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At least 973 records · Page 54Linked to original sources
PubMed2004

Strategy choices in simple and complex addition: Contributions of working memory and counting knowledge for children with mathematical disability.

Groups of first-grade (mean age = 82 months), third-grade (mean age = 107 months), and fifth-grade (mean age = 131 months) children with a learning disability in mathematics (MD, n = 58) and their normally achieving peers (n = 91) were administered tasks that assessed their knowledge of counting principles, working memory, and the strategies used to solve simple (4+3) and complex (16+8) addition problems. In all grades, the children with MD showed a working memory deficit, and in first grade, the children with MD used less sophisticated strategies and committed more errors while solving simple and complex addition problems. The group differences in strategy usage and accuracy were related, in part, to the group difference in working memory and to group and individual differences in counting knowledge. Across grade-level and group, the switch from simple to complex addition problems resulted in a shift in the mix of problem-solving strategies. Individual differences in the strategy mix and in the strategy shift were related, in part, to individual differences in working memory capacity and counting knowledge.

Adolescent↗
PubMed1995

Verbal working memory dysfunction in schizophrenia: use of a Brown-Peterson paradigm.

Recent studies of schizophrenia have implicated deficits in processes related to working memory, but the cognitive features of these deficits have been incompletely characterized. We used a modified Brown-Peterson paradigm to compare working memory in patients with schizophrenia and in normal control subjects. Distractor conditions differed in processing demand, increasing in complexity from no distractor to counting backwards (serial threes). We found significant effects of group, of distractor condition, and of a group x distractor condition interaction. The significant interaction was the result of a more rapid decline in the performance of schizophrenic patients with concurrent articulation. In addition, the schizophrenic group also made significantly more intrusion errors. The study suggests that schizophrenic patients exhibit dysfunction of the verbal working memory system due to a diminution in its overall processing resources.

Adult↗
PubMed1997

Differential effects of three 5-HT receptor antagonists on the performance of rats in attentional and working memory tasks.

The effects of three different serotonin (5-HT) receptor antagonists (ketanserin, methysegide, methiothepin) in the modulation of attention, working memory and behavioural activity were investigated in this study by assessing the performance of rats in two separate cognitive models; the 5-choice serial reaction time (5-CSRT) task, which measures attention, and the delayed non-matching to position (DNMTP) task, which measures working memory. Methysergide and methiothepin bind at the 5-HT1 and 5-HT2 as well as the 5-HT5-7 receptors, with varying degrees of selectivity, and ketanserin binds at the 5-HT2A receptors rather selectively. None of these agents bind to any significant extent to 5-HT3 or 5-HT4 receptors. In the 5-CSRT task, neither methiothepin (0.15 mg/kg) nor ketanserin (1.0 and 3.0 mg/kg) impaired the choice accuracy of rats, although they induced sedation. The low doses of methysergide (1.5 and 3.0 mg/kg) slightly increased the behavioural activity of rats, whereas the high dose of methysergide (15.0 mg/kg) reduced behavioural activity and slightly reduced choice accuracy of the rats in the attentional task (monitoring of visual stimuli) under the baseline conditions or curtailed stimulus duration. This effect was not augmented at the reduced stimulus intensity. These findings suggest that the high dose of methysergide did not interfere with the visual discrimination of rats. Furthermore, methysergide did not reduce motivation for this task, since it did not increase food collection latencies. In the DNMTP task, methiothepin (0.15 mg/kg) induced a delay non-dependent deficit in choice accuracy. This could be due to an impaired alternation ability or akinesia, which increases an actual delay between sample and choice. Methiothepin (0.15 mg/kg) also interfered with behavioural activity of rats. Interestingly, ketanserin (1.0 mg/kg and 3.0 mg/kg) and methysergide (3.0-15.0 mg/kg) neither impaired the choice accuracy nor reduced the behavioural activity of rats in the DNMTP task. These results suggest that the blockade of 5-HT2A receptors does not interfere with attention and working memory per se. However, all three serotonin receptor antagonists interfered with behavioural activity of rats in the 5-CSRT task more severely than in the DNMTP task. The possible role of serotonin and non-serotonin receptors underlying the influence of these antagonists on behavioural activity will be discussed.

Animals↗
PubMed1997

Working memory constraints on linear reasoning with spatial and temporal contents.

The present article reports two experiments testing the use of working memory components during reasoning with temporal and spatial relations in four-term series problems. In the first experiment four groups of subjects performed reasoning tasks with temporal and with spatial contents either without (control) or with a secondary task (articulatory suppression, visuo-spatial suppression or central executive suppression). The second experiment tested the secondary task effects in a within-subjects design either on problems with a spatial content or on problems with a temporal content, and within each content domain either under conditions of self-paced or of fixed presentation of the premises. Both experiments found effects of all three secondary tasks on reasoning accuracy. This supports the hypothesis that the subjects construct spatial representations of the premise information with the support of visuo-spatial resources of working memory. The second experiment also showed that during premise intake, only visuo-spatial and central executive secondary tasks had an effect. The implications of the data for the working memory requirements of reasoning and for theories of linear reasoning are discussed.

Adult↗
PubMed2001

Interference with performance of a response selection task that has no working memory component: an rTMS comparison of the dorsolateral prefrontal and medial frontal cortex.

It has been suggested that the dorsolateral prefrontal cortex (DLPFC) is involved in free selection (FS), the process by which subjects themselves decide what action to perform. Evidence for this proposal has been provided by imaging studies showing activation of the DLPFC when subjects randomly generate responses. However, these response selection tasks have a hidden working memory element and it has been widely reported that the DLPFC is activated when subjects perform tasks which involve working memory. The primary aim of this experiment was to establish if the DLPFC is genuinely involved in response selection. We used repetitive transcranial magnetic stimulation (rTMS) to investigate whether temporary interference of the DLPFC could disrupt performance of a response selection task that had no working memory component. Subjects performed tasks in which they made bimanual sequences of eight nonrepeating finger movements. In the FS task, subjects chose their movements at random while a computer monitor displayed these moves. This visual feedback obviated the need for subjects to maintain their previous moves "on-line." No selection was required for the two control tasks as responses were cued by the visual display. The attentional demands of the control tasks varied. In the high load (HL) version, subjects had to maintain their attention throughout the sequence, but this requirement was absent in the low load (LL) task. rTMS over the DLPFC slowed response times on the FS task and at the end of the sequence on the HL task, but had no effect on the LL task. rTMS over the medial frontal cortex (MFC) slowed response times on the FS task but had no effect on the HL task. This suggests that a response selection task without a working memory load will depend on the DLPFC and the MFC. The difference appears to be that the DLPFC is important when selecting between competing responses or when concentrating if there is a high attentional demand, but that the MFC is only important during the response selection task.

Attention↗
PubMed2001

Differential effects of delta 9-THC on spatial reference and working memory in mice.

RATIONALE: Marijuana remains the most widely used illicit drug in the U.S., and recent attention has been given to putative therapeutic uses of marijuana and cannabinoid derivatives. Thus, developing a better understanding of delta9-THC (tetrahydrocannabinol)-induced mnemonic deficits is of critical importance. OBJECTIVES: These experiments were conducted to determine whether delta9-THC has differential effects on spatial reference and working memory tasks, to investigate its receptor mechanism of action, and to compare these effects with those produced by two other compounds--scopolamine and phencyclidine--known to produce mnemonic deficits. In addition, the potency of delta9-THC in these memory tasks was compared with its potency in other pharmacological effects traditionally associated with cannabinoid activity. METHODS: Two different versions of the Morris water maze were employed: a working memory task and a reference memory task. Other effects of delta9-THC were assessed using standard tests of hypomotility, antinociception, catalepsy, and hypothermia. RESULTS: delta9-THC disrupted performance of the working memory task (3.0 mg/kg) at doses lower than those required to disrupt performance of the reference memory task (100 mg/kg), or elicit hypomotility, antinociception, catalepsy, and hypothermia. These performance deficits were reversed by SR 141716A. The effects of delta9-THC resembled those of scopolamine, which also selectively disrupted the working maze task. Conversely, phencyclidine disrupted both tasks only at a dose that also produced motor deficits. CONCLUSIONS: These data indicate that delta9-THC selectively impairs performance of a working memory task through a CB, receptor mechanism of action and that these memory disruptions are more sensitive than other pharmacological effects of delta9-THC.

Animals↗
PubMed2005

Spatial working memory function in twins with schizophrenia and bipolar disorder.

BACKGROUND: Family studies are in conflict as to whether schizophrenia and bipolar disorder have independent genetic etiologies. Given the relatively low prevalence (approximately 1%) of these disorders, the use of quantitative endophenotypic markers of genetic liability might provide a more sensitive strategy for evaluating their genetic overlap. We have previously demonstrated that spatial working memory deficits increase in a dose-dependent fashion with increasing genetic proximity to a proband among the unaffected co-twins of schizophrenic patients. Here, we evaluated whether such deficits might also mark genetic susceptibility to bipolar disorder. METHODS: The Wechsler Memory Scale-Revised Visual Memory Span and Digit Span subtests were administered to 46 schizophrenic patients, 32 of their unaffected co-twins, 22 bipolar patients, 16 of their unaffected co-twins, and 100 control twins, representing unselectively nationwide twin samples. RESULTS: Schizophrenic patients and their unaffected co-twins performed significantly worse than control subjects on the spatial working memory task, whereas only the schizophrenic patients performed significantly below the control subjects on the verbal working memory task. Neither bipolar patients nor their unaffected co-twins differed from control subjects on these measures. CONCLUSIONS: Our findings support the hypothesis that impairment in spatial working memory might effectively reflect an expression of genetic liability to schizophrenia but less clearly to bipolar disorder.

Aged↗
PubMed1997

Visuospatial working memory in patients with schizophrenia.

Recent investigations have documented abnormalities in working memory related processes in schizophrenics on tasks assessing the central executive component of this cognitive model. This preliminary study investigated the function of another component of the working memory system, the visuospatial scratch pad in schizophrenia. The "scratch pad's" passive visual store--responsible for the temporary retention of visual material--was assessed via a computerized spatial delayed response task, whereas its active spatial rehearsal subsystem--specialized for retaining the temporal properties--was explored through visual block span. To assess elemental visual spatial abilities we used the Judgment of Line Orientation test. Thirty-two schizophrenics and 27 controls were tested. Although we discovered the basic perceptual abilities of patients to be intact, we determined that whenever memory was necessitated on spatial tasks, patients demonstrated marked deficits. This pattern of cognitive dysfunction is consistent with impairments in a neural network involving prefrontal and/or posterior brain regions in schizophrenia.

Adult↗
PubMed1988

Primary and working memory functioning in Alzheimer-type dementia.

This paper reviews recent neuropsychological studies of primary-memory functioning in early Alzheimer-type dementia (AD) with specific reference to recent research on working memory. The deficits in primary memory follow a fairly distinct pattern with a comparatively unimpaired recency effect in free recall, a moderate impairment in memory span, and a more substantial impairment in short-term retention following distraction. The nature of these deficits is considered in relation to the Working Memory Model (Baddeley & Hitch, 1974). It is suggested that the Articulatory Loop System is functioning normally but that there is an impairment in the control processes of working memory.

Alzheimer Disease↗
PubMed2001

Behavioral and neurophysiological correlates of episodic coding, proactive interference, and list length effects in a running span verbal working memory task.

Updating refers to (1) discarding items from, (2) repositioning items in, and (3) adding items to a running working memory span. Our behavioral and fMRI experiments varied three factors: trial length, proactive interference (PI), and group integrity. Group integrity reflected whether the grouping of items at the encoding stage was violated at discarding. Behavioral results were consistent with the idea that updating processes have a relatively short refractory period and may not fatigue, and they revealed that episodic information about group context is encoded automatically in working memory stimulus representations. The fMRI results did not show evidence that updating requirements in a task recruit executive control processes other than those supporting performance on nonupdating trials. They did reveal an item-accumulation effect, in which signal increased monotonically with the number of items presented during the trial, despite the insensitivity of behavioral measures to this factor. Behavioral and fMRI correlates of PI extended previous results and rejected an alternative explanation of PI effects in working memory.

Adult↗
PubMed2005

Children's working memory: investigating performance limitations in complex span tasks.

Three experiments investigated the roles of resource-sharing and intrinsic memory demands in complex working memory span performance in 7- and 9-year-olds. In Experiment 1, the processing complexity of arithmetic operations was varied under conditions in which processing times were equivalent. Memory span did not differ as a function of processing complexity. In Experiment 2, complex memory span was assessed under three conditions designed to vary both processing and intrinsic storage demands: mental arithmetic (significant attentional demands-requires storage), odd/even judgments (significant attentional demands-no storage required), and articulatory suppression (minimal attentional demands--no storage required). The highest memory spans were found in the articulatory suppression task. Span was at an intermediate level with arithmetic processing and was lowest for processing involving odd/even judgments. This difference in memory span for processing tasks involving arithmetic processing and odd/even judgments was eliminated in Experiment 3 when the pacing requirements of the arithmetic and odd/even processing tasks were equated. The results are consistent with the view that complex memory span performance is disrupted by processing activities that divert attentional resources from storage.

Child↗
PubMed2002

Working memory in capuchin monkeys (Cebus apella).

It has been suggested that delayed (non-) matching to sample (DNMTS/DMTS) tasks using trial-unique stimuli and short, as well as longer delay intervals, can provide important insights into animal cognition. Therefore, this research examined the capability of the New World capuchin monkey (Cebus apella) in perform trial-unique DMTS and DNMTS tasks across delay intervals ranging between 8 s and 10 min. Subjects were tested using a version of the Wisconsin General Test Apparatus mounted in front of the animal's home cage. They were first trained on a basic DMTS/DNMTS task with an 8 s interval until they reached a learning criterion of nine correct responses in ten consecutive trials. All subjects reached the learning criterion in both DMTS/DNMTS tasks, and the number of trials to criterion did not differ between tasks. After reaching the criterion, subject's memory performance was successively assessed at delay intervals of 15 s, 60 s, 120 s and 10 min. For both DMTS/DNMTS tasks, the mean percentage of correct responses across delays was above chance and, interestingly, performance did not significantly decrease as function of delay increments. Comparisons based on each group's scores, averaged across the four delays, showed no difference between DMTS and DNMTS memory performance. These results indicate that capuchin monkeys are able to learn DMTS/DNMTS tasks in which they are required to respond to new pairs of stimuli on every trial. This demonstrates the capability of 'concept' learning in this species. Moreover, above chance performance on the memory tests indicates a working memory ability similar to that reported for the genus Macaca. Taken together, these data indicates that capuchin monkeys can be a valuable alternative model for investigations of the neuropsychological basis of memory.

Animals↗
PubMed1998

Event-based prospective memory and executive control of working memory.

In 5 experiments, the character of concurrent cognitive processing was manipulated during an event-based prospective memory task. High- and low-load conditions that differed only in the difficulty of the concurrent task were tested in each experiment. In Experiments 1 and 2, attention-demanding tasks from the literature on executive control produced decrements in prospective memory. In Experiment 3, attention was divided by different loads of articulatory suppression that did not ultimately lead to decrements in prospective memory. A high-load manipulation of a visuospatial task requiring performance monitoring resulted in worse prospective memory in Experiment 4, whereas in Experiment 5 a visuospatial task with little monitoring did not. Results are discussed in terms of executive functions, such as planning and monitoring, that appear to be critical to successful event-based prospective memory.

Adult↗
PubMed2003

The subtype-selective nicotinic acetylcholine receptor agonist SIB-1553A improves both attention and memory components of a spatial working memory task in chronic low dose 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated monkeys.

Monkeys that receive chronic low dose (CLD) 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration develop deficits in spatial delayed-response task performance. The present study examined the extent to which SIB-1553A [(+/-)-4-[[2-(1-methyl-2-pyrrolidinyl)ethyl]thio]phenol hydrochloride], a novel neuronal nicotinic acetylcholine receptor (nAChR) agonist with selectivity for beta4 subunit-containing nAChRs, could counteract this cognitive deficit produced by CLD MPTP exposure. Prior to MPTP treatment, monkeys displayed a delay-dependent decrement in performance on a variable delayed response task. CLD MPTP treatment caused a shift to a delay-independent pattern of responding on this task, such that short-delay trials were performed as poorly as long-delay trials. At lower doses (e.g., 0.025 mg/kg), SIB-1553A significantly improved performance on short-delay trials but only at 24 h after drug administration. At higher doses (e.g., 0.50 mg/kg), SIB-1553A significantly improved performance on both short- and long-delay trials at both 20 min and 24 h after drug administration. When tested 24 h after drug administration, monkeys performed long-delay trials with greater accuracy than they did under normal (pre-MPTP) conditions. These results suggest that at lower doses, SIB-1553A may be more effective in improving attentional deficits associated with CLD MPTP exposure, whereas at higher doses, SIB-1553A may effectively improve both attentional and memory performance.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2005

Executive functioning and working memory in fetal alcohol spectrum disorder.

The goal of this report is to critically review research on executive functioning (EF) and working memory in individuals with fetal alcohol spectrum disorder (FASD). Individuals with FASD exhibit EF deficits in the areas of cognitive flexibility, planning and strategy use, verbal reasoning, some aspects of inhibition, set shifting, fluency, working memory, and, recently, on tests of emotion-related or hot EF. Some researchers have linked prenatal alcohol exposure to abnormalities in the development of the frontal cortex of affected individuals or animals. One common finding is that these EF deficits persist regardless of whether the individual has facial dysmorphology. Furthermore, EF deficits are not simply due to a low IQ in these individuals. More research with larger sample sizes, smaller age ranges, and consistent measurement tools is needed in this area to ameliorate some inconsistencies in the literature. Furthermore, researchers should now focus on studying the pattern of weakness in EF in individuals with FASD as well as relations among working memory and EF, which will help to identify specific areas of weakness, to enhance diagnosis, and to improve treatment. There is limited research on the development of EF in individuals with FASD, which can have important implications for understanding of how these deficits unfold from childhood through adulthood.

Adolescent↗
PubMed1998

Working memory deficits of reading disabled children.

Aims of the study were to investigate the specificity of reading disabled childrens deficits in working memory capacity and to pursue whether their deficits could be accounted for by deficient processing or impairments in verbal short-term storage capacity. A group of 10-year-old reading disabled children was compared with two groups of normal reading children, matched for chronological age and reading age, respectively. Measures for working memory capacity, short-term capacity and processing speed related to the language and to the numerical domain were administered. Results indicated that reading disabled children performed worse on all measures of working memory capacity, irrespective of the domain which these measures reflected. Their poorer performance could neither be explained by inefficient processing nor to their deficits in verbal short-term storage capacity. Reading disabled children seem to have a general lack of capacity for the concurrent processing and storage of verbal information.

Child↗
PubMed1990

The relationship of working memory to the immediate recall of stories following unilateral temporal or frontal lobectomy.

Patients undergoing unilateral temporal lobectomy were tested preoperatively for working memory capacity, sentence comprehension, and rapid-naming ability, and were retested on these same measures 3 to 5 days and 2 weeks postoperatively. Immediate recall of stories was assessed twice only: preoperatively, and 2 weeks postoperatively. The left temporal-lobe group demonstrated transient deficits in working memory capacity, sentence comprehension, and rapid-naming ability over the 2 week postoperative period. No significant group differences in working memory capacity were evident two weeks after operation, even though the story recall of the left temporal-lobe group was impaired. A second experiment, with additional patients, explored the possible contribution of the hippocampus and of the frontal lobes to performance on these same tasks. Extent of hippocampal excision did not affect performance differentially on any task. Story recall was impaired following left temporal lobectomy, whereas left frontal lobectomy impaired sentence comprehension and rapid-naming ability. These results indicate a double dissociation of verbal deficits 2 weeks after left temporal- and left frontal-lobe excisions.

Adolescent↗
PubMed2006

Event-related desynchronization/synchronization during an auditory-verbal working memory task in mild Parkinson's disease.

OBJECTIVE: Event-related desynchronization (ERD) and synchronization (ERS) were studied during an auditory-verbal working memory task in patients suffering from Parkinson's disease (PD). METHODS: PD patients (n=7, mean age 59) at a mild stage of the disease volunteered in the study. A group of healthy subjects (n=10, mean age 61) served as control group. ERD and ERS of the 1-25 Hz EEG frequencies were studied using wavelet transforms during memory encoding and retrieval. RESULTS: Both groups performed equally well on the memory task. Statistically significant differences in ERD/ERS responses were observed in posterior electrodes during encoding of the memory set due to the fact that alpha ( approximately 10-15 Hz) ERS was elicited in the controls, but not in the PD group. In broad frequency bands ( approximately 6-25 Hz) ERD responses were observed in both groups during memory retrieval. A pre-stimulus alpha ERS seen in the control group was absent in the PD group. CONCLUSIONS: The results of this preliminary study indicate that Parkinson's disease might affect brain oscillatory responses in the alpha frequency range in the encoding phase of auditory-verbal working memory. SIGNIFICANCE: The ERD/ERS patterns may reflect neurophysiological alterations in the processes underlying working memory deficits in PD.

Acoustic Stimulation↗