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PubMed2000

Developmental instability and working memory ability in children: a magnetic resonance spectroscopy investigation.

This study of children (ages 7 through 12) wishes to determine (a) whether variation in frontal lobe brain chemistry, determined from proton magnetic resonance spectroscopy (1H-MRS), is related to performance on a working memory task in children, and (b) whether developmental instability (DI; the imprecise expression of the genetic plan for development due to several known genetic and environmental effects) underlies phenotypic variation in brain chemistry. 1H-MRS assessed neurometabolites in a right frontal white matter voxel. The Visual Two-Back test assessed working memory. A composite measure of DI was created from measures of minor physical anomalies, fluctuating asymmetry of body characteristics, and fluctuating asymmetry of dermatoglyphic features. Greater DI strongly predicted lower concentrations of creatine-phosphocreatine (Cre) and choline-containing compounds, whereas Cre and N-acetyl-aspartate positively correlated with working memory skills. Working memory skills thus seem related to frontal lobe energy metabolism, which in turn is related to DI.

Aspartic Acid↗
PubMed2000

Working memory deficits in children with low achievements in the national curriculum at 7 years of age.

BACKGROUND: Close links between children's capacities to store and manipulate information over brief periods have been found with achievements on standardised measures of vocabulary, language comprehension, reading, and mathematics. AIM: The study aimed to investigate whether working memory abilities are also associated with attainment levels in the national curriculum assessments at 7 years of age. SAMPLE: Eighty-three children aged 6 and 7 years attending local education authority schools participated in the study. METHODS: Working memory skills were assessed by a test battery designed to tap individual components of Baddeley and Hitch's (1974) working memory model. Children were assigned to normal and low achievement groups on the basis of their performance on national curriculum tasks and tests in the areas of English and mathematics. RESULTS: Children with low levels of curriculum attainment showed marked impairments on measures of central executive function and of visuo-spatial memory in particular. A single cut-off score derived from the test battery successfully identified the majority of the children failing to reach nationally expected levels of attainment. CONCLUSIONS: Complex working memory skills are closely linked with children's academic progress within the early years of school. The assessment of working memory skills may offer a valuable method for screening children likely to be at risk of poor scholastic progress.

Aptitude Tests↗
PubMed2005

N-back working memory paradigm: a meta-analysis of normative functional neuroimaging studies.

One of the most popular experimental paradigms for functional neuroimaging studies of working memory has been the n-back task, in which subjects are asked to monitor the identity or location of a series of verbal or nonverbal stimuli and to indicate when the currently presented stimulus is the same as the one presented n trials previously. We conducted a quantitative meta-analysis of 668 sets of activation coordinates in Talairach space reported in 24 primary studies of n-back task variants manipulating process (location vs. identity monitoring) and content (verbal or nonverbal) of working memory. We found the following cortical regions were activated robustly (voxelwise false discovery rate = 1%): lateral premotor cortex; dorsal cingulate and medial premotor cortex; dorsolateral and ventrolateral prefrontal cortex; frontal poles; and medial and lateral posterior parietal cortex. Subsidiary meta-analyses based on appropriate subsets of the primary data demonstrated broadly similar activation patterns for identity monitoring of verbal stimuli and both location and identity monitoring of nonverbal stimuli. There was also some evidence for distinct frontoparietal activation patterns in response to different task variants. The functional specializations of each of the major cortical components in the generic large-scale frontoparietal system are discussed. We conclude that quantitative meta-analysis can be a powerful tool for combining results of multiple primary studies reported in Talairach space. Here, it provides evidence both for broadly consistent activation of frontal and parietal cortical regions by various versions of the n-back working memory paradigm, and for process- and content-specific frontoparietal activation by working memory.

Brain↗
PubMed2003

The complexities of complex span: explaining individual differences in working memory in children and adults.

Two studies are presented that investigated the constraints underlying working memory performance in children and adults. In each case, independent measures of processing efficiency and storage capacity are assessed to determine their relative importance in predicting performance on complex span tasks,which measure working memory capacity. Results show that complex span performance was independently constrained by individual differences in domain-general processing efficiency and domain-specific storage capacity. Residual variance, which may reflect the ability to coordinate storage and processing, also predicted academic achievement. These results challenge the view that complex span taps a limited-capacity resource pool shared between processing and storage operations. Rather, they are consistent with a multiple-component model in which separate resource pools support the processing and storage functions of working memory.

Adult↗
PubMed1995

Visuo-spatial working memory limitations in low visuo-spatial high verbal intelligence children.

Visuo-spatial working memory was investigated in a group of 37 children aged between 10 and 14 years with low visuo-spatial intelligence. Their performance was poorer than that of a matched control group on a series of tests devised to ascertain visuo-spatial working memory yet was broadly similar in a language test and in school achievement tests. It is argued that low visuo-spatial intelligence children typically present limitations in the storage capacity of a passive system of the visuo-spatial working memory (with a raw measure of four-five stored elements) and especially in the operations required to process that information.

Adolescent↗
PubMed2001

Domain-specific distribution of working memory processes along human prefrontal and parietal cortices: a functional magnetic resonance imaging study.

This study reinvestigated the functional neuroanatomy of phonological and visual working memory in humans. Articulatory suppression was used to deprive the human subjects of species-specific verbal strategies in order to make the functional magnetic resonance imaging results more comparable to findings in non-human primates. Both phonological and visual working memory processes activated similar prefronto-parietal networks but were found to be differentially distributed along several cortical structures, in particular along the anterior and posterior parts of the intermediate frontal sulcus. These results suggest that a domain-specific topographical organization of neural working memory mechanisms in the primate brain is conserved in evolution. However, the findings also underline the critical dynamic influence that the additional availability of language may have on working memory processes and their functional implementation in the human brain.

Adult↗
PubMedDate not supplied

The relationship between age, processing speed, working memory capacity, and language comprehension.

A total of 50 elderly individuals and 48 college students were tested on several measures of processing speed and of working memory capacity. Language processing was tested with an on-line measure of sentence processing efficiency, an end-of-sentence acceptability judgement task, and a paragraph comprehension test. Elderly individuals performed more poorly than college students on the speed of processing and working memory measures and had longer listening times overall on the sentence processing measures. Elderly individuals did not, however, have overall longer listening times at the most capacity-demanding regions of the harder sentence types. Correlational analyses failed to establish a relationship between the increase in syntactic processing load at the capacity-demanding region of the harder sentence type and the measures of working memory capacity, but did establish a relationship between paragraph comprehension and working memory capacity. The data are argued to provide evidence that the WM system used to structure sentences syntactically is separate from that used in other aspects of language comprehension.

Adult↗
PubMed2001

Time reproduction, working memory, and behavioral inhibition in children with ADHD.

Barkley (1997a) proposed that the central deficit in Attention Deficit Hyperactivity Disorder (ADHD) is in behavioral inhibition, resulting in deficits both in working memory and sense of time. To test this theory, 21 children with ADHD and a matched sample (ages 6-13) completed a variety of tasks that measured behavioral inhibition, working memory, attention, and time reproduction. Children with ADHD performed significantly below controls on measures of inhibition, attention, and time reproduction. They did not differ significantly from controls, however, on tasks of working memory. In addition, performance on the working memory tasks was not correlated with the time reproduction task. We discuss the relevance of these results in the context of current theories of ADHD.

Attention Deficit Disorder with Hyperactivity↗
PubMed2006

Inter- and intra-hemispheric EEG coherence in patients with mild cognitive impairment at rest and during working memory task.

OBJECTIVE: To assess functional relationship by calculating inter- and intra-hemispheric electroencephalography (EEG) coherence at rest and during a working memory task of patients with mild cognitive impairment (MCI). METHODS: The sample consisted of 69 subjects: 35 patients (n=17 males, n=18 females; 52-71 years old) and 34 normal controls (n=17 males, n=17 females; 51~63 years old). Mini-mental state examination (MMSE) of two groups revealed that the scores of MCI patients did not differ significantly from those of normal controls (P>0.05). In EEG recording, subjects were performed at rest and during working memory task. EEG signals from F3-F4, C3-C4, P3-P4, T5-T6 and O1-O2 electrode pairs are resulted from the inter-hemispheric action, and EEG signals from F3-C3, F4-C4, C3-P3, C4-P4, P3-O1, P4-O2, T5-C3, T6-C4, T5-P3 and T6-P4 electrode pairs are resulted from the intra-hemispheric action for delta (1.0-3.5 Hz), theta (4.0-7.5 Hz), alpha-1 (8.0-10.0 Hz), alpha-2 (10.5-13.0 Hz), beta-1 (13.5-18.0 Hz) and beta-2 (18.5-30.0 Hz) frequency bands. The influence of inter- and intra-hemispheric coherence on EEG activity with eyes closed was examined using fast Fourier transformation from the 16 sampled channels. RESULTS: During working memory tasks, the inter- and intra-hemispheric EEG coherences in all bands were significantly higher in the MCI group in comparison with those in the control group (P<0.05). However, there was no significant difference in inter- and intra-hemispheric EEG coherences between two groups at rest. CONCLUSION: Experimental results comprise evidence that MCI patients have higher degree of functional connectivity between hemispheres and in hemispheres during working condition. It suggests that MCI may be associated with compensatory processes during working memory tasks between hemispheres and in hemispheres. Moreover, failure of normal cortical connections may exist in MCI patients.

Aged↗
PubMed2005

Genetic ablation of the mammillary bodies in the Foxb1 mutant mouse leads to selective deficit of spatial working memory.

Mammillary bodies and the mammillothalamic tract are parts of a classic neural circuitry that has been implicated in severe memory disturbances accompanying Korsakoff's syndrome. However, the specific role of mammillary bodies in memory functions remains controversial, often being considered as just an extension of the hippocampal memory system. To study this issue we used mutant mice with a targeted mutation in the transcription factor gene Foxb1. These mice suffer perinatal degeneration of the medial and most of the lateral mammillary nuclei, as well as of the mammillothalamic bundle. Foxb1 mutant mice showed no deficits in such hippocampal-dependent tasks as contextual fear conditioning and social transmission of food preference. They were also not impaired in the spatial reference memory test in the radial arm maze. However, Foxb1 mutants showed deficits in the task for spatial navigation within the Barnes maze. Furthermore, they showed impairments in spatial working memory tasks such as the spontaneous alternation and the working memory test in the radial arm maze. Thus, our behavioural analysis of Foxb1 mutants suggests that the medial mammillary nuclei and mammillothalamic tract play a role in a specific subset of spatial tasks, which require combined use of both spatial and working memory functions. Therefore, the mammillary bodies and the mammillothalamic tract may form an important route through which the working memory circuitry receives spatial information from the hippocampus.

Animals↗
PubMed2006

Mesocortical dopamine modulation of executive functions: beyond working memory.

RATIONALE: Dopamine (DA) neurotransmission in the prefrontal cortex (PFC) is known to play an essential role in mediating executive functions such as the working memory. DA exerts these effects by acting on D1 receptors because blockade or stimulation of these receptors in the PFC can impair performance on delayed response tasks. However, comparatively less is known about dopaminergic mechanisms that mediate other executive functions regulated by the PFC. Furthermore, the functional importance of other DA receptor subtypes that reside on PFC neurons (D2 and D4) is unclear. OBJECTIVES: This review will summarize previous findings and previously unpublished data addressing the contribution of PFC DA to higher-order cognition. We will compare the DA receptor mechanisms, which regulate executive functions such as working memory, behavioral flexibility, and decision-making. RESULTS AND CONCLUSIONS: Whereas PFC D1 receptor activity is of primary importance in working memory, D1 and D2 receptors act in a cooperative manner to facilitate behavioral flexibility. We note that the principle of the "inverted U-shaped" function of D1 receptor activity mediating working memory does not necessarily apply to other PFC functions. DA in different subregions of the PFC also mediates decision-making assessed with delay discounting or effort-based procedures, and we report that D1, D2, and D4 receptors in the medial PFC contribute to decision-making when animals must bias the direction of behavior to avoid aversive stimuli, assessed with a conditioned punishment procedure. Thus, mesocortical DA modulation of distinct executive functions is subserved by dissociable profiles of DA receptor activity in the PFC.

Animals↗
PubMed1996

Testing hypotheses about working memory capacity.

When an individual is engaged in sampling from a finite population, an assessment of their working memory for previously sampled objects is often desired. An extension of the classical occupancy distribution provides a framework for testing hypotheses about working memory capacity, based on a general model of working memory in which the individual retains a record of m previous inspections (and hence does not make the mistake of resampling these objects) and samples with replacement objects outside the current memory set. The buffer size m provides a common metric for assessing the effect of variables on performance in search tasks involving different numbers of items, or locations.

Animals↗
PubMed2003

Reasoning and working memory: common and distinct neuronal processes.

The neuronal processes underlying reasoning and the related working memory subsystems were examined with functional magnetic resonance imaging (fMRI). Twelve volunteers solved relational reasoning problems which either supported a single (determinate) or several alternative solutions (indeterminate). In a second condition, participants maintained the identical premises of these problems in working memory without making inferences. Although problems were presented in auditory format, activity was detected for both reasoning and maintenance in a network comprising bilaterally the secondary visual cortex, the posterior cingulate cortex, and the medial anterior frontal cortex. In direct comparisons, reasoning was associated with stronger dorsolateral and medial prefrontal activation than maintenance, whereas maintenance led to stronger lateral parietal activation than reasoning. Participants' visuo-spatial abilities ("Block Design" score) covaried positively with behavioral performance and negatively with activity of the precuneus for reasoning, but not for maintenance. These results support the notion that relational reasoning is based on visuo-spatial mental models, and they help to distinguish the neuronal processes related to reasoning itself versus to the maintenance of problem information in working memory.

Adult↗
PubMedDate not supplied

Effects of organization and working memory on age differences in memory for scene information.

We examined the effects of organization and working memory on young and older adults' scene memory. Subjects discriminated transformed pictures from unchanged study items in organized or unorganized scenes. Memory was tested independently for two types of scene transformations: (a) relocations (two objects rearranged and one moved) and (b) substitutions (one object replaced by another). Organization had similar effects on young and older adults, improving memory for relocations but not substitutions. Working memory significantly predicted scene memory, except for relocations in organized scenes, and partially mediated the observed age effects. The results are discussed in relation to the resource and environmental support views of cognitive aging.

Adult↗
PubMed2004

Impaired performance in a working memory binding task in patients with schizophrenia.

This study investigated feature binding in a working memory task in patients with schizophrenia and in normal controls. Twenty-five patients and 25 controls participated. On each trial, three drawings of familiar objects were presented sequentially, each in a different cell of a 3 x 3 grid. In different blocks of trials, participants remembered either individual features (object and location conditions) or an object and its location (combination condition). The results showed that patients were slower and less accurate than controls under all conditions. Accuracy of both groups was reduced in the combination condition relative to the single-feature conditions, but patients showed disproportionately poorer performance in the combination condition than in the object and location conditions. Thus, patients with schizophrenia exhibit deficits in working memory, particularly when the task requires binding objects to their locations. This finding demonstrates that processes that establish coherent and temporary episodic representations in working memory are impaired in schizophrenia.

Adult↗
PubMed2001

Working memory limitation as a source of confusion in the abstract THOG task.

Limitations of working memory are proposed as a major determinant of problem difficulty in the THOG task. This task is a logical reasoning task which uses an exclusive disjunction and requires hypothetico-deductive reasoning. Four experiments with students of mathematics or psychology were used to test the hypotheses that, first, guiding participants' attention facilitates the task and, second, the use of paper and pencil as external problem representation reliefs working memory load. Focusing participants' attention upon a critical aspect of the task does not improve solution rates. Students of mathematics were better than students of psychology, but only if they were allowed to use paper and pencil or to work on the task repeatedly. These results partially support the working memory hypothesis. They point toward the importance of training and practice in relatively simple meta-cognitive skills in logical reasoning.

Attention↗
PubMed2001

Activity in fusiform face area modulated as a function of working memory load.

Previous fMRI results suggest that extrastriate visual areas have a predominant role in perceptual processing while the prefrontal cortex (PFC) has a predominant role in working memory. In contrast, single-unit recording studies in monkeys have demonstrated a relationship between extrastriate visual areas and visual working memory tasks. In this study we tested whether activity in both the PFC and fusiform face area (FFA) changed with increasing demands of an n-back task for gray-scale faces. Since stimulus presentation was identical across conditions, the n-back task allowed us to parametrically vary working memory demands across conditions while holding perceptual and motor demands constant. This study replicated the result of PFC areas of activation that increased directly with load n of the task. The novel finding in all subjects was FFA activation that also increased directly with load n of the task. Since perceptual demands were equivalent across the three task conditions, these findings suggest that activity in both the PFC and the FFA vary with face working memory demands.

Adolescent↗
PubMed1989

Septal alpha-noradrenergic antagonism in vivo blocks the testing-induced activation of septo-hippocampal cholinergic neurones and produces a concomitant deficit in working memory performance of mice.

In order to test the hypothesis that alpha-noradrenergic receptors in the septum 1) play an important functional role in the mediation of trans-synaptic control of the neurones of the cholinergic septo-hippocampal pathway and 2) produce resultant modulation of working memory performance, we have investigated the effects in vivo of the acute intraseptal injection of an alpha-antagonist, phenoxybenzamine, in mice. Neurochemical analysis was performed using measures of the kinetics of sodium-dependent high-affinity choline uptake in samples of hippocampus from injected mice and their relevant controls in both quiet conditions and immediately following selective working memory testing in an 8-arm radial maze. Results show that whereas the injection of phenoxybenzamine produces no significant alteration of the activity of the cholinergic septo-hippocampal neurones in quiet conditions, the pretrial (20 min) administration of this drug almost totally abolished the usually observed increase in hippocampal cholinergic activity induced by testing. This inhibition of cholinergic activation was associated with a parallel working memory deficit. The results provide further direct support for the hypothesis that septal noradrenergic afferents via alpha-receptors mediate a phasic and net excitatory trans-synaptic influence on the cholinergic septo-hippocampal pathway during working memory testing and thereby significantly contribute to the modulation of the level of working memory performance.

Action Potentials↗