High Working Memory Load Conditions Research Articles

Working memory load increases movement-related alpha and beta desynchronization

Working memory (WM) load has been well-documented to impair selective attention and inhibitory control. However, its effects on motor function remain insufficiently explored. To extend the existing literature, we investigated the impact of WM load on force control and movement-related brain activity. Sixteen healthy young participants performed a visual static force matching task using a pinch grip under varying WM loads. The task included low and high WM load conditions (memorizing one digit or six digits), and the precision level required to control force was adjusted by manipulating visual gain (low vs. high visual gains), with higher visual gain necessitating more precise force control. Peri-movement alpha and beta event-related desynchronization (ERD), along with force accuracy and steadiness, were measured using electroencephalography recorded over the central areas during the force control task. Results indicated that while force accuracy and steadiness significantly improved with higher visual gain, there was no significant effect of WM load on these measures. Alpha and beta ERD were greater under high than low visual gain, and also greater under high than low WM load. These findings suggest that in young adults, increased WM load leads to compensatory increases in sensorimotor cortical activity to mitigate potential declines in static force control performance that may result from the depletion of neural resources caused by WM load. Our findings extend current understanding of the interaction between WM and sensorimotor processes by offering new insights into how movement-related brain activity is influenced by heightened WM load.

Working Memory and Automaticity in Relation to Mental Addition among American Elementary Students

This study investigated the effects of working memory load (WML) and automaticity on mental addition through an examination of both task and individual characteristics within the framework of cognitive load theory. Seventy-three fourth-grade students in New York City public schools completed the Digit Span-Backward task of the Wechsler Intelligence Scale for Children-Fifth Edition, the Math Fluency subtest of the Wechsler Individual Achievement Test-Third Edition, and a 24-item computer-assisted addition task. Results showed that working memory load, automaticity, and their interaction had significant effects on mental addition. Automaticity had a differential effect on response time under low and high WML conditions. Results also showed that working memory, math fluency, and their interaction could predict a significant portion of variance in accuracy. However, math fluency was the only significant predictor for mental addition on the measure of response time. The study confirmed the interaction effect between working memory and automaticity and underscored the importance of automaticity in arithmetic learning.

The Role of Explicit Memory Across Second Language Syntactic Development: A Structural Priming Study

AbstractWe tested whether second language (L2) learners rely more on explicit memory during structural priming at lower than at higher proficiency levels (Hartsuiker & Bernolet, 2017). We compared within‐L2 priming with lexical overlap in 100 low and 100 high proficiency French L2 speakers under low versus high working memory load conditions induced with a letter series recall task presented between primes and targets. The high load condition would prevent explicit recall of primes during target production. Both groups primed more under low than high load. The effect of load was similar across groups, but exploratory analyses with proficiency as a continuous variable suggested that, with increasing proficiency, participants primed less under high load. We discuss how these findings support the idea that learners exploit explicit memory more during priming in early versus later stages of acquisition. Overall, this study showed that explicit memory influences syntactic processing across the L2 learning trajectory.

An experimental and simulation study of the impact of emotional information on analogical reasoning

We investigated whether and how emotional information would affect analogical reasoning. We hypothesized that task-irrelevant emotional information would impair performance whereas task-relevant emotional information would enhance it. In Study 1, 233 undergraduates completed a novel version of the People Pieces Task (Emotional Faces People Task), an analogical reasoning task in which the task characters displayed emotional or neutral facial expressions (within-participants). The emotional faces were relevant or irrelevant to the task (between-participants). We simulated the behavioral results using the Learning and Inference with Schemas and Analogies (LISA) model of relational reasoning. LISA is a neurally plausible, symbolic-connectionist computational model of analogical reasoning. In comparison to neutral trials, participants were slower but more accurate on emotion-relevant trials, and were faster but less accurate on emotion-irrelevant trials. Simulations using the LISA model demonstrated that it is possible to account for the effects of emotional information on reasoning in terms of how emotional stimuli attract attention during a reasoning task. In Study 2, 255 undergraduates completed the Emotional Faces People Task at either a high- or low-working memory load. The high working memory load condition of Study 2 replicated the findings of Study 1, showing that participants were more accurate on emotion-relevant trials than on emotion-irrelevant trials; in Study 2, this increased accuracy could not be accounted for by a speed-accuracy tradeoff. The working memory manipulation influenced the manner in which the congruence (with the correct answer) of emotion-irrelevant emotion influenced performance. Simulations using the LISA model showed that manipulating the salience of emotion, the error penalty, as well as vigilance (which determines the likelihood that LISA will notice it has attended to an irrelevant relation), could reasonably reproduce the behavioral results of both low and high working memory load conditions of Study 2.

Working memory load modulates the processing of audiovisual distractors: A behavioral and event-related potentials study.

The interplay between different modalities can help to perceive stimuli more effectively. However, very few studies have focused on how multisensory distractors affect task performance. By adopting behavioral and event-related potentials (ERPs) techniques, the present study examined whether multisensory audiovisual distractors could attract attention more effectively than unisensory distractors. Moreover, we explored whether such a process was modulated by working memory load. Across three experiments, n-back tasks (1-back and 2-back) were adopted with peripheral auditory, visual, or audiovisual distractors. Visual and auditory distractors were white discs and pure tones (Experiments 1 and 2), pictures and sounds of animals (Experiment 3), respectively. Behavioral results in Experiment 1 showed a significant interference effect under high working memory load but not under low load condition. The responses to central letters with audiovisual distractors were significantly slower than those to letters without distractors, while no significant difference was found between unisensory distractor and without distractor conditions. Similarly, ERP results in Experiments 2 and 3 showed that there existed an integration only under high load condition. That is, an early integration for simple audiovisual distractors (240-340 ms) and a late integration for complex audiovisual distractors (440-600 ms). These findings suggest that multisensory distractors can be integrated and effectively attract attention away from the main task, i.e., interference effect. Moreover, this effect is pronounced only under high working memory load condition.

Neural resources shift under Methylphenidate: A computational approach to examine anxiety-cognition interplay

The reciprocal interplay between anxiety and cognition is well documented. Anxiety negatively impacts cognition, while cognitive engagement can down-regulate anxiety. The brain mechanisms and dynamics underlying such interplay are not fully understood. To study this question, we experimentally and orthogonally manipulated anxiety (using a threat of shock paradigm) and cognition (using methylphenidate; MPH). The effects of these manipulations on the brain and behavior were evaluated in 50 healthy participants (25 MPH, 25 placebo), using an n-back working memory fMRI task (with low and high load conditions). Behaviorally, improved response accuracy was observed as a main effect of the drug across all conditions. We employed two approaches to understand the neural mechanisms underlying MPH-based cognitive enhancement in safe and threat conditions. First, we performed a hypothesis-driven computational analysis using a mathematical framework to examine how MPH putatively affects cognitive enhancement in the face of induced anxiety across two levels of cognitive load. Second, we performed an exploratory data analysis using Topological Data Analysis (TDA)-based Mapper to examine changes in spatiotemporal brain activity across the entire cortex. Both approaches provided converging evidence that MPH facilitated greater differential engagement of neural resources (brain activity) across low and high working memory load conditions. Furthermore, load-based differential management of neural resources reflects enhanced efficiency that is most powerful during higher load and induced anxiety conditions. Overall, our results provide novel insights regarding brain mechanisms that facilitate cognitive enhancement under MPH and, in future research, may be used to help mitigate anxiety-related cognitive underperformance.

Working Memory Load Impact on Effective Connectivity: a Dynamic Causal Modeling Study

This study aims to examine the roles of the brain regions in working memory (WM) processing and the modulatory effects of WM load. Electroencephalogram (EEG) signals were recorded when participants perform a letter-version n-back task with three different levels of WM load. The directional causal connections between brain regions were estimated using Dynamic Causal Modeling (DCM). The directions and strengths of the connections were compared for different WM load conditions. The results showed a right-lateralized, backward-only connection pattern for the high WM load condition. The results also showed changes in the roles of the brain regions when the WM load increases. These findings of the modulatory effects of WM load may be utilized in measuring cognitive states, and designing adaptive automation in augmented cognition programs.

Adolescent-specific memory effects: evidence from working memory, immediate and long-term recognition memory performance in 8-30 yr olds.

Working memory and recognition memory develop across adolescence, but the relationship between them is not fully understood. We investigated associations between n-back task performance and subsequent recognition memory in a community sample (8-30 yr, n = 150) using tasks from the Adolescent Brain Cognitive Development Study (ABCD Study) to cross-sectionally assess memory in an age range that will be sampled longitudinally. We added a 24-h delay condition to assess long-term recognition. Overall working memory, immediate and long-term recognition performance peaked in adolescence. Age effects in recognition memory varied by items (old targets, old distractors, and new items) and delay (0 and 24 h). For immediate recognition, accuracy was higher for targets and new items than for distractors, with accuracy for targets peaking in adulthood and accuracy for new items peaking during adolescence. For long-term recognition, adolescents' accuracy was higher for targets than distractors, while adults showed similarly high accuracy for targets and distractors and children showed low accuracy for both. This pattern appeared to be specific to recognition of items from the high working memory load condition. The results suggest that working memory may facilitate long-term recognition of task-relevant over irrelevant items and may benefit the detection of new information during adolescence.

The effect of working memory load on feedback processing: Evidence from an event-related potentials (ERP) study

<p id=C2>Feedback processing plays an important role in behavior modification and knowledge acquisition. Previous research has explored the neurophysiological basis and psychological functions of feedback processing and proposed corresponding theoretical models, but little is known about how working memory (WM) load affects feedback processing. Studies have reported electrophysiological indicators, such as the reward positivity (RewP) and the related theta and delta oscillations, the P3 and the late positive potential (LPP), during brain processing feedback. This study will further examine how WM load modulates these electrophysiological components and their corresponding cognitive functions. <break/>In the present study, we used a dual-task paradigm to investigate feedback processing under different WM load conditions. This study included 25 healthy college students and used a 3 (WM load: baseline vs. low WM load vs. high WM load) by 2 (feedback valence: positive vs. negative) within-participant factorial design. During the experiment, participants were asked to perform a simple gambling task and a spatial memory task simultaneously, and the magnitude of the WM load included three conditions: baseline, low WM load and high WM load. The RewP generated in the early stage of feedback processing and the LPP generated in the late stage of feedback processing, as well as the delta and theta oscillations related to feedback evaluation, were analyzed. <break/>The behavioral results showed that the accuracy of the low WM load condition was significantly higher than that of the high WM load condition. The electrophysiological results showed that the amplitudes of the RewP were sensitive to feedback valence, with positive feedback evoking larger RewP than negative feedback, but the RewP was not affected by the WM load. There was no difference in the P3 amplitude under the different WM load conditions. For the LPP, there was a significant interaction between the WM load and feedback valence. Further analysis revealed that, in the high WM load condition, the LPP amplitude was larger for positive feedback than for negative feedback. The theta power differences between negative feedback and positive feedback were larger in the low WM load condition than in the high WM load condition. For delta oscillation, the power was increased after positive feedback compared to after negative feedback, but there was no difference at different WM load levels. <break/>The RewP results indicate that the participants process feedback valence information well under all three WM load conditions in the experiment. The LPP results suggest that the participants assigned additional emotional motivation to the feedback outcome as a result of their cognitive efforts under high WM load conditions. The ERP results for the time domain dimension showed that the effect of the WM load on feedback processing was most noticeable in the later stages of feedback processing. Moreover, these observations support the argument that the RewP and theta power reflect distinct cognitive phenomena; namely, the RewP reflects the processing of feedback valence in the anterior cingulate cortex (ACC), whereas theta oscillations reflect the role of the ACC in cognitive control. The WM load selectively modulates the cognitive control process in the ACC.

Bored, distracted, and forgetful: The impact of mind wandering and boredom on memory encoding.

Mind wandering, defined as focusing attention towards task-unrelated thoughts, is a common mental state known to impair memory encoding. This phenomenon is closely linked to boredom. Very few studies, however, have tested the potential impact of boredom on memory encoding. Thus, the present study aimed at manipulating mind wandering and boredom during an incidental memory encoding task, to test their differential impact on memory encoding. Thirty-two participants performed a variant of the n-back task in which they had to indicate if the current on-screen object was the same as the previous one (1-back; low working memory load) or the one presented three trials before (3-back; high working memory load). Moreover, thought probes assessing either mind wandering or boredom were randomly presented. Afterwards, a surprise recognition task was delivered. Results showed that mind wandering and boredom were highly correlated, and both decreased in the high working memory load condition, while memory performance increased. Although both boredom and mind wandering predicted memory performance taken separately, we found that mind wandering was the only reliable predictor of memory performance when controlling for boredom and working memory load. Model comparisons also revealed that a model with boredom only was outperformed by a model with mind wandering only and a model with both mind wandering and boredom, suggesting that the predictive contribution of boredom in the complete model is minimal. The present results confirm the high correlation between mind wandering and boredom and suggest that the hindering effect of boredom on memory is subordinate to the effect of mind wandering.

High working memory load impairs selective attention: EEG signatures.

According to the load theory of attention, increased working memory load impairs selective attention, resulting in greater distractor interference during inhibitory control processing. However, the EEG signatures correlated with this modulation effect of working memory on inhibitory control remain unclear. In present study, 25 healthy human participants performed a flanker task in a low and high working memory load conditions, while behavioral and electroencephalography (EEG) data were recorded. The results showed a larger reaction time interference effect while increasing working memory load, and this was accompanied by a larger N2 amplitude and a smaller P3 amplitude for incongruent trials. Time-frequency analysis revealed that, increased working memory load had no significant modulation effect on flanker related theta-ERS magnitude. Incongruent trials evoked smaller alpha-ERD magnitude than congruent trials in both low and high working memory load conditions. Increased working memory load was associated with larger flanker related alpha-ERD magnitude. Taken together, these results suggested that increased working memory load can impair top-down cognitive control processes, impairing inhibitory control processes during performance of the flanker task.

Working Memory Load Selectively Influences Response Inhibition in a Stop Signal Task.

Inhibitory control is a key executive function and has been studied extensively using the stop signal task. By applying a simple race model that posits an independent race between a GO process responsible for initiation of responses and a STOP process responsible for inhibition of responses, one can estimate how long it takes an individual to inhibit an ongoing response, the stop signal reaction time. Here, we examined how stop signal reaction time can be affected by working memory. Participants engaged in a dual task; they completed a stop signal task under low and high working memory load conditions. Working memory capacity was also measured. We found that the STOP process was lengthened in the high, compared to the low, working memory load condition, as evidenced by differences in stop signal reaction time. The GO process was unaffected and working memory capacity could not account for differences across the load conditions. These results indicate that inhibitory control can be influenced by placing demands on working memory.

Poor working memory performance in healthy elderly adults with electroencephalographic risk of cognitive decline affects syntactic processing

ObjectiveTo examine the effects of working memory (WM) load and gender agreement on sentence processing as a function of the electroencephalographic risk (i.e., abnormally high values of theta absolute power) of cognitive decline in older adults. MethodsEvent-related potentials (ERPs) were collected from Spanish speakers (22 older adults belonged to the Risk group, mean age = 67.7 years; 22 older adults belonged to the Control group, mean age = 65.2 years) while reading sentences to detect grammatical errors. Sentences varied with regard to (1) the gender agreement of the noun and adjective, where gender of the adjective either agreed or disagreed with the noun, and (2) WM load (i.e., the number of words between the noun and adjective in the sentence). ResultsThe Risk group showed a lower percentage of correct answers and longer reaction times than the Control group. The Risk group also showed a different pattern of ERP components, which was characterized by smaller amplitude and longer latency of the P600a component under high WM load conditions. ConclusionThe findings suggest that the Risk group shows difficulties integrating information associated with the previous sentence context. SignificanceThe electroencephalographic risk factor of cognitive decline might be not only a predictor of but also an indicator of current decline.

Facing recovery: Emotional bias in working memory, rumination, relapse, and recurrence of major depression; an experimental paradigm conducted five years after first episode of major depression

Identifying vulnerability factors for relapse of depression is essential in planning preventive interventions. Emotional face processing in major depression (MDD) shows promise as a potential cognitive marker for depression. The current study investigates how working memory (WM) load in face processing relates to rumination and new episodes of MDD in a novel explorative paradigm. It was expected that history of MDD is associated with reduction of the ability to process sad stimuli in high WM load conditions and reduction of the ability to process happy stimuli in low WM conditions. It was further predicted that these relations are associated with rumination and risk for relapse. The experiment was included as a cross sectional part in a follow-up study of a population that previously experienced first episode (FE) depression. The FE (N = 23) and a healthy control group (N = 22) completed a WM face processing task. In the task, three happy or sad faces were presented, processed in either a high or low WM taxing manner, followed by a target stimulus consisting of one of the previous pictures. Response time and accuracy were dependent variables. Rumination and number of relapses or recurrences were measured. The FE group recalled the placement of significantly fewer happy faces in the low WM load condition, and significantly fewer sad faces in the high WM load condition compared to controls. Significantly different scores between groups predicted trait rumination. Poor accuracy in the sad high WM load condition correlated with high degree of rumination. Relapse or recurrence was predicted by rumination. The present study supports an emotional WM deficit in remitted MDD. This suggests that deficits in manipulation of sad faces could represent a trait bias related to rumination and depression.

Noradrenaline transporter blockade increases fronto-parietal functional connectivity relevant for working memory

Experimental animal work has demonstrated that dopamine and noradrenaline play an essential role in modulating prefrontal cortex-mediated networks underlying working memory performance. Studies of functional connectivity have been instrumental in extending such notions to humans but, so far, have almost exclusively focussed on pharmacological agents with a predominant dopaminergic mechanism of action. Here, we investigate the effect of a single dose of atomoxetine 60mg, a noradrenaline transporter inhibitor, on working memory performance and associated functional connectivity during an n-back task in 19 healthy male volunteers. Atomoxetine increased functional connectivity between right anterior insula and dorsolateral prefrontal cortex, precentral gyrus, posterior parietal cortex and precuneus during the high-working memory load condition of the n-back task. Increased atomoxetine-induced insula-dorsolateral prefrontal cortex functional connectivity during this condition correlated with decreased reaction time variability and was furthermore predicted by working memory capacity. These results show for the first time that noradrenaline transporter blockade-induced increases in cortical catecholamines accentuate fronto-parietal working memory-related network integrity. The observation of significant inter-subject variability in response to atomoxetine has implications for inverted-U frameworks of dopamine and noradrenaline function, which could be useful to predict drug effects in clinical disorders with variable treatment response.

The Role of Cognitive Load in Intentional Forgetting Using the Think/No-Think Task.

We investigated the role of cognitive control in intentional forgetting by manipulating working memory load during the think/no-think task. In two experiments, participants learned a series of cue-target word pairs and were asked to recall the target words associated with some cues or to avoid thinking about the target associated with other cues. In addition to this, participants also performed a modified version of the n-back task which required them to respond to the identity of a single target letter present in the currently presented cue word (n=0 condition, low working memory load), and in either the previous cue word (n=1 condition, high working memory load, Experiment 1) or the cue word presented two trials previously (n=2 condition, high working memory load, Experiment 2). Participants' memory for the target words was subsequently tested using same and novel independent probes. In both experiments it was found that although participants were successful at forgetting on both the same and independent-probe tests in the low working memory load condition, they were only successful at forgetting on the same-probe test in the high working memory load condition. We argue that our findings suggest that the high load working memory task diverted attention from direct suppression and acted as an interference-based strategy. Thus, when cognitive resources are limited participants can switch between the strategies they use to prevent unwanted memories from coming to mind.

Reduced Frontal Activations at High Working Memory Load in Mild Cognitive Impairment: Near-Infrared Spectroscopy

Background: Some functional magnetic resonance imaging studies have reported altered activations in the frontal cortex during working memory (WM) performance in individuals with mild cognitive impairment (MCI), but the findings have been mixed. The objective of the present study was to utilize near-infrared spectroscopy (NIRS), an alternative imaging technique, to examine neural processing during WM performance in individuals with MCI. Methods: Twenty-six older adults with MCI (7 males; mean age 69.15 years) were compared with 26 age-, gender-, handedness-, and education-matched older adults with normal cognition (NC; 7 males; mean age 68.87 years). All of the participants undertook an n-back task with a low (i.e., 0-back) and a high (i.e., 2-back) WM load condition while their prefrontal dynamics were recorded by a 16-channel NIRS system. Results: Although behavioral results showed that the two groups had comparable task performance, neuroimaging results showed that the MCI group, unlike the NC group, did not exhibit significantly increased frontal activations bilaterally when WM load increased. Compared to the NC group, the MCI group had similar frontal activations at low load (p > 0.05 on all channels) but reduced activations at high load (p < 0.05 on 4 channels), thus failing to demonstrate WM-related frontal activations (p < 0.05 on 9 channels). In addition, we found a positive correlation between the left WM-related frontal activations and WM ability primarily in the NC group (r_s = 0.42, p = 0.035), suggesting a relationship between frontal hypoactivation and WM difficulties. Conclusion: The present findings suggest the presence of frontal dysfunction that is dependent on WM load in individuals with MCI.

High Working Memory Load Impairs Language Processing during a Simulated Piloting Task: An ERP and Pupillometry Study.

Given the important amount of visual and auditory linguistic information that pilots have to process, operating an aircraft generates a high working-memory load (WML). In this context, the ability to focus attention on relevant information and to remain responsive to concurrent stimuli might be altered. Consequently, understanding the effects of WML on the processing of both linguistic targets and distractors is of particular interest in the study of pilot performance. In the present work, participants performed a simplified piloting task in which they had to follow one of three colored aircraft, according to specific written instructions (i.e., the written word for the color corresponding to the color of one of the aircraft) and to ignore either congruent or incongruent concurrent auditory distractors (i.e., a spoken name of color). The WML was manipulated with an n-back sub-task. Participants were instructed to apply the current written instruction in the low WML condition, and the 2-back written instruction in the high WML condition. Electrophysiological results revealed a major effect of WML at behavioral (i.e., decline of piloting performance), electrophysiological, and autonomic levels (i.e., greater pupil diameter). Increased WML consumed resources that could not be allocated to the processing of the linguistic stimuli, as indexed by lower P300/P600 amplitudes. Also, significantly, lower P600 responses were measured in incongruent vs. congruent trials in the low WML condition, showing a higher difficulty reorienting attention toward the written instruction, but this effect was canceled in the high WML condition. This suppression of interference in the high load condition is in line with the engagement/distraction trade-off model. We propose that P300/P600 components could be reliable indicators of WML and that they allow an estimation of its impact on the processing of linguistic stimuli.

Deficient interference control during working memory updating in adults with ADHD: An event-related potential study

ObjectiveLittle is known about the underlying mechanisms of poor working memory (WM) performance of adults with attention deficit hyperactivity disorder (ADHD). This study investigates interference and load effects during WM updating by use of event-related potentials. MethodForty ADHD patients and 41 controls performed verbal n-back tasks under conditions of low and high WM load. Intrusion probes, i.e., lures, were implemented to challenge interference control abilities during WM processing. ResultsStimulus-dependent N200 amplitude modulation and behavioral performance in lure trials were reduced in adults with ADHD compared to healthy controls. Also, P300 amplitudes tended to be less sensitive to WM load in patients with ADHD. ConclusionOur findings provide electrophysiological evidence for inaccurate discrimination of stimulus categories. Particularly, deficient interference control may lead to overt WM deficits in adult subjects with ADHD. SignificanceThe current findings contribute to a deeper understanding of the neural substrates of executive dysfunction in adult ADHD, focusing on the domain of WM.

Effects of working memory load on uncertain decision-making: evidence from the Iowa Gambling Task.

The Iowa Gambling Task (IGT) simulates uncertain gains and losses in real life situations and thus is a good measure of uncertain decision-making. The role of working memory (WM) in IGT performance still remains unclear. The present study aimed to examine the effect of WM on IGT performance. Three groups of participants matched on gender ratio were randomly assigned to no WM load, low WM load, and high WM load conditions. Initially the three groups did not show significant difference in WM capacity. They finished a modified version of IGT and then their implicit learning effect and explicit cognition on IGT were assessed. Results indicated a linear increasing trend of IGT performance among high WM load, low WM load and no WM load groups; participants in the no WM load and low WM load groups revealed implicit learning effect, while participants in the high WM load group did not; all participants showed explicit cognition on IGT to the same level. These results suggested that participants in the high WM load group showed good explicit cognition to IGT but showed poor performance. This pattern is similar to frontal patients. Further studies should be conducted to explore this issue.