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 523 records · Page 29Linked to original sources
PubMed2000

Working memory dysfunction in major depression: an event-related potential study.

OBJECTIVES: To study working memory function in untreated major depression using a digit probe identification and matching task. METHODS: We compared behavioural performance and event-related potentials during processing of the Sternberg working memory task in 14 depressed patients and 14 healthy matched control subjects. RESULTS: Patients made more mistakes than controls as the memory load was increased from one to 5 digits and had significantly slower reaction times at all levels of memory load. The patients' event-related potentials (ERPs) differed significantly from controls. Pathological changes were similar for auditory and visual presentation. Surface negative activity in the 157-210 ms section of the waveform was reduced for all levels of memory load, suggesting abnormal sensory/perceptual processing in the modality-specific association cortices, possibly due to a failure of selective attention mechanisms. In the 375-840 ms epoch, the patients' responses showed large amplitude sustained negative activity, maximal at Cz and a reduced late positive wave. The large prolonged negativity in the patients' ERPs suggests activation of additional neuronal assemblies than those normally participating in the task. This could reflect either compensatory mechanism or dysfunction of inhibitory systems. These changes were sensitive to memory load, suggesting that they reflect alterations of memory-related processes. CONCLUSIONS: This study provides objective evidence that major depression significantly affects working memory. The ERP changes in depression could be accounted for by dysfunction of the central executive control of working memory.

Adult↗
PubMed2003

Encoding strategies dissociate prefrontal activity from working memory demand.

It is often proposed that prefrontal cortex is important in organization and control of working memory contents. In some cases, effective reorganization can decrease task difficulty, implying a dissociation between frontal activity and basic memory demand. In a spatial working memory task, we studied the improvement of performance that occurs when materials can be reorganized into higher level groups or chunks. Structured sequences, encouraging reorganization and chunking, were compared with unstructured sequences. Though structured sequences were easier to remember, event-related functional magnetic resonance imaging (fMRI) showed increased activation of lateral frontal cortex, in particular during memory encoding. The results show that, even when memory demand decreases, organization of working memory contents into higher level chunks is associated with increased prefrontal activity.

Adult↗
PubMed1999

Estrogen and NMDA receptor antagonism: effects upon reference and working memory.

Since both estrogen and NMDA receptor antagonists act on the hippocampus CA1 region and behaviorally affect hippocampal memory tasks, we examined how estrogen depletion (ovariectomy) and NMDA receptor antagonism interact upon spatial memory of the mouse. After ovariectomy or sham operation, mice were given a 2-week recovery before behavioral tests began under the influence of vehicle or (+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP 2, 5 and 10 mg/kg) intraperitoneal injections. CPP is a competitive, full NMDA receptor antagonist. Spatial reference memory was tested by the water maze, spatial working memory was tested by the radial arm maze, while overall locomotive activity was monitored by the Y-maze. Results from the water maze and the Y-maze did not show any spatial reference memory or activity differences between sham-operated and ovariectomized mice. The radial arm maze, however, highlighted some working memory differences between intact and ovariectomized mice. CPP treatment impaired dose dependently--the performance of ovariectomy and sham-operated mice equally on both water maze and radial arm maze, while the drug had no effect on Y-maze performance. These results suggest that short term estrogen deprivation has no effect upon spatial-reference memory, while it impairs spatial working memory. This effect is probably not mediated by NMDA receptors.

Animals↗
PubMed1994

Somatostatin alleviates impairment of working memory induced by hippocampal muscarinic M1 receptor blockade in rats.

The effects of somatostatin on the impairment of working memory induced in rats by blockade of hippocampal muscarinic M1 or NMDA receptors were examined, using a three-panel runway task. Both the muscarinic M1 receptor antagonist pirenzepine (1.0 microgram/side) and the competitive NMDA receptor antagonist CPP ((+/-)-3(2-carboxypiperazin-4-yl)-propyl-1-phosphonoic acid) (32 ng/side) significantly increased the number of working memory errors (attempts to pass through two incorrect panels of the three panel-gates at four choice points), when injected bilaterally into the dorsal hippocampus. This effect of intrahippocampal pirenzepine on working memory was alleviated by concurrent injection of 0.32 microgram/side somatostatin. However, concurrent somatostatin (0.1 or 0.32 microgram/side) had no significant effect on the intrahippocampal CPP-induced increase in working memory errors. These results suggest that somatostatin ameliorates the impairment of working memory resulting from hippocampal muscarinic M1 receptor blockade, possibly through activation of cholinergic functions.

Animals↗
PubMed1996

Individual differences in working memory capacity: more evidence for a general capacity theory.

The causes of the positive relationship between comprehension and measures of working memory capacity remain unclear. This study tests three hypotheses for the relationship by equating the difficulty, for 48 individual subjects, of processing demands in complex working memory tasks. Even with difficulty of processing equated, the relationship between number of words recalled in the working memory measure and comprehension remained high and significant. The results favour a general capacity view. We suggest that high working memory span subjects have more limited-capacity attentional resources available to them than low span subjects and that individual differences in working memory capacity will have implications for any task that requires controlled effortful processing.

Analysis of Variance↗
PubMed2003

Spatial working memory deficits in obsessive compulsive disorder are associated with excessive engagement of the medial frontal cortex.

Recent studies have shown that obsessive compulsive disorder (OCD) is associated with a specific deficit in spatial working memory, especially when task difficulty (i.e., working memory load) is high. It is not clear whether this deficit is associated with dysfunction of the brain system that subserves spatial working memory, or whether it is associated with a more generalized effect on executive functions. In contrast to studies in healthy volunteers and schizophrenia, spatial working memory in OCD has not been investigated before using functional neuroimaging techniques. We conducted a functional MRI study in 11 treatment-free female patients with OCD and 11 for sex-, age-, education-, and handedness pairwise-matched healthy controls in order to assess performance on a parametric spatial n-back task as well as the underlying neuronal substrate and its dynamics. Patients with OCD performed poorly at the highest level of task difficulty and engaged the same set of brain regions as the matched healthy controls. In this set, the effect of difficulty on magnitude of brain activity was the same in patients and in controls except for a region covering the anterior cingulate cortex. In this region activity was significantly elevated in patients with OCD at all levels of the parametric task. These findings do not provide evidence for a deficit of the spatial working memory system proper, but suggest that the abnormal performance pattern may be secondary to another aspect of executive dysfunctioning in OCD.

Adult↗
PubMed2006

Modafinil-induced modulation of working memory and plasma corticosterone in chronically-stressed mice.

The original aims of our study were to investigate the dose-effect relationship of modafinil administration on working memory performance, in parallel with the measurement of plasma corticosterone in chronically-stressed mice, as compared to control mice. Memory performance was evaluated by spontaneous alternation in a T-maze. Vehicle or modafinil (8, 16 or 32 mg/kg) were administered after or without chronic stress (immobilization and exposure to light) for 15 min/day over a period of consecutive 14 days. Immediately after behavioral testing, blood was sampled to measure plasma corticosterone levels. Under non-stress conditions, corticosterone significantly increased with 16 and 32 mg/kg modafinil administration. Interestingly, optimal working memory performance was revealed at the 16 mg/kg dose. Moreover, no correlation was evidenced between working memory performance and plasma corticosterone level in modafinil-treated animals. Under stress conditions, corticosterone level was lowered at 8 mg/kg and remained unchanged at 16 and 32 mg/kg modafinil. An optimal working memory performance was evidenced at 8 mg/kg, which indicated a decrease in the efficiency threshold of modafinil under stress. Furthermore, an inverse correlation emerged between working memory performance and corticosterone level. Our study evidenced for the first time the interaction between stress and memory, in the emotional modulation of working memory performance, as a function of the administered dose of modafinil.

Animals↗
PubMedDate not supplied

Deterioration of spatial and nonspatial reference and working memory in aged rats: protective effect of life-long calorie restriction.

Two different aspects of learning (spatial and nonspatial) and two different types of memory (reference and working) were simultaneously measured in populations of 3- (young), 11- (adult), and 25-month-old (aged) rats fed ad libitum either a standard (ST) or a hypocaloric (HY) diet. All groups, regardless of age or diet, showed ability in learning all four versions of the task. However, old ST rats were significantly slower and less efficient at learning than the young and adult ST rats. In contrast, senescent HY rats' cognitive abilities did not differ from those of their young and adult counterparts. The decline in reference and working memory in the aged ST rats was more pronounced in the spatial than the nonspatial version of the task. This study confirms and extends to more specific aspects of memory our earlier finding that age-related cognitive deterioration in rats was antagonized by life-long calorie restriction.

Aging↗
PubMed1997

Cholinergic stimulation alters performance and task-specific regional cerebral blood flow during working memory.

Modulation of the cholinergic neurotransmitter system results in changes in memory performance, including working memory (WM), in animals and in patients with Alzheimer disease. To identify associated changes in the functional brain response, we studied performance measures and regional cerebral blood flow (rCBF) using positron emission tomography (PET) in healthy subjects during performance of a WM task. Eight control subjects received an infusion of saline throughout the study and 13 experimental subjects received a saline infusion for the first 2 scans followed by a continuous infusion of physostigmine, an acetylcholinesterase inhibitor, for the subsequent 8 scans. rCBF was measured using H215O and PET in a sequence of 10 PET scans that alternated between rest and task scans. During task scans, subjects performed the WM task for faces. Physostigmine both improved WM efficiency, as indicated by faster reaction times, and reduced WM task-related activity in anterior and posterior regions of right midfrontal gyrus, a region shown previously to be associated with WM. Furthermore, the magnitudes of physostigmine-induced change in reaction time and right midfrontal rCBF correlated. These results suggest that enhancement of cholinergic function can improve processing efficiency and thus reduce the effort required to perform a WM task, and that activation of right prefrontal cortex is associated with task effort.

Adult↗
PubMed2001

Computational approaches to the architecture and operations of the prefrontal cortical circuit for working memory.

1. This article reviews recent progress in the computational studies towards the architecture and operations of the prefrontal cortical circuit, which are keys to understand the mechanisms of working memory processing. 2. The recurrent excitatory connections form closed-loop circuits, which contribute to the sustainment of delay-period activity. These connections subserve the cortical amplification of the activity. 3. Recent experimental studies (Wilson et al. 1994; Rao et al. 1999, 2000) suggested that at least two architectonically distinct types of intracortical inhibition, isodirectional and cross-directional inhibition, play significant roles in the formation of memory fields. 4. Computer simulations of a prefrontal cortical circuit model (Tanaka 1999, 2000a) showed that the isodirectional inhibition in the model regulated the amplitude of memory fields (i.e., the maximum firing rate) while the cross-directional inhibition contributed to the sharpening of the memory fields or the tuning curves. 5. The above characteristics enable the prefrontal cortical circuit to control memory fields, which would be necessary to general working memory processing. It would also be interesting to know whether different subtypes of the interneurons have distinct roles. 6. Another important issue is how neuromodulators contribute to working memory processing. Recent computer simulations by Durstewitz et al. (1999, 2000) showed that stronger dopamine action required stronger intervening input to destroy working memory, suggesting that dopamine contributes to the stabilization of working memory representation. 7. Further elucidation of these issues based on more detailed anatomical data of the cortical circuitry would make the architecture and operations of the prefrontal cortical circuit be more clearly described.

Animals↗
PubMed2005

Keeping priorities: the role of working memory and selective attention in cognitive aging.

Cognitive aging is associated with impairments to working memory and top-down control in selective attention, two components of cognitive control associated with the frontal lobes. Recent findings indicate that working memory and selective attention may be interdependent, making a better understanding of their involvement in cognitive aging particularly challenging. A paper in a recent issue of Nature Neuroscience has provided evidence that a reduction in the ability to keep a clear distinction between information to be stored in working memory and information that should be ignored and subsequently suppressed is associated with poor working memory performance. These results are in line with previous evidence for a specific age-related impairment in the ability to separate irrelevant from relevant information and may be able to explain a range of age-related cognitive changes.

Aged↗
PubMed2006

Proactive interference and item similarity in working memory.

Proactive interference (PI) may influence the predictive utility of working memory span tasks. Participants in one experiment (N=70) completed Ravens Advanced Progressive Matrices (RAPM) and multiple versions of operation span and probed recall, modified for the type of memoranda (digits or words). Changing memoranda within- or across-trials released PI, but not doing so permitted PI buildup. Scores from PI-build trials, but not PI-release trials, correlated with RAPM and accounted for as much variance in RAPM as unmodified tasks. These results are consistent with controlled attention and inhibition accounts of working memory, and they elucidate a fundamental component of working memory span tasks.

Adult↗
PubMedDate not supplied

[Working memory dysfunction in patients suffering from schizophrenia and their first-degree relatives].

UNLABELLED: Working memory deficits are considered to play an important role affecting not only the pathogenesis but also the course of schizophrenia. Numerous studies of schizophrenic patients and their first-degree relatives suggest that this impairment may be an indicator of susceptibility to developing schizophrenia. AIM: A comparison of selected working memory indicators in patients with schizophrenia, their first-degree relatives, and healthy controls. METHOD: Participants in the study were 99 patients with the diagnosis of schizophrenia (according to the ICD- 10-DCR criteria) in an early period of remission, their healthy first-degree relatives (N = 42), relatives with a history of psychiatric disorder (N = 14), and a control group of participants (N = 54) unrelated to the subjects and with no psychiatric history. Selected tests from the computer-aided Vienna Test Battery were used, measuring: reaction time (RT) in a task that required choosing among complex stimuli of two modalities, a tendency to perseveration (PERSEV), and immediate visuospatial memory span (CORSI). RESULTS: Schizophrenic patients' performance was found to be significantly inferior to that of controls on all the cognitive tests related to working memory: they had a longer reaction time in forced choice tasks, elevated perseverative tendencies and reduced immediate visuospatial memory span. Moreover, healthy relatives of schizophrenic patients performed significantly poorer than did the controls both as regards perseverative tendencies and visuospatial memory scan. Schizophrenic patients did not differ significantly from their close relatives in the degree of visuospatial memory span impairment. CONCLUSIONS: The findings indicate that working memory deficits as assessed by the tests used in the study may be related to familial susceptibility to schizophrenia. Therefore, the dysfunction may be taken into account in the capacity of endophenotype of such susceptibility.

Adult↗
PubMed1999

At which steps of spatial working memory processing do striatofrontal circuits intervene in humans?

Striatofrontal circuits have been implicated in spatial working memory in non-human and human primates. To determine at which steps of information processing (stimulus encoding, storage or response programming) they intervene, we compared 32 levodopa-treated patients with idiopathic Parkinson's disease (PD) and 32 matched control subjects in a visuo-spatial pattern span paradigm. Our testing procedure allowed us to evaluate the influence of: (1) the type of encoding (controlled vs free); (2) the nature of interference during a 10 s delay (spatial vs verbal); and (3) response elaboration (reproduction vs error detection). As expected, the performance of control subjects was significantly better in controlled than in free encoding, in verbal than in spatial interference and in detection than in reproduction, clearly demonstrating the sensitivity of the procedure to these factors. Compared to controls, PD patients were impaired in all conditions and the severity of the deficit was significantly correlated with that observed in tests of executive functions. The global pattern of performance, however, was identical to that of controls. These data confirm the involvement of striatofrontal circuits in spatial working memory in humans and suggest that the executive working memory component intervenes at all steps of working memory processing.

Antiparkinson Agents↗
PubMed2000

Verbal working memory impairment in schizophrenia patients and their first-degree relatives: evidence from the digit span task.

OBJECTIVE: The evidence for verbal working memory deficits in schizophrenia has been inconsistent. Few studies have evaluated verbal working memory in the first-degree relatives of schizophrenia patients, who likely share the genetic diathesis for schizophrenia but not the potential confounds associated with chronic mental illness. METHOD: The Wechsler Digit Span Task was used to investigate verbal working memory in 52 schizophrenia patients, 56 of their first-degree relatives, and 73 nonpsychiatric comparison subjects. RESULTS: The nonpsychotic relatives showed no impairment on the forward digit span task, a measure of general attention, but did show impairment on the backward digit span task, a measure of verbal working memory. Schizophrenia patients showed impairment on both the forward and backward digit span tasks. CONCLUSIONS: These results indicate that the forward and backward digit span tasks tap different cognitive abilities that are differentially associated with the diathesis for schizophrenia. Working memory deficits associated with schizophrenia appear to be generalized and not limited to the spatial modality.

Adult↗
PubMed2002

Thought suppression, intelligence, and working memory capacity.

The importance of individual differences in intelligence and working memory capacity in predicting the ability to intentionally suppress thoughts was investigated. Sixty participants completed a thought suppression task, and measures of working memory capacity (OSPAN), fluid intelligence (Raven's Matrices), and crystallised intelligence (the National Adult Reading Test). As predicted, the results indicated that more effective thought suppression was independently related to higher working memory capacity and greater fluid intelligence, but was unrelated to crystallised intelligence. The findings have theoretical implications for understanding the mechanisms underlying a failure to inhibit unwanted intrusions and clinical implications for disorders involving high levels of intrusive thoughts and memories.

Adolescent↗
PubMed1996

Effect of cholinergic activation by physostigmine on working memory failure caused in rats by pharmacological manipulation of hippocampal glutamatergic and 5-HTergic neurotransmission.

The muscarinic receptor antagonist scopolamine significantly increased the number of errors in the working memory task with a three-panel runway setup, when injected bilaterally at 3.2 micrograms/side into the dorsal hippocampus. The increase in working memory errors induced by intrahippocampal 3.2 micrograms/side scopolamine was reduced by concurrent injection of the cholinesterase inhibitor physostigmine (1.0 and 3.2 micrograms/side. However, physostigmine (3.2 micrograms/side) did not affect an increase in working memory errors induced by intrahippocampal injection of the competitive N-methyl-D-aspartate (NMDA) receptor antagonist (+/)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) at 32 ng/side. Likewise, physostigmine (3.2 micrograms/side) was ineffective in reducing an increase in working memory errors caused by intrahippocampal administration of the 5-hydroxytryptamine1A (5-HT1A) receptor agonist (+/-)-8-hydroxy-2-(di-n-pro-pylamino)tetralin (8-OH-DPAT) at 10 micrograms/side. These results suggest that the septohippocampal cholinergic activity is necessary for normal working memory processes, but that cholinergic activation neither compensates loss of hippocampal NMDA receptor-mediated neurotransmission nor counteracts the overstimulation of hippocampal 5-HT1A receptors in terms of working memory function.

Acetylcholine↗
PubMed2004

Working memory and mental practice outcomes after stroke.

OBJECTIVE: To examine the relationship between working memory and motor improvement obtained after a single training session combining mental and physical practice. DESIGN: Before-after trial. SETTING: Laboratory of a university-affiliated research rehabilitation center. PARTICIPANTS: A sample of 12 patients with stroke and 14 age- and gender-matched healthy subjects. INTERVENTION: In a single session, patients were trained with combined mental and physical practice to increase the loading on the affected leg while standing up and sitting down. MAIN OUTCOME MEASURES: Motor improvement as measured by the percentage change in limb loading on the affected limb after training and 24 hours later (follow-up), and the relationship between working memory and percentage motor improvement. RESULTS: The loading on the affected leg was improved after training (P< .01) and at follow-up (P< .05), and working memory scores at follow-up correlated significantly (P< .004 to P< .007) with the level of improvement. The visuospatial domain yielded the strongest correlation (r= .83), followed by the verbal (r= .62) and kinesthetic (r= .59) domains. CONCLUSIONS: These results suggest that the outcome (improved limb loading) of mental rehearsal with motor imagery depends on the ability to maintain and manipulate information in working memory.

Adult↗