Individual differences in working memory capacity and the regulation of arousal

Task sequencing does not systematically affect the factor structure of cognitive abilities

Latent variable analyses of cognitive abilities are among the major means by which cognitive psychologists test theories regarding the structure of human cognition. Models are fit to observed variance-covariance structures, and the fit of those models are compared to assess the merits of competing theories. However, an often unconsidered and potentially important methodological issue is the precise sequence in which tasks are delivered to participants. Here we empirically tested whether differences in task sequences systematically affect the observed factor structure. A large sample (N = 587) completed a battery of 12 cognitive tasks measuring four constructs: working memory, long-term memory, attention control, and fluid intelligence. Participants were assigned to complete the assessment in one of three sequences: fixed and grouped by construct vs. fixed and interleaved across constructs vs. random by participant. We generated and tested two hypotheses: grouping task sequences by construct (i.e., administering clusters of tasks measuring a cognitive construct consecutively) would (1) systematically increase factor loadings and (2) systematically decrease interfactor correlations. Neither hypothesis was supported. The measurement models were largely invariant across the three conditions, suggesting that latent variable analyses are robust to such subtle methodological differences as task sequencing.

Pupillary correlates of individual differences in n-back task performance

We used pupillometry during a 2-back task to examine individual differences in the intensity and consistency of attention and their relative role in a working memory task. We used sensitivity, or the ability to distinguish targets (2-back matches) and nontargets, as the measure of task performance; task-evoked pupillary responses (TEPRs) as the measure of attentional intensity; and intraindividual pretrial pupil variability as the measure of attentional consistency. TEPRs were greater on target trials compared with nontarget trials, although there was no difference in TEPR magnitude when participants answered correctly or incorrectly to targets. Importantly, this effect interacted with performance: high performers showed a greater separation in their TEPRs between targets and nontargets, whereas there was little difference for low performers. Further, in regression analysis, larger TEPRs on target trials predicted better performance, whereas larger TEPRs on nontarget trials predicted worse performance. Sensitivity positively correlated with average pretrial pupil diameter and negatively correlated with intraindividual variability in pretrial pupil diameter. Overall, we found evidence that both attentional intensity (TEPRs) and consistency (pretrial pupil variation) predict performance on an n-back working memory task.

Revealing visual working memory operations with pupillometry: Encoding, maintenance, and prioritization

Pupillary dynamics reflect effects of distinct and important operations of visual working memory: encoding, maintenance, and prioritization. Here, we review how pupil size predicts memory performance and how it provides novel insights into the mechanisms of each operation. Visual information must first be encoded into working memory with sufficient precision. The depth of this encoding process couples to arousal-linked baseline pupil size as well as a pupil constriction response before and after stimulus onset, respectively. Subsequently, the encoded information is maintained over time to ensure it is not lost. Pupil dilation reflects the effortful maintenance of information, wherein storing more items is accompanied by larger dilations. Lastly, the most task-relevant information is prioritized to guide upcoming behavior, which is reflected in yet another dilatory component. Moreover, activated content in memory can be pupillometrically probed directly by tagging visual information with distinct luminance levels. Through this luminance-tagging mechanism, pupil light responses reveal whether dark or bright items receive more attention during encoding and prioritization. Together, conceptualizing pupil responses as a sum of distinct components over time reveals insights into operations of visual working memory. From this viewpoint, pupillometry is a promising avenue to study the most vital operations through which visual working memory works. This article is categorized under: Psychology > Attention Psychology > Memory Psychology > Theory and Methods.

[Formula: see text] Neurocognition in children with cognitive disengagement syndrome: accurate but slow

Cognitive disengagement syndrome (CDS), previously termed sluggish cognitive tempo (SCT), is characterized by excessive daydreaming, mental confusion, and slowed behavior or thinking. Prior research has found inconsistent relations between CDS and neurocognition, though most studies have used small or ADHD-defined samples, non-optimal measures of CDS, and/or examined limited neurocognitive domains. Accordingly, this study examined the association of parent- and teacher-reported CDS symptoms using a comprehensive neurocognitive battery in a sample of 263 children (aged 8-12) selected with a range of CDS symptomatology. Parents and teachers provided ratings of CDS and ADHD inattentive (ADHD-IN) symptoms. Path analyses were conducted to examine CDS and ADHD-IN as unique predictors of neurocognitive functioning after covarying for age, sex, and family income. CDS symptoms were uniquely associated with slower performance across a range of cognitive domains, including verbal inhibition, rapid naming/reading, planning, divided attention, and set shifting. In contrast, ADHD-IN symptoms were uniquely associated with poorer performance on a Go/NoGo task (inhibition/distractibility), visual scanning and discrimination, and interference control. Findings from the current study, amongst the first to recruit children based on levels of CDS symptomatology, provide the strongest evidence to date that the neurocognitive phenotype of CDS is characterized by slowed cognitive processing, and add to its validity as a separate syndrome from ADHD. If replicated, these findings have implications for assessment, treatment, and school accommodations for CDS. Neuroimaging studies exploring the neurobiological basis of CDS are also needed.

Stress and Right Prefrontal Transcranial Direct Current Stimulation (tDCS) Interactive Effects on Visual Working Memory and Learning

Stress impacts prefrontal cortex (PFC) activity and modulates working memory performance. In a recent study, stimulating the dorsolateral PFC (dlPFC) using transcranial direct current stimulation (tDCS) interacted with social stress in modulating participants' working memory. More specifically, stress disrupted the enhancing effects of dlPFC tDCS on working memory performance. The current study aimed to further explore these initial findings by randomizing healthy females to four experimental conditions (N = 130); stimulation (right dlPFC tDCS vs. sham) and stress manipulation (social stress vs. control). Participants performed cognitive tasks (i.e., visual working memory task and a visual declarative memory task) at baseline and post-stimulation. They also completed self-report measures of stress and anxiety. A significant stimulation × stress interaction was evident in the declarative memory (One-Card Learning, OCL) task, while working memory performance was unaffected. Though tDCS stimulation and stress did not interact to affect working memory, further research is warranted as these initial findings suggest that immediate visual-memory learning may be affected by these factors. The limited number of earlier studies, as well as the variability in their designs, provides additional impetus for studying the interactive effects of stress and tDCS on human visual learning.

Baseline pupil diameter does not correlate with fluid intelligence

There has been debate regarding the correlation between baseline/resting state measures of pupil diameter and cognitive abilities such as working memory capacity and fluid intelligence. A positive correlation between baseline pupil diameter and cognitive ability has been cited as evidence for a role of the locus coeruleus-norepinephrine (LC-NE) and its functional connection with cortical networks as a reason for individual differences in fluid intelligence (Tsukahara & Engle, Proceedings of the National Academy of Sciences, 118(46), e2110630118, 2021a). Several recent attempts to replicate this correlation have failed. The current studies make another attempt and find substantial evidence against a positive correlation between pupil diameter and intelligence. Given the data from the current studies in combination with other recent failures to replicate, we conclude that individual differences in baseline pupil diameter should not be used as evidence for a role of the LC-NE system in goal-directed cognitive activity.

Genuine beta bursts in human working memory: controlling for the influence of lower-frequency rhythms

Human working memory is associated with significant modulations in oscillatory brain activity. However, the functional role of brain rhythms at different frequencies is still debated. Modulations in the beta frequency range (15-40 Hz) are especially difficult to interpret because they could be artifactually produced by (more prominent) oscillations in lower frequencies that show non-sinusoidal properties. In this study, we investigate beta oscillations during working memory while controlling for the possible influence of lower frequency rhythms. We collected electroencephalography (EEG) data in 31 participants who performed a spatial working-memory task with two levels of cognitive load. In order to rule out the possibility that observed beta activity was affected by non-sinusoidalities of lower frequency rhythms, we developed an algorithm that detects transient beta oscillations that do not coincide with more prominent lower frequency rhythms in time and space. Using this algorithm, we show that the amplitude and duration of beta bursts decrease with memory load and during memory manipulation, while their peak frequency and rate increase. In addition, interindividual differences in performance were significantly associated with beta burst rates. Together, our results show that beta rhythms are functionally modulated during working memory and that these changes cannot be attributed to lower frequency rhythms with non-sinusoidal properties.

Testing locus coeruleus-norepinephrine accounts of working memory, attention control, and fluid intelligence

The current set of studies examined the relationship among working memory capacity, attention control, fluid intelligence, and pupillary correlates of tonic arousal regulation and phasic responsiveness in a combined sample of more than 1,000 participants in two different age ranges (young adults and adolescents). Each study was designed to test predictions made by two recent theories regarding the role of the locus coeruleus-norepinephrine (LC-NE) system in determining individual differences in cognitive ability. The first theory, proposed by Unsworth and Robison (2017a), posits two important individual differences: the moment-to-moment regulation of tonic arousal, and the phasic responsiveness of the system to goal-relevant stimuli. The second theory, proposed by Tsukahara and Engle (2021a), argues that people with higher cognitive abilities have greater functional connectivity between the LC-NE system and cortical networks at rest. These two theories are not mutually exclusive, but they make different predictions. Overall, we found no evidence consistent with a resting-state theory. However, phasic responsiveness was consistently correlated with working memory capacity, attention control, and fluid intelligence, supporting a prediction made by Unsworth and Robison (2017a). Tonic arousal regulation was not correlated with working memory or fluid intelligence and was inconsistently correlated with attention control, which offers only partial support for Unsworth and Robison's (2017a) second prediction.

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. Across two experiments, we explore pupil dynamics using real-time triggering in conjunction with an interleaved sustained attention and working memory task. In Experiment 1, we use behavioral real-time triggering and replicate recent findings from our lab (deBettencourt et al., 2019) that sustained attention fluctuates concurrently with the number of items maintained in working memory. Furthermore, highly attentive moments, detected via behavior, also exhibited larger pupil sizes. In Experiment 2, we develop a novel real-time pupil-triggering technique to track pupil size fluctuations in real time and trigger working memory probes. We show that this pupil triggering procedure reveals differences in sustained attention, as indexed by response time. These experiments reflect methodological advances in real-time triggering and further disentangle the relationship among general arousal, sustained attention, and working memory.

Patience is a virtue: Individual differences in cue-evoked pupil responses under temporal certainty

Attention control is often examined behaviorally by measuring task performance and self-reported mind wandering. However, recent studies have also used pupillometry to measure task engagement versus task disengagement/mind wandering. In the current study, we investigated participants' ability to engage versus relax attention control in anticipation of hard (antisaccade) versus easy (prosaccade) trials within a saccade task, creating a "Cue-Evoked" Pupillary Response (CEPR). Participants completed the Automated OSPAN as a measure of working memory capacity (WMC) followed by a saccade task with a constant 5,000 ms delay between cue and stimulus. Occasional thought probes were included to gauge on- versus off-task attentional state. Consistent with recent findings (Hutchison et al., 2020, Journal of Experimental Psychology: Learning, Memory, and Cognition, 46, 280-295; Wang et al., 2015, European Journal of Neuroscience, 41, 1102-1110), we found better performance and more Task-Unrelated Thoughts (TUTs) on prosaccade trials, larger pupil diameters when preparing for antisaccade trials, and larger pupil diameters when on-task. Further, lower WMC individuals showed pupil dilation throughout the fixation delay for both types of trials, whereas higher WMC individuals only showed dilation immediately before stimulus onset when expecting an antisaccade trial. Saccade accuracy was predicted by WMC, smaller early CEPR, larger late CEPR, and less CEPR variability, but not self-reported TUTs. These findings demonstrate that, under temporal certainty, higher WMC individuals may be more efficient in their exertion of attention control. Further, they indicate that physiological measures can not only validate self-report measures, but also help identify situations in which self-report may be inaccurate.

Pupillary correlates of individual differences in long-term memory

The present study is the first to examine individual differences in long-term memory, arousal dysregulation, and intensity of attention within the same experiment. Participants (N = 106) completed 28 lists of an immediate free-recall task while their pupil diameter was recorded via an eye-tracker during the encoding period. Two main pupillary measures were extracted: intraindividual variability in pre-list pupil diameter and evoked pupillary responses during item encoding. Variability in pre-list pupil diameter served as a measure of arousal dysregulation, and evoked pupillary responses served as a measure of intensity of attention. Based on prior work, we hypothesized that there would be a positive association between intensity of attention and recall ability, and that there would be a negative association between arousal dysregulation and recall ability. Collectively these two measures accounted for 19% of interindividual variance in recall, with 5% attributable uniquely to intensity of attention and 12% attributable uniquely to arousal regulation. The findings demonstrate that there are sources of individual differences in long-term memory that can be revealed via pupillometry, notably the amount of effort deployed during item encoding and the degree to which people exhibit dysregulated arousal. Both findings are consistent with recent theorizing regarding the role of the locus coeruleus (LC)-norepinephrine (NE) system's role in goal-directed cognition. Specifically, the LC governs both moment-to-moment arousal and NE release to cortical regions subserving cognitive processing. Among people for whom this system operates most optimally, long-term memory retention is superior.