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PubMed2006

The role of interference control in working memory: a study with children at risk of ADHD.

The study aimed to test whether the impairment in a working memory task observed in children at risk of ADHD was due to a lack of control of interfering information being processed whilst carrying out the memory task. Two groups of children at risk of ADHD with or without a learning disability (reading impairment) were compared to a control group in a working memory task. Activation of irrelevant items was tested with a lexical decision task presented immediately after the final recall in about half of the trials. Results showed a poor working memory performance in children at risk of ADHD and reading disability associated with a larger activation of irrelevant information than that of control children. Results indicated that the to-be-excluded and interfering items are still highly accessible to working memory in children that fail the working memory task. The examination of working memory and interference control of children at risk of ADHD with a learning disability revealed a counterintuitive picture of children with poor working memory showing better recall/activation of processed information. This picture is consistent with a view of working memory related to an efficient inhibitory control that influences cognitive functioning.

Attention Deficit Disorder with Hyperactivity↗
PubMedDate not supplied

Laterality of phonological working memory: dependence on type of stimulus, memory load, and sex.

Investigations of the laterality of phonological working memory have not always yielded consistent results. The present experiment investigated working memory for letters and numbers in two memory load conditions. In the low load condition, working memory for letters and numbers was similar. However, in the high load condition, males were more accurate at the recall of letters. This effect was not observed with numbers, in which both sexes performed more poorly. Furthermore, we observed consistent RVF advantages for both tasks, although males were more asymmetrical for the recall of letters and females were more asymmetrical for the recall of numbers. This result indicates that laterality of working memory for letters and numbers differs, and these asymmetries depend upon the sex of the participant.

Adult↗
PubMed2006

Neural correlates of verbal and nonverbal working memory deficits in individuals with schizophrenia and their high-risk siblings.

Impaired working memory and functional brain activation deficits within prefrontal cortex (PFC) may be associated with vulnerability to schizophrenia. This study compared working memory and PFC activation in individuals with schizophrenia, their unaffected siblings and healthy comparison participants. We administered a "2back" version of the "nback" task. Functional MRI (fMRI) was used to measure brain activity. Nineteen individuals with DSM-IV schizophrenia, 18 of their siblings, and 72 healthy comparison participants underwent fMRI scans while performing word and face "nback" working memory tasks. Repeated trials (items whose prior presentation was not in the correct nback position) allowed us to assess group differences in the ability to code the temporal order of items. Individuals with schizophrenia and their siblings performed worse than controls on repeated lure trials, suggesting an association between schizophrenia and impairments in the coding of temporal order within working memory. Both individuals with schizophrenia and their siblings also demonstrated abnormal brain activation in PFC, such that both groups had hyperactivation in response to word stimuli and hypoactivation in response to face stimuli. These results provide further evidence that individuals with schizophrenia and their siblings are impaired in their ability to encode the temporal order of items within working memory and that disturbances in working memory and PFC activation may be genetic markers of the vulnerability to schizophrenia.

Adult↗
PubMed2000

On the interpretation of working memory span in adults.

Experimental research into children's working memory span has shown that retention duration contributes substantially to span performance, while processing efficiency need not be related to concurrent memory load (Towse, Hitch, & Hutton, 1998). These findings have been used to argue for a model of working memory span that emphasizes time-based forgetting rather than the popular resource-sharing or tradeoff framework. The present paper considers whether adults perform working memory span tasks in a qualitatively different way. Data from reading span and operation span tasks show that adults' performance can be distinguished from that of children, but also that a task-switching model of working memory span can explain some important aspects of performance.

Adolescent↗
PubMed2001

Human verbal working memory impairments associated with thalamic damage.

Although animal studies, human neuroimaging studies, and numerous theoretical models suggest possible contributions of the thalamus to working memory, there are very few reported deficits in human working memory following thalamic lesions. The present study examined working memory performance in six individuals with isolated thalamic stroke and found evidence of impairment on a number of working memory span tasks, but not on a forward digit-span measure. Examination of additional aspects of working memory performance (e.g., spatial and object working memory), analysis of subjects with other sites of thalamic stroke, and functional neuroimaging suggest a role of the thalamus in working memory.

Aged↗
PubMed2004

Motor affordance and its role for visual working memory: evidence from fMRI studies.

We examined the role of motor affordances of objects for working memory retention processes. Three experiments are reported in which participants passively viewed pictures of real world objects or had to retain the objects in working memory for a comparison with an S2 stimulus. Brain activation was recorded by means of functional magnetic resonance imaging (fMRI). Retaining information about objects for which hand actions could easily be retrieved (manipulable objects) in working memory activated the hand region of the ventral premotor cortex (PMC) contralateral to the dominant hand. Conversely, nonmanipulable objects activated the left inferior frontal gyrus. This suggests that working memory for objects with motor affordance is based on motor programs associated with their use. An additional study revealed that motor program activation can be modulated by task demands: Holding manipulable objects in working memory for an upcoming motor comparison task was associated with left ventral PMC activation. However, retaining the same objects for a subsequent size comparison task led to activation in posterior brain regions. This suggests that the activation of hand motor programs are under top down control. By this they can flexibly be adapted to various task demands. It is argued that hand motor programs may serve a similar working memory function as speech motor programs for verbalizable working memory contents, and that the premotor system mediates the temporal integration of motor representations with other task-relevant representations in support of goal oriented behavior.

Adult↗
PubMed2026

Childhood Trauma and Frontoparietal Network Connectivity During Working Memory Task Performance in Individuals With Schizophrenia and Healthy Participants.

Schizophrenia is associated with altered frontoparietal connectivity, which supports higher-order cognition, including working memory. Childhood trauma has been linked to altered functional connectivity and reduced cognitive performance in individuals with schizophrenia and controls. Prior evidence suggests that trauma-related default mode dysconnectivity mediates the association between trauma and cognition. We hypothesised that childhood trauma would be associated with altered frontoparietal connectivity during a working memory task and that such connectivity changes would mediate the relationship between trauma and working memory. Childhood trauma, working memory and fMRI data were collected from individuals with schizophrenia or schizoaffective disorder (n = 38) and controls (n = 128). fMRI data were preprocessed in CONN, and seed-based connectivity analyses were performed for four frontoparietal seeds (bilateral dorsolateral prefrontal and posterior parietal cortices). Connectivity was contrasted across (a) diagnosis and (b) trauma severity. Moderated mediation analyses tested the associations between trauma, connectivity and working memory, with diagnosis as a moderator. Across all participants, higher physical neglect severity predicted poorer working memory performance. Stronger inverse connectivity between left dorsolateral prefrontal and frontal medial cortices predicted better working memory performance. As expected, patients showed widespread frontoparietal dysconnectivity relative to controls, but no differences in frontoparietal connectivity were observed across trauma severity groups. Frontoparietal connectivity did not mediate the association between trauma and working memory, although diagnosis moderated both the trauma-connectivity and connectivity-cognition associations. We conclude that, unlike previous evidence suggesting a mediating role for the default mode network, frontoparietal connectivity did not mediate the trauma-cognition association, possibly suggesting the unique significance of default mode network dysconnectivity in linking trauma to cognition in psychosis.

Humans↗
PubMed2005

Working memory period: the endurance of mental representations.

Working memory span assesses the maximum number of items that can be remembered in the face of concurrent processing. Models of working memory differ on several dimensions, yet many rely exclusively on this span procedure for their evidence. Three experiments consider an alternative paradigm that attempts to capture the endurance limits for remembering a fixed number of items during concurrent processing. Eight-year-old children performed two versions of this working memory period measure--operation period and reading period. Period scores show healthy test-retest reliability and external validity for scholastic attainment, comparing well with span scores in these respects. In addition, period is highly correlated with span and shows similar effects of varying the order in which stimuli are presented. We conclude that the durability of representations is an important factor in both span and period.

Achievement↗
PubMed2003

c-Fos expression in supramammillary and medial mammillary nuclei following spatial reference and working memory tasks.

To investigate brain substrates of spatial memory, neuronal expression of c-Fos protein was studied. Two groups of rats were trained in two spatial memory tasks in the Morris water maze, where the rats have to apply a reference memory rule or a working memory rule. In addition to the experimental groups, two control groups were used to study c-fos activation not specific to the memory processes studied. After immunohistochemical procedures, the number of c-Fos positive neuronal nuclei was quantified in the mammillary body (MB) region (medial mammillary nucleus [MMn] and supramammillary nucleus [SuM]). The results have shown that some MMn neurons expressed c-Fos nuclear immunoreactivity related to spatial working memory but not to spatial reference memory. The increased number of c-Fos immunoreactive neuronal nuclei in the SuM was related to spatial training but not to either working or reference memory demands of the tasks.

Animals↗
PubMed2003

Working memory deficit as a core neuropsychological dysfunction in schizophrenia.

OBJECTIVE: This study tested the hypothesis that impaired working memory is a core deficit underlying multiple neuropsychological deficits in schizophrenia patients. METHOD: The subjects were 27 men with stable chronic schizophrenia treated with atypical antipsychotics and 38 normal participants. They were assessed with a battery of neuropsychological tests. Verbal working memory was measured with the WAIS digit span tests, and the Dot Test was used to test spatial working memory. RESULTS: In the patients, verbal working memory showed significant correlations with visual retention, visual orientation, simple motor function, visuomotor coordination, and executive function but not with memory for objects, memory for faces, recognition of facial emotions, or attention. Spatial working memory showed significant correlations with visual retention, visual orientation, memory for objects, memory for faces, and simple motor function but not attention, executive function, or visuomotor coordination. In the comparison group, no correlations between working memory and other neuropsychological functions were found. CONCLUSIONS: These findings support the hypothesis that working memory is a core deficit in schizophrenia. The authors postulate that the lower capacity for verbal and spatial "on-line storage" is rate limiting in the performance of other cognitive functions. Executive functions rely critically on the phonetic loop, complex visual functions such as object and face memory rely on the spatial on-line storage system (visuospatial scratch pad), while other functions such as visual orientation depend critically on both capacities.

Adult↗
PubMed2000

Gender differences in the functional organization of the brain for working memory.

Gender differences in brain activation during working memory tasks were examined with fMRI. Seventeen right-handed subjects (nine males, eight females) were studied with four different verbal working memory tasks of varying difficulty using whole brain echo-planar fMRI. Consistent with prior studies, we observed activation of the lateral prefrontal cortices (LPFC), the parietal cortices (PC), and additionally, caudate activation in both sexes. The volume of activated brain tissue increased with increasing task difficulty. For all four tasks, the male subjects showed bilateral activation or right-sided dominance (LPFC, PC and caudate), whereas females showed activation predominantly in the left hemisphere. The task performance data demonstrated higher accuracy and slightly slower reaction times for the female subjects. Our results show a highly significant (p < 0.001) gender differences in the functional organization of the brain for working memory. These gender-specific differences in functional organization of the brain may be due to gender-differences in problem solving strategies or the neurodevelopment. Therefore, gender matching or stratification is required for studies of brain function using imaging techniques.

Adult↗
PubMed2000

The relation between phonological awareness and working memory.

Previous research has failed to show a relation between children's working memory and performance on the phonological sound categorization task (M. J. Snowling, C. Hulme, A. Smith, & J. Thomas, 1994). However, the test used to assess working memory in that experiment was more comparable to a short-term memory task, which assesses storage capacity, than to a working memory task, which has both storage and processing components. In the present study, we compared the predictive power of both types of memory tasks on 2 measures of phonological awareness, the sound categorization task and a phoneme deletion task, in 7- and 8-year-olds (mean age = 8 years 1 month). The children's reading ability was also assessed. Fixed-order multiple-regression analyses showed that the sound categorization task has a higher working memory demand than the phoneme deletion task: Working memory predicted independent variance in performance only on the sound categorization task. The short-term memory task did not account for significant independent variance in performance on either of the measures of phonological awareness.

Awareness↗
PubMed2001

The pharmacology of human working memory.

Experimental studies conducted primarily on non-human primates have begun to address the anatomical and neurochemical correlates of working memory. There is an associated growing body of experimental literature investigating whether modulating key neurotransmitters can facilitate working memory in humans. This paper reviews evidence that acute modulation of dopamine in particular, but also noradrenaline, acetylcholine and serotonin may influence working-memory performance in humans. Differences in neurochemical specificity with regard to stages of working memory, type of working memory (spatial or non-spatial) and cortical effects are also discussed. This evidence has contributed to neuropharmacological understanding of working memory in humans. The important therapeutic consequences of a better understanding of facilitation of working memory is discussed in reference to schizophrenia, Parkinson's disease and Alzheimer's disease.

Brain Chemistry↗
PubMed2004

Working memory deficits after traumatic brain injury: catecholaminergic mechanisms and prospects for treatment -- a review.

PRIMARY OBJECTIVE: To review the neural circuitry and neurochemistry of working memory and outline the evidence for working memory deficits after traumatic brain injury, and the evidence for the use of catecholaminergic agents in the amelioration of these deficits. Current knowledge gaps and research needs are identified. MAIN OUTCOMES AND RESULTS: Impairments in working memory are a core component of the cognitive deficits associated with traumatic brain injury. Recent progress in understanding the neural circuitry and neurochemistry of working memory suggests that catecholamines play a central role in the activation and regulation of working memory and thus lays a framework in which to consider the use of catecholaminergic agents (dopaminergic and alpha-2 adrenergic agonists) in the treatment of specific cognitive deficits after traumatic brain injury. CONCLUSIONS: The combined methods of cognitive neuroscience, functional brain imaging and neuropharmacology are proposed as an excellent method for studying working memory deficits. A strong rationale exists for the targeted use of catecholaminergic agonists in the treatment of working memory deficits after traumatic brain injury.

Adrenergic alpha-Agonists↗
PubMed2005

The contribution of sleep to improvements in working memory scanning speed: a study of prolonged sleep restriction.

Working memory scanning and motor response speeds were assessed in chronically sleep restricted participants using the Sternberg item recognition paradigm (SIRP). Twenty-two healthy volunteers (ages 21-30) living in a controlled hospital environment were allowed either 4h of sleep opportunity (50% of habitual sleep) or 8h of sleep opportunity (100% of habitual sleep) for 12 days. Working memory scanning efficiency (time taken to access an item in working memory) was tested for the first 9 days of sleep restriction and improved over time in participants permitted an 8h sleep period, but did not change significantly in participants permitted a 4h sleep period. Speed of motor response (reaction time independent of cognitive processing) did not change significantly in either group. These results indicate that the efficiency of working memory scanning can improve with repeated practice given sufficient sleep, and that prolonged sleep restriction to 50% of habitual sleep prevents this improvement.

Adult↗
PubMedDate not supplied

Prefrontal cortex and working memory for spatial response, spatial location, and visual object information in the rat.

In the first experiment, rats were trained on a working memory task for a spatial response (right-left turn) information using a delayed matching-to-sample procedure. Following lesions of the medial prefrontal cortex (MPF), which includes anterior cingulate and medial precentral cortex, there was a profound working memory deficit even at the shortest delay. In the second experiment, rats were trained on a working memory task for spatial location information using a delayed matching-to-sample procedure. Following lesions of the MPF, there was only a mild working memory deficit, whereas following dorsal hippocampal lesions there was a profound working memory deficit even at the shortest delay. In the third experiment, rats were trained on a working memory task for visual object information using a delayed nonmatching-to-sample procedure. Following lesions of the MPF, there were no working memory deficits, whereas following lesions of the prelimbic and infralimbic cortex there was a profound working memory deficit even at the shortest delay. The results suggest that different neural subregions of the prefrontal cortex mediate working memory for specific attribute information.

Animals↗
PubMedDate not supplied

[Working memory in children with phonological deviation].

BACKGROUND: working memory. AIM: to verify the performance of children with normal speech development (NSD) and with evolutional phonological deviation (EPD), in tasks which demand the use of working memory. METHOD: as a research instrument, subtest 5 of the Illinois Test of Psycholinguistics Abilities (ITPA) was used, as well as the meaningless word repetition test. The answers were analyzed based on the results of the digit repetition test and the meaningless word repetition test, comparing the performance of both groups. RESULTS: when comparing the groups, it was verified that the performance of children with EPD is lower than children with NSD in both of the analyzed tests. CONCLUSION: the obtainded results confirm that the working memory is fundamental for the development of speech and for the phoneme choice when producing words.

Articulation Disorders↗
PubMed2002

A comparative review of rodent prefrontal cortex and working memory.

The prefrontal cortex is critical to working memory processes. Current theories of prefrontal function are largely based on primate behavioural and electrophysiological data. As molecular genetic techniques advance in mice, so investigations into the rodent prefrontal cortex should expand, such that rodent models of prefrontal function during working memory may be used to study the synaptic and molecular basis of the phenomenon. This review attempts to summarize aspects of published data that pertain to working memory and suggest directions that will allow a coherent comparison of prefrontal function and interaction in monkey, rat and mouse.

Animals↗