Task goals modulate the activation of part-based versus object-based representations in visual working memory

Zooming in on what counts as core and auxiliary: A case study on recognition models of visual working memory

Research on best practices in theory assessment highlights that testing theories is challenging because they inherit a new set of assumptions as soon as they are linked to a specific methodology. In this article, we integrate and build on this work by demonstrating the breadth of these challenges. We show that tracking auxiliary assumptions is difficult because they are made at different stages of theory testing and at multiple levels of a theory. We focus on these issues in a reanalysis of a seminal study and its replications, both of which use a simple working-memory paradigm and a mainstream computational modeling approach. These studies provide the main evidence for "all-or-none" recognition models of visual working memory and are still used as the basis for how to measure performance in popular visual working-memory tasks. In our reanalysis, we find that core practical auxiliary assumptions were unchecked and violated; the original model comparison metrics and data were not diagnostic in several experiments. Furthermore, we find that models were not matched on "theory general" auxiliary assumptions, meaning that the set of tested models was restricted, and not matched in theoretical scope. After testing these auxiliary assumptions and identifying diagnostic testing conditions, we find evidence for the opposite conclusion. That is, continuous resource models outperform all-or-none models. Together, our work demonstrates why tracking and testing auxiliary assumptions remains a fundamental challenge, even in prominent studies led by careful, computationally minded researchers. Our work also serves as a conceptual guide on how to identify and test the gamut of auxiliary assumptions in theory assessment, and we discuss these ideas in the context of contemporary approaches to scientific discovery.

Electrophysiological hallmarks for event relations and event roles in working memory

The ability to maintain events (i.e., interactions between/among objects) in working memory is crucial for our everyday cognition, yet the format of this representation is poorly understood. The current ERP study was designed to answer two questions: How is maintaining events (e.g., the tiger hit the lion) neurally different from maintaining item coordinations (e.g., the tiger and the lion)? That is, how is the event relation (present in events but not coordinations) represented? And how is the agent, or initiator of the event encoded differently from the patient, or receiver of the event during maintenance? We used a novel picture-sentence match-across-delay approach in which the working memory representation was "pinged" during the delay, replicated across two ERP experiments with Chinese and English materials. We found that maintenance of events elicited a long-lasting late sustained difference in posterior-occipital electrodes relative to non-events. This effect resembled the negative slow wave reported in previous studies of working memory, suggesting that the maintenance of events in working memory may impose a higher cost compared to coordinations. Although we did not observe significant ERP differences associated with pinging the agent vs. the patient during the delay, we did find that the ping appeared to dampen the ongoing sustained difference, suggesting a shift from sustained activity to activity silent mechanisms. These results suggest a new method by which ERPs can be used to elucidate the format of neural representation for events in working memory.

Sensory Delay Activity: More than an Electrophysiological Index of Working Memory Load

Sustained contralateral delay activity emerges in the retention period of working memory (WM) tasks and has been commonly interpreted as an electrophysiological index of the number of items held in a discrete-capacity WM resource. More recent findings indicate that these visual and tactile components are sensitive to various cognitive operations beyond the storage of discrete items in WM. In this Perspective, we present recent evidence from unisensory and multisensory visual and tactile WM tasks suggesting that, in addition to memory load, sensory delay activity may also be indicative of attentional and executive processes, as well as reflecting the flexible, rather than discrete, allocation of a continuous WM resource. Together, these findings challenge the traditional model of the functional significance of the contralateral delay activity as a pure measure of item load, and suggest that it may also reflect executive, attentional, and perceptual mechanisms operating in hierarchically organized WM systems.

Brain Processing of Complex Geometric Forms in a Visual Memory Task Increases P2 Amplitude

We study the cognitive processing of visual working memory in three different conditions of memory load and configuration change. Altering this features has been shown to alter the brain's processing in memory tasks. Most studies dealing with this issue have used the verbal-phonological modality. We use complex geometric polygons to assess visual working memory in a modified change detection task. Three different types of backgrounds were used to manipulate memory loading and 18 complex geometric polygons to manipulate stimuli configuration. The goal of our study was to test whether the memory load and configuration affect the correct-recall ratios. We expected that increasing visual items loading and changing configuration of items would induce differences in working memory performance. Brain activity related to the task was assessed through event-related potentials (ERP), during the test phase of each trial. Our results showed that visual items loading and changing of item configuration affect working memory on test phase on ERP component P2, but does not affect performance. However frontal related ERP component-P3-was minimally affected by visual memory loading or configuration changing, supporting that working memory is related to a filtering processing in posterior brain regions.

Object features reinstated from episodic memory guide attentional selection

When observers search for an object in the environment, they compare the incoming sensory information to the attentional template, a representation of the target in visual working memory (VWM). Previous studies have shown that visual search is more efficient when the attentional template is precise. We pursued the hypothesis that the attentional template in VWM is automatically complemented by features from long-term memory, possibly to increase its precision. At the beginning of the experiment, observers learned associations between shape and color. Then, we tested whether selecting one of these shapes was influenced by the previously associated color. To this end, we ran a saccadic selection task consisting of a memory and choice display. In the memory display, the target shape was presented at central fixation and participants were instructed to foveate this shape in the subsequent choice display. In the choice display, the target shape appeared together with a distractor shape at eccentric positions. Importantly, the target shape was colorless (gray) in the memory display so that only shape, but not color was loaded into VWM. However, saccades went more frequently to the target shape when it was shown in the learned color than when this color was shown in the distractor. Thus, the color of the target shape was reinstated from episodic memory to complement the attentional template in VWM.

Retrospective Selection in Visual and Tactile Working Memory Is Mediated by Shared Control Mechanisms

Selective attention regulates the activation of working memory (WM) representations. Retro-cues, presented after memory sample stimuli have been stored, modulate these activation states by triggering shifts of attention to task-relevant samples. Here, we investigated whether the control of such attention shifts is modality-specific or shared across sensory modalities. Participants memorized bilateral tactile and visual sample stimuli before an auditory retro-cue indicated which visual and tactile stimuli had to be retained. Critically, these cued samples were located on the same side or opposite sides, thus requiring spatially congruent or incongruent attention shifts in tactile and visual WM. To track the attentional selection of retro-cued samples, tactile and visual contralateral delay activities (tCDA and CDA components) were measured. Clear evidence for spatial synergy effects from attention shifts in visual WM on concurrent shifts in tactile WM were observed: Tactile WM performance was impaired, and tCDA components triggered by retro-cues were strongly attenuated on opposite-sides relative to same-side trials. These spatial congruency effects were eliminated when cued attention shifts in tactile WM occurred in the absence of simultaneous shifts within visual WM. Results show that, in contrast to other modality-specific aspects of WM control, concurrent attentional selection processes within tactile and visual WM are mediated by shared supramodal control processes.