2-back Condition Research Articles

Working memory performance impaired after exposure to acute social stress: The evidence comes from ERPs.

Using event-related potentials (ERPs), we examined the time course of 39 healthy novice drivers during a blocked working memory task (numerical N-back) under acute social stress or control conditions, which were induced by the Trier Social Stress Task (TSST) or control procedure. Subjective measures were used to assess stress manipulation throughout the experiment. An elevated negative effect in response to a stress condition indicated a successful stress induction. The behavioral results showed that the stress group had a longer response time and larger differences in accuracy than the control group. On a neural level, the control group had larger P3 amplitude in the 1-back condition than in the 2-back condition; this load effect, however, disappeared in the stress group. These results revealed that acute social stress had a disruptive effect on both working memory behavioral performance and cognitive neural process. These findings provide us with a basis to understand the correlation between acute stress and cognitive processes of working memory at a cognitive neural level.

Increasing pain inhibition by working memory with anodal transcranial direct current stimulation of the left dorsolateral prefrontal cortex

The aim of this study was to examine whether transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (DLPFC) enhances pain inhibition by improving working memory (WM). Forty healthy volunteers participated in two tDCS sessions. Pain was evoked by electrical stimulation at the ankle. Participants performed an n-back task (0-back and 2-back). The experimental protocol comprised five counterbalanced conditions (0-back, 2-back, pain, 0-back with pain and 2-back with pain) that were performed twice (pre-tDCS baseline and during tDCS). Compared with the pre-tDCS baseline values, anodal tDCS decreased response times for the 2-back condition (p 0.5). Anodal tDCS also decreased pain ratings marginally in the 2-back with pain condition, but not the 0-back with pain condition (p = 0.052 and p > 0.2, respectively). No effect was produced by sham tDCS for any condition (p > 0.2). These results indicate that tDCS of the left DLPFC may enhance pain inhibition by improving WM. © 2018, The Physiological Society of Japan and Springer Japan KK, part of Springer Nature.

Polygenic risk for depression and the neural correlates of working memory in healthy subjects

IntroductionMajor depressive disorder (MDD) patients show impairments of cognitive functioning such as working memory (WM), and furthermore alterations during WM-fMRI tasks especially in frontal and parietal brain regions. The calculation of a polygenic risk score (PRS) can be used to describe the genetic influence on MDD, hence imaging genetic studies aspire to combine both genetics and neuroimaging data to identify the influence of genetic factors on brain functioning. We aimed to detect the effect of MDD-PRS on brain activation during a WM task measured with fMRI and expect healthy individuals with a higher PRS to be more resembling to MDD patients. MethodIn total, n=137 (80 men, 57 women, aged 34.5, SD=10.4years) healthy subjects performed a WM n-back task [0-back (baseline), 2-back and 3-back condition] in a 3T-MRI-tomograph. The sample was genotyped using the Infinium PsychArray BeadChip and a polygenic risk score was calculated for MDD using PGC MDD GWAS results. ResultsA lower MDD risk score was associated with increased activation in the bilateral middle occipital gyri (MOG), the bilateral middle frontal gyri (MFG) and the right precentral gyrus (PCG) during the 2-back vs. baseline condition. Moreover, a lower PRS was associated with increased brain activation during the 3-back vs. baseline condition in the bilateral cerebellum, the right MFG and the left inferior parietal lobule. A higher polygenic risk score was associated with hyperactivation in brain regions comprising the right MFG and the right supplementary motor area during the 3-back vs. 2-back condition. DiscussionThe results suggest that part of the WM-related brain activation patterns might be explained by genetic variants captured by the MDD-PRS. Furthermore we were able to detect MDD-associated activation patterns in healthy individuals depending on the MDD-PRS and the task complexity. Additional gene loci could contribute to these task-dependent brain activation patterns.

Evidence of systematic attenuation in the measurement of cognitive deficits in schizophrenia.

Cognitive tasks that are too hard or too easy produce imprecise measurements of ability, which, in turn, attenuates group differences and can lead to inaccurate conclusions in clinical research. We aimed to illustrate this problem using a popular experimental measure of working memory-the N-back task-and to suggest corrective strategies for measuring working memory and other cognitive deficits in schizophrenia. Samples of undergraduates (n = 42), community controls (n = 25), outpatients with schizophrenia (n = 33), and inpatients with schizophrenia (n = 17) completed the N-back. Predictors of task difficulty-including load, number of word syllables, and presentation time-were experimentally manipulated. Using a methodology that combined techniques from signal detection theory and item response theory, we examined predictors of difficulty and precision on the N-back task. Load and item type were the 2 strongest predictors of difficulty. Measurement precision was associated with ability, and ability varied by group; as a result, patients were measured more precisely than controls. Although difficulty was well matched to the ability levels of impaired examinees, most task conditions were too easy for nonimpaired participants. In a simulation study, N-back tasks primarily consisting of 1- and 2-back load conditions were unreliable, and attenuated effect size (Cohen's d) by as much as 50%. The results suggest that N-back tasks, as commonly designed, may underestimate patients' cognitive deficits as a result of nonoptimized measurement properties. Overall, this cautionary study provides a template for identifying and correcting measurement problems in clinical studies of abnormal cognition. (PsycINFO Database Record

Muscular and Aerobic Fitness, Working Memory, and Academic Achievement in Children

This study investigated the relationship between aerobic and muscular fitness with working memory and academic achievement in preadolescent children. Seventy-nine 9- to 11-yr-old children completed an aerobic fitness assessment using a graded exercise test; a muscular fitness assessment consisting of upper body, lower body, and core exercises; a serial n-back task to assess working memory; and an academic achievement test of mathematics and reading. Hierarchical regression analyses indicated that after controlling for demographic variables (age, sex, grade, IQ, socioeconomic status), aerobic fitness was associated with greater response accuracy and d' in the 2-back condition and increased mathematic performance in algebraic functions. Muscular fitness was associated with increased response accuracy and d', and longer reaction time in the 2-back condition. Further, the associations of muscular fitness with response accuracy and d' in the 2-back condition were independent of aerobic fitness. The current findings suggest the differential relationships between the aerobic and the muscular aspects of physical fitness with working memory and academic achievement. With the majority of research focusing on childhood health benefits of aerobic fitness, this study suggests the importance of muscular fitness to cognitive health during preadolescence.

Decreased Fronto-Parietal and Increased Default Mode Network Activation is Associated with Subtle Cognitive Deficits in Elderly Controls

Background: Cognitive functions progressively deteriorate during aging and neurodegenerative diseases. The present study aims at investigating differences in working memory performance as well as functional brain changes during the earliest stages of cognitive decline in health elderly individuals. Methods: 62 elderly individuals (41 females), including 41 controls (35 females) and 21 middle cognitive impairment subjects (6 females), underwent neuropsychological assessment at baseline and an fMRI examination in a N-back paradigm contrasting 2-back vs. 0-back condition. Upon a 18 months follow-up, we identified stable controls (sCON) with preserved cognition and deteriorating controls (dCON) with -1SD decrease of performances in at least two neuropsychological tests. Data analyses included accuracy and reaction time (RT) for the 2-back condition and general linear model (GLM) for the fMRI sequence. Results: At the behavioral level, sCON and dCON performed better than MCI in terms of accuracy and reaction time. At the brain level, functional differences in regions of the fronto-parietal network (FPN) and of the Default Mode Network (DFM) were observed. Significantly lower neural activations in the bilateral inferior and middle frontal gyri were found in MCI versus both dCON / sCON and for dCON versus sCON. Significantly increased activations in the anterior cingulate cortex and posterior cingulate cortex and bilateral insula were found in MCI versus both dCON / sCON and in dCON versus sCON. Conclusion: The present study suggests that brain functional changes in FPN and DMN anticipate differences in cognitive performance in healthy elderly individuals with subsequent subtle cognitive decline.

Sensitivity evaluation of the visual, tactile, and auditory detection response task method while driving

ABSTRACTObjectives: In this article, we evaluate the sensitivity to cognitive load of 3 versions of the Detection Response Task method (DRT), proposed in ISO Draft Standard DIS-17488.Methods: We present a user study with 30 participants in which we compared the sensitivity to cognitive load of visual, audio, and tactile DRT in a simulated driving environment. The amount of cognitive load was manipulated with secondary n-back tasks at 2 levels of difficulty (0-back and 1-back). We also explored whether the DRT method is least sensitive to cognitive load when the stimuli and secondary task are of the same modality. For this purpose, we used 3 forms to present the n-back task stimuli: visual, audio, and tactile. Responses to the task were always vocal. The experiment was based on a between-subject design (the DRT modalities) with 2 levels of within-subject design study (modalities and difficulty of the secondary n-back tasks). The participants' primary task in the study was to drive safely, and a second priority was to answer to DRT stimuli and perform secondary tasks.Results: The results indicate that all 3 versions of the DRT tested were sensitive to detecting the difference in cognitive load between the reference driving period and driving and engaging in the secondary tasks. Only the visual DRT discriminated between the 0-back and 1-back conditions on mean response time. Contrary to expectations, no interaction was observed between DRT modality and the stimuli modality used for presentation of the secondary tasks.Conclusions: None of the 3 methods of presenting DRT stimuli showed a consistent advantage in sensitivity in differentiating multiple levels of cognitive load if all response times, hit rates, and secondary task performance are considered. If only response time is considered, the visual presentation of the DRT stimulus used in this study showed some advantages. In interpreting these data, it should be noted that the methods of DRT stimulus presentation varied somewhat from the currently proposed draft ISO standard and it is possible that the relative salience level of the visual DRT stimulus influenced the findings. It is further suggested that more than 2 levels of difficulty of the n-back task should be considered for further investigation of the relative sensitivity of different DRT stimuli modalities. Parameters that indicate change in cognitive load (response time, hit rate, task performance) should be analyzed together in assessing the overall impact on the driver and not individually, in order to obtain a fuller insight of the assessed cognitive load.

Frontal Hypoactivation During a Working Memory Task in Children With 22q11 Deletion Syndrome.

Impairments in executive function, such as working memory, are almost universal in children with chromosome 22q11.2 deletion syndrome. Delineating the neural underpinnings of these functions would enhance understanding of these impairments. In this study, children and adolescents with 22q11 deletion syndrome were compared with healthy control participants in a functional magnetic resonance imaging (MRI) study of working memory. When the 2-back condition was contrasted with the 1-back and 0-back conditions, the participants with 22q11 deletion syndrome showed lower activation in several brain areas involved in working memory-notably dorsolateral prefrontal cortex, anterior cingulate, and precuneus. This hypoactivation may be due to reduced gray matter volumes or white matter connectivity in the frontal and parietal regions, differences that have previously been documented in children with 22q11 deletion syndrome. Understanding differences in brain function will provide a foundation for future interventions to address the wide range of neurodevelopmental deficits observed in 22q11 deletion syndrome.

Event-related potentials elicited during working memory are altered in mild cognitive impairment

Persons with Mild Cognitive Impairment (MCI) can experience deficits in working memory. In the present study, we investigated working memory in persons with MCI and cognitively healthy older adults using event-related potentials (ERPs). Participants performed an n-back working memory task with baseline (0-back), low load (1-back), and high load (2-back) working memory conditions. MCI participants' performance was less accurate than that of healthy older adults in both the 1-back and 2-back conditions, and reaction times were longer in MCI than control participants in the 0-back, 1-back and 2-back conditions. ERP analyses revealed delayed P200 and N200 latencies and smaller P300 amplitudes in MCI relative to control participants in the 0-back, 1-back and 2-back conditions. Deterioration in working memory performance concomitant with marked electrophysiological alterations suggests that persons with MCI exhibit deficits in several cognitive processes that include early attention, stimulus discrimination and classification, and updating and manipulation of information held in working memory.

Tracking the relationship between children's aerobic fitness and cognitive control.

To investigate if changes in aerobic fitness over a 3-year period are associated with modulations in children's cognitive control. A sample of 2nd/3rd-grade children (N = 290) completed baseline measures in Fall of 2011, and again in Spring of 2014 at the end of 4th/5th grade. Children completed the Progressive Aerobic Cardiovascular Endurance Run (PACER) test to measure aerobic capacity, a flanker task to evaluate inhibitory control, and an n-back task to assess working memory. Aerobic fitness was included as an independent variable in hierarchical regression analyses conducted at both time points, in addition to analyses examining changes in cognition over time. At baseline, higher fit children exhibited shorter overall flanker reaction time (RT), as well as superior accuracy and d' scores (i.e., target discrimination) for both 1- and 2-back conditions. Approximately 3 years later, higher levels of fitness were associated with better performance for only the most difficult conditions of each task, including greater incongruent flanker accuracy and less interference during the compatible condition, as well as better accuracy and target discrimination for the 2-back condition of the n-back task. Importantly, increases in fitness were independently related to improvements in incongruent flanker accuracy and 2-back d' scores. The current findings indicate that both higher aerobic fitness levels as well as increases in children's fitness are associated with better performance for task conditions eliciting greater cognitive demand. Such evidence is vital for implementing future health recommendations intended to foster improved cognitive performance in children. (PsycINFO Database Record

The Role Of Sex As A Moderator Of Cognitive Outcome Following A Sport-related Concussion

Despite increasing research, results regarding sex as a moderator of outcome following a concussion are conflicting and management guidelines remain uncertain. PURPOSE: To determine if there is a gender difference in the long-term cognitive outcomes of athletes with a history of concussion (HOC). METHODS: 196 collegiate athletes (49 HOC women, HOC 49 men, 49 women matched controls, 49 men matched controls) completed a modified Cogstate test battery, to which a 2-back condition (N-back task) was added to increase our ability to detect persistent deficits in higher cognition. All participants were symptom-free at time of testing and those with a HOC were 6+ months from injury (24.0 ± 15.8 months, 1.44 ± 1.3 prior concussions). RESULTS: A significant interaction of error type × HOC × sex was observed. Specifically, HOC men exhibited a greater number of omission errors relative to HOC women (2.94 ± 2.5 vs. 0.31 ± 0.9, p<0.05). Moreover, irrespective of sex, HOC athletes exhibited a greater number of errors on the 1-back (2.30 ± 1.5 vs. 0.79 ± 0.9, p<0.01) and 2-back conditions (3.34 ± 2.6 vs. 1.46 ± 1.4, p<0.01), relative to controls. HOC athletes also exhibited decreased accuracy on the 1-back (95.45 ± 3.0% vs. 98.21± 2.2%, p<0.01) and 2-back conditions (93.98 ± 4.1% vs. 96.65 ± 3.3%, p<0.05). CONCLUSIONS: The current results suggest that beyond the acute phase of the injury, sex does not seem as a moderating variable of cognitive outcomes following concussion. Furthermore, the results reaffirm that concussive injuries can result in persistent deficits in aspects of higher cognition.

Increased superior frontal gyrus activation during working memory processing in psychosis: Significant relation to cumulative antipsychotic medication and to negative symptoms

ObjectivesImpairment in working memory (WM) is a core symptom in schizophrenia. However, little is known about how clinical features influence functional brain activity specific to WM processing during the development of first-episode psychosis (FEP) to schizophrenia (SZ). We compared functional WM-specific brain activity in FEP and SZ patients, including the effects of the duration of illness, psychopathological factors and antipsychotic medication. MethodsCross-sectional study of male FEP (n=22) and SZ (n=20) patients performing an n-back task when undergoing functional magnetic resonance imaging (fMRI). Clinical features were collected by semi-structured interviews and medical records. ResultsThe SZ group performed significantly worse than the FEP group in the 2-back condition. The SZ group also showed significantly higher activation in the left superior frontal gyrus in the 2-back versus 0-back condition (2-back>0-back). This frontal activation correlated positively with negative symptoms and with cumulative antipsychotic medication during the year before the fMRI examination. There were no significant correlations between activation and duration of illness. ConclusionThere was greater frontal neural activation in SZ than in FEP. This indicated differences in WM processing, and was significantly related to cumulative antipsychotic exposure and negative symptoms, but not to the duration of illness.

A pilot study of changes in functional brain activity during a working memory task after mSMT treatment: The MEMREHAB trial

BackgroundWorking memory deficits are common in multiple sclerosis (MS). The modified Story Memory Technique (mSMT) has been shown to improve new learning and memory in MS, but its effects on working memory (WM) are currently unknown. ObjectiveThe present study presents a secondary analysis of data from a larger double-blind, placebo-controlled, randomized clinical trial and examines changes in cerebral activation on a WM task following mSMT treatment. MethodsSixteen participants with clinically definite MS were randomly assigned to treatment (n=7) or placebo-control groups (n=9) matched for gender, age and education. Baseline and immediate follow-up functional Magnetic Resonance Imaging (fMRI) was obtained for all subjects. During fMRI participants completed an N-back task, consisting of 0-, 1-and 2-back conditions. ResultsSignificant increases in cerebral activation were noted in the dorsolateral prefrontal cortex, supplementary motor area and inferior parietal lobule at follow-up in the treatment group. No significant changes were noted in the placebo control group. ConclusionDue to the small sample size, results of the current study should be interpreted as preliminary. However, the observed pattern of activation of the frontoparietal network involved in WM found in the treatment group, suggests that mSMT training increases recruitment of attention- and WM-related neural networks. We conclude that mSMT treatment leads to changes in WM-related cerebral activation.

Deficits in GABAA receptor function and working memory in non-smokers with schizophrenia

BackgroundAlthough altered gamma-aminobutyric acid (GABA) neurotransmission has been implicated in the pathophysiology of schizophrenia, it is unclear whether the influence of GABA on working memory processes is confounded by nicotine use in this population. It is therefore crucial to evaluate working memory and its underlying mechanisms in non-smokers with schizophrenia to eliminate the confounding effects of nicotine on behavior and neurophysiology. MethodsIn this cross-sectional study, working memory was assessed using the verbal N-back task, while GABAergic function was assessed through motor cortical inhibition using single and paired-pulse transcranial magnetic stimulation (TMS) to the left primary motor cortex in 11 non-smokers with schizophrenia and 13 non-smoker healthy subjects. ResultsSimilar to previously published studies, working memory performance was significantly impaired in the 3-back condition in patients with schizophrenia compared to healthy subjects (p=0.036). In addition, GABAA receptor function was significantly reduced in schizophrenia as assessed by short interval cortical inhibition (SICI) (p=0.005). A positive correlation was found between GABAA inhibition and working memory performance on the 3-back task (r(23)=0.55, p=0.006), suggesting that greater GABAA inhibition is associated with better performance on tasks of working memory. ConclusionsOur findings highlight the role of GABAA receptor dysfunction in working memory and the pathophysiology of schizophrenia, and may represent a selective characteristic of schizophrenia. Moreover, these findings suggest a potential therapeutic role for targeting GABA receptor activity to improve cognition and quality of life in patients with schizophrenia.

Intact working memory in non-manifesting LRRK2 carriers--an fMRI study.

Cognitive impairments are prevalent in patients with Parkinson's disease. Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most common cause of genetic Parkinsonism. Non-manifesting carriers of the G2019S mutation in the LRRK2 gene were found to have lower executive functions as measured by the Stroop task. This exploratory study aimed to assess whether the cognitive impairment in non-manifesting carriers is specific for executive functions or includes other cognitive domains such as working memory. We recruited 77 non-manifesting first-degree relatives of Parkinson's disease patients (38 carriers). A block-design fMRI N-back task, with 0-back, 2-back and 3-back conditions, was used in order to assess working memory. Participants were well matched on the Montreal Cognitive Assessment, University of Pennsylvania Smell Identification Test, Unified Parkinson's Disease Rating Scale part III, digit span, age, gender and Beck Depression Inventory. The task achieved the overall expected effect in both groups with longer reaction times and lower accuracy rates with increasing task demands. However, no whole-brain or region-of-interest between-groups differences were found on any of the task conditions. These results indicate that non-manifesting carriers of the G2019S mutation in the LRRK2 gene have a specific cognitive profile with executive functions, as assessed by the Stroop task, demonstrating significant impairment but with working memory, as assessed with the N-back task, remaining relatively intact. These finding shed light on the pre-motor cognitive changes in this unique 'at risk' population and should enable more focused cognitive assessments of these cohorts.

Working memory and behavioral inhibition in boys with ADHD: An experimental examination of competing models

ABSTRACTWorking memory (WM) and behavioral inhibition impairments have garnered significant attention as candidate core features, endophenotypes, and/or associated neurocognitive deficits of attention-deficit/hyperactivity disorder (ADHD). The relationship between ADHD-related WM and inhibition deficits remains relatively unclear, however, with inferences about the constructs’ directional relationship stemming predominantly from correlational research. The current study utilized a dual-task paradigm to experimentally examine the relationship between ADHD-related WM and behavioral inhibition deficits. A total of 31 boys (15 ADHD and 16 typically developing [TD]) aged 8–12 years completed WM (1-back and 2-back), behavioral inhibition (stop-signal task [SST]), and dual-condition (1-back/SST and 2-back/SST) experimental tasks. Children with ADHD exhibited significant, large-magnitude WM deficits for the 1-back condition but were not significantly different from children in the TD group for the 2-back, 1-back/SST, and 2-back/SST conditions. Children with ADHD also exhibited significant inhibition deficits for the SST, 1-back/SST, and 2-back/SST conditions, but the within-group effect was not significant. The findings suggest that ADHD-related stop-signal demands are upstream, or compete for, resources involved in controlled-focused attention and/or other central executive (CE), WM processes.

Fish Oil Supplementation Increases Event-Related Posterior Cingulate Activation in Older Adults with Subjective Memory Impairment.

To determine the effects of long-chain omega-3 (LCn-3) fatty acids found in fish oil, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on cortical blood oxygen level-dependent (BOLD) activity during a working memory task in older adults with subjective memory impairment. Randomized, double-blind, placebo-controlled study. Academic medical center. Healthy older adults (62-80 years) with subjective memory impairment, but not meeting criteria for mild cognitive impairment or dementia. Fish oil (EPA+DHA: 2.4 g/d, n=11) or placebo (corn oil, n=10) for 24 weeks. Cortical BOLD response patterns during performance of a sequential letter n-back working memory task were determined at baseline and week 24 by functional magnetic resonance imaging (fMRI). At 24 weeks erythrocyte membrane EPA+DHA composition increased significantly from baseline in participants receiving fish oil (+31%, p ≤ 0.0001) but not placebo (-17%, p=0.06). Multivariate modeling of fMRI data identified a significant interaction among treatment, visit, and memory loading in the right cingulate (BA 23/24), and in the right sensorimotor area (BA 3/4). In the fish oil group, BOLD increases at 24 weeks were observed in the right posterior cingulate and left superior frontal regions during memory loading. A region-of-interest analysis indicated that the baseline to endpoint change in posterior cingulate cortex BOLD activity signal was significantly greater in the fish oil group compared with the placebo group during the 1-back (p=0.0003) and 2-back (p=0.0005) conditions. Among all participants, the change in erythrocyte EPA+DHA during the intervention was associated with performance in the 2-back working memory task (p = 0.01), and with cingulate BOLD signal during the 1-back (p = 0.005) with a trend during the 2-back (p = 0.09). Further, cingulate BOLD activity was related to performance in the 2-back condition. Dietary fish oil supplementation increases red blood cell omega-3 content, working memory performance, and BOLD signal in the posterior cingulate cortex during greater working memory load in older adults with subjective memory impairment suggesting enhanced neuronal response to working memory challenge.

Caffeine differentially alters cortical hemodynamic activity during working memory: a near infrared spectroscopy study.

BackgroundCaffeine is a widely used stimulant with potentially beneficial effects on cognition as well as vasoconstrictive properties. In functional magnetic imaging research, caffeine has gained attention as a potential enhancer of the blood oxygenation level-dependent (BOLD) response. In order to clarify changes of oxy- and deoxyhemoglobin (HbO and HbR) induced by caffeine during a cognitive task, we investigated a working memory (WM) paradigm (visual 2-back) using near-infrared spectroscopy (NIRS).ResultsBehaviorally, caffeine had no effect on the WM performance but influenced reaction times in the 0-back condition. NIRS data demonstrate caffeine-dependent alterations of the course of the hemodynamic response. The intake of 200 mg caffeine caused a significant decrease of the HbO response between 20 and 40 s after the onset of a 2-back task in the bilateral inferior frontal cortex (IFC). In parallel, the HbR response of the left IFC was significantly increased due to caffeine intake.ConclusionsIn line with previous results, we did not detect an effect of caffeine on most aspects of behavior. Effects of caffeine on brain vasculature were detected as general reduction of HbO. Neuronal effects of caffeine are reflected in an increased concentration of HbR in the left hemisphere when performing a verbal memory task and suggest influences on metabolism.

Central load reduces peripheral processing: Evidence from incidental memory of background speech.

Is there a trade-off between central (working memory) load and peripheral (perceptual) processing? To address this question, participants were requested to undertake an n-back task in one of two levels of central/cognitive load (i.e., 1-back or 2-back) in the presence of a to-be-ignored story presented via headphones. Participants were told to ignore the background story, but they were given a surprise memory test of what had been said in the background story, immediately after the n-back task was completed. Memory was poorer in the high central load (2-back) condition in comparison with the low central load (1-back) condition. Hence, when people compensate for higher central load, by increasing attentional engagement, peripheral processing is constrained. Moreover, participants with high working memory capacity (WMC) - with a superior ability for attentional engagement - remembered less of the background story, but only in the low central load condition. Taken together, peripheral processing - as indexed by incidental memory of background speech - is constrained when task engagement is high.

Possible Association of APOE Genotype with Working Memory in Young Adults.

BackgroundPossession of the ε4 allele of the Apolipoprotein E (APOE) gene is associated with an increased risk of Alzheimer’s disease. Early adult life effects of ε4 are less well understood. Working memory has been relatively little studied (compared to episodic memory) in relation to APOE genotype despite its importance in cognitive functioning. Our hypothesis was that ε4 would lead to an impairment in working memory in young adults.MethodsWe studied working memory using a computerised n-back task in the Avon Longitudinal Study of Parents and Children (ALSPAC) at age 18. Data was available for 1049–1927 participants and for the 2- and 3-back versions of the task. Using multiple and multi-level regression controlling for important confounders we examined the association between APOE genotype on accuracy and reaction times.ResultsThere was no evidence of a genotype effect on accuracy when the two difficulty levels were examined separately. There was some evidence to support a deleterious effect of the ε4 allele on n-back accuracy in the multi-level regression. There was weak evidence that the ε22 group were less accurate but the numbers were very low in this group. The ε34 group had faster reaction times than the reference ε33 group in all adjusted analyses but the ε44 group were only faster in the 3-back condition in multi-level analyses.ConclusionsThere was no evidence of benefit in ε4 carriers, but there was some evidence of a detrimental effect on working memory in this large study.