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PubMedDate not supplied

The relationship between short-term memory and working memory: complex span made simple?

This experiment addresses the question of what makes a working memory measure a good predictor of higher-level abilities. Verbal and visuospatial processing episodes were interleaved with distinct verbal and visuospatial storage episodes to form four complex span tasks. Although these measures were reliable predictors of reading and mathematics ability in children, they were no more predictive of these abilities than corresponding simple span tasks involving storage alone. However, when individual differences in storage ability and processing capacity were controlled for, residual variance in complex span performance was related to academic ability in some cases. These findings indicate that complex span tasks are multiply determined, and that differences in task structure can dramatically influence the relative importance of these multiple constraints and the predictive power of a complex span measure.

Child↗
PubMed1997

Dissociation of spatial reference memory, spatial working memory, and hippocampal mossy fiber distribution in two rat strains differing in emotionality.

Rats of the inbred strains DA/Han and BDE/Han were compared on two complex spatial learning tasks, a spatial reference memory task in a 16-unit multiple T-maze and a spatial working memory task in an eight-arm radial-maze. In addition, sizes of hippocampal mossy fiber terminal fields were measured. BDE rats showed marked superiority in multiple T-maze learning whereas DA rats outperformed BDE rats on the radial-maze task. DA rats had significantly larger intra- and infrapyramidal mossy fiber terminal fields (IIP-MF). This is consistent with findings from other studies suggesting that large IIP-MF are related to excellent spatial radial-maze learning, but it also indicates that size of IIP-MF is correlated with processing of a specific type of spatial information rather than with overall spatial abilities. BDE rats had more extended suprapyramidal mossy fiber projections (SP-MF) and a larger hilus. Rats of both strains differed in exploratory behaviour and emotionality: DA rats revealed little freezing and had a high rearing activity, whereas BDE rats showed frequent freezing and reared rarely. Results suggest that IIP-MF are involved with flexible expression of memory, updating environmental information and parallel processing whereas SP-MF might be linked to processing of familiar information. Presumably, emotional factors contribute to performance differences.

Animals↗
PubMed2006

The real relationship between short-term memory and working memory.

Storage-oriented memory span tasks with no explicit concurrent processing are usually referred as short-term memory (STM) tasks, whereas tasks involving storage plus concurrent processing requirements are designated as working memory (WM) tasks. The present study explores a question that remains unsolved: Do STM and WM tasks clearly tap distinguishable theoretical constructs? For that purpose, a large sample of 403 participants was tested through 12 diverse memory span tasks. Half of those tasks are widely accepted as measures of STM, whereas the other half measure WM. The results show that STM and WM share largely overlapping underlying capacity limitations, suggesting that all memory span tasks tap essentially the same construct. Some implications are discussed.

Adult↗
PubMed1992

N-methyl-D-aspartate receptor antagonist MK-801 and spatial memory representation: working memory is impaired in an unfamiliar environment but not in a familiar environment.

Female Sprague-Dawley rats were injected with the noncompetitive N-methyl-D-aspartate (NMDA) antagonist MK-801 or saline 30 min before daily testing in spatial working memory (WM) and reference memory (RM) procedures in an 8-arm radial maze. MK-801 impaired RM and WM acquisition but not performance when rats were trained to criterion before drug administration. Neither a 2-hr nor a 4-hr delay between the first and last 2 correct WM choices impaired long-term WM. MK-801 impaired WM performance in trained rats only when rats were tested in a new environment. Thus, 2 mechanisms may be required for relational memory: an NMDA-dependent mechanism for acquiring long-term spatial representations and an NMDA-insensitive mechanism for operating on these stored representations.

Animals↗
PubMed2003

Language comprehension and working memory language comprehension and working memory deficits in patients with schizophrenia.

The present study examined the hypothesis that patients with schizophrenia have deficits in language comprehension compared to normal controls, and that these deficits are associated with disturbances in working memory (WM). In addition, we hypothesized that language comprehension deficits would be associated with the severity of specific symptoms in the patients (formal thought disorder and hallucinations). Participants were 27 stable outpatients with schizophrenia and 28 demographically similar controls. Language comprehension was measured by presenting sentences auditorily that varied in length and syntactic complexity, followed by two or three comprehension questions. We measured working memory by administering a reading span task. Results indicated that, as predicted, language comprehension deficits were significantly greater in patients with schizophrenia than controls. Also as predicted, working memory was strongly correlated with language comprehension performance in both patients with schizophrenia and controls. Contrary to our predictions, language comprehension and working memory deficits were not associated with either formal thought disorder or hallucinations.

Adult↗
PubMed2004

Visual search does not remain efficient when executive working memory is working.

Working memory (WM) has been thought to include not only short-term memory stores but also executive processes that operate on the contents of memory. The present study examined the involvement of WM in search using a dual-task paradigm in which participants performed visual search while manipulating or simply maintaining information held in WM. Experiments 1a and 2a involved executive WM tasks that required counting backward from a target digit and sorting a string of letters alphabetically, respectively. In both experiments, the search slopes in the dual-task condition were significantly steeper than those in a search-alone condition, indicating that performing the WM manipulation tasks influenced the efficiency of visual search. In contrast, when information was simply maintained in WM (Experiments 1b and 2b), search slopes did not differ between the single- and dual-task conditions. These results suggest that WM resources related to executive functions may be required in visual search.

Cognition↗
PubMed2004

Semantic memory and verbal working memory correlates of N400 to subordinate homographs.

N400 is an event-related brain potential that indexes operations in semantic memory conceptual space, whether elicited by language or some other representation (e.g., drawings). Language models typically propose three stages: lexical access or orthographic- and phonological-level analysis; lexical selection or word-level meaning and associate activation; and lexical integration, sentence- and discourse-level operations. The exact stage that N400 reflects is unknown, although opinion favors lexical integration over lexical selection. Surprisingly, little research has assessed relationships between neuropsychological measures of semantic memory fund of information or verbal working memory capacity and N400. Subjects performed a homograph disambiguation comprehension task with minimal working memory load. Short sentences read: The noun was adjective/verb. The nouns were either homographs or unambiguous. The adjective/verb was disambiguating for the homograph, and congruent or incongruent for the unambiguous noun. The primary noun of interest was the subordinate homograph. Comprehension of the subordinate meaning should correlate with semantic memory stores, reflecting greater knowledge. If N400 primarily reflects lexical access operations, it should also correlate with measures of semantic knowledge. If N400 reflects lexical integration, it should correlate with measures of working memory capacity. Comprehension errors were associated with semantic memory stores, but not working memory capacity. N400 was related to working memory capacity, but not semantic knowledge, suggesting that N400 primarily reflects late-stage working memory operations. N400 to subordinate disambiguating words was larger with greater working memory capacity, and thus may index the absolute capacity of working memory rather than difficulty in contextual integration.

Adult↗
PubMedDate not supplied

How does the severity of a learning disability affect working memory performance?

Working memory performance was examined in children aged 11-12 years who had borderline, mild, and moderate learning disabilities. Comparisons with children of average abilities were used to determine whether those with more severe learning disabilities had greater impairments in working memory. Seven measures of working memory span were used to assess temporary phonological short-term storage (digit span, word span), temporary visuo-spatial short-term storage (pattern span, spatial span), and temporary short-term storage with additional processing, or central executive, demands (listening span. odd one out span, reverse digit span). Children with mild and moderate learning disabilities were impaired on all measures of working memory compared to children of average abilities. Children with borderline learning disabilities were just as good as children with average abilities on visuo-spatial and complex span tasks, but showed an impairment on phonological span tasks. Children with moderate learning disabilities were indistinguishable from children with mild learning disabilities on simple span tasks, but were significantly poorer than the mild group on the more demanding complex span tasks. For the group as a whole, working memory was strongly related to mental age.

Case-Control Studies↗
PubMed2003

Chronic administration of corticosterone impairs spatial reference memory before spatial working memory in rats.

Corticosterone (CORT), the predominant glucocorticoid in rodents, elevated for 21 days damages hippocampal subregion CA3. We tested the hypothesis that CORT would impair spatial memory, a hippocampal function. In each of the three experiments, rats received daily, subcutaneous injections of either CORT (26.8 mg/kg body weight in sesame oil) or sesame oil vehicle alone (VEH). CORT given for 21 or 56 days effectively attenuated body weight gain and reduced selective organ and muscle weights. All behavioral testing was done on tasks that are minimally stressful and avoid deprivation. For each experiment, testing commenced 24h after the last injection. CORT given for 21 days did not impair spatial working memory in the Y-maze (Experiments 1 and 2). After 56-day administration of CORT, spatial working memory was impaired in the Y-maze (Experiment 2). CORT given for 21 days also failed to impair spatial working memory in the Barnes maze (Experiment 3). However, in trials that depended solely on reference memory, the VEH group improved in performance, whereas the CORT group did not. In conclusion, CORT elevated over a period of 21 days did not impair spatial working memory, but impaired the formation of a longer-term form of memory, most likely reference memory. Impairments in spatial working memory are seen only after longer durations of CORT administration.

Animals↗
PubMed2001

Working memory in another dimension: functional imaging of human olfactory working memory.

The majority of working memory research has been carried out within the visual and auditory modalities, leaving it unclear how other modalities would map onto currently proposed working memory models. In this study we examined the previously uninvestigated area of olfactory working memory. Our aim was to investigate if olfactory working memory would engage prefrontal regions known to be involved in working memory for other sensory modalities. Using positron emission tomography we measured cerebral blood flow changes in 12 volunteers during an olfactory working memory task and a comparison visual working memory task. Our findings indicate that both olfactory and face working memory engaged dorsolateral and ventrolateral frontal cortex when the task requirements were matched; a conjunction analysis indicated overlap in the distribution of activity in the two tasks. Similarities and differences in activity were noted in parietal lobe regions, with both tasks engaging inferior areas of 40/7, but only visual working memory showing increased activity within left superior parietal cortex. The findings support the idea that working memory processes engage frontal cortical areas independent of the modality of input, but do not rule out the possibility of modality-specific neural populations within dorsolateral or ventrolateral cortex.

Adult↗
PubMed2000

Lidocaine reversible inactivation of the median raphe nucleus has no effect on reference memory but enhances working memory versions of the Morris water maze task.

Numerous studies in the past have dealt with the role of serotonergic system lesions in tasks aimed at measurement of cognitive behavior, but the literature concerning the role of serotonin in cognition remains controversial. Rats with electrolytic lesions of the median raphe nucleus (MRN) were found to display a profound impairment in both the acquisition and retention of spatial memory task. In this study, the lidocaine inactivation was employed to evaluate the involvement of the rat's median raphe nucleus in reference and working memory versions of the Morris water maze (MWM) task. Lidocaine (0.5 microl, 2%) was injected through a single cannula aimed at the MRN; control groups were treated in the same way with a 0.5 microl injection of saline. In Experiment 1, rats were trained in a reference memory version of the MWM with two blocks of four trials per day for three consecutive days, with intra-cerebral injection made 5 min before training. No significant difference was found. In Experiment 2, intra-cerebral injection was applied immediately after two blocks of four trials, and in Experiment 3, the drug was injected 5 min before retention test in rats that had received eight trials per day on three consecutive days. Again, no significant difference between control and treatment groups was found. These results indicate that MRN has no role in acquisition, consolidation and retrieval of spatial reference memory. In subsequent experiments, rats were trained in a working memory version of the MWM task to find a new target position in trial 1, and retrieval was tested 75 min later. MRN inactivation 5 min before (Experiment 4) and immediately after the acquisition trial (Experiment 5) enhanced spatial working memory. It is concluded that normal activity of the MRN has no role in formation and retrieval of reference memory, but it has an inhibitory role in working memory. Our results are confirmed with other studies suggesting that the serotonergic system has a different role in long-term and short-term memory. Interaction with other neurotransmitter systems like acetylcholine may be involved in this case.

Anesthetics, Local↗
PubMedDate not supplied

The development of visuo-spatial working memory.

Children's performance on tests of visuo-spatial working memory improves with age, although relatively little is known about why this happens. One explanation concerns the development of the ability to recode visually presented information into phonological form. This process appears to be used from around 8 years of age and is a major contributor to tasks in which stimuli can be verbally labelled. However, evidence suggests that phonological recoding cannot account for all of the age-related change in performance on visuo-spatial working memory tasks. In this review, four other mechanisms (knowledge, processing strategies, processing speed, and attentional capacity) are considered in terms of their contribution to children's visuo-spatial working memory development.

Child↗
PubMed2003

Castration in rats impairs performance during acquisition of a working memory task and exacerbates deficits in working memory produced by scopolamine and mecamylamine.

RATIONALE: Although much research has focused on the effects of ovarian hormones on learning and memory in females, less information is available regarding the effects of testicular hormones on learning and memory in males. Additionally, despite evidence of an interaction of testicular hormones and the cholinergic system in areas of the brain implicated in learning and memory, no information is available regarding the behavioral consequences of that interaction. OBJECTIVES: We assessed the effect of castration in male rats on working memory during acquisition of a radial maze. We also assessed the interactive effects of castration and scopolamine, a muscarinic receptor antagonist, as well as mecamylamine, a nicotinic receptor antagonist, on behavior. METHODS: Young adult male rats were castrated or underwent sham surgeries. Beginning 10 days after surgeries, performance on a task of working memory was assessed across 24 days of acquisition in an eight-arm radial maze. Following acquisition, scopolamine and mecamylamine dose-effect curves were established. RESULTS: Castration of male rats significantly decreased arm-choice accuracy during acquisition. Castration significantly exacerbated impairments in arm-choice accuracy produced by scopolamine as well as mecamylamine, without altering the disruptive effects of the drugs on the rate at which rats entered the arms of the maze. CONCLUSIONS: These results indicate that castration in male rats impairs working memory during acquisition of a spatial maze task. Additionally, these results suggest that the absence of testicular hormones increases the sensitivity of male rats to the impairing effects of scopolamine as well as mecamylamine on working memory.

Animals↗
PubMed2006

Event-related potential measures of visual working memory.

Visual working memory is a limited capacity system that temporarily maintains information about objects in the immediate visual environment. Psychophysical experiments have shown that most people are able to actively maintain 3 or 4 items in visual working memory at any point in time. To better understand how this process works and why our working memory capacity is so limited, a variety of neurophysiological approaches have been employed. In recent years, there has been a surge of interest in understanding how visual information is maintained in working memory at the neural level. Single-cell research with nonhuman primates has shown that neuronal firing during the retention period reflects the information that is currently held in working memory. In humans, event-related potentials (ERPs) have been used to examine the maintenance of information in working memory. An event-related potential component, known as the negative slow wave (NSW), has been used to measure the maintenance of information in working memory "online" during a given trial. More recently, another ERP component, the contralateral delay activity (CDA) has been shown to be a fairly specific correlate of the current contents of working memory. This component is sensitive to an individual's working memory capacity and may provide a window into the operations of this central cognitive construct.

Animals↗
PubMed2001

[Current trends and future directions in working memory research].

Working memory is a set of processes or a system that allows us to temporarily maintain task-relevant information during performance of complex cognitive tasks. It has recently been an intensively investigated topic in cognitive psychology, cognitive neuroscience, and other related disciplines, and important empirical and theoretical advances have been made during the last several years. In this article, we review the current state of working memory research, focusing on important recent methodological and theoretical developments in the field. Specifically, we provide an update of recent influential working memory theories (e.g., Baddeley's multicomponent model and an ACT-R model) and discuss the current status of various controversial theoretical issues, such as the unitary versus non-unitary nature of working memory, the nature of working memory limitations, the control and regulation of working memory, and the relationship of working memory to long-term memory. We conclude our review by pointing out some important future directions for working memory research.

Humans↗
PubMedDate not supplied

The effects of eye and limb movements on working memory.

Three experiments examined the role of eye and limb movements in the maintenance of information in spatial working memory. In Experiment 1, reflexive saccades interfered with memory span for spatial locations but did not interfere with memory span for letters. In Experiment 2, three different types of eye movements (reflexive saccades, pro-saccades, and anti-saccades) interfered with working memory to the same extent. In all three cases, spatial working memory was much more affected than verbal working memory. The results of these two experiments suggest that eye movements interfere with spatial working memory primarily by disrupting processes localised in the visuospatial sketchpad. In Experiment 3, limb movements performed while maintaining fixation produced as much interference with spatial working memory as reflexive saccades. These results suggest that the interference produced by eye movements is not the result of their visual consequences. Rather, all spatially directed movements appear to have similar effects on visuospatial working memory.

Extremities↗
PubMed2001

Neuromodulatory control of interacting medial temporal lobe and neocortex in memory consolidation and working memory.

A model of the interacting medial temporal lobe and neocortical association areas is formulated and applied to memory consolidation and working memory. A simplified connectivity in terms of superassemblies and assemblies of neurons representing types and values, respectively, of object features is underlying the model. Realistic low-dimensional model neurons, developed in particular to take neuronal adaptation into account, are employed. Observed short- and long-term potentiation and depression of plastic synaptic couplings are incorporated. It is shown that memory consolidation by long-term potentiation, based on repeated activations of neocortical patterns, may be guided by neuromodulated dynamics of the medial temporal lobe via short-term couplings acting as pointers. Bifurcations, i.e. transitions between different modes of network dynamics, with respect to developing synaptic couplings are shown to depend on the adaptivity of excitatory neurons in the medial temporal lobe and thus to be under neuromodulatory control. At weak adaptivity, after an initial temporal segmentation of several objects accounting for the capacity of working memory to resolve several items, attention is selectively focused on a single object according to the model. At intermediate adaptivity, reactivations may persist and long-term synaptic couplings gradually develop. At strong adaptivity, the model predicts attention and memory consolidation to be subsequently terminated. The neuromodulatory control of the interacting medial temporal lobe and neocortical system via the adaptivity of excitatory neurons may account for several observations on the influence of neuromodulators on various cognitive processes and brain disorders.

Animals↗
PubMed2002

Mecamylamine blocks enhancement of reference memory but not working memory produced by post-training injection of nicotine in rats tested on the radial arm maze.

The focus of this study was to analyze whether the psychostimulant nicotine would enhance reference and working memory consolidation in rats tested on the 8-arm radial arm maze. Mecamylamine, a nicotine antagonist, was used to attempt to block the enhancement of memory consolidation. All rats were given one training trial/day for 12 consecutive days, and 4 arms were baited. Rats were separated into five groups: the saline-nicotine group received an intraperitoneal (i.p.) injection of saline immediately after each trial followed 15 min later by an subcutaneous (s.c.) injection of nicotine (0.6 mg/kg free base); the nicotine-delay group received an s.c. injection of nicotine 2 h after each training trial, two groups received an i. p. injection of one of two different doses of mecamylamine (2.5 and 6.0 mg/kg) immediately after each trial, which was followed 15 min later by an s.c. nicotine injection, and a control group received an i.p. injection of saline immediately and 15 min after each training trial. Results showed that the saline-nicotine group made fewer reference and working memory errors than the saline- or nicotine-delay groups, but only the effect of nicotine on reference memory was blocked by the higher dose of mecamylamine. It appears from these results that nicotine's effects on reference and working memory may be mediated through different mechanisms.

Animals↗