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PubMed1999

Breakfast cereal and caffeinated coffee: effects on working memory, attention, mood, and cardiovascular function.

This study examined the effects of breakfast cereal and caffeinated coffee on working memory, attention, mood, and cardiovascular function. One hundred and forty-four volunteers (72 male, 72 female, mean age 21 years) were assigned to one of the groups formed by combining breakfast (cereal versus no breakfast) and caffeine (caffeinated versus decaffeinated coffee) conditions. The volunteers completed a baseline session between 0800 and 0845 h. The breakfast/caffeine administration took place between 0845 and 0915 h. They then completed another test session (starting at 0945) and had a coffee break at 1045, followed by a final session starting at 1145. The results showed that those who consumed breakfast cereal had a more positive mood at the start of the test sessions, performed better on a spatial memory task, and felt calmer at the end of the test session than those in the no breakfast condition. Ingestion of caffeine had no effect on initial mood or working memory, but it did improve encoding of new information and counteracted the fatigue that developed over the test session. Caffeine increased blood pressure and pulse rate, whereas breakfast cereal consumption only had an effect on pulse. Overall, these results confirm previous findings on the effects of breakfast and caffeine, and demonstrate distinct profiles for two common examples of early-morning food and drink, breakfast cereal and caffeinated coffee.

Adult↗
PubMed1997

Encoding into working memory of spatial location, color, and shape: electrophysiological investigations.

Event-related potentials (ERP) were recorded while subjects memorized either the location, the color or the shape of stimuli which could be located in 1 of 4 positions relative to a central fixation point (top, bottom, left or right), be of 1 of 4 positions relative to a central fixation point (top, bottom, left or right), be of 1 of 4 colors (white, green, red or blue), and present 1 of 4 shapes (triangle, cross, circle or square). These ERP were compared to ERP recorded while subjects looked at the same stimuli but performed other control, nonmemory tasks. Only ERP corresponding to the memorization of spatial location showed a differential pattern which could be specifically attributed to memory encoding processes. This reveals an important difference in ERP modulation between a working memory subsystem for spatial location and other subsystem (or subsystems) for color or shape, which would provide evidence supporting the existence of different working memory subsystems for visual information in the brain.

Adolescent↗
PubMedDate not supplied

Physical activity moderates time-of-day differences in older adults' working memory performance.

Based on a synthesis of the literature on time of day and physical fitness effects on cognition, the current study examined whether physical activity moderated time-of-day differences in older adults' performance on a working memory task. Sedentary older adults' working memory performance declined significantly from morning to evening, whereas more active older adults performed similarly across the day. This interaction did not extend to performance on a simple reaction time task. A novel explanation based on the selective effect of mental fatigue on executive control processes is proposed.

Aged↗
PubMed2005

Neurophysiological correlates of increased verbal working memory in high-dissociative participants: a functional MRI study.

BACKGROUND: Dissociation, defined as a disruption in usually integrated mental functions, is found not only in DSM-IV dissociative disorders, but also in post-traumatic stress disorder and eating disorders. Dissociative phenomena are also common in the general population, and may reflect a constitutionally determined cognitive style rather than a pathological trait acquired through experiencing adverse life events. In pathological dissociation, evidence has been presented for episodic memory dysfunction. In contrast, in high-dissociative subjects increased performance has been found for episodic memory and dual task performance. These findings have been linked to changes in working memory capacity. METHOD: In the present study, the authors sought to extend these findings by using functional magnetic resonance imaging during performance of two parametric working memory tasks. We tested 21 healthy low- and high-dissociative participants. RESULTS: High-dissociative participants performed slightly better during both tasks. Imaging data showed that both groups activated similar networks for both tasks, i.e. (bilateral) dorsolateral (DL) and ventrolateral prefrontal cortex (PFC), parietal cortex, and supplementary motor area. Group x task interactions were found in the high-dissociative group in L DLPFC and L parietal cortex; in the low-dissociative group in R fusiform gyrus. The differences in the high-dissociative group were independent from performance differences, implying that high-dissociative subjects generally recruit this network to a greater extent. CONCLUSIONS: These results confirm earlier findings using a verbal WM task in high-dissociative participants, and are compatible with the conceptualization of non-pathological dissociation as an information-processing style, characterized by distinct attentional and mnemonic abilities.

Adult↗
PubMed2006

Prefrontal dysfunction in schizophrenia controlling for COMT Val158Met genotype and working memory performance.

Earlier studies with functional imaging in schizophrenia have demonstrated dysfunction of the dorsolateral prefrontal cortex during working memory. Controlling for behavioral performance and for catechol-O-methyltransferase (COMT) Val158Met genotype, we here demonstrate in a functional magnetic resonance imaging paradigm that patients recruit greater neuronal resources in prefrontal cortex during working memory, suggesting that this phenotype is a core functional trait of the disease. We also replicated earlier findings that the Val allele of the COMT polymorphism is associated with greater engagement of the prefrontal cortex.

Adult↗
PubMed2003

Children's working-memory processes: a response-timing analysis.

Recall response durations were used to clarify processing in working-memory tasks. Experiment 1 examined children's performance in reading span, a task in which sentences were processed and the final word of each sentence was retained for subsequent recall. Experiment 2 examined the development of listening-, counting-, and digit-span task performance. Responses were much longer in the reading-and listening-span tasks than in the other span tasks, suggesting that participants in sentence-based span tasks take time to retrieve the semantic or linguistic structure as cues to recall of the sentence-final words. Response durations in working-memory tasks helped to predict academic skill and achievement, largely separate from the contributions of the memory spans themselves. Response durations thus are important in the interpretation of span task performance.

Child↗
PubMed2003

Dissecting contributions of prefrontal cortex and fusiform face area to face working memory.

Interactions between prefrontal cortex (PFC) and stimulus-specific visual cortical association areas are hypothesized to mediate visual working memory in behaving monkeys. To clarify the roles for homologous regions in humans, event-related fMRI was used to assess neural activity in PFC and fusiform face area (FFA) of subjects performing a delay-recognition task for faces. In both PFC and FFA, activity increased parametrically with memory load during encoding and maintenance of face stimuli, despite quantitative differences in the magnitude of activation. Moreover, timing differences in PFC and FFA activation during memory encoding and retrieval implied a context dependence in the flow of neural information. These results support existing neurophysiological models of visual working memory developed in the nonhuman primate.

Adult↗
PubMed2005

Load- and practice-dependent increases in cerebro-cerebellar activation in verbal working memory: an fMRI study.

Load-dependent and practice-related changes in neocortical and cerebellar structures involved in verbal working memory (VWM) were investigated using functional MRI (fMRI) and a two alternative forced choice Sternberg paradigm. Using working memory loads ranging from 2 to 6 letters, regions exhibiting linear and quadratic trends in load-dependent activations were identified. Behaviorally, reaction time measurements revealed significant linear increases with increasing memory load, and significant decreases with increased task practice. Brain activations indicated a preponderance of linear load-dependent responses in both superior (lobule VI/Crus I) and inferior (lobule VIIB/VIIIA) cerebellar hemispheres, as well as in areas of neocortex including left precentral (BA 6), inferior frontal (BA 47), parahippocampal (BA 35), inferior parietal (BA 40), cingulate (BA 32), and right inferior and middle frontal (BA 46/47) regions. Fewer voxels exhibited quadratic without linear trends with the most prominent of these activations located in left inferior parietal (BA 40), precuneus, and parahippocampal regions. Analysis of load x session interactions revealed that right inferior cerebellar and left inferior parietal activations increased with practice, as did the correlations between activation in each region with reaction time, suggesting that changes in this cerebro-cerebellar network underlie practice-related increases in efficiency of VWM performance. These results replicate and extend our previous findings of fMRI activation in the cerebellum during VWM, and demonstrate predominately linear increases in cerebro-cerebellar activation with increasing memory load as well as changes in network function with increased task proficiency.

Adult↗
PubMed1992

Individual differences in working memory and comprehension: a test of four hypotheses.

A relationship has consistently been found between measures of working memory and reading comprehension. Four hypotheses for this relationship were tested in 3 experiments. In the first 2 experiments, a moving window procedure was used to present the operation-word and reading span tasks. High- and low-span subjects did not differentially trade off time on the elements of the tasks and the to-be-remembered word. Furthermore, the correlation between span and comprehension was undiminished when the viewing times were partialed out. Experiment 3 compared a traditional experimenter-paced simple word-span and a subject-paced span in their relationship with comprehension. The experimenter-paced word-span correlated with comprehension but the subject-paced span did not. The results of all 3 experiments support a general capacity explanation for the relationship between working memory and comprehension.

Adult↗
PubMedDate not supplied

Executive control emerging from dynamic interactions between brain systems mediating language, working memory and attentional processes.

In this theoretical paper, we review findings from a series of recent behavioral and functional neuroimaging studies of working memory and executive control which provide evidence for the following theses: 1. Working memory in humans is represented by two brain systems which differ from each other with respect to their functional-neuroanatomical organization and probably also with respect to their evolutionary origin. 2. One of these brain systems relies on prefronto-parietal and prefronto-temporal cortical networks that presumably also mediate attentional selection by the top-down modulation of domain-specific sensory association areas towards behaviorally relevant information. 3. The other system is implemented by mainly left-hemispheric premotor and parietal brain regions which to a greater part also underlie language functions and which may also be involved in the retrieval and maintenance of verbal goal representations during advance preparation for task switches. 4. Context-sensitive behavioral adaptation is supported by a complementary mechanism for the detection of conflicts and for the triggering of cognitive control processes that relies on parts of the medial frontal cortex. Based on these empirical results reported in the literature we propose a neurocognitive model of executive control according to which the human ability to flexibly adapt to changing behavioral requirements, i.e. executive control, depends on dynamic and context-sensitive interactions between these brain systems.

Attention↗
PubMed2004

Simultaneous cognitive operations in working memory after dual-task practice.

The authors tested the hypothesis that with adequate practice, people can execute 2 cognitive operations in working memory simultaneously. In Experiment 1, 6 students practiced updating 2 items in working memory through 2 sequences of operations (1 numerical, 1 spatial). In different blocks, imperative stimuli for the 2 sequences of operations were presented either simultaneously or sequentially. Initially, most participants experienced substantial dual-task costs. After 24 sessions of practice, operation latencies for simultaneous presentation were equal to the maximum of times for the 2 operations in the sequential condition, suggesting perfect timesharing. Experiment 2 showed that a reduction of dual-task costs requires practice on the combination of the 2 updating tasks, not just practice on each individual task. Hence, the reduction of dual-task costs cannot be explained by shortening or automatization of individual operations.

Cognition↗
PubMed2005

Effects of prenatal alcohol exposure on attention and working memory at 7.5 years of age.

BACKGROUND: A broad range of attentional and neuropsychological impairments have been demonstrated in children with fetal alcohol exposure. This study was designed to investigate which specific aspects of attentional function are most directly affected by moderate to heavy doses of prenatal alcohol exposure. METHODS: A total of 337 black children who were aged 7.5 years and recruited prospectively to overrepresent prenatal alcohol exposure at moderate to heavy levels were assessed on a diverse battery of neuropsychological tests. Principal components analyses were used to replicate and extend Mirsky et al.'s (1991) four-component model of attention. The relation of prenatal alcohol exposure to empirically derived attentional constructs was examined. RESULTS: Both the replicated and the extended attentional models produced solutions similar to the original Mirsky et al. model, reflecting elements of encode (working memory), shift, and focused and sustained attention, as well as a distinct component reflecting impulsivity. Adverse effects of maternal drinking across pregnancy were found primarily for working memory, and these effects were exacerbated when mothers were aged 30 or older at the time of the child's birth. CONCLUSIONS: These data confirm previous studies using diverse methods that suggest that working memory may be the most important aspect of attention that is adversely affected by prenatal alcohol exposure.

Adult↗
PubMedDate not supplied

A re-examination of the role of basal forebrain cholinergic neurons in spatial working memory.

The basal forebrain cholinergic system, which innervates widespread cortical and limbic structures, has traditionally been considered important for learning and memory. The use of an immunotoxin, 192 IgG-saporin, has brought this functional designation into question; selective immunolesions of basal forebrain cholinergic neurons have failed to reproduce a number of behavioral deficits that were observed with less selective lesion methods. Recent reports, however, have indicated that a mild impairment is observed in rats on a spatial working memory task after 192 IgG-saporin lesions of the rostral groups of cholinergic neurons located in the medial septal area (MSA). Those studies used a lesion protocol in which a single large volume injection of the immunotoxin was made into the MSA. In the current study, multiple small injections were made at the locations of cholinergic neurons in the MSA, producing a cholinergic depletion comparable to that reported in the earlier studies where deficits were observed. In the current study, however, rats with cholinergic lesions had no impairment in the spatial working memory task, even when delays ranging from 60 s to 8 h were imposed within a trial. The current report indicates that selective removal of cholinergic neurons in the basal forebrain may not be sufficient to produce a deficit in spatial working memory.

Animals↗
PubMed2005

Working memory in the chick: parallel and lateralized mechanisms for encoding of object- and position-specific information.

Working memory of chicks was probed in a delayed-response task, with either object- or position-specific information available in order to locate a goal that had disappeared behind one of two screens in a test arena. When the position of the correct screen was the only available cue (i.e., the two screens were identical) binocular and monocular chicks could easily locate the goal, and the same occurred when the visual characteristics of the screens (no matter what their spatial position) were the only relevant information available and when object- and position-specific cues were both available and in agreement (i.e., the two screens were different and maintained fixed spatial locations). In contrast, when object- and position-specific cues were available but were put in conflict (the two screens were different and were swapped during the delay time) left-eyed and binocular chicks went to the correct position, whereas right-eyed chicks seemed to choose both the correct spatial position and the correct object cue to the same degree. When during the delay the correct screen was substituted by an entirely novel screen, no left-right asymmetry associated with response to novelty was observed; monocular chicks preferentially approached the novel screen in the correct position, whereas binocular chicks did not show any clear choice. The results suggest that both object- and position-specific information is available to the two cerebral hemispheres in working memory tasks; however, when a conflict between cues arises, the right hemisphere preferentially attends to position-specific cues, whereas the left hemisphere tends to attend to object-specific cues.

Animals↗
PubMedDate not supplied

Cognitive aging and inhibitory efficiency in the Daneman and Carpenter's working memory task.

This study tests the hypothesis that the ability to inhibit already processed and actually irrelevant information influences performance in the reading span task (RST). French versions of the Stroop color-word task and of the Daneman and Carpenter's RST were administered to 151 participants from 30 to 80 years. In addition to the traditional span score, a score of vulnerability to intrusions was also computed as the number of intruding responses (words from preceding trials of the RST or nonfinal words). An analysis of variance showed a significant age effect on the reading span and on the resistance to interference, but no significant age effect on the vulnerability to intruding responses. A multiple-regression analysis was also made with the reading span score as the dependent variable, and with age, vulnerability to intrusions, and resistance to Stroop interference as independent variables. This analysis revealed that there was a relation between participants' vulnerability to intruding responses and their working memory span scores; the contribution of age and resistance to interference were very weak. In conclusion the present findings first support the idea that the working memory capacity undoubtedly involves some inhibitory control; however, because the participants' vulnerability to intruding responses is not clearly affected by age, the present findings also suggest that some part of age effects upon the working memory span has to be explained by another factor than a growing inefficiency in inhibitory control.

Adult↗
PubMedDate not supplied

Assessing markers of working memory function in dissociative identity disorder using neutral stimuli: a comparison with clinical and general population samples.

OBJECTIVES: Memory functioning is a central conceptual and phenomenological aspect of dissociative identity disorder (DID). Most empirical work on memory functions in DID has focused on retrieval deficits either within or between dissociated identities. The current study attempted to remedy the scant attention given to working memory functioning. METHOD: In samples representing the DID, non-clinical, depressed, posttraumatic stress disorder (PTSD) and psychosis populations (n = 10 per group), neutral stimuli were used to examine three markers of working memory functioning: one measuring inhibition; one assessing facilitation; and one measuring interference. RESULTS: With the exception of the psychosis sample all groups displayed significant negative priming in the distractor inhibition condition. Facilitation effects were demonstrated by the DID and PTSD groups only. Interference effects were evident in all samples, though the DID and non-clinical groups demonstrated significantly more interference than the psychosis cohort. Distractor inhibition was related to overall schizotypy scores, and dissociation was related to scores in the facilitation condition. CONCLUSIONS: The DID sample displayed a completely distinct functional working memory profile to the psychosis sample when assessed with emotionally neutral stimuli. However, the working memory profile in the DID sample was not entirely dissimilar to the other comparison groups.

Adolescent↗
PubMed1994

Event-related brain potential evidence for a verbal working memory deficit in multiple sclerosis.

Memory deficits are frequently identified in patients with multiple sclerosis. Both working (short-term) and long-term memory appear affected, particularly on free-recall tasks. The focus of our study was to examine neurophysiological correlates of working memory processes and to identify the specific components responsible for the working memory deficits reported in multiple sclerosis. Event-related brain potentials (ERPs) were recorded from the scalp of mildly afflicted multiple sclerosis patients and their matched normal controls during the performance of phonological and visuo-spatial working memory tasks. Neuropsychological test, behavioural performance and ERP data all indicated that verbal working memory is especially susceptible to impairment by multiple sclerosis, while visuospatial working memory is less susceptible. The pattern of results further indicated that the verbal working memory dysfunction in multiple sclerosis is at least partially due to impairment in the phonological loop, a rehearsal mechanism for retaining verbal information in working memory.

Adult↗
PubMed2000

Complementary neural mechanisms for tracking items in human working memory.

Recognition of a specific visual target among equally familiar distracters requires neural mechanisms for tracking items in working memory. Event-related functional magnetic resonance imaging revealed evidence for two such mechanisms: (i) Enhanced neural responses, primarily in the frontal cortex, were associated with the target and were maintained across repetitions of the target. (ii) Reduced responses, primarily in the extrastriate visual cortex, were associated with stimulus repetition, regardless of whether the stimulus was a target or a distracter. These complementary neural mechanisms track the status of familiar items in working memory, allowing for the efficient recognition of a currently relevant object and rejection of irrelevant distracters.

Cerebral Cortex↗