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PubMed2003

[Inhibition and working memory: effect of acute sleep deprivation on a random letter generation task].

The literature contains inconsistent data on the effects of acute sleep deprivation on the superior cognitive functions. The primary purpose of this study is to determine the effectiveness of inhibition, one of the functions of the working memory executive centre (EC), over an extended, 36-hour waking period. Inhibition is a cognitive mechanism whereby individuals ignore non-relevant information recorded in their working memory. We also tested the effects of a 36-hour period of acute sleep deprivation on simple reaction time. Twelve young, healthy volunteers (M = 21.5 years, sigma = 2.3) performed a random generation task involving letters and a simple reaction time psychomotor test over four sessions held at 10-hour intervals. Each participant was assigned a "constant routine." Participants were kept awake in a prone position within a room whose environment was held strictly constant (light, noise, temperature, meals, etc.). This control procedure provided assurance that any variation in participant performance was solely caused by sleep deprivation. The random generation task, nearly two minutes in length, consisted in verbally producing a sequence of 100 letters in a random fashion (i.e. by inhibiting, for example, alphabetical order) and by keeping to a set rhythm. Our assumption was that capacity for inhibition diminished as the number of hours of sleep deprivation increased. The simple reaction test, 10 minutes in length, involved pressing a button as swiftly as possible to cause a black square to disappear from a screen. In this case our assumption was that acute sleep deprivation alters simple reaction time. Analysis of variance (ANOVA) through repeated measures using the "sessions" factor as an intra-subject variable showed no significant changes in randomization indices of the random generation task, contrary to analysis of average simple reaction times. Participants' reaction times deteriorated over the first two minutes of the test during the night they were deprived of sleep. It would seem that the contradictory results of previous studies of the effects of acute sleep deprivation on the inhibition function would be due to errors in factor identification. In conclusion, the inhibition function, as measured during the performance of a brief task, seems to remain intact during an extended, 36-hour waking period. Simple reaction time assessed by means of a brief psychomotor test is affected during a night of sleep deprivation. The working-memory inhibition executive function shows greater resistance to acute sleep deprivation than does psychomotor reaction time for the performance of short tasks.

Adolescent↗
PubMed2003

Intraventricular 5,7-dihydroxytryptamine lesions disrupt acquisition of working memory task rules but not performance once learned.

The serotonergic system is implicated in learning and memory and its disorder, e.g. after 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") abuse. This study examined the effects of widespread depletion of serotonin (5-HT) using intraventricular injection of 5,7-dihydroxytryptamine (5,7-DHT) on the learning of a working memory task in the dark agouti (DA) rat. The lesion impaired acquisition but not later performance of a nonspatial working memory rule, as measured using nonmatch to sample object recognition in the Y-maze. The lesion had a marginal effect on choice completion times over the course of testing. However, nonspecific effects did not provide a good account of the reduction in choice accuracy as this persisted when completion times were taken into account statistically. Similarly, in a second experiment, the same lesioned rats were slowed in the acquisition of spatial alternation in the T-maze. However, in the open field, there were no comparably long-lasting effects of the serotonergic depletion on line crossings and defecation, only a transient reduction in activity on the first day.Together, these data suggest that the serotonergic system is important in the acquisition of working memory tasks in the rat and that this outcome was unlikely to be the result of nonspecific effects of the lesion.

5,7-Dihydroxytryptamine↗
PubMed2006

Enhancing effects of nicotine and impairing effects of scopolamine on distinct aspects of performance in computerized attention and working memory tasks in marmoset monkeys.

With the CAmbridge Neuropsychological Test Automated Battery (CANTAB), computerized neuropsychological tasks can be presented on a touch-sensitive computer screen, and this system has been used to assess cognitive processes in neuropsychiatric patients, healthy volunteers, and species of non-human primate, primarily the rhesus macaque and common marmoset. Recently, we reported that the common marmoset, a small-bodied primate, can be trained to a high and stable level of performance on the CANTAB five-choice serial reaction time (5-CSRT) task of attention, and a novel task of working memory, the concurrent delayed match-to-position (CDMP) task. Here, in order to increase understanding of the specific cognitive demands of these tasks and the importance of acetylcholine to their performance, the effects of systemic delivery of the muscarinic receptor antagonist scopolamine and the nicotinic receptor agonist nicotine were studied. In the 5-CSRT task, nicotine enhanced performance in terms of increased sustained attention, whilst scopolamine led to increased omissions despite a high level of orientation to the correct stimulus location. In the CDMP task, scopolamine impaired performance at two stages of the task that differ moderately in terms of memory retention load but both of which are likely to require working memory, including interference-coping, abilities. Nicotine tended to enhance performance at the long-delay stage specifically but only against a background of relatively low baseline performance. These data are consistent with a dissociation of the roles of muscarinic and nicotinic cholinergic receptors in the regulation of both sustained attention and working memory in primates.

Acetylcholine↗
PubMed2003

Measures of working memory span and verbal rehearsal speed in deaf children after cochlear implantation.

Large individual differences in spoken word recognition performance have been found in deaf children after cochlear implantation. Recently, Pisoni and Geers (2000) reported that simple forward digit span measures of verbal working memory were significantly correlated with spoken word recognition scores even after potentially confounding variables were statistically controlled for. The present study replicates and extends these initial findings to the full set of 176 participants in the CID cochlear implant study. The pooled data indicate that despite statistical "partialling-out" of differences in chronological age, communication mode, duration of deafness, duration of device use, age at onset of deafness, number of active electrodes, and speech feature discrimination, significant correlations still remain between digit span and several measures of spoken word recognition. Strong correlations were also observed between speaking rate and both forward and backward digit span, a result that is similar to previously reported findings in normal-hearing adults and children. The results suggest that perhaps as much as 20% of the currently unexplained variance in spoken word recognition scores may be independently accounted for by individual differences in cognitive factors related to the speed and efficiency with which phonological and lexical representations of spoken words are maintained in and retrieved from working memory. A smaller percentage, perhaps about 7% of the currently unexplained variance in spoken word recognition scores, may be accounted for in terms of working memory capacity. We discuss how these relationships may arise and their contribution to subsequent speech and language development in prelingually deaf children who use cochlear implants.

Child↗
PubMed2005

Differential involvement of internal clock and working memory in the production and reproduction of duration: a study on older adults.

The present study uses the inter-individual variability in time perception of a group of elderly participants to differentiate the processes underlying time production and time reproduction. Participants performed duration production and reproduction tasks. They were also administered working memory tests and a spontaneous motor tempo task. The findings suggest that duration production and duration reproduction involve different mechanisms. Correlational analyses revealed a double dissociation: production was only correlated with spontaneous motor tempo and reproduction only with working memory measures. These findings suggest that the internal clock rate modulates the production of duration and that reproduced duration varies according to working memory capacities.

Aged↗
PubMed2000

Differential roles for visuospatial and verbal working memory in situation model construction.

Two experiments investigated the processing of the spatial and causal dimensions of situation models. In Experiment 1, participants read texts varying in spatial and causal demands while responding to on-line spatial and causal probes. Experiment 2 used the same design, but used texts that more tightly integrated spatial and causal information. In both experiments, spatially oriented dependent measures were generally influenced by spatial, but not causal, demands, whereas causally oriented measures were influenced by causal, but not spatial, demands. In addition, spatially oriented dependent measures were generally correlated with a measure of spatial working memory capacity, whereas causally oriented measures were correlated with a measure of verbal working memory capacity. These results indicate that spatial and causal dimensions of situation models are maintained and elaborated independently in different working memory subsystems.

Adult↗
PubMed1993

Amygdaloid NMDA and muscarinic receptors involved in working memory performance of rats.

In a three-panel runway task, the competitive N-methyl-D-aspartate (NMDA) receptor antagonist, 3-[(+-)-2-carboxypiperazin-4-yl]propyl-1-phosphonic acid (CPP) (56 ng/side), injected bilaterally into the basolateral subdivision of the amygdala, significantly increased the number of errors (attempts to pass through two incorrect panels of the three panel gates at four choice points) in a test of working memory. Intra-amygdaloid injection of the muscarinic receptor antagonist scopolamine (5.6 micrograms/side) also significantly increased working memory errors. In a test of reference memory, neither CPP nor scopolamine affected the number of errors when injected into the basolateral amygdala at doses up to 56 ng/side or 5.6 micrograms/side, respectively. These results indicate that processes mediated by NMDA and muscarinic receptors in the basolateral amygdala are involved in the performance of working memory, but not in reference memory.

Amygdala↗
PubMed2006

Working memory and sentence comprehension of Hong Kong Chinese children with specific language impairment.

Children with Specific Language Impairment present with delayed language development, but do not have a history of hearing impairment, mental deficiency, or associated social or behavioral problems. Non-word repetition was suggested as an index to reflect the capacity of phonological working memory. There is a paucity of such studies among Hong Kong Chinese children. This preliminary study aimed to examine the relationship between phonological working memory and Specific Language Impairment, through the processes of non-word repetition and sentence comprehension, of children with Specific Language Impairment and pre-school children with normal language development. Both groups of children were screened by a standardized language test. A list of Cantonese (the commonest dialect used in Hong Kong) multisyllabic nonsense utterances and a set of 18 sentences were developed for this study. t-tests and Pearson correlation were used to study the relationship between non-word repetition, working memory and specific language impairment. Twenty-three pre-school children with Specific Language Impairment (mean age = 68.30 months; SD = 6.90) and another 23 pre-school children (mean age = 67.30 months; SD = 6.16) participated in the study. Significant difference performance was found between the Specific Language Impairment group and normal language group in the multisyllabic nonsense utterances repetition task and the sentence comprehension task. Length effect was noted in Specific Language Impairment group children, which is consistent with the findings of other literature. In addition, correlations were also observed between the number of nonsense utterances repeated and the number of elements comprehended. Cantonese multisyllabic nonsense utterances might be worth further developing as a screening tool for the early detection of children with Specific Language Impairment.

Child↗
PubMed2004

Depressive symptoms account for deficient information processing speed but not for impaired working memory in early phase multiple sclerosis (MS).

Depressive symptoms may influence neuropsychological functioning negatively. A substantial proportion of multiple sclerosis (MS) patients exhibit neuropsychological impairments and depressive symptomatology is more common in MS as compared to healthy controls and to other neurological diseases. The objectives of the present study were to assess information processing speed, working memory and executive functions in early phase MS and to investigate whether severity of depressive symptoms account for these aspects of cognition in MS. The patients show slowed information processing speed and impaired working memory, whereas executive functioning, as measured with the Wisconsin Card Sorting Test, is unaffected. Depressive symptoms account for slowed information processing speed, but not for impaired working memory.

Adult↗
PubMed2005

Intermittent hypoxia during development induces long-term alterations in spatial working memory, monoamines, and dendritic branching in rat frontal cortex.

Exposure to intermittent hypoxia (IH), such as occurs in sleep-disordered breathing, is associated with increased apoptosis in vulnerable brain regions as well as with spatial reference memory deficits in adult and developing rats. The latter are more susceptible to IH, suggesting that early exposure to IH may have long-term consequences. Rats were exposed to 14 d of room air (RA) or IH starting at postnatal d 10. Working memory was then assessed in the water maze at 4 mo of age using a delayed matching to place task in which the rats were required to locate a submerged platform hidden in a novel location on the first trial (T1 or acquisition trial), and then remember that position after a delay (T2 or test trial). Mean escape latencies and swim distances were derived and the savings (T1-T2) were used as a measure of working memory. Male but not female rats exposed to IH showed working memory deficits at both a 10- and 120-min delay (for both latency and pathlength). Additionally, Sholl analysis of Golgi-stained neurons revealed decreased dendritic branching in the frontal cortex, but not the hippocampus, of male rats exposed to IH. Norepinephrine concentrations, dopamine turnover, and tyrosine hydroxylase activity were increased similarly in males and females. However, increased dopamine concentrations were present only in the frontal cortex of female rats. In conclusion, exposure to IH during a critical developmental period is associated with long-term alterations in frontal cortical dopaminergic pathways that may underlie gender differences in neurobehavioral deficits.

Animals↗
PubMed2005

Strategy use, the development of automaticity, and working memory involvement in complex multiplication.

Participants practiced a set of complex multiplication problems (e.g., 3 x 18) in a pre-/postpractice design. Before, during, and after practice, the participants gave self-reports of problem-solving strategies. At prepractice, the most common strategy was a mental version of the standard multidigit algorithm, and dual tasks revealed that working memory load was high and heavier for problems solved via nonretrieval strategies. After practice, retrieval was used almost exclusively, and participant variability, automaticity level of problems (proportion of trials on which retrieval was used over the entire experiment), and error rates were significant predictors of problem-solving latencies. Practice reduced working memory involvement to minimal levels, and there was no relationship between automaticity level and working memory load. The commonalities between the present findings and findings related to automaticity development in simple arithmetic are discussed.

Automatism↗
PubMedDate not supplied

Tower of Hanoi and working memory in adult persons with intellectual disability.

Persons with intellectual disability (ID) have been found to perform more poorly than their mental age would suggest in the visuo-spatial problem solving task Tower of Hanoi (TOH). Inefficient performance has been assumed to be related to inability to use sophisticated problem solving strategies because of restricted working memory capacity. In the present study, the TOH performance of adult persons with ID was found to be equal to that of fluid-intelligence-matched general children. However, persons with ID violated the rules of the TOH more often, and needed more trials to solve the TOH problems than the children did. Visuo-spatial and executive working memory tasks were significantly connected to the TOH performance of persons with ID, whereas phonological working memory tasks were not. Poor inhibition ability was related to the poor performance of subjects with ID in the TOH. We suggest that for persons with ID, TOH performance is determined by individual differences in fluid intelligence, controlled attention, and inhibition ability.

Adult↗
PubMed2002

Effects of time of day on age differences in working memory.

This study investigated the hypothesis that the influence of time of day on the efficiency of working memory is greater for older than younger adults. Groups of younger and older adults performed a working memory task on 4 consecutive days, twice in the morning and twice in the evening. Objective (body temperature) and subjective (alertness ratings) measures of arousal were taken during each session. Temperature increased across the day equally for younger and older adults, whereas alertness ratings were higher in the morning for older adults and in the evening for younger adults. The efficiency of the access and deletion functions paralleled the subjective alertness rating for younger and older adults, and age-related differences in these functions were greater when individuals were tested at nonoptimal times of day. The efficiency of the response inhibition function was similar for younger and older adults and paralleled changes in body temperature.

Adult↗
PubMed2005

Neural substrates of manipulation in visuospatial working memory.

The present study aimed to investigate in humans whether similar neuronal mechanisms underlie the manipulation and active processing of visual and visuospatial stimuli. Simultaneous and successive mental rotation and identity judgment of 2-D matrices and 3-D cube figures were contrasted using functional magnetic resonance imaging (fMRI). Results demonstrate that activation patterns during mental rotation with low working memory demands differ depending on stimulus type (2-D vs. 3-D). Comparison of simultaneous mental rotation of matrices and 3-D cubes resulted in activation of frontal as well as inferior and superior parietal cortices. The opposite contrast (mental rotation of 3-D cubes vs. 2-D matrices) yielded only frontal cortex activation. The findings also yield evidence for converging, overlapping activation patterns for 2-D and 3-D stimuli if working memory demands are increased. Results are discussed within the framework of current working memory models.

Adult↗
PubMed2004

Effects of ethanol and GABAB drugs on working memory in C57BL/6J and DBA/2J mice.

RATIONALE: It has been suggested that GABA(B) receptors may be part of a neural substrate mediating some of the effects of ethanol. OBJECTIVE: The purpose of this experiment was to investigate, in mice, the effects of ethanol on working memory in a delayed matching-to position (DMTP) task, and additionally to determine if these effects were modulated by GABA(B) receptors. METHODS: Female C57BL/6J and DBA/2J mice were trained in the DMTP task, and after asymptotic levels of performance accuracy were achieved, injections (IP) of ethanol, baclofen, or phaclofen were administered. Baclofen or phaclofen were then co-administered with ethanol. Each test was repeated twice. RESULTS: Ethanol caused deficits in working memory at 2.0 g/kg and higher. The highest dose (2.5 g/kg) produced additional non-specific effects, indicative of sedation. Baclofen increased performance accuracy (2.5 mg/kg), while decreasing the total number of trials completed. When combined with ethanol (1.5 g/kg), baclofen increased memory deficits at the highest dose (7.5 mg/kg). Phaclofen increased performance accuracy at 10 and 30 mg/kg but had no effect on the total number of trials completed. When combined with ethanol (2.5 g/kg), phaclofen did not significantly alter ethanol-induced deficits in performance. CONCLUSIONS: Analyses of performance accuracy, total trials completed and variables indexing bias and motor impairment indicated that GABA(B) drugs modulate working memory in a behaviorally specific manner. Overall, these receptors may be part of a neural substrate that modulates some of the effects of ethanol.

Animals↗
PubMed1995

Are non-relevant objects represented in working memory? The effect of non-target objects on reach and grasp kinematics.

The role of visual information and the precise nature of the representations used in the control of prehension movements has frequently been studied by having subjects reach for target objects in the absence of visual information. Such manipulations have often been described as preventing visual feedback; however, they also impose a working memory load not found in prehension movements with normal vision. In this study we examined the relationship between working memory and visuospatial attention using a prehension task. In this study six healthy, right-handed adult subjects reached for a wooden block under conditions of normal vision, or else with their eyes closed having first observed the placement of the target. Furthermore, the role of visuospatial attention was examined by studying the effect, on transport and grasp kinematics, of placing task-irrelevant "flanker" objects (a wooden cylinder) within the visual field on a proportion of trials. Our results clearly demonstrated that the position of flankers produced clear interference effects on both transport and grasp kinematics. Furthermore, interference effects were significantly greater when subjects reached to the remembered location of the target (i.e., with eyes closed). The finding that the position of flanker objects influences both transport and grasp components of the prehension movement is taken as support for the view that these components may not be independently computed and that subjects may prepare a coordinated movement in which both transport and grasp are specifically adapted to the task in hand. The finding that flanker effects occur primarily when reaching to the remembered location of the target object is interpreted as supporting the view that attentional processes do not work efficiently on working memory representations.

Adult↗
PubMed2001

Working memory in ADHD: prefrontal/parietal connections.

Current theories of dopaminergic and noradrenergic mechanisms, which are thought to be of importance in the regulation of attention are reviewed. A biphasic model of dopaminergic function is described, in which tonic dopamine exerts a suppressive influence on subcortical dopamine systems by altering tonic/phasic dopaminergic relationships. Noradrenergic mechanisms are of importance in modulating sensory processing at the prefrontal cortical level. The work of Silberstein and colleagues utilizing Steady-State Visually Evoked Potential, during the course of an A-X Continuous Performance Task enables examination of the spatial distribution and dynamics of electrical brain activity during the task. The maintenance of activation in the interval between A and X provides a measure of working memory, thought to be related to prefrontal-parietal activation, which is facilitated by administration of methylphenidate to children with ADHD, suggesting that working memory may be a core deficiency in children with ADHD. While tonic dopamine activity in ventral striatum/accumbens gates inhibitory activity, dorsolateral prefrontal-parietal connections allow maintenance of working memory required for goal completion.

Animals↗
PubMed2004

A low dose of the alpha2 agonist clonidine ameliorates the visual attention and spatial working memory deficits produced by phencyclidine administration to rats.

RATIONALE: Psychotomimetic N-methyl-D-aspartate/glutamate receptor antagonists, such as phencyclidine (PCP), have been shown to produce a spectrum of behavioral, neurochemical and anatomical changes in rats that are relevant to aspects of schizophrenia, including impairments of working memory and visual attention. The alpha(2) noradrenergic receptor agonist clonidine prevents some of the behavioral effects of NMDA antagonists, suggesting that monoaminergic systems mediate some aspects of these deficits. OBJECTIVES: We sought to determine the ability of clonidine to modify the PCP-induced deficits of visual attention and spatial working memory in rats. RESULTS: In a lateralized reaction time task, a lower dose of clonidine (10 microg/kg) ameliorated the impairment of choice accuracy produced by PCP (2.5 mg/kg, IP), while the higher dose of clonidine (50 microg/kg) slowed response times and induced a deficit of choice accuracy on its own. The high dose of clonidine effectively prevented the motor impulsivity produced by PCP. In addition, clonidine (10 microg/kg) prevented PCP-induced performance deficits in a delayed non-match to sample task. CONCLUSIONS: These data indicate that clonidine may attenuate deficits of attention and working memory produced by PCP, perhaps in part by preventing some of the downstream neurochemical and anatomical effects of this psychotomimetic drug.

Adrenergic alpha-2 Receptor Agonists↗