Fronto-parietal activity changes associated with changes in working memory load: Evidence from simultaneous electroencephalography and functional near-infrared spectroscopy analysis.

Working memory (WM) involves the capacity to maintain and manipulate information over short periods. Previous research has suggested that fronto-parietal activities play a crucial role in WM. However, there remains no agreement on the effect of working memory load (WML) on neural activities and haemodynamic responses. Here, our study seeks to examine the effect of WML through simultaneous electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS). In this study, a delay change detection task was conducted on 23 healthy volunteers. The task included three levels: one item, three items and five items. The EEG and fNIRS were simultaneously recorded during the task. Neural activities and haemodynamic responses at prefrontal and parietal regions were analysed using time-frequency analysis and weighted phase-lag index (wPLI). We observed a significant enhancement in prefrontal and parietal ß suppression as WML increased. Furthermore, as WML increased, there was a notable enhancement in fronto-parietal connectivity (FPC), as evidenced by both EEG and fNIRS. Correlation analysis indicated that as WML increased, there was a potential for enhancement of neurovascular coupling (NVC) of FPC.

Working memory load does not interfere with distractor suppression in the additional singleton task.

Over the last decade, the additional singleton task has been widely used to study visual statistical learning. In this paradigm, participants are instructed to find a target while ignoring a series of distractors. In some trials, a salient singleton distractor is added to the search display, making the task more difficult. However, if the singleton appears more frequently in one particular location of the display, participants eventually learn to suppress attention towards this location. It has been suggested that this type of learning is probably implicit and independent of working memory (WM) resources. To our knowledge, only one study has explored the impact of WM in suppression effect (Gao & Theeuwes, Psychonomic Bulletin & Review, 27, 96-104, 2020). However, there are reasons to suspect that the amount and type of WM load used in that study may have been suboptimal to detect any effects on distractor suppression. The aim of the present study was to explore the impact of WM load on distractor suppression addressing these issues. Contrary to our expectations, our results confirm that this type of learning is indeed highly resilient even to strong manipulations of WM load.

Attention switching through text dissimilarity: a cognition research on fragmented reading behavior.

People tend to obtain information through fragmented reading. However, this behavior itself might lead to distraction and affect cognitive ability. To address it, it is necessary to understand how fragmented reading behavior influences readers' attention switching. In this study, the researchers first collected online news that had 6 theme words and 60 sentences to compose the experimental material, then defined the degree of text dissimilarity, used to measure the degree of attention switching based on the differences in text content, and conducted an EEG experiment based on P200. The results showed that even after reading the fragmented text content with the same overall content, people in subsequent cognitive tasks had more working memory capacity, lower working memory load, and less negative impact on cognitive ability with the text content with lower text dissimilarity. Additionally, attention switching caused by differences in concept or working memory representation of text content might be the key factor affecting cognitive ability in fragmented reading behavior. The findings disclosed the relation between cognitive ability and fragmented reading and attention switching, opening a new perspective on the method of text dissimilarity. This study provides some references on how to reduce the negative impact of fragmented reading on cognitive ability on new media platforms.

Semantic Stroop interference is modulated by the availability of executive resources: Insights from delta-plot analyses and cognitive load manipulation.

We investigated whether, during visual word recognition, semantic processing is modulated by attentional control mechanisms directed at matching semantic information with task-relevant goals. In previous research, we analyzed the semantic Stroop interference as a function of response latency (delta-plot analyses) and found that this phenomenon mainly occurs in the slowest responses. Here, we investigated whether this pattern is due to reduced ability to proactively maintain the task goal in these slowest trials. In two pairs of experiments, participants completed two semantic Stroop tasks: a classic semantic Stroop task (Experiment 1A and 2A) and a semantic Stroop task combined with an n-back task (Experiment 1B and 2B). The two pairs of experiments only differed in the trial pace, which was slightly faster in Experiments 2A and 2B than in Experiments 1A and 1B. By taxing the executive control system, the n-back task was expected to hinder proactive control. Delta-plot analyses of the semantic Stroop task replicated the enhanced effect in the slowest responses, but only under sufficient time pressure. Combining the semantic Stroop task with the n-back task produced a change in the distributional profile of semantic Stroop interference, which we ascribe to a general difficulty in the use of proactive control. Our findings suggest that semantic Stroop interference is, to some extent, dependent on the available executive resources, while also being sensitive to subtle variations in task conditions.

The effect of working memory load on selective attention to emotional faces for social anxiety individuals.

Research has confirmed that individuals with social anxiety (SA) show an attentional bias towards threat-related stimuli. However, the extent to which this attentional bias depends on top-down cognitive control processes remains controversial. The present study investigated the effect of working memory (WM) load on selective attention to emotional faces in both high social anxiety (HSA) and low social anxiety (LSA) groups by manipulating WM load through the inclusion of forward counting in multiples of two (low load) or backward counting in multiples of seven (high load) within a modified flanker task. In the flanker task, emotional faces (angry, happy, or neutral faces) were used as targets and distractors. A total of 70 participants (34 HSA participants; 36 LSA participants) completed the flanker task in the laboratory. The results showed that the HSA individuals performed worse when responding to angry targets. Relative to LSA individuals, HSA individuals showed interference from angry distractors in the flanker task, resulting in significantly lower accuracy in identifying angry targets compared to happy targets. These results were unaffected by the manipulation of WM load. The findings imply HSA individuals have impaired attentional control, and that their threat-related attentional bias relies more on the bottom-up automatic attentional process.

Age differences in the recruitment of syntactic analysis and semantic plausibility during sentence comprehension.

Syntactic analysis and semantic plausibility provide important cues to build the meaningful representation of sentences. The purpose of this research is to explore the age-related differences in the use of syntactic analysis and semantic plausibility during sentence comprehension under different working memory load conditions. A sentence judgment task was implemented among a group of older and younger adults. Semantic plausibility (plausible, implausible) and syntactic consistency (consistent, inconsistent) were manipulated in the experimental stimuli, and working memory load (high, low) was varied by manipulating the presentation of the stimuli. The study revealed a stronger effect of semantic plausibility in older adults than in younger adults when working memory load was low. But no significant age difference in the effect of syntactic consistency was discovered. When working memory load was high, there was a stronger effect of semantic plausibility and a weaker effect of syntactic consistency in older adults than in younger adults, which suggests that older adults relied more on semantic plausibility and less on syntactic analysis than younger adults. The findings indicate that there is an age-related increase in the use of semantic plausibility, and a reduction in the use of syntactic analysis as working memory load increases.

The impact of spatial and verbal working memory load on semantic relatedness judgements.

Studies using a relatedness judgement task have found differences between prime-target word pairs that vary in the degree of semantic relatedness. However, the influence of working memory load on semantic processing in this task and the role of the type of working memory task have not yet been investigated. The present study therefore investigated for the first time the effect of working memory load (low vs. high) and working memory type (verbal vs. spatial) on semantic relatedness judgements. Semantically strongly related (e.g., hip - KNEE), weakly related (e.g., muscle - KNEE) and unrelated (e.g., office - KNEE) Polish word pairs were presented in an experiment involving a dual working memory and semantic relatedness task. The data revealed that, relative to semantically unrelated word pairs, responses were faster for strongly related pairs but slower for weakly related pairs. Importantly, the verbal working memory task decreased facilitation for strongly related pairs and increased inhibition for weakly related pairs relative to the spatial working memory task. Furthermore, working memory load impacted only weakly related pairs in the verbal but not in the spatial working memory task. These results show that working memory type and load influence semantic relatedness judgements, but the direction and size of the impact depend on the strength of semantic relations.

The effect of working memory load on inattentional deafness during aeronautical decision-making.

Operating an aircraft requires pilots to handle a significant amount of multi-modal information, which creates a high working memory load. Detecting auditory alarms in this high-load scenario is crucial for aviation safety. According to cognitive control load theory, an increase in working memory load may enhance distractor interference, resulting in improved detection sensitivity for task-irrelevant stimuli. Therefore, understanding the effect of working memory load on auditory alarm detection is of particular interest in aviation safety research. The studies were designed to investigate the effect of storage load and executive function load of working memory on auditory alarm detection during aeronautical decision-making through three experiments. In Experiment 1 and 2, participants performed an aeronautical decision-making task while also detecting an auditory alarm during the retention interval of a working memory task (visual-spatial, visual-verbal and auditory-verbal). In Experiment 3, participants were required to detect an auditory alarm while performing the 2-back and 3-back aeronautical decision-making tasks. Experiment 1 found that the auditory alarm sensitivity was higher in conditions of low visual-spatial working memory storage load compare to high load conditions. Experiment 2 found that a high storage load of visual-verbal working memory reduced auditory alarm sensitivity but auditory-verbal working memory load did not. Experiment 3 found that, unlike storage load, auditory alarm sensitivity was stronger under high executive function load relative to low executive function load. These findings show that working memory storage load and executive function load have different effects on auditory alarm sensitivity. The relationship between executive function and auditory alarm sensitivity supports cognitive control load theory, while the impact of the storage function on auditory alarm sensitivity does not adhere to this theory.

The linear impact of visual working memory load on visual awareness: Evidence from motion-induced blindness.

Despite the close relationship between visual working memory (VWM) and visual awareness, the question of how these two constructs interact with each other is still under debate. The current study aimed to further address this issue by investigating whether and how visual awareness is influenced by VWM load. In Experiment 1, participants were asked to perform a motion-induced blindness (MIB) task while simultaneously memorizing different numbers of items in VWM. The results indicated that the latency of MIB was prolonged gradually as the VWM load increased, revealing a linear trend in the modulation effect of VWM load on visual awareness. Experiments 2 and 3 tested the other potential explanations and validated the initial finding by confirming that VWM load was indeed responsible for the observed effect on visual awareness. These findings have important implications for a better understanding of the relationship between VWM and visual awareness.

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.

Visual processing of food stimuli: The impact of working memory load and color.

Our environment is surrounded by appetizing food stimuli that contribute to an increase in health problems such as obesity and overweight. Understanding the cognitive factors underlying the processing of food stimuli can play an important role in health interventions. Recent studies showed that high-calorie food stimuli impair working memory (WM) task performance, and some individuals, such as restrained eaters, are more susceptible to this WM performance decrement. The present study investigated the effect of low and high WM load on the processing of food stimuli in restrained and unrestrained eaters. Using an n-back task, identical food (low and high calorie) and non-food (object) stimuli were presented in colored (Experiment 1A) or in grayscale (Experiment 1B) versions. Performance was assessed by reaction time (RT), d-prime, and response bias C variables. Results revealed differences in the different WM load conditions. While no effects were observed in the low load, higher WM load impaired task performance. Processing the food stimuli, compared to objects, led to longer RTs and decreased task performance, indicated by d prime and response bias, only when the stimuli were presented in color but not in grayscale. Though no difference was observed in restrained and unrestrained eaters, the role of WM load on the visual processing of the food stimuli remains to be further examined.

Scale-Free Dynamics in Instantaneous Alpha Frequency Fluctuations: Validation, Test-Retest Reliability and Its Relationship with Task Manipulations.

Previous studies showed that scale-free structures and long-range temporal correlations are ubiquitous in physiological signals (e.g., electroencephalography). This is supposed to be associated with optimized information processing in human brain. The instantaneous alpha frequency (IAF) (i.e., the instantaneous frequency of alpha band of human EEG signals) may dictate the resolution at which information is sampled and/or processed by cortical neurons. To the best of our knowledge, no research has examined the scale-free dynamics and potential functional significance of IAF. Here, through three studies (Study 1: 25 participants; Study 2: 82 participants; Study 3: 26 participants), we investigated the possibility that time series of IAF exhibit scale-free property through maximum likelihood based detrended fluctuation analysis (ML-DFA). This technique could provide the scaling exponent (i.e., DFA exponent) on the basis of presence of scale-freeness being validated. Then the test-retest reliability (Study 1) and potential influencing factors (Study 2 and Study 3) of DFA exponent of IAF fluctuations were investigated. Firstly, the scale-free property was found to be inherent in IAF fluctuations with fairly high test-retest reliability over the parietal-occipital region. Moreover, the task manipulations could potentially modulate the DFA exponent of IAF fluctuations. Specifically, in Study 2, we found that the DFA exponent of IAF fluctuations in eye-closed resting-state condition was significantly larger than that in eye-open resting-state condition. In Study 3, we found that the DFA exponent of IAF fluctuations in eye-open resting-state condition was significantly larger than that in visual n-back tasks. The DFA exponent of IAF fluctuations in the 0-back task was significantly larger than in the 2-back and 3-back tasks. The results in studies 2 and 3 indicated that: (1) a smaller DFA exponent of IAF fluctuations should signify more efficient online visual information processing; (2) the scaling property of IAF fluctuations could reflect the physiological arousal level of participants.

Planning on Autopilot? Associative Contributions to Proactive Control.

Proactive cognitive control is thought to rely on the active maintenance of goals or contextual information in working memory. It is often measured using the AX-CPT, in which antecedent cues (A/B) are used to proactively prepare a response to a subsequently-presented probe (X/Y). Although control in this task purportedly requires active maintenance of information in working memory, it also provides conditions in which learning the contingencies between relevant events could influence performance via associative learning. We tested this hypothesis using a dot-pattern expectancy version of the AX-CPT whereby a set of new rules (test phase) for responding changed the control operations required for some previously trained cues, while keeping the operations the same for others, allowing us to measure associative interference. We also tested the relationship between associative interference and working memory capacity (operation span; Experiments 1-3) and tested the effect of applying working memory load during the initial acquisition period (Experiment 2) and during the test phase (Experiment 3). We found robust evidence of interference after the rule change based on previously learnt contingencies, suggesting that learnt contingencies come to influence proactive planning, even when they are task-irrelevant. This associative effect had no relationship with working memory capacity or load, based on a load manipulation commonly used in executive control tasks. The findings suggest that proactive control does not always require active maintenance of current goals and environmental cues in working memory. Instead, proactive control may run on autopilot if the individual can rely upon stable relationships in the environment to trigger planning and preparation. SIGNIFICANCE: Navigating daily life requires us to anticipate future events and plan our thoughts and actions accordingly to achieve our goals. This forward planning, or proactive control, is thought to be a resource-intensive and metabolically costly process that recruits higher-order cognitive functions, such as working memory, where relevant thoughts and actions have to be maintained online. The current study challenged this notion by finding that proactive control can be incrementally relegated to simpler processes based on one's learning of stable relationships in the environment, thereby reducing the need to actively maintain information online. Individuals can come to rely on underlying contingencies in stimuli associated with proactive control, even when it is detrimental to their goals.

Coexistence of the social semantic effect and non-semantic effect in the default mode network.

Neuroimaging studies have found both semantic and non-semantic effects in the default mode network (DMN), leading to an intense debate on the role of the DMN in semantic processes. Four different views have been proposed: (1) the general semantic view holds that the DMN contains several hub regions supporting general semantic processes; (2) the non-semantic view holds that the semantic effects observed in the DMN (especially the ventral angular gyrus) are confounded by difficulty and do not reflect semantic processing per se; (3) the multifunction view holds that the same areas in the DMN can support both semantic and non-semantic functions; and (4) the multisystem view holds that the DMN contains multiple subnetworks supporting different aspects of semantic processes separately. Using an fMRI experiment, we found that in one of the subnetworks of the DMN, called the social semantic network, all areas showed social semantic activation and difficulty-induced deactivation. The distributions of two non-semantic effects, that is, difficulty-induced and task-induced deactivations, showed dissociation in the DMN. In the bilateral angular gyri, the ventral subdivisions showed social semantic activation independent of difficulty, while the dorsal subdivisions showed no semantic effect but difficulty-induced activation. Our findings provide two insights into the semantic and non-semantic functions of the DMN, which are consistent with both the multisystem and multifunction views: first, the same areas of the DMN can support both social semantic and non-semantic functions; second, similar to the multiple semantic effects of the DMN, the non-semantic effects also vary across its subsystems.

Investigating the role of working memory resources across aesthetic and non-aesthetic judgements.

Aesthetic judgements dominate much of daily life by guiding how we evaluate objects, people, and experiences in our environment. One key question that remains unanswered is the extent to which more specialised or largely general cognitive resources support aesthetic judgements. To investigate this question in the context of working memory, we examined the extent to which a working memory load produces similar or different response time interference on aesthetic compared with non-aesthetic judgements. Across three pre-registered experiments that used Bayesian multi-level modelling approaches (N > 100 per experiment), we found clear evidence that a working memory load produces similar response time interference on aesthetic judgements relative to non-aesthetic (motion) judgements. We also showed that this similarity in processing across aesthetic versus non-aesthetic judgements holds across variations in the form of art (people vs. landscape; Experiments 1-3), medium type (artwork vs. photographs; Experiment 2), and load content (art images vs. letters; Experiments 1-3). These findings suggest that across a range of experimental contexts, as well as different processing streams in working memory (e.g., visual vs. verbal), aesthetic and motion judgements commonly rely on a domain-general cognitive system, rather than a system that is more specifically tied to aesthetic judgements. In doing so, these findings shine new light on the working memory resources that support aesthetic judgements, as well as on how domain-general cognitive systems operate more generally in cognition.

The neural coding of tonal working memory load: An functional magnetic resonance imaging study.

Tonal working memory load refers to the number of pitches held in working memory. It has been found that different verbal working memory loads have different neural coding (local neural activity pattern). However, whether there exists a comparable phenomenon for tonal working memory load remains unclear. In this study, we used a delayed match-to-sample paradigm to evoke tonal working memory. Neural coding of different tonal working memory loads was studied with a surface space and convolution neural network (CNN)-based multivariate pattern analysis (SC-MVPA) method. We found that first, neural coding of tonal working memory was significantly different from that of the control condition in the bilateral superior temporal gyrus (STG), supplement motor area (SMA), and precentral gyrus (PCG). Second, neural coding of nonadjacent tonal working memory loads was distinguishable in the bilateral STG and PCG. Third, neural coding is gradually enhanced as the memory load increases. Finally, neural coding of tonal working memory was encoded in the bilateral STG in the encoding phase and shored in the bilateral PCG and SMA in the maintenance phase.

Concurrent working memory task increases or decreases the flanker-related N2 amplitude.

Concurrent working memory (WM) task reduces available attentional control resources to perform the flanker task. However, controversy exists as to whether concurrent WM task increases or decreases flanker-related N2 amplitude. In a flanker task experiment, individuals were confronted with a low, middle, or high WM load task, while electroencephalography (EEG) data were recorded. The ERP results showed a larger flanker-related N2 amplitude while completing a middle or high WM load task compared to a low one. However, completing an additional high WM load task could not increase flanker-related N2 amplitude versus completing an additional middle WM load task. In sum, these results suggest that WM load can impair top-down cognitive control processes, thereby hampering flanker task performance. Importantly, the present study supports the account of flanker-related N2 processes linked to top-down attentional control resource allocation, but challenges the account of flanker-related N2 reflecting response conflict processes.

The bottom-up information transfer process and top-down attention control underlying tonal working memory.

Tonal working memory has been less investigated by neuropsychological and neuroimaging studies and even less in terms of tonal working memory load. In this study, we analyzed the dynamic cortical processing process of tonal working memory with an original surface-space-based multivariate pattern analysis (sf-MVPA) method and found that this process constituted a bottom-up information transfer process. Then, the local cortical activity pattern, local cortical response strength, and cortical functional connectivity under different tonal working memory loads were investigated. No brain area's local activity pattern or response strength was significantly different under different memory loads. Meanwhile, the interactions between the auditory cortex (AC) and an attention control network were linearly correlated with the memory load. This finding shows that the neural mechanism underlying the tonal working memory load does not arise from changes in local activity patterns or changes in the local response strength, but from top-down attention control. Our results indicate that the implementation of tonal working memory is based on the cooperation of the bottom-up information transfer process and top-down attention control.

Morality in the time of cognitive famine: The effects of memory load on cooperation and honesty.

Though human social interaction in general seems effortless at times, successful engagement in collaborative or exploitative social interaction requires the availability of cognitive resources. Research on Dual-Process suggests that two systems, the affective (non-reflective) and the cognitive (reflective), are responsible for different types of reasoning. Nevertheless, the evidence on which system leads to what type of behavioral outcome, in terms of prosociality, is at best contradicting and perplexing. In the present paper, we examined the role of the two systems, operationalized as working memory depletion, in prosocial decision-making. We hypothesize that the nature of the available cognitive resources could affect whether humans engage in collaborative or exploitative social interaction. Using Operation Span to manipulate the availability of working memory, we examined how taxing the cognitive system affects cooperation and cheating. In two experiments, we provide evidence that concurrent load, but not cumulative load is detrimental to cooperation, whereas neither concurrent nor cumulative load seems to affect cheating behavior. These findings are in contrast to several previous assumptions. We discuss limitations, possible explanations, and future directions.

High working memory load impairs reappraisal but facilitates distraction - An event-related potential investigation.

The present experiments investigated the impact of working memory (WM) load on emotion regulation (ER) efficacy using reappraisal (Experiment 1, n = 30) and distraction (Experiment 2, n = 30). Considering that WM is necessary for storage, elaboration, and manipulation of information and that reappraisal acts by storing, elaborating, and manipulating the stimulus meaning, we hypothesized that high (versus low) WM-load would reduce reappraisal efficacy. By contrast, given that distraction acts by blocking elaborated processing of the stimulus meaning, we expected that high WM-load would enhance distraction efficacy. To test these predictions, we employed a dual-task paradigm in which a low- or high WM-load task was combined with an ER (reappraisal or distraction) task. We measured the Late Positive Potential (LPP)-an electrocortical marker of sustained motivated attention, and a well-established index of emotional arousal-in response to negative pictures. Results confirmed that although reappraisal successfully reduced the LPP amplitude in the down- compared to up-regulation condition in low WM-load trials, high WM-load eliminated this difference, suggesting the disrupting influence of high WM-load on ER for reappraisal (Experiment 1). By contrast, although distraction failed to modulate the LPP amplitude in low WM-load trials, the difference between down- and no-regulation conditions was significant when distraction was combined with high WM-load, suggesting the facilitatory influence of high WM-load on ER for distraction (Experiment 2). Our findings show that the effect of WM-load on ER is strategy-dependent, and that the availability of WM resources is an important situational moderator of ER efficacy in healthy young adults.