueing and testing (Rerko & Oberauer, 2013;Souza, Rerko, & Oberauer, 2015) or are subsequently encoded into WM (Gorgoraptis, Catalao, Bays, & Husain, 2011;. In sum, focused attention can be used to prioritize one WM item in a manner that is robust against distractions from the external or internal focus of attention.…”

Evidence for two attentional components in visual working memory.

“…In contrast, errors reflecting confusion or binding problems within the sequence were only significantly increased, and only above chance, at the middle position in the sequence. Such a response might be characterized as reflecting a binding error, that is an incorrect pairing of features from two objects (see also Gorgoraptis et al (2011), and may reflect a role for executive resources in preventing conjunction errors emerging between temporally adjacent items in a sequence.…”