Behavioral signatures of the rapid recruitment of long-term memory to overcome working memory capacity limits.

Working- and long-term memory are often studied in isolation. To better understand the specific limitations of working memory, effort is made to reduce the potential influence of long-term memory on performance in working memory tasks (e.g.

Encoded and updated spatial working memories share a common representational format in alpha activity.

Working memory (WM) flexibly updates information to adapt to the dynamic environment. Here, we used alpha-band activity in the EEG to reconstruct the content of dynamic WM updates and compared this representational format to static WM content. An inverted encoding model using alpha activity precisely tracked both the initially encoded position and the updated position following an auditory cue signaling mental updating.

Sequential encoding paradigm reliably captures the individual differences from a simultaneous visual working memory task.

Converging behavioral and neural evidence have suggested that visual stimuli could be attached to existing visual working memory sequentially in time. However, whether individual differences in sequential visual working memory paradigm are similar to those measured by the classical simultaneous change detection paradigm remain unknown. Here, we first show that sequentially presented visual stimuli exhibit similar working memory capacity bottlenecks as previous research using simultaneously presented items.

Pupillometry signatures of sustained attention and working memory.

There exists an intricate relationship between attention and working memory. Recent work has further established that attention and working memory fluctuate synchronously, by tightly interleaving sustained attention and working memory tasks. This work has raised many open questions about physiological signatures underlying these behavioral fluctuations.

Storage in Visual Working Memory Recruits a Content-Independent Pointer System.

Past work has shown that storage in working memory elicits stimulus-specific neural activity that tracks the stored content. Here, we present evidence for a distinct class of load-sensitive neural activity that indexes items without representing their contents per se. We recorded electroencephalogram (EEG) activity while adult human subjects stored varying numbers of items in visual working memory.

Inter-electrode correlations measured with EEG predict individual differences in cognitive ability.

Human brains share a broadly similar functional organization with consequential individual variation. This duality in brain function has primarily been observed when using techniques that consider the spatial organization of the brain, such as MRI. Here, we ask whether these common and unique signals of cognition are also present in temporally sensitive but spatially insensitive neural signals.

The visual arrays task: Visual storage capacity or attention control?

Extant literature suggests that performance on visual arrays tasks reflects limited-capacity storage of visual information. However, there is also evidence to suggest that visual arrays task performance reflects individual differences in controlled processing. The purpose of this study is to empirically evaluate the degree to which visual arrays tasks are more closely related to memory storage capacity or measures of attention control.

Perceptual Grouping Reveals Distinct Roles for Sustained Slow Wave Activity and Alpha Oscillations in Working Memory.

Multiple neural signals have been found to track the number of items stored in working memory (WM). These signals include oscillatory activity in the alpha band and slow-wave components in human EEG, both of which vary with storage loads and predict individual differences in WM capacity. However, recent evidence suggests that these two signals play distinct roles in spatial attention and item-based storage in WM.

Sustained Attention and Spatial Attention Distinctly Influence Long-term Memory Encoding.

Our attention is critically important for what we remember. Prior measures of the relationship between attention and memory, however, have largely treated "attention" as a monolith. Here, across three experiments, we provide evidence for two dissociable aspects of attention that influence encoding into long-term memory.

Controlling the Flow of Distracting Information in Working Memory.

Visual working memory (WM) must maintain relevant information, despite the constant influx of both relevant and irrelevant information. Attentional control mechanisms help determine which of this new information gets access to our capacity-limited WM system. Previous work has treated attentional control as a monolithic process-either distractors capture attention or they are suppressed.

Estimating the statistical power to detect set-size effects in contralateral delay activity.

The contralateral delay activity (CDA) is an event-related potential component commonly used to examine the online processes of visual working memory. Here, we provide a robust analysis of the statistical power that is needed to achieve reliable and reproducible results with the CDA. Using two very large EEG datasets that examined the contrast between CDA amplitude with set sizes 2 and 6 items and set sizes 2 and 4 items, we present a subsampling analysis that estimates the statistical power achieved with varying numbers of subjects and trials based on the proportion of significant tests in 10,000 iterations.

Multivariate analysis reveals a generalizable human electrophysiological signature of working memory load.

Working memory (WM) is an online memory system that is critical for holding information in a rapidly accessible state during ongoing cognitive processing. Thus, there is strong value in methods that provide a temporally resolved index of WM load. While univariate EEG signals have been identified that vary with WM load, recent advances in multivariate analytic approaches suggest that there may be rich sources of information that do not generate reliable univariate signatures.

No Evidence for an Object Working Memory Capacity Benefit with Extended Viewing Time.

Visual working memory is the ability to hold visual information temporarily in mind. A key feature of working memory is its starkly limited capacity, such that only a few simple items can be remembered at once. Prior work has shown that this capacity limit cannot be circumvented by providing additional encoding time, whether providing just 200 ms or up to 1300 ms, capacity is still limited to only three to four items.

Attention fluctuations impact ongoing maintenance of information in working memory.

Working memory maintains information in a readily accessible state and has been shown to degrade as the length of the retention interval increases. Previous research has suggested that this decline is attributable to changes in precision as well as sudden loss of item representations. Here, by measuring trial-to-trial variations in performance, we examined an orthogonal distinction between the maximum number of items that an individual can store, and the probability of achieving that maximum.

Unconscious Number Discrimination in the Human Visual System.

How do humans compute approximate number? According to one influential theory, approximate number representations arise in the intraparietal sulcus and are amodal, meaning that they arise independent of any sensory modality. Alternatively, approximate number may be computed initially within sensory systems. Here we tested for sensitivity to approximate number in the visual system using steady state visual evoked potentials.

Δ-Tetrahydrocannabinol (THC) impairs visual working memory performance: a randomized crossover trial.

With the increasing prevalence of legal cannabis use and availability, there is an urgent need to identify cognitive impairments related to its use. It is widely believed that cannabis, or its main psychoactive component Δ-tetrahydrocannabinol (THC), impairs working memory, i.e.

Distinguishing cognitive effort and working memory load using scale-invariance and alpha suppression in EEG.

Despite being intuitive, cognitive effort has proven difficult to define quantitatively. Here, we proposed to study cognitive effort by investigating the degree to which the brain deviates from its default state, where brain activity is scale-invariant. Specifically, we measured such deviations by examining changes in scale-invariance of brain activity as a function of task difficulty and posited suppression of scale-invariance as a proxy for exertion of cognitive effort.

Perturbing Neural Representations of Working Memory with Task-irrelevant Interruption.

Working memory maintains information so that it can be used in complex cognitive tasks. A key challenge for this system is to maintain relevant information in the face of task-irrelevant perturbations. Across two experiments, we investigated the impact of task-irrelevant interruptions on neural representations of working memory.

Visual short-term memory capacity predicts the "bandwidth" of visual long-term memory encoding.

We are capable of storing a virtually infinite amount of visual information in visual long-term memory (VLTM) storage. At the same time, the amount of visual information we can encode and maintain in visual short-term memory (VSTM) at a given time is severely limited. How do these two memory systems interact to accumulate vast amount of VLTM? In this series of experiments, we exploited interindividual and intraindividual differences VSTM capacity to examine the direct involvement of VSTM in determining the encoding rate (or "bandwidth") of VLTM.

Alpha-band oscillations track the retrieval of precise spatial representations from long-term memory.

A hallmark of episodic memory is the phenomenon of mentally reexperiencing the details of past events, and a well-established concept is that the neuronal activity that mediates encoding is reinstated at retrieval. Evidence for reinstatement has come from multiple modalities, including functional magnetic resonance imaging and electroencephalography (EEG). These EEG studies have shed light on the time course of reinstatement but have been limited to distinguishing between a few categories.

Real-time triggering reveals concurrent lapses of attention and working memory.

Attention and working memory are clearly intertwined, as shown by co-variations in individual ability and the recruitment of similar neural substrates. Both processes fluctuate over time, and these fluctuations may be a key determinant of individual variations in ability. If these fluctuations are due to the waxing and waning of a common cognitive resource, attention and working memory should co-vary on a moment-to-moment basis.

Item-specific delay activity demonstrates concurrent storage of multiple active neural representations in working memory.

Persistent neural activity that encodes online mental representations plays a central role in working memory (WM). However, there has been debate regarding the number of items that can be concurrently represented in this active neural state, which is often called the "focus of attention." Some models propose a strict single-item limit, such that just 1 item can be neurally active at once while other items are relegated to an activity-silent state.

Dissecting the Neural Focus of Attention Reveals Distinct Processes for Spatial Attention and Object-Based Storage in Visual Working Memory.

Complex cognition relies on both on-line representations in working memory (WM), said to reside in the focus of attention, and passive off-line representations of related information. Here, we dissected the focus of attention by showing that distinct neural signals index the on-line storage of objects and sustained spatial attention. We recorded electroencephalogram (EEG) activity during two tasks that employed identical stimulus displays but varied the relative demands for object storage and spatial attention.