Verbal Working Memory Task Research Articles

The interaction of concreteness and phonological similarity in verbal working memory.

Although phonological representations have been a primary focus of verbal working memory research, lexical-semantic manipulations also influence performance. In the present study, the authors investigated whether a classic phenomenon in verbal working memory, the phonological similarity effect (PSE), is modulated by a lexical-semantic variable, word concreteness. Phonological overlap and concreteness were factorially manipulated in each of four experiments across which presentation modality (Experiments 1 and 2: visual presentation; Experiments 3 and 4: auditory presentation) and concurrent articulation (present in Experiments 2 and 4) were manipulated. In addition to main effects of each variable, results show a Phonological Overlap x Concreteness interaction whereby the magnitude of the PSE is greater for concrete word lists relative to abstract word lists. This effect is driven by superior item memory for nonoverlapping, concrete lists and is robust to the modality of presentation and concurrent articulation. These results demonstrate that in verbal working memory tasks, there are multiple routes to the phonological form of a word and that maintenance and retrieval occur over more than just a phonological level. (PsycINFO Database Record (c) 2009 APA, all rights reserved).

Working memory training in older adults: Evidence of transfer and maintenance effects.

Few studies have examined working memory (WM) training-related gains and their transfer and maintenance effects in older adults. This present research investigates the efficacy of a verbal WM training program in adults aged 65-75 years, considering specific training gains on a verbal WM (criterion) task as well as transfer effects on measures of visuospatial WM, short-term memory, inhibition, processing speed, and fluid intelligence. Maintenance of training benefits was evaluated at 8-month follow-up. Trained older adults showed higher performance than did controls on the criterion task and maintained this benefit after 8 months. Substantial general transfer effects were found for the trained group, but not for the control one. Transfer maintenance gains were found at follow-up, but only for fluid intelligence and processing speed tasks. The results are discussed in terms of cognitive plasticity in older adults.

Age differences in prefontal recruitment during verbal working memory maintenance depend on memory load

Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studies have revealed age-related under-activation, where older adults show less regional brain activation compared to younger adults, as well as age-related over-activation, where older adults show greater activation compared to younger adults. These differences have been found across multiple task domains, including verbal working memory (WM). Curiously, both under-activation and over-activation of dorsolateral prefrontal cortex (DLPFC) have been found for older adults in verbal WM tasks. Here, we use event-related fMRI to test the hypothesis that age-related differences in activation depend on memory load (the number of items that must be maintained). Our predictions about the recruitment of prefrontal executive processes are based on the Compensation-Related Utilization of Neural Circuits Hypothesis (CRUNCH; Reuter-Lorenz and Cappell, 2008). According to this hypothesis, more neural resources are engaged by older brains to accomplish computational goals completed with fewer resources by younger brains. Therefore, seniors are more likely than young adults to show over-activations at lower memory loads, and under-activations at higher memory loads. Consistent with these predictions, in right DLPFC, we observed age-related over-activation with lower memory loads despite equivalent performance accuracy across age groups. In contrast, with the highest memory load, older adults were significantly less accurate and showed less DLPFC activation compared to their younger counterparts. These results are considered in relation to previous reports of activation–performance relations using similar tasks, and are found to support the viability of CRUNCH as an account of age-related compensation and its potential costs.

Recruitment and Stabilization of Brain Activation Within a Working Memory Task; an fMRI Study

Seventeen subjects underwent functional magnetic resonance imaging (fMRI) performing a 2-Back verbal working memory (VWM) task alternating with a control task to characterize the temporal dynamics of the specific brain regions involved in VWM. Serial sampling of 2-Back sub-blocks revealed many small areas of activation that grew and merged over time. Significant temporal effects for volume recruitment were seen in specific brain regions known to be involved in VWM, including the bilateral dorsolateral prefrontal (DLPFC), medial frontal (MFC), posterior parietal (PPC) cortices and also some extra-cortical and subcortical regions of interest (ROIs). Signal intensity increased over time in most ROIs recruited early in the task, including the DLPFC, MFC, and PPC but excluding dorsal premotor areas. MFC intensity increased rapidly then stabilized with time. The uniqueness of the MFC response raises the possibility that it drives the recruitment process. Increases in intensity and volume were associated with worsening VWM performance over time, suggesting that recruitment of brain resources is necessary in attempting to sustain difficult tasks. Worsening of performance over sub-blocks despite stable task demands reinforces this temporal "load effect".

A Functional Magnetic Resonance Imaging Study of Verbal Working Memory in Young People at Increased Familial Risk of Depression

BackgroundPatients with depression show abnormalities in the neural circuitry supporting working memory. These abnormalities apparently persist into clinical remission, raising the possibility that they might be trait markers indicating vulnerability to depression.MethodsWe studied 17 young people who had a depressed parent but no personal history of depressive illness (FH) and 15 healthy control subjects with no family history of depression. Participants performed a verbal working memory task of varying cognitive load (n-back) while undergoing functional magnetic resonance imaging scanning. We used multiple regression analyses to assess overall capacity (1-, 2-, 3-back vs. 0-back) as well as linear and quadratic modulation of cognitive demand.ResultsPerformance accuracy and response latency did not differ between groups, and overall capacity was similar. However, for both linear and quadratic load response activity, FH participants showed greater activation in lateral occipital cortex, superior temporal cortex, and superior parietal cortex.ConclusionsOur data suggest that, as in depressed patients, maintenance of task performance in FH participants is associated with a significant increase in the load-response activity of the cortical regions involved in working memory. This neural abnormality could form part of the predisposition to develop depressive disorders.

Sex Differences in the Functional Neuroanatomy of Working Memory in Adults With ADHD

Although attention deficit hyperactivity disorder (ADHD) in adults is associated with significant morbidity and dysfunction and afflicts both sexes, relatively few imaging studies have examined female subjects and none have had sufficient power to adequately examine sex differences. The authors examined sex differences in the neural functioning of adults with ADHD during performance of a verbal working memory task. The participants were 44 adults with ADHD matched on age, sex, and estimated IQ to 49 comparison subjects. Accuracy and reaction time on an N-back task were measured to assess working memory. The blood-oxygen-level-dependent functional MRI response was used as a measure of neural activity. A group-by-sex analysis of variance showed no between-group differences in either reaction time or percent correct for the working memory task. For both sexes combined, the adults with ADHD showed less activity than comparison subjects in prefrontal regions. However, sex-by-group analyses revealed an interaction, such that male ADHD subjects showed significantly less activity in right frontal, temporal, and subcortical regions and left occipital and cerebellar regions relative to male comparison subjects, whereas female ADHD subjects showed no differences from female comparison subjects. Exploratory correlation analyses revealed negative associations between working-memory-related activation and number of hyperactive symptoms for men and number of inattentive symptoms for women. Male but not female adults with ADHD showed significantly altered patterns of neural activity during a verbal working memory task. Men and women showed different associations between neural activity and ADHD symptoms.

Functional brain network abnormalities during verbal working memory performance in adolescents and young adults with dyslexia

Behavioral and functional neuroimaging studies indicate deficits in verbal working memory (WM) and frontoparietal dysfunction in individuals with dyslexia. Additionally, structural brain abnormalities in dyslexics suggest a dysconnectivity of brain regions associated with phonological processing. However, little is known about the functional neuroanatomy underlying cognitive dysfunction in dyslexia. In this study, functional magnetic resonance imaging and multivariate analytic techniques were used to investigate patterns of functional connectivity during a verbal WM task in individuals with dyslexia (n=12) and control subjects (n=13). Dyslexics were not significantly slower than controls; however, they were less accurate with increasing WM demand. Independent component analysis identified 18 independent components (ICs) among which two ICs were selected for further analyses. These ICs included functional networks which were positively correlated with the delay period of the activation task in both healthy controls and dyslexics. Connectivity abnormalities in dyslexics were detected within both networks of interest: within a "phonological" left-lateralized prefrontal network, increased functional connectivity was found in left prefrontal and inferior parietal regions. Within an "executive" bilateral frontoparietal network, dyslexics showed a decreased connectivity pattern comprising bilateral dorsolateral prefrontal and posterior parietal regions, while increased connectivity was found in the left angular gyrus, the left hippocampal cortex and the right thalamus. The functional connectivity strength in the latter regions was associated with WM task accuracy and with the numbers of errors during a spelling test. These data suggest functional connectivity abnormalities in two spatiotemporally dissociable brain networks underlying WM dysfunction in individuals with dyslexia.

Symptomatic and functional correlates of regional brain physiology during working memory processing in patients with recent onset schizophrenia

Patients with schizophrenia show altered patterns of functional activation during working memory processing; specifically, high-performing patients appear to hyper-activate and low-performing patients appear to hypo-activate when compared with controls. It remains unclear how these individual differences in neurophysiological activation relate to the clinical presentation of the syndrome. In this functional magnetic resonance imaging (fMRI) study, the relationship is examined using partial least squares (PLS), a multivariate statistical technique that selects underlying latent variables based on the covariance between two sets of variables, in this case, clinical variables and regional fMRI activations during a verbal working memory task. The PLS analysis extracted two latent variables, and the significance of these associations was confirmed through permutation. Lower levels of activation during task performance across frontal and parietal regions of interest in the left hemisphere were found to covary with poorer role functioning and greater severity of negative and disorganized symptoms, while lower activation in right frontal and subcortical regions of interest was found to covary with better social functioning and fewer positive symptoms. These results suggest that appropriately lateralized patterns of functional activation during working memory processing are related to the severity of negative and disorganized symptoms and to the level of role and social functioning in schizophrenia.

A fMRI Study of Verbal Working Memory, Cardiac Output, and Ejection Fraction in Elderly Patients with Cardiovascular Disease

Cardiovascular disease (CVD) is associated with cognitive deficits even in the absence of stroke. We examined the relationship between cardiac performance, as measured by cardiac output (CO) and ejection fraction (EF), and brain activity during a verbal working memory (VWM) task in elderly CVD patients who tend to be at increased risk for vascular cognitive impairments. Seventeen patients were recruited from a cohort participating in an ongoing prospective study examining the effects of CVD on cognitive function in the elderly. Participants were diagnosed with CVD (age 68±8) and completed a 2-back VWM task in a 1.5T fMRI paradigm. CO and EF were calculated from echocardiogram measures. Task-related activation was averaged in a priori regions of interest. The relationship between CO, EF, and 2-back-related activity was modeled using partial correlations (two-tailed p<.05) controlling for age and 2-back accuracy. All participants were globally cognitively intact as indicated by Mini-Mental Status Exam and Dementia Rating Scale scores. Mean accuracy on the 2-back was 78±9% while reaction time averaged 1,027±192 ms. Mean CO and EF values showed a large range (CO: 3.55 to 6.31; EF: 0.36 to 0.76) but average values were within the normal range. After controlling for age and 2-back accuracy, lower EF was related to decrease in left insula activity (r=0.61, p=0.03). There were trends for EF to be related to accuracy (r=0.47, p=0.09) and reaction time (r=-0.48, p=0.09). CO was also related to insula activity (r=0.60, p=0.04) and activity in the supplementary motor area activity (r=0.66, p=0.01). Cardiac performance was related to decreased efficiency in task related brain areas and tended to be related to performance on a VWM task in elderly patients with CVD. Results have implications for a line of investigation indicating that cardiac and systemic vascular indices could be used as proxy measures to examine mechanisms of cerebrovascular dysfunction in the elderly.

The dopamine D2 receptor antagonist sulpiride modulates striatal BOLD signal during the manipulation of information in working memory

RationaleDopamine (DA) plays an important role in working memory. However, the precise functions supported by different DA receptor subtypes in different neural regions remain unclear.ObjectiveThe present study used pharmacological, event-related fMRI to test the hypothesis that striatal dopamine is important for the manipulation of information in working memory.MethodsTwenty healthy human subjects were scanned twice, once after placebo and once after sulpiride 400 mg, a selective DA D2 receptor antagonist, while performing a verbal working memory task requiring different levels of manipulation.ResultsWhilst there was no overall effect of sulpiride on task-dependent activation, individual variation in sulpiride plasma levels predicted the effect of working memory manipulation on activation in the putamen, suggesting a dose-dependent effect of DA antagonism on a striatally based manipulation process. These effects occurred in the context of a drug-induced improvement in performance on trials requiring the manipulation of information in working memory but not on simple retrieval trials. No significant drug effects were observed in the prefrontal cortex.ConclusionsThese results support models of dopamine function that posit a ‘gating’ function for dopamine D2 receptors in the striatum, which enables the flexible updating and manipulation of information in working memory.

Working memory resources in young children with mathematical difficulties

Working memory (WM) (Baddeley, 1986, 1997) is argued to be one of the most important cognitive resources underlying mathematical competence (Geary, 2004). Research has established close links between WM deficits and mathematical difficulties. This study investigated the possible deficits in WM, language and fluid intelligence that seem to characterize 4- to 6-year-old children with poor early mathematical skills before formal mathematics education. Children with early mathematical difficulties showed poor performance in both verbal and visuospatial WM tasks as well as on language tests and a fluid intelligence test indicating a thoroughly lower cognitive base. Poor WM performance was not moderated by fluid intelligence, but the extent of WM deficits was related to language skills. The educational implications are discussed.

Temporally anticorrelated brain networks during working memory performance reveal aberrant prefrontal and hippocampal connectivity in patients with schizophrenia

Functional neuroimaging studies on cognitive dysfunction in schizophrenia have suggested regional brain activation changes in the dorsolateral prefrontal cortex and the medial temporal lobe. However, less is known about the functional coupling of these areas during cognitive performance. In this study, we used functional magnetic resonance imaging, a verbal working memory (WM) task and multivariate statistical techniques to investigate the functional coupling of temporally anticorrelated neural networks during cognitive processing in patients with schizophrenia ( n = 16) compared to healthy controls ( n = 16). Independent component analysis identified 18 independent components (ICs) among which two ICs were selected for further analyses. These ICs included temporally anticorrelated networks which were most highly associated with the delay period of the task in both healthy controls and patients with schizophrenia. Functional network abnormalities in patients with schizophrenia were detected within a “task-positive” lateral frontoparietal network, where increased functional connectivity was found in bilateral dorsolateral prefrontal regions. In addition, aberrant functional coupling of the hippocampal cortex in patients with schizophrenia was detected within a “task-negative” medial frontotemporal network. In patients with schizophrenia, functional connectivity indices in the left dorsolateral prefrontal cortex and the right hippocampal cortex were positively correlated with accuracy during the WM task, while the connectivity strength in the right dorsolateral prefrontal cortex was negatively correlated with measures of symptom severity. These data suggest that within two temporally anticorrelated network states, patients with schizophrenia exhibit increased and persistent dorsolateral prefrontal and hippocampal connectivity during WM performance.

Cardiac vagal control predicts spontaneous regulation of negative emotional expression and subsequent cognitive performance

The present research investigated whether cardiac vagal control (as measured by respiratory sinus arrhythmia, RSA) predicts an individual's predisposition to suppress negative emotional expressions. One hundred thirty-six participants watched either a negative film or a neutral film. Facial expressions were recorded during the film and subjective emotional responses were assessed afterwards. Participants performed verbal and spatial working memory tasks both before and after the film clips. We found that resting RSA modulated the degree of coherence between facial expressions of emotion and subjective emotional experience in the negative film condition. Specifically, participants with higher resting RSA expressed less but reported feeling just as much negative emotion as those with lower resting RSA. Moreover, higher resting RSA predicted smaller pre-film to post-film improvements in spatial working memory performance in the negative film condition, suggesting that expressive suppression among high RSA participants temporarily undermined the operation of working memory. In the neutral film condition, resting RSA did not relate to expressive or subjective responses or subsequent working memory performance. These results support the notion that cardiac vagal control reflects an internal marker of self-regulatory tendencies and suggest that spontaneous self-regulation associated with individual differences in resting RSA may temporarily deplete self-regulatory resources.

Verbal working memory and its relationship to sentence‐level reading and listening comprehension in persons with aphasia

Background: Working memory (WM) has gained recent attention as a cognitive construct that may account for language comprehension deficits in persons with aphasia (PWA) (Caspari, Parkinson, LaPointe, & Katz, 1998; Martin, Kohen, & Kalinyak‐Fliszar, 2008; Wright, Downey, Gravier, Love, & Shapiro, 2007). However, few studies have investigated individual differences in performance on sentence comprehension tasks as a function of WM capacity in PWA when WM demands are manipulated. Aims: The purposes of the current study were: (1) to examine the relationships among verbal WM, sentence comprehension, and severity of impairment in PWA and (2) to investigate the differential performance of high versus low verbal WM groups on sentence comprehension tasks in which task demands were manipulated by the length of the sentence stimuli, complexity of syntactic structure, and by presentation method which varied the time over which the linguistic material was available for computation. Methods & Procedures: A total of 20 PWA were divided into high and low WM groups based on a listening version of a WM sentence span task. Each participant completed a listening version (CRTT) and three reading versions (CRTT‐R) of the Computerised Revised Token Test as the sentence comprehension tasks. Outcomes & Results: The WM task significantly predicted performance on the CRTT conditions in which information was only temporarily available, thereby imposing greater WM demands on sentence comprehension. The verbal WM task was significantly correlated with aphasia severity and a principal components analysis revealed that the WM task, overall aphasia severity, and overall reading impairment level loaded on a single factor with 76% of shared variance. The low WM group's performance was significantly lower than the high WM group on the CRTT subtests with syntactically more complex structures and on the CRTT conditions with temporally restricted presentation methods. Conclusions: This verbal WM task was significantly and moderately correlated with the overall severity of aphasia as well as with both listening and reading sentence comprehension. The WM group differences emerged only in sentence comprehension tasks with greater WM demands. These results are consistent with the notion that WM effects are most evident when WM capacity is sufficiently taxed by the task demands (e.g., Caplan & Waters, 1999; Just & Carpenter, 1992).

Brain Activity Elicited by Emotional Stimuli During a Verbal Working Memory Task: A Comparison of Healthy Adults and Patients with Chronic Schizophrenia

Brain Activity Elicited by Emotional Stimuli During a Verbal Working Memory Task: A Comparison of Healthy Adults and Patients with Chronic Schizophrenia

Modulation of medial temporal lobe activity in epilepsy patients with hippocampal sclerosis during verbal working memory

It has been traditionally assumed that medial temporal lobe (MTL) is not required for working memory (WM). However, animal lesion and electrophysiological studies and human neuropsychological and neuroimaging studies have provided increasing evidences of a critical involvement of MTL in WM. Based on previous findings, the central aim of this study was to investigate the contribution of the MTL to verbal WM encoding. Here, we used magnetoencephalography (MEG) to compare the patterns of MTL activation of 9 epilepsy patients suffering from left hippocampal sclerosis with those of 10 healthy matched controls while they performed a verbal WM task. MEG recordings allow detailed tracking of the time course of MTL activation. We observed impaired WM performance associated with changes in the dynamics of MTL activity in epilepsy patients. Specifically, whereas patients showed decreased activity in damaged MTL, activity in the contralateral MTL was enhanced, an effect that became significant in the 600- to 700-ms interval after stimulus presentation. These findings strongly support the crucial contribution of MTL to verbal WM encoding and provide compelling evidence for the proposal that MTL contributes to both episodic memory and WM. Whether this pattern is signaling reorganization or a normal use of a damaged structure is discussed.

Cardiac Autonomic Control During Simulated Driving With a Concurrent Verbal Working Memory Task

The objective of the study was to illustrate sensitivity and diagnosticity differences between cardiac measures and lane-keeping measures of driving performance. Previous research suggests that physiological measures can be sensitive to the effects of driving and side task performance and diagnostic of the source of the attentional demands. We hypothesized that increases in side task difficulty would elicit physiological change without reduction of driving task performance and that the side task demands would elicit patterns ofautonomic activity that map to specific attentional processing resources. Separately and concurrently, thirty-two participants performed a simulated driving task and verbal working memory task (with two levels of difficulty, 0 back and 3 back) separately and concurrently. Attentional demands were assessed through physiological and performance measures. Cardiac measures reflected changes in attentional demand from single- to dual-task driving with an n-back task, whereas lane-keeping measures did not. Furthermore, patterns of autonomic activity elicited by driving, n-back task, and dual-task driving with a 3-back task were consistent with our predictions about autonomic activity. Changes in cardiac measures without changes in lane-keeping measures provide evidence that cardiac measures can be sensitive to hidden costs in attention that do not manifest in coarse measures of driving performance. Furthermore, correct predictions regarding the patterns of autonomic activity elicited suggests that cardiac measures can serve as diagnostic tools for attention assessment. Because of the demonstrated differences in sensitivity and diagnosticity, researchers should consider the use of cardiac measures in addition to driving performance measures when studying attention in a driving simulator environment.

Picture span test: Measuring visual working memory capacity involved in remembering and comprehension

The working memory system is assumed to operate with domain-specific (verbal and visuospatial) resources that support cognitive activities. However, in research on visuospatial working memory, an appropriate visual working memory task has not been established. For the present study, a novel task was developed: the picture span test (PST). This test requires memorizing parts of scene images while comprehending various scene situations simultaneously. Results of correlation analyses and a factor analysis among college students (n = 52) validated that PST can predict visuospatial cognitive skills whereas a simple visual storage task and a verbal working memory task cannot. Furthermore, an error analysis indicated that inhibition is important for visuospatial working memory. Additionally, PST is considered to reflect individual differences in the visual working memory capacity. These findings suggest that the PST is appropriate for measuring visual working memory capacity and can elucidate its relationship to higher cognition.

An fMRI Study of Functional Abnormalities in the Verbal Working Memory System and the Relationship to Clinical Symptoms in Chronic Schizophrenia

There has been evidence for functional abnormalities of the verbal working memory system in schizophrenia. Verbal working memory crucially involves the interplay between the anterior and posterior language systems, and previous studies have shown converging evidence for abnormalities in the posterior language system in schizophrenia. In this functional magnetic resonance imaging study, we measured cortical activity in chronic schizophrenic patients and matched healthy controls during auditory and visual verbal working memory tasks. We employed 1) regional analyses specifically targeting the posterior language system and 2) analyses of functional connectivity between anterior and posterior language regions. We performed these analyses separately for each memory stage and modality. In the regional analyses, the left sylvian-parietal-temporal (Spt) area consistently showed reduced activation during encoding and retrieval stages in schizophrenia. Magnitudes of activation in the left posterior superior temporal sulcus were correlated with the severity of delusions at every memory stage. Functional connectivity analyses revealed reduced connectivity between the left Spt and the anterior insula during the encoding of auditory words. In addition, the connectivity strength was correlated with the severity of auditory hallucinations. These findings identify abnormal components in the verbal working memory system and illustrate their possible overlap with the mechanisms of core schizophrenic symptoms.

Brain pathways of verbal working memory: A lesion–function correlation study

Working memory relies on information processing by several well-identified gray matter regions. However, the white matter regions and pathways involved in this cognitive process remain unknown. An attractive and underexplored approach to study white matter connectivity in cognitive functions is through the use of non-aprioristic models, which specifically search disrupted white matter pathways. For this purpose, we used voxel-based lesion–function mapping to correlate white matter lesions on the magnetic resonance images of 54 multiple sclerosis patients with their performance on a verbal working memory task. With this approach, we have identified critical white matter regions involved in verbal working memory in humans. They are located in the cingulum, parieto-frontal pathways and thalamo-cortical projections, with a left-sided predominance, as well as the right cerebellar white matter. Our study provides direct evidence on the white matter pathways subserving verbal working memory in the human brain.