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PubMed2005

Effects of alcohol and performance incentives on immediate working memory.

RATIONALE AND OBJECTIVES: The Sternberg Memory Scanning task was used to test the hypotheses that immediate working memory (WM) would be impaired during moderate rising blood alcohol concentrations (BACs), and provision of a rewarding incentive for good performance under alcohol would counteract this impairment. METHODS: Two groups (n=18) of social drinkers received either 0.62 g/kg alcohol (A) or a placebo (P). Reward (verbal feedback and money) for good performance was provided to another pair of alcohol and placebo groups (n=18) (AR and PR). All participants completed two tests when BACs in the alcohol groups were rising (68 and 80 mg/100 ml) and two tests during declining BACs (73 and 64 mg/100 ml). RESULTS: Comparisons of A and P groups showed that rising BACs impaired immediate WM [increased errors, slowed rate of mental scanning, slowed reaction time (RT) when a larger number of items had to be held in WM]. Comparisons of AR and PR groups showed that reward for good performance during rising BACs counteracted impairment in scanning rate and RT but did not reduce errors. Tests during declining BACs of 73 mg/100 ml indicated some symptoms of impairment abated before others. When BAC declined to 64 mg/106 ml, the groups no longer differed on any measure of WM. CONCLUSIONS: An acute dose of alcohol can impair aspects of immediate WM performance while BACs are rising, and some of these effects can be reversed when incentives to perform well are provided.

Administration, Oral↗
PubMed1985

Differential acquisition of a "working memory" task by the Roman strains of rats.

Twenty-eight male rats of the Roman strains-fourteen RHA (Roman High Avoidance) and fourteen RLA (Roman Low Avoidance)-were submitted to a positively reinforced task, the delayed reinforced alternation test (DRA), in a T-maze. Performances of RLA rats were significantly better than those of RHA; RLA rats also had higher VTE (vicarious trial and error) and spontaneous alternation (SA) scores. These data confirm the fact that RLA may acquire positively reinforced learning as rapidly, or even more rapidly, than RHA rats, and that the differences in active avoidance behavior between these strains depend more on differential freezing behavior than on learning and memory capacities. Since the delayed reinforced alternation is considered as a working memory test, our results suggest that the Roman strains could be used as a genetic model for the neurobiological study of this form of memory.

Animals↗
PubMed1997

The role of working memory capacity in retrieval.

The verbal fluency task requires generation of category exemplars and appears to be an example of what M. Moscovitch (1995) calls a strategic test of memory retrieval. Four experiments explored the role of individual differences in working memory (WM) capacity on verbal fluency under various secondary load conditions. High WM participants consistently recalled more exemplars. However, load conditions caused a decline in recall only for high WM participants. Low WM participants showed no effect of secondary workload on exemplar generation. WM group differences and load effects were observed even in the 1st min of retrieval, which suggests that differences were not due to differences in knowledge. A model of retrieval is supported that relies on cue-based-automatic activation, monitoring of output for errors, controlled suppression of previously recalled items, and controlled strategic search.

Analysis of Variance↗
PubMed1999

Spatial working memory in Asperger's syndrome and in patients with focal frontal and temporal lobe lesions.

Spatial working memory (SWM) was investigated in 15 patients with Asperger's syndrome (AS) comparing their performance to 18 age- and IQ-matched control subjects. An additional comparison was made with 20 unilateral frontal excision patients [9 right (RFL); 11 left (LFL)] and with 38 unilateral temporal lobectomy patients [18 right (RTL); 18 left (LTL)], the frontal and temporal lobe patients having separate matched control groups. SWM was tested using the Executive Golf Task, a test that also measures spatial strategy formation. The AS group showed a substantial deficit on SWM, but no impairment in strategy formation. The LFL showed the same pattern of impairment, but with a less substantial deficit. The RFL group showed a large deficit, but some of this was accounted for by a strategy formation impairment. Of the temporal lobe lesions groups, only the RTL group was impaired on SWM, but this group showed normal strategy formation. It was concluded that the SWM deficit in AS may reflect a more general difficulty in accessing different types of representations in order to guide voluntary behavior, providing at least a partial explanation for the executive deficits found in AS.

Adolescent↗
PubMed1998

Age-related changes in regional cerebral blood flow during working memory for faces.

Young and old adults underwent positron emission tomography during the performance of a working memory task for faces (delayed match-to-sample), in which the delay between the sample and choice faces was varied from 1 to 21 s. Reaction time was slower and accuracy lower in the old group, but not markedly so. Values of regional cerebral blood flow (rCBF) were analyzed for sustained activity across delay conditions, as well as for changes as delay increased. Many brain regions showed similar activity during these tasks in both young and old adults, including left anterior prefrontal cortex, which had increased rCBF with delay, and ventral extrastriate cortex, which showed decreased rCBF with delay. However, old adults had less activation overall and less modulation of rCBF across delay in right ventrolateral prefrontal cortex than did the young adults. Old adults also showed greater rCBF activation in left dorsolateral prefrontal cortex across all WM delays and increased rCBF at short delays in left occipitoparietal cortex compared to young adults. Activity in many of these regions was differentially related to performance in that it was associated with decreasing response times in the young group and increasing response times in the older individuals. Thus despite the finding that performance on these memory tasks and associated activity in a number of brain areas are relatively preserved in old adults, differences elsewhere in the brain suggest that different strategies or cognitive processes are used by the elderly to maintain memory representations over short periods of time.

Adult↗
PubMed1993

Administration of LHRH analog can improve working memory in aged female rats.

We had previously found that an age-related deficit in working memory appeared in middle-aged females, possibly related to their ageing reproductive system. This experiment investigates the effect of administering an analog of luteinizing hormone-releasing hormone (LHRH), D-Trp6-LHRH, to 22-mo-old female rats submitted to successive trainings in a water-reinforced matching to sample task since the age of three months. Animals were injected SC with a long-lasting microcapsule formulation (800 micrograms/kg continuously releasing 5 micrograms D-Trp6-LHRH per day for at least 28 days). The action of the analog on ovary weight and estradiol and progesterone levels was also studied. Administration of D-Trp6-LHRH counteracted the deleterious effect of age on performance and inhibited ovary function. However, hormone plasma levels were not modified. These results suggest that the hypothalamo-ovarian axis might be implicated in memory deficits of middle-aged females.

Aging↗
PubMed2006

The relationship between performance and fMRI signal during working memory in patients with schizophrenia, unaffected co-twins, and control subjects.

While behavioral research shows working memory impairments in schizophrenics and their relatives, functional neuroimaging studies of patients and healthy controls show conflicting findings of hypo- and hyperactivation, possibly indicating different relationships between physiological activity and performance. In a between-subjects regression analysis of fMRI activation and performance, low performance was associated with relatively lower activation in patients than controls, while higher performance was associated with higher activation in patients than controls in DLPFC and parietal cortex, but not occipital cortex, with unaffected twins of schizophrenics being intermediate between the groups. Accordingly, this supports the idea that both hyper and hypoactivation may be possible along a continuum of behavioral performance in a way consistent with a neural inefficiency model. Further, this study offers preliminary evidence that the relationship between behavior and physiology in schizophrenia may be heritable.

Aged↗
PubMed2003

Sentence comprehension and working memory limitation in aphasia: a dissociation between semantic-syntactic and phonological reactivation.

The relation between working memory (WM) limitation and sentence comprehension was assessed in Hebrew-speaking aphasics, three conduction aphasics and three agrammatics. The study compared sentences that required different types of reactivation-syntactic-semantic reactivation, in relative clauses, and word form/phonological reactivation, in sentences with reanalysis of lexical ambiguity. The effect of phonological memory load, manipulated by number of words intervening between the activation and the reactivation, on comprehension of the two sentence types was examined. The findings were that agrammatic aphasics failed in the comprehension of object relatives but not on subject relatives irrespective of their antecedent-gap distance. Conduction aphasics, on the other hand, who showed severe WM limitation, comprehended well all types of relative clauses and were unaffected by antecedent-gap distance. The conduction aphasics failed to understand the sentences that required phonological reactivation when the phonological distance was long. These results suggest that the type of reactivation required by the sentence, as well as the type of memory overload are crucial in determining the effect of WM limitation on sentence comprehension.

Adult↗
PubMed2003

Co-ordination within and between verbal and visuospatial working memory: network modulation and anterior frontal recruitment.

Attention switching between items being stored and manipulated in working memory (WM) is proposed to be an elementary executive function. Experiment 1 reveals a similar attentional limitation within and between verbal and visuospatial WM and identifies a supramodal switching process required for switching between WM items. By using functional magnetic resonance imaging, Experiment 2 investigated brain activation correlates of parametrically varied attention switching within and between these two WM modalities. Attention switching activation was broadly distributed, was quite similar across the three conditions, and, in almost all areas, increased with increasing switching demand, indicating that attention switching recruits and modulates the entire WM network. Dorsolateral prefrontal cortex was implicated in both within- and between-modality attention switching, but no significant activation was found in ventrolateral areas, supporting dorsal-ventral process models of prefrontal organization. A functional dissociation between anterior frontal and dorsolateral prefrontal cortex was found with the former being more activated when switching attention between modalities was required. The data challenge the notion of an anatomically separate attention switching executive function, but suggest that anterior frontal areas are recruited for the additional demand of coordinating the verbal and visuospatial WM slave systems.

Adolescent↗
PubMed1992

Within-context assessment of age differences in working memory.

Five experiments were conducted to investigate the mechanisms by which age-related reductions in working memory capacity might mediate age-related declines in cognitive functioning. A prototypical cognitive task, cube comparison, was implemented on a computer to allow measures of the availability of different types of information while subjects were attempting to solve the task. Young and old adults were equivalent in a measure postulated to reflect the temporary preservation of untransformed stimulus information. However, older adults, relative to young adults, exhibited greater reductions in accuracy as the processing requirements increased, and they made significantly more redundant or repetitive requests for information. These results are consistent with the view that increased age may be associated with a decreased ability to transform or abstract information while also preserving the products of earlier processing.

Adult↗
PubMed1995

Visuospatial working memory, movement control and executive demands.

Developments in the concept of a specialist visuospatial resource in working memory owe much to a pair of tasks originally developed by Brooks (1967), involving respectively the generation and retention of a mental image of a matrix pattern and the retention of a verbal sequence. Previous literature has demonstrated that the matrix task calls on cognitive resources which are involved in both the processing of visual input and the generation of movement sequences. Using dual task methodology, the study reported here demonstrates that the matrix and verbal versions of the task do indeed rely on separate, specialized cognitive resources, one of which is also involved in generation of action. However, when the secondary task (random generation of numbers) was very demanding of general purpose cognitive resources both the matrix and verbal tasks were performed poorly, suggesting that each of these tasks draw heavily on a common, general purpose resource as well as on their respective specialist resources. It is argued that random generation offers a means to assess general purpose cognitive resources and that the cognitive processes involved in the Brooks tasks may be more complex than has been previously assumed.

Adult↗
PubMed2001

Working memory capacity and strategy use.

In this study, we examine the role of strategy use in working memory (WM) tasks by providing short-term memory (STM) task strategy training to participants. In Experiment 1, the participants received four sessions of training to use a story-formation (i.e., chaining) strategy. There were substantial improvements from pretest to posttest (after training) in terms of both STM and WM task performance. Experiment 2 demonstrated that WM task improvement did not occur for control participants, who were given the same amount of practice but were not provided with strategy instructions. An assessment of participants' strategy use on the STM task before training indicated that more strategic participants displayed better WM task performance and better verbal skills. These results support our hypothesis that strategy use influences performance on WM tasks.

Adolescent↗
PubMed2003

Probability judgment and subadditivity: the role of working memory capacity and constraining retrieval.

In this research, we examined the role that individual differences in working memory (WM) capacity, the strength of alternatives, and time constraints play in probability judgment and subadditivity. With a laboratory-based learning task, Experiment 1 revealed that the degree to which participants' probability judgments were subadditive was negatively correlated with a measure of WM capacity, even when variance due to short-term memory capacity was removed. In addition, participants were more subadditive when the viable alternatives were all rather weak. Experiment 2 extended the WM-capacity-subadditivity correlation to a population judgment task and revealed that subadditivity increases when the judgment task is performed under time constraints. Results support a model that assumes that people make probability judgments by comparing the focal hypothesis with relevant alternatives retrieved from long-term memory and that people high in WM span include more alternatives in the comparison process. Time constraints are assumed to truncate the alternative generation process, leading to fewer alternatives being recalled from long-term memory.

Humans↗
PubMed2003

Differential effects of iloperidone, clozapine, and haloperidol on working memory of rats in the delayed non-matching-to-position paradigm.

RATIONALE: Because cognitive function, particularly working memory (WM), is severely impaired in schizophrenia, evaluation of neuroleptic medication should include investigation of possible effects on cognition. Iloperidone is a promising, novel atypical neuroleptic drug (NL), for which no cognitive data is presently available. OBJECTIVE: To investigate whether the novel atypical NL iloperidone would affect performance of rats on a WM test, using a delayed non-matching-to-position (DNMTP) paradigm, and compare its effects with those of the atypical NL clozapine and the typical NL haloperidol. METHODS: Male Lister Hooded rats trained to criterion in an operant DNMTP task (0-64 s delay intervals) were administered vehicle, iloperidone (0.03, 0.1 mg/kg, i.p.), clozapine (0.1, 0.3 mg/kg, s.c.), haloperidol (0.003, 0.01, 0.03 mg/kg, s.c.), or scopolamine (0.05 mg/kg, s.c.). Together with choice accuracy, the motor performance of the task was measured. RESULTS: It was found that: (1) iloperidone significantly improved choice accuracy delay-dependently while impairing task performance; (2) the atypical NL clozapine had no effect on choice accuracy and parameters related to motor function, but significantly increased the number of uncompleted trials; (3) haloperidol did not affect choice accuracy except at the longest delay with the highest dose, but in contrast to clozapine it significantly impaired task performance. CONCLUSION: In accordance with their different pharmacological profiles, the three NLs iloperidone, clozapine, and haloperidol have different effects in this preclinical cognitive task. These results might provide important information for the development of NLs with beneficial effects on cognition.

Analysis of Variance↗
PubMed2003

Frontal activations associated with accessing and evaluating information in working memory: an fMRI study.

To investigate the involvement of frontal cortex in accessing and evaluating information in working memory, we used a variant of a Sternberg paradigm and compared brain activations between positive and negative responses (known to differentially tax access/evaluation processes). Participants remembered two trigrams in each trial and were then cued to discard one of them and maintain the other one as the target set. After a delay, a probe letter was presented and participants made decisions about whether or not it was in the target set. Several frontal areas--anterior cingulate (BA32), middle frontal gyrus (bilateral BA9, right BA10, and right BA46), and left inferior frontal gyrus (BA44/45)--showed increased activity when participants made correct negative responses relative to when they made correct positive responses. No areas activated significantly more for the positive responses than for the negative responses. It is suggested that the multiple frontal areas involved in the test phase of this task may reflect several component processes that underlie more general frontal functions.

Adult↗
PubMed2004

Modality effects in verbal working memory: differential prefrontal and parietal responses to auditory and visual stimuli.

The neural bases of verbal (nonspatial) working memory (VWM) have been primarily examined using visual stimuli. Few studies have investigated the neural bases of VWM using auditory stimuli, and fewer have explored modality differences in VWM. In this study, we used functional magnetic resonance imaging (fMRI) to examine similarities and differences between visual VWM (vis-VWM) and auditory VWM (aud-VWM) utilizing identical stimuli and a within-subjects design. Performance levels were similar in the two modalities and there was extensive overlap of activation bilaterally in the dorsolateral and ventrolateral prefrontal cortex (DLPFC and VLPFC), intraparietal sulcus, supramarginal gyrus and the basal ganglia. However, a direct statistical comparison revealed significant modality differences: the left posterior parietal cortex, primarily along the intraparietal sulcus, showed greater responses during vis-VWM whereas the left dorsolateral prefrontal cortex showed greater responses during aud-VWM. No such differences were observed in the right hemisphere. Other modality differences in VWM were also observed, but they were associated with relative decreases in activation. In particular, we detected bilateral suppression of the superior and middle temporal (auditory) cortex during vis-VWM, and of the occipital (visual) cortex during aud-VWM, thus suggesting that cross-modal inhibitory processes may help to provide preferential access to high-order heteromodal association areas. Taken together, our findings suggest that although similar prefrontal and parietal regions are involved in aud-VWM and vis-VWM, there are important modality differences in the way neural signals are generated, processed and routed during VWM.

Adolescent↗
PubMed2005

A special role for numbers in working memory? An fMRI study.

Although numbers carry averbal semantics (i.e., magnitude), they are often utilized in verbal Working Memory (vWM) tasks. However, vWM is thought to rely on a purely phonological code. Here, we tested the influence of (a) averbal semantics and (b) different tasks on performance in a vWM context by examining stimulus and task-specific variation of activity in the horizontal parts of the intraparietal sulcus (hIPS). The hIPS has previously been shown to subserve magnitude processing modulated by (a) specific stimuli and (b) specific tasks. Two variants of an n-back paradigm (comparison and identity match tasks) utilizing letters and numbers as stimulus material at different levels of vWM load were administered in 16 participants. Behavioral and functional imaging data reveal stimulus-specific modulation of activity in the hIPS suggesting a semantic influence of numbers. In the identity match task, numbers induced additional hIPS activation compared to letters while letters never induced additional hIPS activation when compared to numbers. Letters as compared to numbers only induced additional hIPS activation in the comparison task. These results question the assumption of a purely phonological code in vWM because hIPS activation subserving magnitude processing is modulated by stimulus semantics and task demands.

Adult↗
PubMed2006

Evidence from two genetic syndromes for the independence of spatial and visual working memory.

This study aimed at investigating the possible dissociation between visual-object and visual-spatial working memory (WM) in individuals with Williams syndrome (WS) and Down syndrome (DS). Four study groups were included: WS group (10 males, 5 females) with a mean chronological age (CA) of 19 years 8 months (SD 6y 1mo) and a mean mental age (MA)of 6 years 11 months (SD 1y 5mo); WS comparison group (7 males, 8 females) comprised of typically developing children with a mean CA of 6 years 10 months (SD 10mo) and a mean MA of 6 years 11 months (SD 8mo)matched as a group with the participants with WS on the basis of mental age; DS group (11 males, 7 females) with a mean CA of 15 years 10 months (SD 5y 8mo) and a mean MA of 5 years 2 months (SD 8mo); and DS comparison group (10 males, 8 females) with a mean CA of 5 years and 1 month (SD 7mo)and a mean MA of 5 years 2 months (SD 8mo) selected to match the DS group on the basis of mental age. They were all administered tests that explored visual perception (Visual Perception Test - Subtest 4 and Line Orientation tests), visual imagery (imaging the colour of objects and the tail length of well-known animals), spatial imagery (mental rotation of visually presented or verbally evoked objects), and WM for visual-object and visual-spatial information. Individuals with WS exhibited specific difficulties in the visual-spatial, but not the visual-object, WM task. Instead, people with DS showed reduced performance in both tests. However, whereas the observed deficit in individuals with DS persisted when perceptual abilities were taken into account, the deficit in individuals with DS was compensated when their scores were adjusted for performance on perceptual tasks. These results support the hypothesis of a dissociation within the sketch-pad slave system in the WM model and reinforce the view of intellectual disability as a non-unitary condition.

Adolescent↗