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PubMed1995

Effects of scopolamine on spatial working memory in rats pretreated with the serotonergic depleter p-chloroamphetamine.

The present study investigated the mnemonic consequences of muscarinic blockade in rats pretreated with the serotonergic depleter p-chloroamphetamine (PCA). Subjects were initially injected with either PCA (2.5 mg/kg) or saline (SAL) approximately 1 week prior to testing on a working memory version of the Morris water maze (four daily trials for 4 days). Fifteen minutes before each daily session, PCA- and SAL-pretreated subjects were injected either with SAL or with one of two doses of scopolamine (SCOP; 0.5, 1.0 mg/kg). Latency to find the platform on each trial served as the major dependent measure. The results indicated that SCOP increased escape latencies. However, the dose needed to produce this effect was dependent upon whether subjects were pretreated with PCA. Significant increases in escape latencies in SAL-pretreated rats were induced with 1.0 mg/kg SCOP (on Day 1), while 0.5 mg/kg SCOP produced the same effect in PCA-pretreated subjects (on Days 1-4). Thus, although it was clearly demonstrated that muscarinic blockade did impair spatial working memory, the present data indicated that the dose necessary to produce this effect was dependent upon the status of the serotonergic system. More generally, these results imply that the cholinergic and serotonergic systems interact in a functionally important, as yet undetermined manner.

Animals↗

PubMed2004

Complementary tasks to measure working memory in distinct prefrontal cortex subregions in rats.

Acquisition of odor-guided or visually-guided delayed win-shift behavior was evaluated in rats after lidocaine-induced inactivation within the agranular insular area of the prefrontal cortex (PFC) or the prelimbic area of the PFC. Additional sites and tasks were used to control for neuroanatomical and behavioral specificity of lidocaine inactivation of the agranular insular and prelimbic areas. Results showed that acquisition of the odor-guided delayed win-shift task was dependent on the agranular insular area, whereas acquisition of the visually-guided version was dependent on the prelimbic area. This dissociation suggests that the stimulus modality used is critical for revealing working memory functions of different PFC subregions. The described methods provide a complementary means to study working memory in PFC subregions using a radial-arm maze.

Animals↗

PubMed1991

Working memory in children with specific arithmetical learning difficulties.

Siegel & Ryan (1989) reported that children with specific arithmetical learning difficulties (ALD) were impaired if they had to retain temporary information concurrently with counting visual arrays, but not if the concurrent operations were non-mathematical. This selective deficit was attributed to an impaired arithmetical working memory system. In the present study 15 children aged eight to nine with ALD were compared with 15 normally achieving controls. Experiment 1 examined performance on a number of tasks assessing span for information storage during concurrent operations. The results confirmed that children with ALD are impaired on concurrent span only when the operations involve counting and showed that this holds independently of the visuospatial or auditory-verbal characteristics of the task. Experiment 2 went on to investigate the possibility that children with ALD might be impaired at counting or retaining temporary information when each is assessed in isolation. The ALD group tended to count more slowly than controls and had lower auditory digit spans. It is argued that these deficits can account for the selective impairment of ALD children on concurrent counting span, without appealing to a special, arithmetical working memory system. Possible interpretations of the cognitive deficits associated with ALD and their implications for the ability to perform arithmetical skills are discussed.

Aptitude↗

PubMed1999

The role of working memory, field dependence, visual search, and reaction time in the left turn performance of older female drivers.

Older drivers have difficulties at intersections, especially in their performance of left turns. Older females are especially at risk in intersection maneuvers. Information processing abilities have been most promising in explaining the crash involvement of elderly drivers. This study examines the relationship of field dependence, visual search skills, and working memory to the decision to make a left turn at an intersection as well as to gap choice. Participants included thirty-three women ranging in age from 61 to 84 years. The results show that working memory plays a very important role in left-turn performance. Implications for appropriate interventions are discussed.

Accidents, Traffic↗

PubMed1989

Visuospatial working memory in Parkinson's disease.

Visuospatial impairment is frequently reported in Parkinson's disease but the psychological mechanisms which subserve the impaired abilities and the way in which breakdown of the mechanisms leads to performance deficits have not been precisely delineated. This paper reports experimental investigations designed to test the hypothesis that the locus of the impairment is the visuospatial subsystem of working memory. Subjects were a group of sixteen patients with Parkinson's disease of mild to moderate severity and a matched control group. They performed complex visuospatial and verbal memory tasks. The Parkinsonian group were significantly slower than the control group when performing the visuospatial task. They were not significantly slower and made no more errors than the control group on the verbal task. The findings are compatible with the hypothesis that the visuospatial subsystem of working memory is impaired in Parkinson's disease. It is demonstrated that the impairment is not the result of a reduction in the capacity of this subsystem but is due to difficulty in utilising information stored in the subsystem to perform complex visuospatial tasks.

Aged↗

PubMed1999

Lesions of the prelimbic-infralimbic cortices in rats do not disrupt response selection processes but induce delay-dependent deficits: evidence for a role in working memory?

Effects of neurotoxic lesions of the prelimbic-infralimbic cortex (PL-IL) were examined in rats performing 2 conditional tasks. PL-IL-lesioned rats showed normal acquisition of a visuospatial conditional discrimination in a Y maze as well as a tone-light conditional discrimination in an operant chamber, indicating that the PL-IL is not necessary for response selection processes. When the working memory load was subsequently increased in the tone-light conditional discrimination, rats with PL-IL lesions showed a delay-dependent disruption of performance. This suggests a role of the PL-IL in some working memory processes. However, the present results, considered along with previous studies, suggest that the PL-IL does not seem to be directly involved in the processes necessary to maintain specific items over a delay period but rather in the planning of forthcoming behavioral responses on the basis of previously acquired information.

Animals↗

PubMed2005

Altered functional connectivity related to white matter changes inside the working memory network at the very early stage of MS.

Functional magnetic resonance imaging (fMRI) using paced auditory serial addition test (PASAT) as paradigm was used to study the functional connectivity in 18 patients at the very early stage of multiple sclerosis (MS) compared with 18 controls, to determine the existence of circuitry disturbance inside the working memory network and its relationship with white matter abnormalities assessed by conventional MRI and magnetization transfer ratio (MTR) imaging. The left BA 45/46 was selected as the seed region to compute correlation maps with other brain regions. After obtaining the correlation map for each subject, between-group comparisons were performed using random effect procedure. Compared with controls, patients did not show any greater functional connectivity between left BA 45/46 and other regions during PASAT. In contrast, decrease in functional connectivity was observed in patients between left BA 45/46 and left BA 9, right BA 3, and the anterior cingulate cortex (BA 24). In patients, no correlations were found between altered functional connectivity and clinical data. However, functional connectivity observed between left BA 45/46 and BA 24 in patients was correlated with the MTR of normal appearing white matter, and with brain T(2) lesion load. Altered functional connectivity is present inside the working memory network of patients at the very early stage of MS and is related to the extent of diffuse white matter changes.

Acoustic Stimulation↗

PubMed1997

Effects of methylphenidate on spatial working memory and planning in healthy young adults.

Previous studies of the effects of the psychomotor stimulant, methylphenidate, have concentrated on vigilance and reaction time tasks. In this study, the effects of methylphenidate on more complex aspects of cognition were studied using tasks from the CANTAB battery and related tests which have been shown to be sensitive to frontal lobe dysfunction. Twenty-eight young healthy men participated in a counterbalanced, double-blind, placebo-controlled study of the effects of methylphenidate. Cognitive assessment included tests of spatial working memory, planning, verbal fluency, attentional set-shifting and sustained attention. Methylphenidate had significant effects on performance of the tests of spatial working memory and planning but not on the attentional and fluency tests. When the drug was taken on the first test session, performance on the spatial tests was enhanced by the drug compared to placebo. However, when the drug was taken second, performance accuracy was impaired whereas response latencies were decreased. These results are consistent with a hypothesis that methylphenidate influences performance in two conflicting ways; enhancing executive aspects of spatial function on novel tasks but impairing previously established performance. This pattern of effects is discussed within the framework of dual, interacting arousal mechanisms.

Adult↗

PubMed2001

Working memory deficits associated with chronic fatigue syndrome.

Cognitive impairments are among the most frequently reported and least investigated components of the chronic fatigue syndrome (CFS). As part of a multifaceted study of the CFS, the present study investigated the cognitive functioning of chronic fatigue patients. The performance of 20 CFS patients was compared to that of controls (N = 20) on 4 tests of working memory (WM). Digit Span Forward was used to assess the storage capacity of WM. Multiple aspects of central executive functioning were assessed using several standard measures: Digit Span Backward, and Trails A and Trails B. More recently developed measures of WM were used to assess control of processing under temporal demands (working memory task) and resistance to interference (a sustained attention task). Deficits were restricted to more demanding tasks, requiring resistance to interference and efficient switching between processing routines. The overall results clearly implicate deficits in the control aspects of central executive function in CFS.

Adolescent↗

PubMedDate not supplied

Visuospatial working memory in Turner's syndrome.

Turner's syndrome is a genetic disorder, specific to women, in which one of the X chromosomes is partially or completely deleted. This syndrome is associated with physical features such as short stature or failure in primary and secondary sexual development, together with a specific pattern of cognitive functions. It has been suggested that women affected by Turner's syndrome perform poorly in tasks measuring visuospatial abilities and have a verbal IQ significantly higher than performance IQ. Although this result has received strong empirical support, the nature of the visuospatial deficit is still unclear. Recent studies on visuospatial processes have highlighted that the underlying cognitive structure is more complex than previously suggested and several dissociations have been reported (e.g., visual vs spatial, sequential vs simultaneous, or passive vs active processes). In the present study we analyze in detail the characteristics of the visuospatial deficit associated with Turner's syndrome by presenting four young women with a comprehensive battery of tasks designed to tap all aspects of visuospatial working memory. Results confirm that Turner's syndrome is associated with a general visuospatial working memory deficit, but the pattern of performance of different cases can be different, with a greater emphasis on active visuospatial processes. and on either sequential or simultaneous spatial processes.

Adult↗

PubMed2002

Anterograde and retrograde influence of vestibular stimulation on spatial working memory.

Rats were trained in an eight-arm radial maze to explore the apparatus in search of a food reward. After completion of the training phase, some animals were submitted to a hemicerebellectomy (HCbed group), while others were used as a control group. To study the effects of vestibular stimulation on the recall of ongoing working memory information, both groups were exposed to radial maze sessions: in the first session (no-rotation), animals were confined for 30 s to the fourth arm visited without being further manipulated; in the second session (rotation), the animals were again confined for 30 s to the fourth arm visited, while the apparatus was rotated five times around its vertical axis. The effects of these manipulations on successive visits to complete the task were assessed, as well as the solving time and kinds of errors made. Errors were significantly more frequent in the control animals during the rotation session; HCbed animals were unaffected by confinement alone or by vestibular stimulation, but showed a decreased search speed. It was concluded that vestibular input is required for an adequate functioning of the working memory system devoted to the formation and consolidation of spatial mnesic traces and that the amnesic effect due to vestibular stimulation is both anterograde and retrograde in nature.

Animals↗

PubMed2001

Syntactic working memory and the establishment of filler-gap dependencies: insights from ERPs and fMRI.

In this contribution, we review an ERP experiment and an fMRI experiment which investigated the processing of German wh-questions. On the basis of the ERP results, we will discuss current models of sentence processing and resource distribution during sentence comprehension. We argue that there exists a separate cognitive or neural resource that supports syntactic working memory processes necessary for the temporary maintenance of syntactic information for the parser. In the context of wh-movement, such a memory component is necessary for establishing filler-gap dependencies. The data obtained from the fMRI experiment will be used to discuss the results of previous neuroimaging studies of sentence processing. It is claimed that syntactic working memory, rather than syntactic processing per se, is supported by Broca's Area.

Brain↗

PubMed2000

fMRI evidence of age-related hippocampal dysfunction in feature binding in working memory.

Richly detailed memories for particular events depend on processes that bind individual features of experience together. Previous cognitive behavioral research indicates that older adults have more difficulty than young adults in conditions requiring feature binding. We used functional magnetic resonance imaging (fMRI) during a working memory task to identify neural substrates of this age-related deficit in feature binding. For young, but not older, adults there was greater activation in left anterior hippocampus on combination trials (remember objects together with their locations) than on trials in which participants were told to remember only which objects or only which locations occurred. The results provide neuroimaging evidence for an age-related hippocampal dysfunction in feature binding in working memory.

Adult↗

PubMed2004

Event-related potentials in young and elderly adults during a visual spatial working memory task.

The P300 event-related brain potential (ERP) was examined in 14 young (20-29 years of age) and 16 elderly (60-82 years of age) subjects during the performance of a visuospatial memory task requiring recognition of locations. Elderly and young adults exhibited similar recognition accuracy, but recognition reaction times were significantly slower in the elderly. Midline P300 amplitudes recorded in response to visuospatial probe stimuli were significantly attenuated in the elderly, and, depending on the nature of the probe, P300 latency-derived indices indicated that both cognitive and motoric slowness characterized visuospatial recognition in the aged. The results, discussed in relation to neural mechanisms supporting working memory function, suggest that alterations in attention and processing speed may play a role in visual-spatial working memory deficits associated with normal and pathological aging.

Adult↗

PubMed2001

Interactions between frontal cortex and basal ganglia in working memory: a computational model.

The frontal cortex and the basal ganglia interact via a relatively well understood and elaborate system of interconnections. In the context of motor function, these interconnections can be understood as disinhibiting, or "releasing the brakes," on frontal motor action plans: The basal ganglia detect appropriate contexts for performing motor actions and enable the frontal cortex to execute such actions at the appropriate time. We build on this idea in the domain of working memory through the use of computational neural network models of this circuit. In our model, the frontal cortex exhibits robust active maintenance, whereas the basal ganglia contribute a selective, dynamic gating function that enables frontal memory representations to be rapidly updated in a task-relevant manner. We apply the model to a novel version of the continuous performance task that requires subroutine-like selective working memory updating and compare and contrast our model with other existing models and theories of frontal-cortex-basal-ganglia interactions.

Basal Ganglia↗

PubMed2000

Magnesium sulfate therapy affects attention and working memory in patients undergoing preterm labor.

OBJECTIVE: Patients commonly consent to undergoing invasive procedures while receiving magnesium sulfate therapy. This study evaluated the effects of magnesium sulfate on attention, comprehension, and memory in patients undergoing preterm labor. STUDY DESIGN: Consenting patients were studied while receiving(study) and not receiving (control) intravenous magnesium sulfate tocolysis for preterm labor. Excluded were patients with possible preeclampsia, imminent delivery, sedative administration, or prior mental illness. Patient comprehension was assessed with the Boston Diagnostic Aphasia Examination. Level of attention and working memory were evaluated with the Paced Auditory Serial Addition Test. Verbal learning, short-term memory, and recognition were determined with the Hopkins Verbal Learning Test. Gross mental-neurologic deficits were evaluated with the Mini-Mental Status Examination. The tests were administered by the same examiner. Control testing was performed >24 hours after intravenous magnesium sulfate was discontinued. Magnesium levels were obtained at the time of testing. The primary outcome measure was the Paced Auditory Serial Addition Test score because of its ability to elicit subtle differences in attention capacity. Statistical analysis included the paired t test and the McNemar test. RESULTS: Fifteen patients completed the study. Paced Auditory Serial Addition Test scores were significantly higher (ie, more errors were made) during magnesium sulfate therapy than periods without therapy (14 +/- 8 vs 7 +/- 7; P <.05). Comprehension (Boston Diagnostic Aphasia Examination score) was not different between the groups (P =.7). There was no difference in short-term memory (Hopkins Verbal Learning Test) or gross mental-neurologic deficits between the 2 groups (all P >.1). CONCLUSIONS: Magnesium sulfate therapy appears to have an effect on attention and working memory but not on long-term memory or comprehension. The significant differences in Paced Auditory Serial Addition Test scores reveal deficits in information-processing ability in patients on a regimen of magnesium sulfate therapy.

Adolescent↗

PubMed2004

Catechol-O-methyltransferase val108/158met genotype predicts working memory response to antipsychotic medications.

BACKGROUND: The gene encoding catechol-O-methyltransferase (COMT), an enzyme that regulates prefrontal cortex dopamine, contains a common functional polymorphism (val(108/158)met) that influences prefrontal cortex function in an allelic dose-dependent manner. A recent study reported that the COMT val(108/158)met polymorphism influences cognitive- and physiologic-related prefrontal cortex responses to antipsychotic treatment. The present study tested the effects of several COMT polymorphisms on the cognitive response to antipsychotic medication in patients with schizophrenia. METHODS: Twenty inpatients with schizophrenia or schizoaffective disorder (5 with the val-val genotype, 11 with val-met, and 4 with met-met) were administered cognitive tests at two time points: once after 4 weeks of treatment with antipsychotic medication and once after 4 weeks of placebo administration, according to a counterbalanced, double-blind, within-subject study design. RESULTS: Patients homozygous for the COMT met allele displayed significant improvement on the working memory task after treatment. Patients homozygous for the COMT val allele did not show working memory improvement with treatment. Other COMT polymorphisms were not associated with significant differences between treatment and placebo conditions. CONCLUSIONS: These results support other data suggesting that the COMT val(108/158)met polymorphism might be an important factor in the cognitive response to antipsychotic medication.

Adult↗

PubMed1991

Working memory and the aged rat: deficient two-choice win-stay water-escape acquisition and retention.

Twelve aged (22 months), 12 adult (12 months) and 12 young (3 months) male Fisher 344 rats were compared on acquisition of a two-choice win-stay (spatial delayed matching-to-sample) water-escape working memory task. The 7 aged, 10 adult and 10 young animals that attained criterion were then compared on performance of the task when the retention interval (RI) was 5, 15, 30, 60 and 120 min. They were also compared on retention after being forced to perform an unsolvable water-escape task in a second maze during the first 5 minutes of a 30-minute RI. The aged animals had longer escape latencies, and required more trials and made more errors in attaining a criterion of 9 correct choices over 10 test trials than did the adult and young animals, who did not differ from one another. Also, comparisons of the animals that attained the acquisition criterion revealed that the aged animals had longer escape latencies and made more errors across all RIs and during trials including an interpolated distraction task than did the adult and young animals. The aged animals failed to perform above chance level on tests at any of the RIs or following the distraction task, while the young animals performed above chance level on tests at all intervals and following distraction. The adult animals failed to perform above chance on tests with the 120-minute RI or following distraction. The aged rats were clearly deficient on acquisition and retention of a two-choice water-escape working memory task.

Aging↗