Performance Of Working Memory Task Research Articles

Rewards Enhance Proactive and Reactive Control in Adolescence and Adulthood.

Cognitive control allows the coordination of cognitive processes to achieve goals. Control may be sustained in anticipation of goal-relevant cues (proactive control) or transient in response to the cues themselves (reactive control). Adolescents typically exhibit a more reactive pattern than adults in the absence of incentives. We investigated how reward modulates cognitive control engagement in a letter-array working memory (WM) task in 30 adolescents (12–17 years) and 20 adults (23–30 years) using a mixed block- and event-related functional magnetic resonance imaging design. After a Baseline run without rewards, participants performed a Reward run where 50% trials were monetarily rewarded. Accuracy and reaction time (RT) differences between Reward and Baseline runs indicated engagement of proactive control, which was associated with increased sustained activity in the bilateral anterior insula (AI), right dorsolateral prefrontal cortex (PFC) and right posterior parietal cortex (PPC). RT differences between Reward and No reward trials of the Reward run suggested additional reactive engagement of cognitive control, accompanied with transient activation in bilateral AI, lateral PFC, PPC, supplementary motor area, anterior cingulate cortex, putamen and caudate. Despite behavioural and neural differences during Baseline WM task performance, adolescents and adults showed similar modulations of proactive and reactive control by reward.

Network-Targeted, Multi-site Direct Cortical Stimulation Enhances Working Memory by Modulating Phase Lag of Low-Frequency Oscillations

Working memory is mediated by the coordinated activation of frontal and parietal cortices occurring in the theta and alpha frequency ranges. Here, we test whether electrically stimulating frontal and parietal regions at the frequency of interaction is effective in modulating working memory. We identify working memory nodes that are functionally connected in theta and alpha frequency bands and intracranially stimulate both nodes simultaneously in participants performing working memory tasks. We find that in-phase stimulation results in improvements in performance compared to sham stimulation. In addition, in-phase stimulation results in decreased phase lag between regions within working memory network, while anti-phase stimulation results in increased phase lag, suggesting that shorter phase lag in oscillatory connectivity may lead to better performance. The results support the idea that phase lag may play a key role in information transmission across brain regions. Thus, brain stimulation strategies to improve cognition may require targeting multiple nodes of brain networks.

Recovery from impaired working memory performance during chronic Δ-9-tetrahydrocannabinol administration to adolescent rhesus monkeys.

The relationship between adolescent cannabis use and susceptibility to persistent cognitive impairments is poorly understood. We examined the effects of repeated exposure to Δ-9-tetrahydrocannabinol (THC) on reinforcement-related learning and performance of spatial working memory (WM) tasks of varying difficulty in adolescent monkeys. Seven pairs of male adolescent rhesus monkeys, matched for baseline cognitive performance, received vehicle or THC intravenously 5 days/week for 12 months. Performance on 4-item spatial WM trials was assessed throughout the 12-month study period. At the 6-month time point, more difficult novel and distractor 8-item spatial WM trials were added. Residual effects on performance were determined 23 or 71 h after THC or vehicle administration throughout the study. Relative to vehicle-exposed animals, repeated THC exposure was initially associated with significantly slower improvement in performance accuracy on 4-item spatial WM trials; however, this performance difference gradually diminished such that by month 12, accuracy did not significantly differ between vehicle and THC groups. Similarly, for the novel and distractor 8-item trials introduced at month 6, performance accuracy improved more slowly in the THC than in the vehicle group, despite comparable performance between groups on the 4-item task during this same period. These findings suggest that compared to vehicle exposure, THC exposure during adolescence impairs the reinforcement-related learning process required for improved performance on spatial WM tasks, but this impairment might be overcome with continued training, even in the face of ongoing THC exposure.

Developmental changes in executive functions during adolescence: A study of inhibition, shifting, and working memory.

The development of executive functions (EFs) has primarily been studied among younger children, despite research suggesting that particular aspects of EFs continue to develop throughout adolescence and into adulthood. This study investigated whether EFs continue to develop during the later stages of adolescence: three related, yet separable EF components - inhibition, shifting, and working memory - were examined in a cross-sectional sample of 347 adolescents (aged 14-18years). After adjusting for covariates, age was found to be a significant predictor of pupils' performance on the inhibition but not the shifting or working memory tasks, suggesting different developmental trajectories for the three EF components. Controlling for non-executive processes implicated in performing the inhibition and working memory tasks had the most pronounced effect on the relationship between performance on those tasks and age. Finally, socioeconomic status was a significant predictor of performance on all tasks. Implications for research and practice are discussed. Statement of contribution What is already known on this subject? Brain regions associated with EFs continue to mature throughout adolescence, implying ongoing development of EFs. Behavioural studies demonstrate that certain EFs have not yet reached their adult levels in early adolescence. What the present study adds Changes in inhibition, but not shifting or working memory task performance, are evident among older adolescents. Lower-order processes tapped by EF tasks act as confounds in the relationship between age and task performance. Socioeconomic status is a significant predictor of adolescents' performance on EF tasks.

Altered working memory-related brain responses and white matter microstructure in extremely preterm-born children at school age

Preterm birth poses a risk for neurocognitive and behavioral development. Preterm children, who have not been diagnosed with neurological or cognitive deficits, enter normal schools and are expected to succeed as their term-born peers. Here we tested the hypotheses that despite an uneventful development after preterm birth, these children might exhibit subtle abnormalities in brain function and white-matter microstructure at school-age. We recruited 7.5-year-old children born extremely prematurely (<28 weeks’ gestation), and age- and gender-matched term-born controls (≥37 weeks’ gestation). We applied fMRI during working-memory (WM) tasks, and investigated white-matter microstructure with diffusion tensor imaging. Compared with controls, preterm-born children performed WM tasks less accurately, had reduced activation in several right prefrontal areas, and weaker deactivation of right temporal lobe areas. The weaker prefrontal activation correlated with poorer WM performance. Preterm-born children had higher fractional anisotropy (FA) and lower diffusivity than controls in several white-matter areas, and in the posterior cerebellum, the higher FA associated with poorer visuospatial test scores. In controls, higher FA and lower diffusivity correlated with faster WM performance. Together these findings demonstrate weaker WM-related brain activations and altered white matter microstructure in children born extremely preterm, who had normal global cognitive ability.

Effects of working memory on naturally occurring cravings

Elaborated Intrusion (EI) theory posits a key role for visuospatial working memory (WM) in craving. In line with the predictions of EI theory, several studies have found that WM and craving show mutually interfering effects - for example, performance of visuospatial WM tasks has been found to attenuate naturally occurring cravings. However, the extent to which these effects are driven specifically by visuospatial processing remains unclear. We conducted two experiments to investigate the effects of WM on naturally occurring cravings in more detail. In experiment 1, we examined whether such effects are driven specifically by visuospatial WM processes or can also be induced by a verbal WM task. Subjective craving ratings were attenuated equally by performance of visuospatial and verbal WM tasks, suggesting that craving is not dependent specifically on visuospatial processing. In experiment 2, we examined whether effects of visuospatial WM on craving could be driven by simple distraction. Naturally occurring cravings were attenuated in a control condition with minimal WM demands (watching a video). However, the magnitude of attenuation was significantly greater in a visuospatial WM condition. Taken together, these findings highlight a key role for WM in the attenuation of naturally occurring craving, but do not support the hypothesis that such effects are dependent specifically on visuospatial processing.

Low intensity white noise improves performance in auditory working memory task: An fMRI study

Research suggests that white noise may facilitate auditory working memory performance via stochastic resonance. Stochastic resonance is quantified by plotting cognitive performance as a function of noise intensity. The plot would appear as an inverted U-curve, that is, a moderate noise is beneficial for performance whereas too low and too much noise attenuates performance. However, knowledge about the optimal signal-to-noise ratio (SNR) needed for stochastic resonance to occur in the brain, particularly in the neural network of auditory working memory, is limited and demand further investigation. In the present study, we extended previous works on the impact of white noise on auditory working memory performance by including multiple background noise levels to map out the inverted U-curve for the stochastic resonance. Using functional magnetic resonance imaging (fMRI), twenty healthy young adults performed a word-based backward recall span task under four signal-to-noise ratio conditions: 15, 10, 5, and 0-dB SNR. Group results show significant behavioral improvement and increased activation in frontal cortices, primary auditory cortices, and anterior cingulate cortex in all noise conditions, except at 0-dB SNR, which decreases activation and performance. When plotted as a function of signal-to-noise ratio, behavioral and fMRI data exhibited a noise-benefit inverted U-shaped curve. Additionally, a significant positive correlation was found between the activity of the right superior frontal gyrus (SFG) and performance in 5-dB SNR. The predicted phenomenon of SR on auditory working memory performance is confirmed. Findings from this study suggest that the optimal signal-to-noise ratio to enhance auditory working memory performance is within 10 to 5-dB SNR and that the right SFG may be a strategic structure involved in enhancement of auditory working memory performance.

Impaired working memory performance in opioid-dependent patients is related to reduced insula gray matter volume: a voxel-based morphometric study.

Opioid-dependent patients frequently show deficits in multiple cognitive domains that might impact on their everyday life performance and interfere with therapeutic efforts. To date, the neurobiological underpinnings of those deficits remain to be determined. We investigated working memory performance and gray matter volume (GMV) differences in 17 patients on opioid maintenance treatment (OMT) and 17 healthy individuals using magnetic resonance imaging and voxel-based morphometry. In addition, we explored associations between substance intake, gray matter volume, and working memory task performance. Patients on OMT committed more errors during the working memory task than healthy individuals and showed smaller insula and putamen GMV. The duration of heroin use prior to OMT was associated with working memory performance and insula GMV in patients. Neither the substitution agent (methadone and buprenorphine) nor concurrent abuse of illegal substances during the 3months prior to the experiment was significantly associated with GMV. Results indicate that impaired working memory performance and structural deficits in the insula of opioid-dependent patients are related to the duration of heroin use. This suggests that early inclusion into OMT or abstinence-oriented therapies that shorten the period of heroin abuse may limit the impairments to GMV and cognitive performance of opioid-dependent individuals.

Cognitive Offloading: Structuring the Environment to Improve Children's Working Memory Task Performance.

Research has shown that adults can engage in cognitive offloading, whereby internal processes are offloaded onto the environment to help task performance. Here, we investigate an application of this approach with children, in particular children with poor working memory. Participants were required to remember and recall sequences of colors by placing colored blocks in the correct serial order. In one condition the blocks were arranged to facilitate cognitive offloading (i.e., grouped by color), whereas in the other condition they were arranged randomly. Across two experiments (total N=166) the ordered condition improved task performance for children with low working memory ability. In addition, participants in Experiment 2 rated the difficulty of the two arrangements and performed a further condition in which they were given an opportunity to freely arrange the blocks before completing the task. Despite performing better in the ordered condition, children with low working memory ability did not rate the ordered arrangement as easier, nor did they choose an ordered arrangement when given the opportunity to do so. This research shows that cognitive offloading can also be a useful process in populations other than typical adults, and the implications of this work for supporting children with poor working memory are discussed.

The Role of Working Memory in Dual-Target Visual Search.

Visual search (VS) for multiple targets is especially error prone. One of these errors is called subsequent search misses (SSM) and represents a decrease in accuracy at detecting a second target after a first target has been found. One of the possible explanations of SSM errors is working memory (WM) resource depletion. Three experiments investigated the role of WM in SSM errors using a dual task paradigm. The first experiment investigated the role of object WM using a classical color change detection task. In the second and the third experiments, a modified change detection task was applied, using shape as the relevant feature. The results of our study revealed no effect of additional WM task on second target detection in dual-target VS. To this end, SSM errors are not related to WM resource depletion. On the contrary, WM task performance was violated by dual-target VS as compared to single-target VS, when the targets in VS task were defined by the same feature used in the WM task.

Appetite effects of prefrontal stimulation depend on COMT Val158Met polymorphism: A randomized clinical trial

The regulation of appetite is supported by dopamine-modulated brain circuits. Recent studies have shown that transcranial direct current stimulation (tDCS) aimed at increasing the excitability of the dorsolateral prefrontal cortex can reduce appetite, but the underlying mechanisms remain unknown, and response variability is large. The aim of this study was to determine whether individual differences in Catechol-O-methyl transferase (COMT) Val158Met polymorphism can influence tDCS effects on appetite. Thirty-eight adult women with obesity, classified as carriers or non-carriers of the Met allele, underwent a randomized, double-blind, sham-controlled tDCS intervention involving three phases: Phase I, target engagement (immediate effects of tDCS on working memory performance), Phase II, tDCS only (10 sessions, two weeks), and Phase III, tDCS + hypocaloric diet: (6 sessions, two weeks, 30% energy intake reduction, inpatient). Data were analyzed using linear mixed-effects models and mixed ANCOVA. Appetite was evaluated using visual analogue scales. We found that Met-carriers receiving active tDCS were the only participants who experienced a significant reduction of appetite over time. Conversely, Met non-carriers maintained high levels of appetite during the intervention; this effect was driven by a delayed paradoxical rise in appetite after stimulation. Working memory task performance at phase I correlated with subsequent appetite change in a COMT-dependent manner: speed improvements during the task predicted appetite increase in Met carriers and appetite reduction in Met non-carriers. Our findings suggest that genotype differences impacting dopamine levels influence prefrontal tDCS effects on appetite. This source of variability should be considered in the design of future studies.

Longitudinal brain functional changes between mania and euthymia in bipolar disorder.

While widespread cortical and subcortical brain functional abnormalities have been found in bipolar disorder, the changes that take place between illness phases and recovery are less clearly documented. Only a small number of longitudinal studies of manic patients, in particular, have been carried out. Twenty-six bipolar patients underwent fMRI during performance of the n-back working memory task when manic and again after recovery. Twenty-six matched healthy controls were also scanned on two occasions. Task-related activations and de-activations were examined. When manic, the patients showed clusters of significantly reduced activation in the left dorsolateral prefrontal cortex (DLPFC)/precentral cortex and the parietal cortex/superior precuneus bilaterally. They also showed failure of de-activation in the ventromedial frontal cortex (vmPFC). After recovery, activation in the left DLPFC/precentral cortex and in the bilateral parietal cortex/superior precuneus clusters increased significantly. However, failure of de-activation remained present in the vmPFC. Recovery from mania is associated with normalization of DLPFC and parietal hypoactivation, but not with vmPFC failure of de-activation, which accordingly appears to represent a trait abnormality in the disorder.

Action video game players require greater EEG coupling between prefrontal cortices to adequately perform a dual task

Action video games require the ability to perform multiple complex activities concurrently, while dual-tasking has been associated with functional changes in sub-regions of the prefrontal cortex, such as the frontopolar (FPPC) and dorsolateral (DLPC) cortices. However, the degree of electroencephalographic synchronization or correlation (rEEG) between these areas has not yet been examined. Thus, the aim of the present study was to characterize rEEG of action video game players (AVGPs) and compare it to inexperienced video game players (NVGPs) during performance of a dual working memory task. rEEG were recorded in AVGPs and NVGPs while performing three distinct working memory tasks: (1) Corsi block-tapping task (CBTT); (2) N-back task; and (3) dual task, which involved performing both CBTT and N-back tasks simultaneously. AVGPs achieved a higher number of correct trials and greater memory span during the dual task than NVGPs, as well as an increased intrahemispheric FPPC-DLPC rEEG, left (Fp1-F3) and right (Fp2-F4), in the beta1, beta2 and gamma bands, and an increased interhemispheric rEEG FPPC (Fp1-Fp2) in all EEG bands. Our results suggest that AVGPs had higher working memory skills as the level of task complex increased, and that they required higher FPPC-DLPC coupling to adequately perform the dual task.

Cognitive Performance, Aerobic Fitness, Motor Proficiency, and Brain Function Among Children Newly Diagnosed With Craniopharyngioma.

Craniopharyngioma survivors experience cognitive deficits that negatively impact quality of life. Aerobic fitness is associated with cognitive benefits in typically developing children and physical exercise promotes recovery following brain injury. Accordingly, we investigated cognitive and neural correlates of aerobic fitness in a sample of craniopharyngioma patients. Patients treated for craniopharyngioma [N=104, 10.0±4.6 years, 48% male] participated in fitness, cognitive and fMRI (n=51) assessments following surgery but before proton radiation therapy. Patients demonstrated impaired aerobic fitness [peak oxygen uptake (PKVO2)=23.9±7.1, 41% impaired (i.e., 1.5 SD&lt;normative mean)], motor proficiency [Bruininks-Oseretsky (BOT2)=38.6±9.0, 28% impaired], and executive functions (e.g., WISC-IV Working Memory Index (WMI)=96.0±15.3, 11% impaired). PKVO2 correlated with better executive functions (e.g., WISC-IV WMI r=.27, p=.02) and academic performance (WJ-III Calculation r=.24, p=.04). BOT2 correlated with better attention (e.g., CPT-II omissions r=.26, p=.04) and executive functions (e.g., WISC-IV WMI r=.32, p=.01). Areas of robust neural activation during an n-back task included superior parietal lobule, dorsolateral prefrontal cortex, and middle and superior frontal gyri (p&lt;.05, corrected). Higher network activation was associated with better working memory task performance and better BOT2 (p&lt;.001). Before adjuvant therapy, children with craniopharyngioma demonstrate significantly reduced aerobic fitness, motor proficiency, and working memory. Better aerobic fitness and motor proficiency are associated with better attention and executive functions, as well as greater activation of a well-established working memory network. These findings may help explain differential risk/resiliency with respect to acute cognitive changes that may portend cognitive late effects. (JINS, 2019, 25, 413-425).

Impaired prefrontal functional connectivity associated with working memory task performance and disorganization despite intact activations in schizophrenia

Working memory (WM) deficits are key features of schizophrenia and are associated with significant functional impairment. The precise mechanisms of WM and their relationship between WM deficits with other clinical symptoms of schizophrenia remain unclear. Contemporary models propose that WM requires synchronous activity across brain regions within a distributed network, including lateral prefrontal cortex (PFC) and task-relevant posterior sensory cortical regions. This suggests that WM deficits in patients may be due to PFC functional connectivity (FC) impairments rather than activation impairments per se. We tested this hypothesis by measuring the magnitude of FC between lateral PFC and visual cortex and univariate activations within these regions during visual WM. We found decreased FC in patients compared to healthy subjects in the context of similar levels of univariate activity. Furthermore, this decreased FC was associated with task performance and clinical symptomatology in patients. The magnitude of FC, particularly during the delay period, was positively correlated with WM task accuracy, while FC during cue was inversely correlated with severity of disorganization. Taken together, these results suggest that impairment in lateral PFC FC is a key aspect of information processing impairment in patients with schizophrenia, and may be a sensitive index of altered neurophysiology.

Alpha modulation during working memory encoding predicts neurocognitive impairment in ADHD.

Attention-deficit/hyperactivity disorder (ADHD) is associated with working memory (WM) deficits. However, WM is a multiprocess construct that can be impaired through several pathways, leaving the source of WM impairments in ADHD unresolved. In this study, we aim to replicate, in an independent sample, previously reported deficits in component processes of WM deficits in ADHD and expand to consider their implications for neurocognitive outcomes. In 119 children (7-14years old, 85 with ADHD), we used electroencephalography measures to quantify component processes during performance of a spatial working memory task. We quantified stimulus encoding using alpha range (8-12Hz) power; vigilance by the P2 event-related potential to cues; and WMmaintenance by occipital-alpha and frontal-theta (4-7Hz) power. These measures were evaluated against metrics of executive function, ADHD symptoms, and academic achievement. Encoding alpha-power decreases and cue P2 amplitude were attenuated in ADHD, whereas occipital-alpha power during maintenance was significantly greater in ADHD, consistent with a compensatory response to weak encoding. Weak alpha modulation during encoding was associated with poorer reading comprehension and executive function, as well as enhanced ADHD symptoms. Previously reported effects in frontal-theta power failed to replicate. Stimulus encoding, a component process of WM coupled to alpha modulation, is impaired in ADHD, and, unlike WM maintenance or vigilance processes, has implications outside of the laboratory via a relationship with executive function, and, to a weaker extent, reading comprehension.

Training state and performance evaluation of working memory based on task-related EEG

The working memory (WM) refers to the information maintaining and manipulation during a short period, and it is corresponding to human ability in many tasks. The correlation between EEG features and the training state of the subjects or their performance in WM tasks had been investigated by many researches. However, there was no research done on the comparison between the training and performance to investigate which one is more correlated with the EEG features and adequately developed practical application of this correlation by now. This paper used phase synchronization methods to build functional brain networks (FBN) of the subjects based on their task-related EEG. Based on this, we investigated the correlation of the global and local features of the FBNs and applied Quadratic Discriminant, Cosine KNN and stacked auto-encoder (SAE) to evaluate the performance and the training state. The accuracy of training state detection was 98.7%, while the accuracy of performance prediction (predict if the score>79) was 81.2% and the MSE of the score prediction was 144.24. The results suggested that the training state is more reliance to the FBN features than performance. The method had the potential to be extended to other fields to assess WM ability or proficiency of people.

Schizophrenia-related abnormalities in the triple network: a meta-analysis of working memory studies.

Previous meta-analyses found abnormal brain activations in schizophrenia patients compared with normal controls when performing working memory tasks. Although most studies focused on dysfunction of the working memory activation network in schizophrenia patients, deactivation abnormalities of the working memory in the default mode network have also been reported in schizophrenia but have received less attention. Our goal was to discover whether deactivation abnormalities can also be consistently found in schizophrenia during working memory tasks and, further, to consider both activation and deactivation abnormalities. Fifty-two English language peer-reviewed studies were included in this meta-analysis. Compared with normal controls, the schizophrenia patients showed activation dysfunction of the bilateral dorsolateral prefrontal cortex and posterior parietal cortex as well as the anterior insula, anterior cingulate cortex, and supplementary motor area, which are core nodes of the central executive and salience network. In addition to dysfunction of the activation networks, the patients showed deactivation abnormalities in the ventral medial prefrontal cortex and posterior cingulate cortex, which are core nodes of the default mode network. These results suggest that both activation and deactivation abnormalities exist in schizophrenia patients and that these abnormalities should both be considered when investigating the pathophysiological mechanism of schizophrenia.

Impaired Cognitive Flexibility After Neonatal Perirhinal Lesions in Rhesus Macaques.

Previous research indicated that monkeys with neonatal perirhinal lesions (Neo-PRh) were impaired on working memory (WM) tasks that generated proactive interference, but performed normally on WM tasks devoid of interference (Weiss et al., 2016). This finding suggested that the early lesions disrupted cognitive processes important for resolving proactive interference, such as behavioral inhibition and cognitive flexibility. To distinguish between these possibilities, the same Neo-PRh monkeys and their controls were tested using the Intradimensional/Extradimensional attentional set-shifting task (Roberts et al., 1988; Dias et al., 1997). Neo-PRh monkeys completed the Simple and Compound Discrimination stages, the Intradimensional Shift stage, and all Reversal stages comparably to controls, but made significantly more errors on the Extradimensional Shift stage of the task. These data indicate that impaired cognitive flexibility was the likely source of increased perseverative errors made by Neo-PRh monkeys when performing WM tasks, rather than impaired behavioral inhibition, and imply that the perirhinal cortex and its interactions with the PFC may play a unique and critical role in the development of attentional set shifting abilities.

Identifying brain changes related to cognitive aging using VBM and visual rating scales.

Aging is often associated with changes in brain structures as well as in cognitive functions. Structural changes can be visualized with Magnetic Resonance Imaging (MRI) using voxel-based grey matter morphometry (VBM) and visual rating scales to assess atrophy level. Several MRI studies have shown that possible neural correlates of cognitive changes can be seen in normal aging. It is still not fully understood how cognitive function as measured by tests and demographic factors are related to brain changes in the MRI. We recruited 55 healthy elderly subjects aged 50–79 years. A battery of cognitive tests was administered to all subjects prior to MRI scanning. Our aim was to assess correlations between age, sex, education, cognitive test performance, and the said two MRI-based measures. Our results show significant differences in VBM grey matter volume for education level (≤ 12 vs. > 12 years), with a smaller amount of grey matter volume in subjects with lower educational levels, and for age in interaction with education, indicating larger grey matter volume for young, higher educated adults. Also, grey matter volume was found to be correlated with working memory function (Digit Span Backward). Furthermore, significant positive correlations were found between visual ratings and both age and education, showing larger atrophy levels with increasing age and decreasing level of education. These findings provide supportive evidence that MRI-VBM detects structural differences for education level, and correlates with educational level and age, and working memory task performance.