Attention In Visual Working Memory Research Articles

Neural Signatures of Competition between Voluntary and Involuntary Influences over the Focus of Attention in Visual Working Memory.

Adaptive behavior relies on the selection and prioritization of relevant sensory inputs from the external environment as well as from among internal sensory representations held in working memory. Recent behavioral evidence suggests that the classic distinction between voluntary (goal-driven) and involuntary (stimulus-driven) influences over attentional allocation also applies to the selection of internal representations held in working memory. In the current EEG study, we set out to investigate the neural dynamics associated with the competition between voluntary and involuntary control over the focus of attention in visual working memory. We show that when voluntary and involuntary factors compete for the internal focus of attention, prioritization of the appropriate item is delayed-as reflected both in delayed gaze biases that track internal selection and in delayed neural beta (15-25 Hz) dynamics that track the planning for the upcoming memory-guided manual action. We further show how this competition is paralleled-possibly resolved-by an increase in frontal midline theta (4-8 Hz) activity that, moreover, predicts the speed of ensuing memory-guided behavior. Finally, because theta increased following retrocues that effectively reduced working-memory load, our data unveil how frontal theta activity during internal attentional focusing tracks demands on cognitive control over and above working-memory load. Together, these data yield new insight into the neural dynamics that govern the focus of attention in visual working memory, and disentangle the contributions of frontal midline theta activity to the processes of control versus retention in working memory.

The influence of depth on object selection and manipulation in visual working memory within a 3D context.

Recent studies have examined whether the internal selection mechanism functions similarly for perception and visual working memory (VWM). However, the process of how we access and manipulate object representations distributed in a 3D space remains unclear. In this study, we utilized a memory search task to investigate the effect of depth on object selection and manipulation within VWM. The memory display consisted of colored items half positioned at the near depth plane and the other half at the far plane. During memory maintenance, the participants were instructed to search for a target representation and update its color. The results showed that under object-based attention (Experiments 1, 3, and 5), the update time was faster for targets at the near plane than for those at the far plane. This effect was absent in VWM when deploying spatial attention (Experiment 2) and in visual search regardless of the type of attention deployed (Experiment 4). The differential effects of depth on spatial and object-based attention in VWM suggest that spatial attention primarily relied on 2D location information irrespective of depth, whereas object-based attention seemed to prioritize memory representations at the front plane before shifting to the back. Our findings shed light on the interaction between depth perception and the selection mechanisms within VWM in a 3D context, emphasizing the importance of ordinal, rather than metric, spatial information in guiding object-based attention in VWM.

Relating microsaccades and EEG-alpha activity during covert spatial attention in visual working memory

Relating microsaccades and EEG-alpha activity during covert spatial attention in visual working memory

Tracking attentional states: Assessing the relationship between sustained and selective focused attention in visual working memory.

Attention has multiple influences on visual working memory (VWM). Fluctuations in sustained attention predict VWM performance. Furthermore, focusing selective attention in VWM by retro-cuing the to-be-tested item during maintenance boosts retrieval. So far, we lack knowledge how the ability to focus selective attention relates to the state of sustained attention during the VWM trial. Here, we combined a retro-cue task and a self-rated attention protocol to test whether focusing selective attention via retro-cues: (1) mitigates spontaneous attention fluctuations, in which case retro-cues should be more helpful under low levels of self-rated attention; (2) depends on an optimal state of sustained attention, in which case retro-cue benefits should be largest under high levels of self-rated attention; or (3) is independent of sustained attention, in which case retro-cue benefits and self-rated attention effects should be additive. Our data supported the additive hypothesis. Across four experiments, self-rated attention levels predicted continuous reproduction of colors. Retro-cue trials produced better recall and higher rated attention. Critically, retro-cues improved recall to a similar extent across all levels of self-rated attention. This indicates that attention has multi-faceted and independent contributions to VWM.

Reduced Attentional Control in Older Adults Leads to Deficits in Flexible Prioritization of Visual Working Memory.

Visual working memory (VWM) resources have been shown to be flexibly distributed according to item priority. This flexible allocation of resources may depend on attentional control, an executive function known to decline with age. In this study, we sought to determine how age differences in attentional control affect VWM performance when attention is flexibly allocated amongst targets of varying priority. Participants performed a delayed-recall task wherein item priority was varied. Error was modelled using a three-component mixture model to probe different aspects of performance (precision, guess-rate, and non-target errors). The flexible resource model offered a good fit to the data from both age groups, but older adults showed consistently lower precision and higher guess rates. Importantly, when demands on flexible resource allocation were highest, older adults showed more non-target errors, often swapping in the item that had a higher priority at encoding. Taken together, these results suggest that the ability to flexibly allocate attention in VWM is largely maintained with age, but older adults are less precise overall and sometimes swap in salient, but no longer relevant, items possibly due to their lessened ability to inhibit previously attended information.

Directing retrospective attention in visual working memory in a graded manner

Directing retrospective attention in visual working memory in a graded manner

A note on the identification of change detection task models to measure storage capacity and attention in visual working memory.

The change detection task is a common method for assessing the storage capacity of working memory, but estimates of memory capacity from this task can be distorted by lapses of attention. When combined with appropriate mathematical models, some versions of the change detection task make it possible to separately estimate working memory and the probability of attentional lapses. In principle, these models should allow researchers to isolate the effects of experimental manipulations, group differences, and individual differences on working memory capacity and on the rate of attentional lapses. However, the present research found that two variants of a widely accepted model of the change detection task are not mathematically identified.

Competition for the focus of attention in visual working memory: perceptual recency versus executive control.

Previous research on memory for a short sequence of visual stimuli indicates that access to the focus of attention (FoA) can be achieved in either of two ways. The first is automatic and is indexed by the recency effect, the enhanced retention of the final item. The second is strategic and based on instructions to prioritize items differentially, a process that draws on executive capacity and boosts retention of information deemed important. In both cases, the increased level of retention can be selectively reduced by presenting a poststimulus distractor (or suffix). We manipulated these variables across three experiments. Experiment 1 generalized previous evidence that prioritizing a single item enhances its retention and increases its vulnerability to interference from a poststimulus suffix. A second experiment showed that the enhancement from prioritizing one or two items comes at a cost to the recency effect. A third experiment showed that prioritizing two items renders memory for both vulnerable to interference from an irrelevant suffix. The results suggest that some but not all items in working memory compete to occupy a narrow FoA and that this competition is determined by a combination of perceptually driven recency and internal executive control.

A neural model of retrospective attention in visual working memory

An informative cue that directs attention to one of several items in working memory improves subsequent recall of that item. Here we examine the mechanism of this retro-cue effect using a model of short-term memory based on neural population coding. Our model describes recalled feature values as the output of an optimal decoding of spikes generated by a tuned population of neurons. This neural model provides a better account of human recall data than an influential model that assumes errors can be described as a mixture of normally distributed noise and random guesses. The retro-cue benefit is revealed to be consistent with a higher firing rate of the population encoding the cued versus uncued items, with no difference in tuning specificity. Additionally, a retro-cued item is less likely to be swapped with another item in memory, an effect that can also be explained by greater activity of the underlying population. These results provide a parsimonious account of the effects of retrospective attention on recall and demonstrate a principled method for investigating neural representations with behavioral tasks.

Dissociation of spatial and feature-based attention in visual working memory: a TMS study

Attention can be deployed to representations in visual working memory (VWM), ensuring that only the most relevant information is maintained. We investigated whether the attentional selection of VWM representations can operate on features just as well as on spatial information, and we used transcranial magnetic stimulation (TMS) to test whether these attentional mechanisms can be dissociated based on the site of cortical stimulation. During the retention interval of a VWM task, a so-called retrocue was presented, which was either uninformative or indicated the item that would be tested at the end of the trial. The test item was cued by its location (spatial attention) or by its shape (feature-based attention). During cue presentation, TMS was applied to the supramarginal gyrus (SMG), which has been implicated in spatial attention, or to the lateral occipital cortex (LO), which is involved in representing object shape. We observed improved memory for objects cued by location and shape, confirming that both spatial as well as featural information can be used for selecting representations in VWM. Importantly, stimulation of SMG selectively facilitated spatial attention and stimulation of LO selectively facilitated feature-based attention. These results show that spatial and feature-based attentional mechanisms in VWM recruit distinct cortical regions. The same regions have been shown to be involved in attention to external events, indicating that attention in the mnemonic and in the perceptual domain are similarly implemented at the neural level. In general, these findings extend our understanding of how attentional mechanisms operating on different types of information optimize the use of the highly limited VWM system, allowing for an efficient and flexible updating of its contents. Meeting abstract presented at VSS 2016

Executive control of stimulus-driven and goal-directed attention in visual working memory.

We examined the role of executive control in stimulus-driven and goal-directed attention in visual working memory using probed recall of a series of objects, a task that allows study of the dynamics of storage through analysis of serial position data. Experiment 1 examined whether executive control underlies goal-directed prioritization of certain items within the sequence. Instructing participants to prioritize either the first or final item resulted in improved recall for these items, and an increase in concurrent task difficulty reduced or abolished these gains, consistent with their dependence on executive control. Experiment 2 examined whether executive control is also involved in the disruption caused by a post-series visual distractor (suffix). A demanding concurrent task disrupted memory for all items except the most recent, whereas a suffix disrupted only the most recent items. There was no interaction when concurrent load and suffix were combined, suggesting that deploying selective attention to ignore the distractor did not draw upon executive resources. A final experiment replicated the independent interfering effects of suffix and concurrent load while ruling out possible artifacts. We discuss the results in terms of a domain-general episodic buffer in which information is retained in a transient, limited capacity privileged state, influenced by both stimulus-driven and goal-directed processes. The privileged state contains the most recent environmental input together with goal-relevant representations being actively maintained using executive resources.

Feature-based and spatial attentional selection in visual working memory.

The contents of visual working memory (VWM) can be modulated by spatial cues presented during the maintenance interval ("retrocues"). Here, we examined whether attentional selection of representations in VWM can also be based on features. In addition, we investigated whether the mechanisms of feature-based and spatial attention in VWM differ with respect to parallel access to noncontiguous locations. In two experiments, we tested the efficacy of valid retrocues relying on different kinds of information. Specifically, participants were presented with a typical spatial retrocue pointing to two locations, a symbolic spatial retrocue (numbers mapping onto two locations), and two feature-based retrocues: a color retrocue (a blob of the same color as two of the items) and a shape retrocue (an outline of the shape of two of the items). The two cued items were presented at either contiguous or noncontiguous locations. Overall retrocueing benefits, as compared to a neutral condition, were observed for all retrocue types. Whereas feature-based retrocues yielded benefits for cued items presented at both contiguous and noncontiguous locations, spatial retrocues were only effective when the cued items had been presented at contiguous locations. These findings demonstrate that attentional selection and updating in VWM can operate on different kinds of information, allowing for a flexible and efficient use of this limited system. The observation that the representations of items presented at noncontiguous locations could only be reliably selected with feature-based retrocues suggests that feature-based and spatial attentional selection in VWM rely on different mechanisms, as has been shown for attentional orienting in the external world.

Orienting attention in visual working memory requires central capacity: Decreased retro-cue effects under dual-task conditions

The retro-cue effect (RCE) describes superior working memory performance for validly cued stimulus locations long after encoding has ended. Importantly, this happens with delays beyond the range of iconic memory. In general, the RCE is a stable phenomenon that emerges under varied stimulus configurations and timing parameters. We investigated its susceptibility to dual-task interference to determine the attentional requirements at the time point of cue onset and encoding. In Experiment 1, we compared single- with dual-task conditions. In Experiment 2, we borrowed from the psychological refractory period paradigm and compared conditions with high and low (dual-) task overlap. The secondary task was always binary tone discrimination requiring a manual response. Across both experiments, an RCE was found, but it was diminished in magnitude in the critical dual-task conditions. A previous study did not find evidence that sustained attention is required in the interval between cue offset and test. Our results apparently contradict these findings and point to a critical time period around cue onset and briefly thereafter during which attention is required.

Attention on our mind: The role of spatial attention in visual working memory

The current study shows that spatial visual attention is used to retrieve information from visual working memory. Participants had to keep four colored circles in visual working memory. While keeping this information in memory we asked whether one of the colors was present in the array. While retrieving this information, on some trials a probe dot was presented. When this probe dot was presented at the location of the color that had to be retrieved, participants responded faster than when it was presented at another location. Our findings further elaborate the role of visual attention in working memory: not only is attention the mechanism by which information is stored into working memory, it is also the mechanism by which information is retrieved from visual working memory.

Orienting attention in visual working memory reduces interference from memory probes.

Given a changing visual environment, and the limited capacity of visual working memory (VWM), the contents of VWM must be in constant flux. Using a change detection task, the authors show that VWM is subject to obligatory updating in the face of new information. Change detection performance is enhanced when the item that may change is retrospectively cued 1 s after memory encoding and 0.5 s before testing. The retro-cue benefit cannot be explained by memory decay or by a reduction in interference from other items held in VWM. Rather, orienting attention to a single memory item makes VWM more resistant to interference from the test probe. The authors conclude that the content of VWM is volatile unless it receives focused attention, and that the standard change detection task underestimates VWM capacity.

Movement and attention in visual working memory.

Three experiments that adopt an interference technique to investigate the involvement of movement in the production of a spatial code are described. Arm movements rather than the more commonly employed eye movements are used to provide initial information about the sorts of movements relevant to the code and to allow an empirical separation of the contributions of movement and attention. The results confirm the interference effects of incompatible movement on the generation of the spatial code and show that movement per se rather than attention to the movement can cause a performance decrement.