Scheduling processes in working memory: instructions control the order of memory search and mental arithmetic

Humans must often use working memory to execute processes one at a time because of its limited capacity. Two experiments tested where limits in access to working memory occur. Subjects searched a short-term memory set for one stimulus digit and performed mental arithmetic with another stimulus digit. In one experiment, they were told to carry out the mental arithmetic before the memory search and to make the arithmetic response first. In the other, they were instructed to perform the tasks in the opposite order. The overt responses were executed in the prescribed order. Moreover, the covert working memory processes were executed in the prescribed order, as revealed by a critical path network analysis of reaction times. Results are explained in terms of a double-bottleneck model in which central processes and responses are constrained to be carried out for one task at a time.     

Hippocampal seizures disrupt working memory performance but not reference memory acquisition.

The effect of hippocampal seizures in rats was assessed in two spatial memory tasks: The reference memory task was a simultaneous two-choice discrimination in a T-maze. The working memory task was a delayed conditional discrimination in a radial arm maze. In each task the hippocampus of each rat was stimulated to seizure after the presentation of the information to be remembered. In the reference memory task, hippocampal seizures did not impair acquisition, whether the stimulation was given immediately after or 4 hr after the presentation of the stimuli to be remembered. In the working memory task, hippocampal seizures did impair performance in a group of the same rats. These results support the distinction between a trial-dependent working memory system that requires hippocampal function and a trial-independent memory system that does not depend on hippocampal function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relationships of working memory, secondary memory, and general fluid intelligence: Working memory is special.

Recent efforts have been made to elucidate the commonly observed link between working memory and reasoning ability. The results have been inconsistent, with some work suggesting that the emphasis placed on retrieval from secondary memory by working memory tests is the driving force behind this association (Mogle, Lovett, Stawski, & Sliwinski, 2008), whereas other research suggests retrieval from secondary memory is only partly responsible for the observed link between working memory and reasoning (Unsworth & Engle, 2006, 2007). In the present study, we investigated the relationship between processing speed, working memory, secondary memory, primary memory, and fluid intelligence. Although our findings show that all constructs are significantly correlated with fluid intelligence, working memory—but not secondary memory—accounts for significant unique variance in fluid intelligence. Our data support predictions made by Unsworth and Engle (2006, 2007) and suggest that the combined need for maintenance and retrieval processes present in working memory tests makes them special in their prediction of higher order cognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

All updateable objects in working memory are updated whenever any of them are modified: Evidence from the memory updating paradigm.

In a series of experiments, participants were required to keep track of 1 or 2 working memory (WM) objects, having to update their values in 80% of the trials. Updating cost, defined as the difference between update and non-update trials, was larger when 2 objects were involved compared with when there was only 1 object was involved. This finding was interpreted as evidence that the updating process encompasses both objects in WM, even though only 1 of them is actually updated. This feature of WM updating is limited to objects defined as "updateable," throughout the trial sequence. The results are explained by the need to reprogram the phonological loop when updating or the need for desynchronization followed by resynchronization of WM contents. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The aging of working memory.

Research concerned with relations between adult age and working memory is reviewed, especially that relevant to the A. D. Baddeley (e.g., see PA, Vol 79:26150; see also Baddeley & G. J. Hitch, 1974) model of working memory. The evidence suggests that although increased age is associated with lower scores on measures of working memory functioning, many of the age-related influences appear to be mediated by a slower speed of processing. Furthermore, recent studies indicate that slower processing primarily influences the time required to achieve a stable encoding of the information rather than the rate at which information is lost across time or subsequent processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fimbria-Fornix lesions impair spatial working memory but not cognitive mapping.

Evaluated the relative merits of 2 theories of hippocampal function, the cognitive mapping theory, and the working memory theory. 49 albino male rats were tested in a series of maze tasks that varied in memory requirements. In Exps I and III, which required cognitive mapping but not working memory, Ss with fimbria–fornix lesions reached stable levels of performance that were as accurate as those of controls, and they also performed accurately during transfer tests, demonstrating that they used a cognitive mapping strategy to solve the discrimination. In Exp II, which required working memory, Ss with fimbria–fornix lesions performed at chance levels during all of postoperative testing, and they distributed their choices randomly between the correct and the incorrect goals. Results are consistent with the predictions of the working memory but not the cognitive mapping theory. Additional analyses examined the nature of a transitory impairment exhibited by Ss with fimbria–fornix lesions in 2 tasks that did not require working memory. Postoperatively, the performance of the Ss with lesions was initially impaired but recovered to normal levels with a time course similar to that seen during preoperative acquisition. Results require an extension of the working memory theory of hippocampal function, and discussion is focused on the possibility of a temporary retrograde amnesia following fimbria–fornix lesions and the distinctions between different types of memory abilities. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

All letters are not equal: Subgraphemic texture in orthographic working memory.

A central issue in the study of reading and spelling has been to understand how the consistency or frequency of letter-sound relationships affects written language processing. We present, for the first time, evidence that the sound–spelling frequency of subgraphemic elements of words (letters within digraphs) contributes to the accuracy with which these letters are produced in spelling. We report findings from 2 studies that demonstrate that letters within digraphs display differential susceptibility to error under conditions of disruption to orthographic working memory (O-WM). In the 1st, O-WM was disrupted as a result of neurological damage; in the 2nd, O-WM disruption was produced in neurologically intact, skilled spellers under dual task conditions with a shadowing task carried out during spelling. In both studies, segments with low versus high levels of sound–letter convergence, a measure of the frequency of sublexical mappings, were more vulnerable to disruption even when factors such as letter position, consonant–vowel context, and phoneme-to-grapheme mapping probability of the digraphs were controlled. These results contribute to our understanding of the internal texture of orthographic representations, providing evidence that individual letters differ in their activation strength and, as a result, in their susceptibility to error. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Manipulation of working memory information is impaired in Parkinson's disease and related to working memory capacity.

It has been suggested that in patients with Parkinson's disease (PD), difficulties in the manipulation of information, which result in problems in executive tasks, are related to a reduction of working memory capacity (J. D. E. Gabrieli, J. Singh, G. T. Stebbins, & C. G. Goetz, 1996). The present study selectively varied the manipulation demand irrespective of the maintenance requirement. In a group of 14 PD patients, performance declined overproportionally with the increasing task demand and was significantly correlated with a measure of working memory capacity. These results suggest that the complexity of working memory processing may decisively contribute to the exhaustion of resources in PD patients. Increasing complexity may either affect their manipulation ability directly or impede the management of inhibitory control requirements inherent to the task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Complex span versus updating tasks of working memory: The gap is not that deep.

How to best measure working memory capacity is an issue of ongoing debate. Besides established complex span tasks, which combine short-term memory demands with generally unrelated secondary tasks, there exists a set of paradigms characterized by continuous and simultaneous updating of several items in working memory, such as the n-back, memory updating, or alpha span tasks. With a latent variable analysis (N = 96) based on content-heterogeneous operationalizations of both task families, the authors found a latent correlation between a complex span factor and an updating factor that was not statistically different from unity (r = .96). Moreover, both factors predicted fluid intelligence (reasoning) equally well. The authors conclude that updating tasks measure working memory equally well as complex span tasks. Processes involved in building, maintaining, and updating arbitrary bindings may constitute the common working memory ability underlying performance on reasoning, complex span, and updating tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Self-report measures of prospective memory are reliable but not valid.

Are self-report measures of prospective memory (ProM) reliable and valid? To examine this question, 240 undergraduate student volunteers completed several widely used self-report measures of ProM including the Prospective Memory Questionnaire (PMQ), the Prospective and Retrospective Memory Questionnaire (PRMQ), the Comprehensive Assessment of Prospective Memory (CAPM) questionnaire, self-reports of retrospective memory (RetM), objective measures of ProM and RetM, and measures of involvement in activities and events, memory strategies and aids use, personality and verbal intelligence. The results showed that both convergent and divergent validity of ProM self-reports are poor, even though we assessed ProM using a newly developed, reliable continuous measure. Further analyses showed that a substantial proportion of variability in ProM self-report scores was due to verbal intelligence, personality (conscientiousness, neuroticism), activities and event involvement (busyness), and use of memory strategies and aids. ProM self-reports have adequate reliability, but poor validity and should not be interpreted as reflecting ProM ability. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Mnemonic search, but not arithmetic transformation, is associated with psychophysiological inhibition.

The possibility that mnemonic search and arithmetic transformation induce transient heart rate (HR) slowing was studied. Transient HR slowing was assumed to result from the inhibition of premature responding during information processing. Twenty young men performed a 2-step reaction time task. Two precues were followed by a choice cue: 2 additional precues and 1 final choice cue. Choice cues were varied to compare spatial and perceptual-motor processing with mnemonic or arithmetic processing. Cardiac interbeat interval and impedance cardiograph measures were taken beat by beat. The preparation for the respond cue was associated with HR slowing followed by HR speeding associated with response initiation. Mnemonic search induced a transient HR slowing before the speeding initiated by the motor response. Arithmetic transformation did not, but processing of the arithmetic series decreased cue-induced transient HR slowing. Mnemonic search may be associated with a psychophysiological inhibition analogous to that observed in perceptual-motor tasks during response selection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuropsychology and working memory: A review.

Reviews the relationship between neuropsychological approaches to human memory and the working memory theory introduced by A. D. Baddeley and G. J. Hitch (1974). It is argued that neuropsychological perspectives have made a number of different contributions to the development of the theory. On occasion, they have provided unique natural experiments that cannot be simulated in the laboratory and that represent a significant input to theoretical refinement. They also yield a rich source of information on a central tenet of working memory theory, which is that the components of working memory support everyday complex cognitive activities. Neuropsychological studies have played an important role in identifying the contributions of the phonological loop to the acquisition and processing of language and of the visuospatial sketchpad to learning to recognize new faces. More generally, neuropsychological investigations have substantially reinforced developments of theory based on work from the experimental laboratory, and they provide convincing evidence for the robustness and generality of the theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Do the contents of working memory capture attention? Yes, but cognitive control matters.

There has been a controversy on whether working memory can guide attentional selection. Some researchers have reported that the contents of working memory guide attention automatically in visual search (D. Soto, D. Heinke, G. W. Humphreys, & M. J. Blanco, 2005). On the other hand, G.F. Woodman and S. J. Luck (2007) reported that they could not find any evidence of attentional capture by working memory. In the present study, we tried to find an integrative explanation for the different sets of results. We report evidence for attentional capture by working memory, but this effect was eliminated when search was perceptually demanding or the onset of the search was delayed long enough for cognitive control of search to be implemented under particular conditions. We suggest that perceptual difficulty and the time course of cognitive control as important factors that determine when information in working memory influences attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of working memory capacity in retrieval.

The verbal fluency task that 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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of working memory in decoding emotions.

Decoding facial expressions of emotion is an important aspect of social communication that is often impaired following psychiatric or neurological illness. However, little is known of the cognitive components involved in perceiving emotional expressions. Three dual task studies explored the role of verbal working memory in decoding emotions. Concurrent working memory load substantially interfered with choosing which emotional label described a facial expression (Experiment 1). A key factor in the magnitude of interference was the number of emotion labels from which to choose (Experiment 2). In contrast the ability to decide that two faces represented the same emotion in a discrimination task was relatively unaffected by concurrent working memory load (Experiment 3). Different methods of assessing emotion perception make substantially different demands on working memory. Implications for clinical disorders which affect both working memory and emotion perception are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual and spatial working memory are not that dissociated after all: A time-based resource-sharing account.

Examinations of interference between visual and spatial materials in working memory have suggested domain- and process-based fractionations of visuo-spatial working memory. The present study examined the role of central time-based resource sharing in visuo-spatial working memory and assessed its role in obtained interference patterns. Visual and spatial storage were combined with both visual and spatial on-line processing components in computer-paced working memory span tasks (Experiment 1) and in a selective interference paradigm (Experiment 2). The cognitive load of the processing components was manipulated to investigate its impact on concurrent maintenance for both within-domain and between-domain combinations of processing and storage components. In contrast to both domain- and process-based fractionations of visuo-spatial working memory, the results revealed that recall performance was determined by the cognitive load induced by the processing of items, rather than by the domain to which those items pertained. These findings are interpreted as evidence for a time-based resource-sharing mechanism in visuo-spatial working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial septal lesions disrupt spatial, but not nonspatial, working memory in rats.

In Exp 1, rats with small medial septal lesions were less able than were control rats to remember the location of the arm of a Y maze they had been forced to enter on the preceding sample run. Moreover, as the retention interval between the sample and choice runs on this spatial delayed nonmatching-to-sample (DNMTS) task was increased to 1 and 2 min, the magnitude of the deficit increased. In contrast, these same lesioned rats were not deficient in Exp 2 in their ability to remember the object they had encountered in the straight alley on the sample run. In fact, when the retention interval was increased to 1 min on this nonspatial DNMTS task, the rats with medial septal lesions were more accurate than were the controls. This pattern of results did not appear to be due to task difficulty, recovery of function, or sequence of training. Rather, these results indicate that damage to the septohippocampal system disrupts spatial working memory more than it disrupts nonspatial working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developments in the concept of working memory.

The authors summarize developments in the concept of working memory as a multicomponent system, beginning by contrasting this approach with alternative uses of the term working memory. According to a 3-component model, working memory comprises a phonological loop for manipulating and storing speech-based information and a visuospatial sketchpad that performs a similar function for visual and spatial information. Both are supervised by a central executive, which functions as an attentional control system. A simple trace-decay model of the phonological loop provides a coherent account of the effects of word length, phonemic similarity, irrelevant speech, and articulatory suppression in verbal short-term memory tasks. This model of the loop has also proved useful in the analysis of neuropsychological, developmental and, cross-cultural data. The notion of the sketchpad is supported by selective interference with imagery in normal adults and by specific neuropsychological impairment. Analysis of the central executive is illustrated by work on deficits in the ability to coordinate subproccesses in Alzheimer's disease (AD). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reduced working memory span in Parkinson's disease: Evidence for the role of frontostriatal system in working and strategic memory.

Working and strategic memory were examined in unmedicated patients with Parkinson's disease who had neither depression nor dementia. The patients, relative to control participants, had reduced working memory spans for verbal and arithmetic materials. They also had impairment on strategic memory tests of fee recall, temporal ordering, and self-ordered pointing, but no impairment on tests of recognition memory and semantic memory. Impairments in working memory capacity correlated with impairments in strategic memory and with a measure of perceptual-motor speed, but not with motor speed. It is hypothesized that a frontostriatal memory system, in which dopamine plays a critical role, mediates perceptual-motor processing speed that contributes to working memory capacity, which in turn, contributes to strategic memory performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)