Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “working memory”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19Linked to original sources
PubMed2007

Selective attention supports working memory maintenance by modulating perceptual processing of distractors.

Selective attention has been shown to bias sensory processing in favor of relevant stimuli and against irrelevant or distracting stimuli in perceptual tasks. Increasing evidence suggests that selective attention plays an important role during working memory maintenance, possibly by biasing sensory processing in favor of to-be-remembered items. In the current study, we investigated whether selective attention may also support working memory by biasing processing against irrelevant and potentially distracting information. Event-related potentials (ERPs) were recorded while subjects (n = 22) performed a delayed-recognition task for faces and shoes. The delay period was filled with face or shoe distractors. Behavioral performance was impaired when distractors were congruent with the working memory domain (e.g., face distractor during working memory for faces) relative to when distractors were incongruent with the working memory domain (e.g., face distractor during shoe working memory). If attentional biasing against distractor processing is indeed functionally relevant in supporting working memory maintenance, perceptual processing of distractors is predicted to be attenuated when distractors are more behaviorally intrusive relative to when they are nonintrusive. As such, we predicted that perceptual processing of distracting faces, as measured by the face-sensitive N170 ERP component, would be reduced in the context of congruent (face) working memory relative to incongruent (shoe) working memory. The N170 elicited by distracting faces demonstrated reduced amplitude during congruent versus incongruent working memory. These results suggest that perceptual processing of distracting faces may be attenuated due to attentional biasing against sensory processing of distractors that are most behaviorally intrusive during working memory maintenance.

Adolescent↗
PubMedDate not supplied

Functional MR imaging of working memory in the human brain.

OBJECTIVE: In order to investigate the functional brain anatomy associated with verbal and visual working memory, functional magnetic resonance imaging was performed. MATERIALS AND METHODS: In ten normal right handed subjects, functional MR images were obtained using a 1.5-T MR scanner and the EPI BOLD technique. An item recognition task was used for stimulation, and during the activation period of the verbal working memory task, consonant letters were used. During the activation period of the visual working memory task, symbols or diagrams were employed instead of letters. For the post-processing of images, the SPM program was used, with the threshold of significance set at p <.001. We assessed activated brain areas during the two stimulation tasks and compared the activated regions between the two tasks. RESULTS: The prefrontal cortex and secondary visual cortex were activated bilaterally by both verbal and visual working memory tasks, and the patterns of activated signals were similar in both tasks. The superior parietal cortex was also activated by both tasks, with lateralization to the left in the verbal task, and bilaterally without lateralization in the visual task. The inferior frontal cortex, inferior parietal cortex and temporal gyrus were activated exclusively by the verbal working memory task, predominantly in the left hemisphere. CONCLUSION: The prefrontal cortex is activated by two stimulation tasks, and this is related to the function of the central executive. The language areas activated by the verbal working memory task may be a function of the phonological loop. Bilateral prefrontal and superior parietal cortices activated by the visual working memory task may be related to the visual maintenance of objects, representing visual working memory.

Adult↗
PubMed1999

Spatial working memory deficits and clinical symptoms in schizophrenia: a 4-month follow-up study.

BACKGROUND: Our goal was to examine spatial working memory function in relation to clinical symptoms of schizophrenia over a period of 4 months. METHODS: We assessed spatial working memory, spatial detection and clinical symptoms in 34 acutely psychotic schizophrenia patients within the first 2 weeks of hospitalization, and 4 months later. Spatial working memory was assessed by a delayed response task. A spatial control task was included to rule out simple sensorimotor deficits. Positive and negative symptoms were assessed by the Positive and Negative Syndrome Scale (PANSS). Thirty-nine matched normal control subjects were also examined on the same tasks over the same period. RESULTS: Patients showed deficits in working memory, but they performed well on the spatial control task. Both positive and negative symptoms improved at the 4-month follow up. Spatial working memory also improved over time but there was still a significant deficit at the follow-up session. CONCLUSIONS: These results indicate that both symptoms and spatial working memory improved 4 months after the initial hospitalization but spatial working memory, hypothesized to be mediated by the dorsolateral prefrontal system, did not normalize. Thus, spatial working memory deficit may be a stable marker for schizophrenia.

Acute Disease↗
PubMed2001

Relation of prefrontal cortex dysfunction to working memory and symptoms in schizophrenia.

OBJECTIVE: The dorsolateral prefrontal cortex has been implicated in both working memory and the pathophysiology of schizophrenia. A relationship among dorsolateral prefrontal cortex activity, working memory dysfunction, and symptoms in schizophrenia has not been firmly established, partly because of generalized cognitive impairments in patients and task complexity. Using tasks that parametrically manipulated working memory load, the authors tested three hypotheses: 1) patients with schizophrenia differ in prefrontal activity only when behavioral performance differentiates them from healthy comparison subjects, 2) dorsolateral prefrontal cortex dysfunction is associated with poorer task performance, and 3) dorsolateral prefrontal cortex dysfunction is associated with cognitive disorganization but not negative or positive symptoms. METHOD: Seventeen conventionally medicated patients with schizophrenia and 16 healthy comparison subjects underwent functional magnetic resonance imaging while performing multiple levels of the "n-back" sequential-letter working memory task. RESULTS: Patients with schizophrenia showed a deficit in physiological activation of the right dorsolateral prefrontal cortex (Brodmann's area 46/9) in the context of normal task-dependent activity in other regions, but only under the condition that distinguished them from comparison subjects on task performance. Patients with greater dorsolateral prefrontal cortex dysfunction performed more poorly. Dorsolateral prefrontal cortex dysfunction was selectively associated with disorganization symptoms. CONCLUSIONS: These results are consistent with the hypotheses that working memory dysfunction in patients with schizophrenia is caused by a disturbance of the dorsolateral prefrontal cortex and that this disturbance is selectively associated with cognitive disorganization. Further, the pattern of behavioral performance suggests that dorsolateral prefrontal cortex dysfunction does not reflect a deficit in the maintenance of stimulus representations per se but points to deficits in more associative components of working memory.

Adult↗
PubMed2005

Beyond capacity limitations: determinants of word recall performance on verbal working memory span tasks in children with SLI.

Reduced verbal working memory capacity has been proposed as a possible account of language impairments in specific language impairment (SLI). Studies have shown, however, that differences in strength of linguistic representations in the form of word frequency affect list recall and performance on verbal working memory tasks. This suggests that verbal memory capacity and long-term linguistic knowledge may not be distinct constructs. It has been suggested that linguistic representations in SLI are weak in ways that result in a breakdown in language processing on tasks that require manipulation of unfamiliar material. In this study, the effects of word frequency, long-term linguistic knowledge, and serial order position on recall performance in the competing language processing task (CLPT) were investigated in 10 children with SLI and 10 age-matched peers (age 8 years 6 months to 12 years 4 months). The children with SLI recalled significantly fewer target words on the CLPT as compared with their age-matched controls. The SLI group did not differ, however, in their ability to recall target words having high word frequency but were significantly poorer in their ability to recall words on the CLPT having low word frequency. Differences in receptive and expressive language abilities also appeared closely related to performance on the CLPT, suggesting that working memory capacity is not distinct from language knowledge and that degraded linguistic representations may have an effect on performance on verbal working memory span tasks in children with SLI.

Child↗
PubMed2004

What happens to information to be suppressed in working-memory tasks? Short and long term effects.

The study explored, from an individual differences point of view, what happens to information to be suppressed in a working-memory task at short and long term. In particular, it was examined whether control mechanisms of irrelevant information in working memory imply their complete elimination from working memory or just the modulation of their activation. To this end, we compared the fate of irrelevant information in groups of subjects with high and low reading comprehension (Experiments 1 and 2) and subjects with high and low working memory (Experiments 1, 2, 3, and 4). All the experiments presented a working-memory task devised by De Beni, Palladino, Pazzaglia, and Cornoldi (1998), which required participants to process lists of words, to tap when a word from a particular category was presented, and then to recall only the last items in each list. Results confirmed that participants with high reading comprehension also have higher working memory and make less intrusion errors due to irrelevant items that have to be processed but then discarded. Furthermore, it was found that participants with low working memory have slightly better implicit (Experiment 1) and explicit memory (Experiments 3 and 4) of highly activated irrelevant information. Nevertheless, in a long-term recognition test, participants with high and low reading comprehension/working memory presented a similar pattern of memory for different types of irrelevant information (Experiment 2), whereas in a short-term memory recognition test, low-span participants presented a facilitation effect in the time required for the recognition of highly activated irrelevant information (Experiment 4). It was concluded that efficient working-memory performance is related to the temporary reduction of activation of irrelevant information but does not imply its elimination from memory.

Adult↗
PubMed2000

Visual perception and working memory in schizotypal personality disorder.

OBJECTIVE: Patients affected by schizophrenia show deficits in both visual perception and working memory. The authors tested early-stage vision and working memory in subjects with schizotypal personality disorder, which has been biologically associated with schizophrenia. METHOD: Eleven subjects who met DSM-III-R criteria for schizotypal personality disorder and 12 normal comparison subjects were evaluated. Performance thresholds were obtained for tests of visual discrimination and working memory. Both form and trajectory processing were evaluated for each task. RESULTS: Subjects with schizotypal personality disorder showed intact discrimination of form and trajectory but were impaired on working memory tasks. CONCLUSIONS: These data suggest that subjects with schizotypal personality disorder, unlike patients affected by schizophrenia, have relatively intact visual perception. Subjects with schizotypal personality disorder do show specific deficits on tasks of comparable difficulty when working memory demands are imposed. Schizotypal personality disorder may be associated with a more specific visual processing deficit than schizophrenia, possibly reflecting disruption of frontal lobe systems subserving visual working memory operations.

Adult↗
PubMed1999

The role of distinct components of visuo-spatial working memory in the processing of texts.

Three experiments examined whether visuo-spatial working memory is involved in processing spatial descriptions and tested whether different processes within the visuo-spatial working memory are involved in processing different kinds of descriptions. Experiment 1 considered the performance of two groups with low and high visuo-spatial working memory abilities in memorizing the description of a city. The high visuo-spatial working memory group had a better memory performance than the low visuo-spatial working memory group. In Experiment 2, the Brooks' (1967) task was adapted to investigate the selective interference of four different concurrent tasks (a verbal, a visual, a spatial-sequential, and a spatial-simultaneous task) on the recall of short abstract, visual and spatial texts. In Experiment 3, the same distinction was extended to longer and natural descriptions of different environments. Participants listened to three descriptions: a description that mainly stressed the visual properties of an environment, a description from a route perspective, and a description from a survey perspective. They also performed the concurrent visual and the two concurrent spatial tasks proposed in Experiment 2. Results of Experiments 2 and 3 demonstrated that tasks involving different cognitive resources (i.e. the verbal, visual, spatial-simultaneous, and the spatial-sequential tasks) had a differential interference with the free recall of different kinds of descriptions.

Cognition↗
PubMed1999

Speech discrimination and phonological working memory in children with ADHD.

This study examined phonological working memory and speech discrimination among children with attention-deficit-hyperactivity disorder (ADHD) with and without motor problems. Forty-one children were assigned to three groups; children with ADHD (N=9), children with ADHD plus developmental coordination disorder (ADHD+, N=13), and age-matched control children (N=19). The subjects' ability to classify stimulus pairs was examined in two experiments. The first experiment required subjects to discriminate pairs of monosyllabic stimuli with contrasting consonants to test speech discrimination without using a working-memory load. In the second protocol, subjects were exposed to two- to five-syllabic non-word pairs with contrasting vowels in order to test speech discrimination with a working-memory load. The subjects classified the pairs as being either the same or different in both experiments. No significant differences were found between the subject groups in the discrimination task with monosyllables. When exposed to the two- to five-syllabic stimuli, the ADHD+ group scored significantly lower than both other groups. This was attributed to a higher sensitivity to working-memory load. Some possible explanations of this effect are discussed.

Adolescent↗
PubMed2003

WAIS-III processing speed index scores after TBI: the influence of working memory, psychomotor speed and perceptual processing.

This study investigates the extent to which working memory, motor speed and perceptual processing speed influence Wechsler Adult Intelligence Scale-III (WAIS-III) Processing Speed Index (PSI) scores. Sixty-eight adult outpatients with Traumatic Brain Injury (TBI) of varying severity and complete data on all outcome measures were identified. Two cases with outlying values on one outcome measure were omitted from the final sample. Working memory was measured by the Working Memory Index score from the WAIS-III. Motor speed was measured as score on the Halstead-Reitan Finger Oscillation Test (finger tapping) and perceptual processing as score on the Trail Making Test--Part B. In hierarchical multiple regression analyses, working memory accounted for 10% of the variance in PSI scores, whereas motor speed only accounted for 3%. An independent measure of perceptual processing, Trail Making Test--B, accounted for 26% of the variance in WAIS-III PSI scores. The total variance accounted for by the three factors was 56%. Findings confirm that the WAIS-III PSI scores of individuals who have received a TBI reflect perceptual processing speed, with an additional component attributable to working memory. Motor speed made only a small contribution to WAIS-III PSI scores in the present sample.

Adolescent↗
PubMed1993

Working memory and strategies in syllogistic-reasoning tasks.

It has often been asserted that working-memory limitations are a major factor contributing to problem difficulty; for example, Johnson-Laird's (1983) mental-models theory appeals to working-memory limitations to explain the difficulty of syllogistic reasoning. However, few studies have directly explored working memory in problem solving in general or syllogistic reasoning in particular. This paper reports two studies. In the first, working-memory load was varied by presenting syllogistic tasks either verbally or visually (so that the premises were continuously available for inspection). A significant effect of memory load was obtained. In the second study, premises were presented visually for a subject-determined time. Dual-task methods were used to assess the role of working-memory components, as identified in Baddeley's (1986) model. Syllogistic performance was disrupted by concurrent random-number generation but not by concurrent articulatory suppression or by concurrent tapping in a preset pattern. Furthermore, the concurrent syllogism task interfered with random generation and to a lesser extent with articulatory suppression, but not with tapping. We conclude that while the central-executive component of working memory played a major role in the syllogistic-task performance reported here, the articulatory loop had a lesser role, and the visuospatial scratch pad was not involved.

Adult↗
PubMedDate not supplied

Object and spatial visual working memory activate separate neural systems in human cortex.

Human and nonhuman primate visual systems are divided into object and spatial information processing pathways. In the macaque, it has been shown that these pathways project to separate areas in the frontal lobe and that the ventral and dorsal frontal areas are, respectively, involved in working memory for objects and spatial locations. A positron emission tomography (PET) study was done to determine if a similar anatomical segregation exists in humans for object and spatial visual working memory. Face working memory demonstrated significant increases in regional cerebral blood flow (rCBF), relative to location working memory, in fusiform, parahippocampal, inferior frontal, and anterior cingulate cortices, and in right thalamus and midline cerebellum. Location working memory demonstrated significant increases in cRBF, relative to face working memory, in superior and inferior parietal cortex, and in the superior frontal sulcus. Our results show that the neural systems involved in working memory for faces and for spatial location are functionally segregated, with different areas recruited in both extrastriate and frontal cortices for processing the two types of visual information.

Adult↗
PubMed2005

Working memory in aphasia: theory, measures, and clinical implications.

Recently, researchers have suggested that deficits in working memory capacity contribute to language-processing difficulties observed in individuals with aphasia (e.g., I. Caspari, S. Parkinson, L. LaPointe, & R. Katz, 1998; R. A. Downey et al., 2004; N. Friedmann & A. Gvion, 2003; H. H. Wright, M. Newhoff, R. Downey, & S. Austermann, 2003). A theoretical framework of working memory can aid in our understanding of a disrupted system (e.g., after stroke) and how this relates to language comprehension and production. Additionally, understanding the theoretical basis of working memory is important for the measurement and treatment of working memory. The literature indicates that future investigations of measurement and treatment of working memory are warranted in order to determine the role of working memory in language processing.

Aphasia↗
PubMed2003

Executive subprocesses in working memory: relationship to catechol-O-methyltransferase Val158Met genotype and schizophrenia.

BACKGROUND: Cognitive dysfunction in the working memory domain seems to be under genetic control and is a candidate intermediate phenotype in schizophrenia. Genes that affect working memory processing may contribute to risk for schizophrenia. METHODS: Working memory and attentional processing were assessed in a large and unselected sample of schizophrenic patients, their healthy siblings, and controls (N = 250). We used the n-back task because it allows parametric analysis over increasing loads and delays and parsing of subcomponents of executive cognition and working memory, including temporal indexing and updating. Participants were genotyped for catechol-O-methyltransferase (COMT) at the Val158Met locus, which has been shown to affect executive cognition and frontal lobe function, likely because of genetically determined variation in prefrontal dopamine signaling. RESULTS: A significant COMT genotype effect was found: Val/Val individuals had the lowest n-back performance, and Met/Met individuals had the highest performance. Effects were similar in the 1- and 2-back conditions and across all groups, whereas no effect on the Continuous Performance Test was seen, suggesting that genotype was not affecting working memory subprocesses related to attention, load, or delay. Siblings also performed significantly worse than controls on the 1- and 2-back conditions. CONCLUSIONS: A prefrontal cognitive mechanism common to the 1- and 2-back conditions, probably executive processes involved in information updating and temporal indexing, is sensitive to the COMT genotype. Considering that the 3 participant groups were affected more or less linearly by the COMT genotype, an additive genetic model in which the effect of allele load is similar in its effects on prefrontally based working memory irrespective of the genetic or environmental background in which it is expressed is suggested. The findings also provide convergent evidence that an intermediate phenotype related to prefrontal cortical function represents a viable approach to understanding neuropsychiatric disorders with complex genetic etiologies and individual differences in cognition.

Adult↗
PubMedDate not supplied

Working memory and comprehension in children with specific language impairment: what we know so far.

Many children with specific language impairments (SLI) demonstrate deficits in the areas of verbal working memory and language learning/processing. In this article, evidence is reviewed suggesting that the lexical/morphological learning and sentence comprehension/processing problems of many of these children are associated with their deficient working memory functioning. Evidence is also reviewed for the possibility that deficient working memory provides a clinical marker of SLI. A number of potentially useful assessment and intervention techniques are offered, as well as several directions for future research. The reader will be introduced to two prominent models of verbal working memory (phonological working memory model, functional working memory) and how each model potentially relates to (a) various language abilities in typically developing children, (b) the morphological and lexical learning abilities in children with specific language impairment (SLI), and (c) the sentence comprehension of children with SLI. The reader will also be provided a variety of clinical suggestions on how to assess and treat the working memory and language processing problems of children with SLI. Finally, some suggestions for future research will also be offered.

Child↗
PubMed2000

Eye movement task measures inhibition and spatial working memory in adults with schizophrenia, ADHD, and a normal comparison group.

Schizophrenia and attention deficit/hyperactivity disorder (ADHD) are both associated with deficits in inhibition and working memory, although in ADHD the working memory deficit is hypothesized to be secondary to the inhibitory deficit. This similarity in cognitive processes has been paralleled by similarities across the two groups in the performance of working memory and inhibition tasks. The delayed oculomotor response task is an alternative task, which may allow greater separation of working memory from inhibitory components, and thus its use may provide additional information on primary vs. secondary deficits in these disorders. Ten young adult ADHD sufferers, 10 schizophrenic subjects, and 10 normal subjects were matched on age, gender, and education. Eye movements were recorded during delayed oculomotor response tasks with 1- and 3-s delays. Both the ADHD and the schizophrenic subjects demonstrated dis-inhibition (an increased percentage of premature saccades); however only schizophrenic subjects demonstrated an impaired working memory (decreased spatial accuracy of the remembered saccade). The results are consistent with the hypothesis that working memory is a primary deficit in schizophrenia, but secondary to the inhibitory deficit in ADHD.

Adult↗
PubMed2005

Cerebellar transcranial magnetic stimulation impairs verbal working memory.

Previous functional magnetic resonance imaging and patient studies indicate cerebellar participation in verbal working memory. In particular, event-related functional magnetic resonance imaging showed superior cerebellar activation during the initial encoding phase of the Sternberg task. This study used functional magnetic resonance imaging-guided transcranial magnetic stimulation (TMS) to test whether disruption of the right superior cerebellum (hemispheric lobule VI/Crus I) impairs verbal working memory performance. Single-pulse TMS was administered immediately after letter presentation during the encoding phase on half the trials. Sham TMS and a Motor Control task were included to test for general distraction and nonmemory-related motor effects. Results showed no effects of TMS on accuracy, but reaction times (RTs) on correct trials were significantly increased on TMS relative to non-TMS trials for the Verbal Working Memory and Motor Control tasks. Additional analyses showed that the increased RT was significantly greater for Verbal Working Memory than for the motor task, suggesting that the effect on working memory was not caused by interference with finger responses. Sham TMS did not affect RTs, indicating that the potentially distracting effects of the postencoding click did not contribute to the increase in RT. The observed effects from cerebellar disruption are consistent with proposed cerebrocerebellar involvement in verbal working memory.

Adolescent↗
PubMed2001

Working memory in schizophrenia and mania: correlation with symptoms during the acute and subacute phases.

OBJECTIVE: The aims of this study were to examine working memory in the acute subacute phase of schizophrenia and mania and to examine correlations between working memory and specific symptom domains. METHOD: Visuospatial working memory and symptom profiles were assessed in three groups (schizophrenia group, n= 19; mania, n= 12; controls, n= 19) on two occasions separated by 4 weeks. RESULTS: Both patient groups had significant deficits on working memory compared to the well controls and the schizophrenia and mania groups were equally impaired. All groups showed equivalent improvement over time. In the patient groups, impaired working memory was significantly correlated with the presence of both negative symptoms and positive thought disorder. CONCLUSION: Impaired working memory is found in both schizophrenia and mania during the acute subacute phases. Further research is required in order to clarify the neurocognitive mechanisms linking impaired working memory with both negative symptoms and positive thought disorder.

Acute Disease↗