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Working Memory
Abstract
Working memory is the capacity to manipulate and maintain information over short periods (2–15 seconds) in order to support simple memory tasks such as remembering a telephone number, or more general cognitive tasks such as problem solving, simple reasoning, or reading. Working memory consists of several distinguishable memory capacities, together with executive functions that manage information retrieval, reactivation, and transformation.
... In such context, it is possible that an overall preference for goal referents may be a reflection of recency effects. Recency effects are a classic finding in cognitive psychology and are usually described as a property of human working memory (Dosher, 2006): Information that is presented last tends to be more active and more easily recalled. When subjects were given complete freedom on what to recall, they may have chosen to resort to goals because these were more active in their working memory. ...
This study investigates pronominal reference assignments across sentences that contain English verbs of transfer in monolingual English speakers and second-language (L2) learners having German as a first language and English as an L2. In a forced-choice task, participants were presented with sentences in perfective or imperfective aspect, like “Elizabeth took/was taking a meal to Mary” (adapted from Ferretti et al., 2009). They were then shown sentences that contained gender-matching pronouns, as in “She breathed in the smell of fresh basil”, and they were finally asked to choose who performed the relevant actions: “Who breathed in the smell of fresh basil? Elizabeth or Mary?”. We found that both groups preferred more often goal-oriented interpretations in the perfective condition, while in the imperfective condition only English monolingual speakers preferred more often source-oriented interpretations. The pattern observed in the perfective condition is consistent with previous studies and indicates that perfective aspect creates a strong bias towards end-states. For the imperfective condition, we argue that the different pattern observed in L2 learners may be due to some features of German, where an overall bias for end-states was previously observed. This indicates an effect of first-language strategies on L2 processing, consistent with previous research on different languages.
Objectives: The present study aimed to confirm the cognitive advantages of bilingualism specifically in the domain of working memory updating. Methods: A total of sixty adults (aged 20 to 26) participated in the study, divided into three groups based on bilingual status: Bilingual-similar (n = 20), Bilingual-Mongolian weighted (n = 20), and Monolingual (n= 20). Participants completed working memory update tasks involving verbal or nonver-bal stimuli. Information updated in working memory could be derived from perceptual input or long-term memory. Results: Bilingual advantages in working memory updating was found in both verbal and nonverbal task. The advantages in working memory updating depending on stimuli (verbal or nonverbal) exhibited similar patterns. However, the patterns of bilingual advantages varied depending on the source of information (percep-tual input or long-term memory). While both bilingual groups showed advantages when the information source was perceptual input, only the Bilingual-similar group showed advantages when the source was long-term memory. Conclusion: The study provides further empirical support for the cognitive benefits associated with bilingualism, particularly in the realm of working memory updating. The current findings underscore the notion that bilin-guals optimize domain-general cognitive control. Further research is needed to investigate the underlying mechanisms of information management in bilingual individuals across different information resources.
The delayed match-to-sample task (DMS) is used to probe working memory (WM) across species. While the involvement of the PFC in this task has been established, limited information exists regarding the recruitment of broader circuitry, especially under the low- versus high-WM load. We sought to address this question by using a variable-delay operant DMS task. Male Sprague-Dawley rats were trained and tested to determine their baseline WM performance across all (0- to 24-sec) delays. Next, rats were tested in a single DMS test with either 0- or 24-sec fixed delay, to assess low-/high-load WM performance. c-Fos mRNA expression was quantified within cortical and subcortical regions and correlated with WM performance. High WM load up-regulated overall c-Fos mRNA expression within the PrL, as well as within a subset of mGlu5+ cells, with load-dependent, local activation of protein kinase C (PKC) as the proposed underlying molecular mechanism. The PrL activity negatively correlated with choice accuracy during high load WM performance. A broader circuitry, including several subcortical regions, was found to be activated under low and/or high load conditions. These findings highlight the role of mGlu5- and/or PKC-dependent signaling within the PrL, and corresponding recruitment of subcortical regions during high-load WM performance.
Memory is worse for items that take longer to pronounce, even when the items are equated for frequency, number of syllables, and number of phonemes. Current explanations of the word-length effect rely on a time-based decay process within the articulatory loop structure in working memory. Using an extension of Nairne's (1990) feature model, we demonstrate that the approximately linear relationship between span and pronunciation rate can be observed in a model that does not use the concept of decay. Moreover, the feature model also correctly predicts the effects of modality, phonological similarity, articulatory suppression, and serial position on memory for items of different lengths. We argue that word-length effects do not offer sufficient justification for including time-based decay components in theories of memory.
We used positron emission tomography (PET) to answer the following question: Is working memory a unitary storage system, or does it instead include different storage buffers for different kinds of information? In Experiment 1, PET measures were taken while subjects engaged in either a spatial-memory task (retain the position of three dots for 3 sec) or an object-memory task (retain the identity of two objects for 3 sec). The results manifested a striking double dissociation, as the spatial task activated only right-hemisphere regions, whereas the object task activated primarily left-hemisphere regions. The spatial (right-hemisphere) regions included occipital, parietal, and prefrontal areas, while the object (left-hemisphere) regions included inferotemporal and parietal areas. Experiment 2 was similar to Experiment 1 except that the stimuli and trial events were identical for the spatial and object tasks; whether spatial or object memory was required was manipulated by instructions. The PET results once more showed a double dissociation, as the spatial task activated primarily right-hemisphere regions (again including occipital, parietal and prefrontal areas), whereas the object task activated only left-hemisphere regions (again including inferotemporal and parietal areas). Experiment 3 was a strictly behavioral study, which produced another double dissociation. It used the same tasks as Experiment 2, and showed that a variation in spatial similarity affected performance in the spatial but not the object task, whereas a variation in shape similarity affected performance in the object but not the spatial task. Taken together, the results of the three experiments clearly imply that different working-memory buffers are used for storing spatial and object information.
Working memory is currently a 'hot' topic in cognitive psychology and neuroscience. Because of their radically different scopes and emphases, however, comparing different models and theories and understanding how they relate to one another has been a difficult task. This volume offers a much-needed forum for systematically comparing and contrasting existing models of working memory. It does so by asking each contributor to address the same comprehensive set of important theoretical questions on working memory. The answers to these questions provided in the volume elucidate the emerging general consensus on the nature of working memory among different theorists and crystallize incompatible theoretical claims that must be resolved in future research. As such, this volume serves not only as a milestone that documents the state-of-the-art in the field but also as a theoretical guidebook that will likely promote new lines of research and more precise and comprehensive models of working memory.
This paper is concerned with the recognition of items in relatively short memorized lists, investigated with reaction time methods. The author describes some of the early experiments that led to the idea of a high speed exhaustive scanning process, and indicates some of the other processing stages that the data seem to require. Then he considers extensions and generalizations of the early findings, obtained in a number of laboratories, that show the phenomenon to be relatively robust, and the estimated scanning rate to be remarkably invariant across subject populations and practice. But effects of duplication of items in the list, their serial positions, and the relative frequency with which they are tested, show the scanning model to be either wrong, or insufficiently detailed in its description of how these effects might arise in the encoding and decision states. Such effects have led others to propose alternative models of the comparison process. He considers 3 contrasting examples: an alternative serial process involving self terminating search, a parallel process, and a direct access process involving trace strength discrimination. Each of these alternatives has weaknesses that appear to be at least as serious as the inadequacies of the exhaustive scanning model. His current preference is for a strategy of theorizing that retains the exhaustive scanning process and elaborates the model by investigating the other processing stages and considering mixtures of processes. Finally he describes 5 recent developments that seem to shed more light on the scanning process as well as on other tissues in memory research. The 'translation effect' tells us about the coding of information in memory. Work with lists of world that are organized into categories suggests that search is partially but not wholly selective. The correlation between slopes and their ratios supports the idea that the high speed of the scanning process may depend on its exhaustiveness. Extension of the paradigm to long lists in long term memory illuminates the role of familiarity in recognition and suggests elaborations of the scanning model for the case of short term memory. And the relations between the scanning rate and the immediate memory span links the recognition reaction time approach to more traditional studies of recall accuracy.
Memory for serial order is important in many aspects of daily life, including language comprehension. Despite the existence of a large and stable empirical data base, theoretical progress has lagged behind experimental work. Some of the theoretical notions to date have included chaining of associations, nonassociative storage in bins, and reverberatory loops. These concepts have been valuable for application to individual paradigms, but a unified approach has been lacking. We present an extension to Murdock's Theory of Distributed Associative Memory (TODAM) based on associative chaining between items. A distributed memory system has a number of a priori advantages; it can sustain local damage without complete failure and requires no memory search for retrieval. We applied TODAM to a number of serial order phenomena—among them serial list learning, delayed recall effects, partial reports effects, and buildup and release from proactive interference—and found that the theory provided a good quantitative description of the data with a small set of parameters. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Forgetting during recall may be one limit on memory span. Output time and accuracy of immediate serial recall using spoken and keypress responses were measured for digit, letter, and word sets approximately matched in phonemic discriminability and in immediate recognition memory. Nonetheless, the materials differed from one another in recall span, in output time during recall, and in pronunciation time (speech rate). Recall output times accounted precisely and completely for the measured memory span for these matched materials. Pronunciation times are correlated with recall output times, but output time gives a slightly better account of recall accuracy. The output time equivalent to the rule that short-term memory span corresponds to the number of items that can be said in about 1.5-2 s is that span corresponds to the number of items that can be recalled in about 4-6 s. Additional variations in span reflect differential item interference.
How do we maintain a novel sequence of items in the correct order? For example, how do we remember the car number plate at the scene of a crime? Or how do we remember an unfamiliar telephone number during the few seconds between putting down the telephone directory and picking up the telephone? This immediate serial recall or ‘memory-span’ task has fascinated psychologists for decades; it has remained the dominant empirical tool behind contemporary theories of short-term memory, such as Alan Baddeley’s working-memory theory (Baddeley, 1986). However, like many questions in cognitive psychology, the apparent ease with which we perform such a simple task (providing the telephone number is not too long!) masks a rich and complex host of issues.
Previous experiments have found that memory span is greater for items that can be pronounced more quickly. For a variety of materials the span equals the number of items that can be pronounced in about 1.5 s, presumably the duration of the verbal trace. This suggests a model for immediate recall: The probability of correctly recalling a list equals the probability that the time to recite the list is less than the variable duration of the trace. Recall probability for lists of various lengths was determined for six materials. Later, subjects read the lists aloud. The standard normal deviates corresponding to probability of correct recall were linear in pronunciation time. Evidently, over subjects, a normal distribution is a reasonable approximation of the distribution of the trace duration. The mean and variance of the trace duration were estimated. The mean (1.88 s) agrees well with previous estimates, and the model accounts for 95% of the variance in immediate recall.
The concept of working memory is central to theories of human cognition because working memory is essential to such human skills as language comprehension and deductive reasoning. Working memory is thought to be composed of two parts, a set of buffers that temporarily store information in either a phonological or visuospatial form, and a central executive responsible for various computations such as mental arithmetic. Although most data on working memory come from behavioural studies of normal and brain-injured humans, there is evidence about its physiological basis from invasive studies of monkeys. Here we report positron emission tomography (PET) studies of regional cerebral blood flow in normal humans that reveal activation in right-hemisphere prefrontal, occipital, parietal and premotor cortices accompanying spatial working memory processes. These results begin to uncover the circuitry of a working memory system in humans.
Working memory is responsible for the short-term storage and online manipulation of information necessary for higher cognitive functions, such as language, planning and problem-solving. Traditionally, working memory has been divided into two types of processes: executive control (governing the encoding manipulation and retrieval of information in working memory) and active maintenance (keeping information available 'online'). It has also been proposed that these two types of processes may be subserved by distinct cortical structures, with the prefrontal cortex housing the executive control processes, and more posterior regions housing the content-specific buffers (for example verbal versus visuospatial) responsible for active maintenance. However, studies in non-human primates suggest that dorsolateral regions of the prefrontal cortex may also be involved in active maintenance. We have used functional magnetic resonance imaging to examine brain activation in human subjects during performance of a working memory task. We used the temporal resolution of this technique to examine the dynamics of regional activation, and to show that prefrontal cortex along with parietal cortex appears to play a role in active maintenance.
A relatively simple model of the phonological loop (A. D. Baddeley, 1986), a component of working memory, has proved capable of accommodating a great deal of experimental evidence from normal adult participants, children, and neuropsychological patients. Until recently, however, the role of this subsystem in everyday cognitive activities was unclear. In this article the authors review studies of word learning by normal adults and children, neuropsychological patients, and special developmental populations, which provide evidence that the phonological loop plays a crucial role in learning the novel phonological forms of new words. The authors propose that the primary purpose for which the phonological loop evolved is to store unfamiliar sound patterns while more permanent memory records are being constructed. Its use in retaining sequences of familiar words is, it is argued, secondary.
The present study used functional magnetic resonance imaging to demonstrate that performance of visual spatial and visual nonspatial working memory tasks involve the same regions of the lateral prefrontal cortex when all factors unrelated to the type of stimulus material are appropriately controlled. These results provide evidence that spatial and nonspatial working memory may not be mediated, respectively, by mid-dorsolateral and mid-ventrolateral regions of the frontal lobe, as widely assumed, and support the alternative notion that specific regions of the lateral prefrontal cortex make identical executive functional contributions to both spatial and nonspatial working memory.
A new model of immediate serial recall is presented: the primacy model. The primacy model stores order information by means of the assumption that the strength of activation of successive list items decreases across list position to form a primacy gradient. Ordered recall is supported by a repeated cycle of operations involving a noisy choice of the most active item followed by suppression of the chosen item. Word-length and list-length effects are attributed to a decay process that occurs both during input, when effective rehearsal is prevented, and during output. The phonological similarity effect is attributed to a second stage of processing at which phonological confusions occur. The primacy model produces accurate simulations of the effects of word length, list length, and phonological similarity.
Measures of retrieval speed indicated that only a small subset of representations in working memory falls within the focus of attention. An n-back task, which required tracking an item 1, 2, or 3 back in a sequentially presented list, was used to examine the representation and retrieval of recent events and how control processes can be used to maintain an item in focal attention while concurrently processing new information. A speed-accuracy trade-off procedure was used to derive measures of the availability and the speed with which recent events can be accessed. Results converge with other time course studies in demonstrating that attention can be concurrently allocated only to a small number of memory representations, perhaps just 1 item. Measures of retrieval speed further demonstrate that order information is retrieved by a slow search process when an item is not maintained within focal attention.
Working memory is currently a 'hot' topic in cognitive psychology and neuroscience. Because of their radically different scopes and emphases, however, comparing different models and theories and understanding how they relate to one another has been a difficult task. This volume offers a much-needed forum for systematically comparing and contrasting existing models of working memory. It does so by asking each contributor to address the same comprehensive set of important theoretical questions on working memory. The answers to these questions provided in the volume elucidate the emerging general consensus on the nature of working memory among different theorists and crystallize incompatible theoretical claims that must be resolved in future research. As such, this volume serves not only as a milestone that documents the state-of-the-art in the field but also as a theoretical guidebook that will likely promote new lines of research and more precise and comprehensive models of working memory.
Brain damage can cause memory to break down in a number of different ways, the analysis of which can illuminate how the intact brain mediates memory processes. After first considering the problems involved in assessing memory, this book provisionally advances a taxonomy of elementary memory disorders and, for each in turn, reviews both the specific processes that are disrupted and the lesions responsible for the disruption. These disorders include short-term memory deficits, deficits in previously well-established memory, memory decifits caused by frontal lobe lesions, the organic amnesias, the disorders of conditioning and skill acquisition. Particular attention is paid to the organic amnesias, about which we know the most, and to the contributions of animal models to our knowledge. Andrew Mayes argues that the memory deficits found in several neurological and psychiatric syndromes comprise co-occurring elementary memory disorders. Finally, he outlines the implications of his taxonomy for our understanding of normal memory. A wide audience of researchers and students will find Human Organic Memory Disorders a helpful guide to a complex problem area.
This chapter is divided into two parts. The first describes the effect of Pat Rabbitt's influence in encouraging the first author to use the increasingly sophisticated methods of ageing research to answer questions about the fundamental characteristics of working memory, together with reflections on why so little of this work reached publication. The second part presents a brief review of the literature on working memory and ageing, followed by an account of more recent work attempting to apply the traditional method of experimental dissociation to research on normal ageing and Alzheimer's disease. The discussion suggests that even such simple methods can throw light on both the processes of ageing and the understanding of working memory.
This text, based on a course taught by Randall O'Reilly and Yuko Munakata over the past several years, provides an in-depth introduction to the main ideas in the computational cognitive neuroscience.
The goal of computational cognitive neuroscience is to understand how the brain embodies the mind by using biologically based computational models comprising networks of neuronlike units. This text, based on a course taught by Randall O'Reilly and Yuko Munakata over the past several years, provides an in-depth introduction to the main ideas in the field. The neural units in the simulations use equations based directly on the ion channels that govern the behavior of real neurons, and the neural networks incorporate anatomical and physiological properties of the neocortex. Thus the text provides the student with knowledge of the basic biology of the brain as well as the computational skills needed to simulate large-scale cognitive phenomena.
The text consists of two parts. The first part covers basic neural computation mechanisms: individual neurons, neural networks, and learning mechanisms. The second part covers large-scale brain area organization and cognitive phenomena: perception and attention, memory, language, and higher-level cognition. The second part is relatively self-contained and can be used separately for mechanistically oriented cognitive neuroscience courses. Integrated throughout the text are more than forty different simulation models, many of them full-scale research-grade models, with friendly interfaces and accompanying exercises. The simulation software (PDP++, available for all major platforms) and simulations can be downloaded free of charge from the Web. Exercise solutions are available, and the text includes full information on the software.
Bradford Books imprint
This book introduces you to the fascinating phenomena involved in human memory: the theories about how memory works, the supporting evidence for those theories, and the methods scientists use to explore human memory. With this emphasis on theory and models as well as on research, the author maintains an ideal balance between historically significant findings and current, state-of-the-art research. He vividly illustrates the process of designing and conducting diagnostic research, and in the process gives you an appreciation of experimental design. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
A number of experiments explored the hypothesis that immediate memory span is not constant, but varies with the length of the words to be recalled. Results showed: (1) Memory span is inversely related to word length across a wide range of materials; (2) When number of syllables and number of phonemes are held constant, words of short temporal duration are better recalled than words of long duration; (3) Span could be predicted on the basis of the number of words which the subject can read in approximately 2 sec; (4) When articulation is suppressed by requiring the subject to articulate an irrelevant sound, the word length effect disappears with visual presentation, but remains when presentation is auditory. The results are interpreted in terms of a phonemically-based store of limited temporal capacity, which may function as an output buffer for speech production, and as a supplement to a more central working memory system.
Individual differences in reading comprehension may reflect differences in working memory capacity, specifically in the trade-off between its processing and storage functions. A poor reader's processes may be inefficient, so that they lessen the amount of additional information that can be maintained in working memory. A test with heavy processing and storage demands was devised to measure this trade-off. Subjects read aloud a series of sentences and then recalled the final word of each sentence. The reading span, the number of final words recalled, varied from two to five for 20 college students. This span correlated with three reading comprehension measures, including verbal SAT and tests involving fact retrieval and pronominal reference. Similar correlations were obtained with a listening span task, showing that the correlation is not specific to reading. These results were contrasted with traditional digit span and word span measures which do not correlate with comprehension.
Single-unit recording studies of posterior parietal neurons have indicated a similarity of neuronal activation to that observed in the dorsolateral prefrontal cortex in relation to performance of delayed saccade tasks. A key issue addressed in the present study is whether the different classes of neuronal activity observed in these tasks are encountered more frequently in one or the other area or otherwise exhibit region-specific properties. The present study is the first to directly compare these patterns of neuronal activity by alternately recording from parietal area 7ip and prefrontal area 8a, under the identical behavioral conditions, within the same hemisphere of two monkeys performing an oculomotor delayed response task. The firing rate of 222 posterior parietal and 235 prefrontal neurons significantly changed during the cue, delay, and/or saccade periods of the task. Neuronal responses in the two areas could be distinguished only by subtle differences in their incidence and timing. Thus neurons responding to the cue appeared earliest and were more frequent among the task-related neurons within parietal cortex, whereas neurons exhibiting delay-period activity accounted for a larger proportion of task-related neurons in prefrontal cortex. Otherwise, the task-related neuronal activities were remarkably similar. Cue period activity in prefrontal and parietal cortex exhibited comparable spatial tuning and temporal duration characteristics, taking the form of phasic, tonic, or combined phasic/tonic excitation in both cortical populations. Neurons in both cortical areas exhibited sustained activity during the delay period with nearly identical spatial tuning. The various patterns of delay-period activity-tonic, increasing or decreasing, alone or in combination with greater activation during cue and/or saccade periods-likewise were distributed to both cortical areas. Finally, similarities in the two populations extended to the proportion and spatial tuning of presaccadic and postsaccadic neuronal activity occurring in relation to the memory-guided saccade. The present findings support and extend evidence for a faithful duplication of receptive field properties and virtually every other dimension of task-related activity observed when parietal and prefrontal cortex are recruited to a common task. This striking similarity attests to the principal that information shared by a prefrontal region and a sensory association area with which it is connected is domain specific and not subject to hierarchical elaboration, as is evident at earlier stages of visuospatial processing.
How do we remember the order of a novel sequence of items, such as the digits in a telephone number? This problem is addressed by eight experiments on serial recall of temporal sequences. These experiments are used to develop a new model of short-term memory for serial order, the Start-End Model (SEM).
Models of Working Memory: Mechanisms of Active Maintenance and Executive Control
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