Information In Short-term Memory Research Articles

Toward an integrative model accounting for typical and atypical development of visuospatial short-term memory

ABSTRACT The origin of visuospatial short-term memory (STM) impairment is poorly investigated and is generally considered to be the result of a more global visuospatial deficit. However, previous studies suggest an important influence of two elements on performance in visuospatial STM tasks, the mode of presentation (i.e., simultaneous and sequential), and the visuospatial arrangement (structured vs. unstructured). With regards to a recent proposal, the aim of this study was to examine the development of the two modes of presentation and the visuospatial arrangement of visuospatial information in STM in a hundred typically developing participants aged from 4 years old to adults. Moreover, we also examined how the model explains the pattern of visuospatial STM deficit in two neurodevelopmental syndromes with different profiles in terms of STM abilities, namely Williams syndrome and Down syndrome. We found distinct performance for sequential and simultaneous presentation only from 11 years old with better performance in simultaneous than in sequential presentation mode and a sensitivity to visuospatial arrangement that increases with age. Both syndromes presented deficits at different levels, people with Williams syndrome for visuospatial arrangement and with Down syndrome for simultaneous visuospatial information in STM. The results demonstrate the importance to consider the influence of preexisting visuospatial knowledge on STM abilities. A two processing route model of STM is an interesting framework to interpret the different results.

Working memory modeling using inverse fuzzy relational approach

The paper proposes a novel approach to fuzzy modeling of human working memory (WM) using electroencephalographic (EEG) signals, acquired during human face encoding and recall experiments in connection with a face recognition problem. The EEG signals acquired from the short term memory (STM) during memory encoding instances are considered as the input of the proposed working memory model. On the other hand, the EEG response of the WM to visual stimuli acquired during WM recall instances are considered as the output of the proposed working memory model. The entire experiment is primarily divided into two phases. In the first phase, the WM of a human subject is modeled by a fuzzy implication relation, describing a mapping from the STM response (during encoding) to the WM responses (during recall) to visual stimuli. During STM encoding, the subject is visually presented with the full face stimulus of a person. During WM recall, four partial face stimuli of the same person (made familiar during encoding) are used for the subject to recall the respective full face.The second phase is undertaken to validate the WM model by visually stimulating the subject again with randomly selected partial faces of people, being familiar in the first phase and the WM EEG responses are recorded. The WM responses along with the WM model, developed in the first phase, are used to retrieve the STM information by using an inverse fuzzy (implication) relation. Besides WM modeling, another important contribution of the paper lies in devising a solution to the inverse fuzzy relation computation in the settings of an optimization problem. An error metric is then defined to measure the discrepancy between the model-predicted STM encoding pattern and the actual pattern encoded by the STM (as captured by the EEG signal during encoding in the first phase). Apparently, smaller the error magnitude better is the accuracy of the proposed model to effectively differentiate people with memory failures. Experimentally it is observed that the proposed model yields a very small error, in the order of 10−4, thus showing a high level of similarity between actual and model predicted STM response for all the healthy subjects. An experiment undertaken using eLORETA software confirms that the orbito-frontal cortex of prefrontal lobe is responsible for STM encoding whereas dorsolateral prefrontal region is responsible for WM recall. An analysis undertaken reveals that the proposed WM model produces the best response in the theta frequency band of EEG spectra, thus assuring the association of the theta frequency range in the face recognition task. Comparative analysis performed also substantiates that the proposed technique of computing max–min inverse fuzzy relation outperforms the existing techniques for inverse fuzzy computation, with a successful retrieval accuracy of 87.92%. The proposed study would find interesting applications to diagnose memory failures for people with Pre-frontal lobe amnesia.

Verbal and Musical Short-Term Memory: Evidence for Shared Serial Order Processes?

This study explored the validity of an integrative framework for verbal and musical short-term memory (STM). Following this framework, access to domain-specific long-term knowledge bases supports the processing of musical and verbal item information in STM, while domain-general ordering processes support the representation of serial order information in the two domains. We exposed participants to verbal and musical STM tasks assessing either item information, order information, or both item and order information. Using an interindividual differences approach, we observed that performance in item-based STM tasks was not strongly associated between musical and verbal domains. In contrast, strong between-domain associations were observed for STM tasks assessing processing of verbal order and musical rhythm information. These preliminary results are overall in agreement with an integrative approach of verbal and musical STM. At the same time, the results highlight the difficulty of measuring serial order processing in the musical STM domain in a direct and specific manner.

Temporal grouping effects in musical short-term memory

ABSTRACTRecent theoretical accounts of verbal and visuo-spatial short-term memory (STM) have proposed the existence of domain-general mechanisms for the maintenance of serial order information. These accounts are based on the observation of similar behavioural effects across several modalities, such as temporal grouping effects. Across two experiments, the present study aimed at extending these findings, by exploring a STM modality that has received little interest so far, STM for musical information. Given its inherent rhythmic, temporal and serial organisation, the musical domain is of interest for investigating serial order STM processes such as temporal grouping. In Experiment 1, the data did not allow to determine the presence or the absence of temporal grouping effects. In Experiment 2, we observed that temporal grouping of tone sequences during encoding improves short-term recognition for serially presented probe tones. Furthermore, the serial position curves included micro-primacy and micro-recency effects, which are the hallmark characteristic of temporal grouping. Our results suggest that the encoding of serial order information in musical STM may be supported by temporal positional coding mechanisms similar to those reported in the verbal domain.

Domain-Generality of Timing-Based Serial Order Processes in Short-Term Memory: New Insights from Musical and Verbal Domains.

Several models in the verbal domain of short-term memory (STM) consider a dissociation between item and order processing. This view is supported by data demonstrating that different types of time-based interference have a greater effect on memory for the order of to-be-remembered items than on memory for the items themselves. The present study investigated the domain-generality of the item versus serial order dissociation by comparing the differential effects of time-based interfering tasks, such as rhythmic interference and articulatory suppression, on item and order processing in verbal and musical STM domains. In Experiment 1, participants had to maintain sequences of verbal or musical information in STM, followed by a probe sequence, this under different conditions of interference (no-interference, rhythmic interference, articulatory suppression). They were required to decide whether all items of the probe list matched those of the memory list (item condition) or whether the order of the items in the probe sequence matched the order in the memory list (order condition). In Experiment 2, participants performed a serial order probe recognition task for verbal and musical sequences ensuring sequential maintenance processes, under no-interference or rhythmic interference conditions. For Experiment 1, serial order recognition was not significantly more impacted by interfering tasks than was item recognition, this for both verbal and musical domains. For Experiment 2, we observed selective interference of the rhythmic interference condition on both musical and verbal order STM tasks. Overall, the results suggest a similar and selective sensitivity to time-based interference for serial order STM in verbal and musical domains, but only when the STM tasks ensure sequential maintenance processes.

Out with the old? The role of selective attention in retaining targets in partial report.

In the partial-report task, subjects are asked to report only a portion of the items presented. Selective attention chooses which objects to represent in short-term memory (STM) on the basis of their relevance. Because STM is limited in capacity, one must sometimes choose which objects are removed from memory in light of new relevant information. We tested the hypothesis that the choices among newly presented information and old information in STM involve the same process-that both are acts of selective attention. We tested this hypothesis using a two-display partial-report procedure. In this procedure, subjects had to select and retain relevant letters (targets) from two sequentially presented displays. If selection in perception and retention in STM are the same process, then irrelevant letters (distractors) in the second display, which demanded attention because of their similarity to the targets, should have decreased target report from the first display. This effect was not obtained in any of four experiments. Thus, choosing objects to keep in STM is not the same process as choosing new objects to bring into STM.

Neural mechanisms of information storage in visual short-term memory

The capacity to briefly memorize fleeting sensory information supports visual search and behavioral interactions with relevant stimuli in the environment. Traditionally, studies investigating the neural basis of visual short term memory (STM) have focused on the role of prefrontal cortex (PFC) in exerting executive control over what information is stored and how it is adaptively used to guide behavior. However, the neural substrates that support the actual storage of content-specific information in STM are more controversial, with some attributing this function to PFC and others to the specialized areas of early visual cortex that initially encode incoming sensory stimuli. In contrast to these traditional views, I will review evidence suggesting that content-specific information can be flexibly maintained in areas across the cortical hierarchy ranging from early visual cortex to PFC. While the factors that determine exactly where content-specific information is represented are not yet entirely clear, recognizing the importance of task-demands and better understanding the operation of non-spiking neural codes may help to constrain new theories about how memories are maintained at different resolutions, across different timescales, and in the presence of distracting information.

Working Memory Models: Insights From Neuroimaging.

FIGURE 1. The Atkinson and Shiffrin Model of memory is diagramed in the gray panel. Sensory information is perceived and suppressed via selective attention processes, then briefly held in the limited-capacity modality-specific sensory register. Information enhanced by selective attention enters into short term memory (STM). The process of rehearsal (maintenance) can sustain information in STM. Information in STM is automatically encoded (stored, consolidated) into long term memory (LTM). Although flawed, this model continues to provide a simple and easy approach to understanding memory. Assumptions that proved to be inconsistent with research included that any information in STM will transfer to LTM and that STM is required

Editorial: Representational states in memory: where do we stand?

Editorial: Representational states in memory: where do we stand?

Common Neural Substrates for Ordinal Representation in Short-Term Memory, Numerical and Alphabetical Cognition

The representation and maintenance of serial order information is one of the main functions of verbal short-term memory (STM) but its neural correlates remain poorly understood. We show here that the neural substrates allowing for coding of order information in STM are shared with those supporting ordinal processing in the numerical and alphabetical domains. We designed an fMRI experiment determining the neural substrates sensitive to ordinal distance effects in numerical judgment, alphabetical judgment and serial order STM tasks. Null conjunction analyses for parametric ordinal distance effects showed a common involvement of the horizontal segment of the left intraparietal sulcus over the three tasks; in addition, right intraparietal sulcus involvement was also observed for ordinal distance effects in the STM and numerical judgment tasks. These findings demonstrate that shared neural correlates in the intraparietal cortex support processing of order information in verbal STM, number and alphabetical domains, and suggest the existence of domain general, potentially ordinal, comparison processes supported by the left intraparietal sulcus.

A common short-term memory retrieval rate may describe many cognitive procedures

We examine the relationship between response speed and the number of items in short-term memory (STM) in four different paradigms and find evidence for a similar high-speed processing rate of about 25–30 items per second (∼35–40 ms/item). We propose that the similarity of the processing rates across paradigms reflects the operation of a very basic covert memory process, high-speed retrieval, that is involved in both the search for information in STM and the reactivation or refreshing of information that keeps it in STM. We link this process to a specific pattern of rhythmic, repetitive neural activity in the brain (gamma oscillations). This proposal generates ideas for research and calls for an integrative approach that combines neuroscientific measures with behavioral cognitive techniques.

Multiple neural states of representation in short-term memory? It’s a matter of attention

Short-term memory (STM) refers to the capacity-limited retention of information over a brief period of time, and working memory (WM) refers to the manipulation and use of that information to guide behavior. In recent years it has become apparent that STM and WM interact and overlap with other cognitive processes, including attention (the selection of a subset of information for further processing) and long-term memory (LTM—the encoding and retention of an effectively unlimited amount of information for a much longer period of time). Broadly speaking, there have been two classes of memory models: systems models, which posit distinct stores for STM and LTM (Atkinson and Shiffrin, 1968; Baddeley and Hitch, 1974); and state-based models, which posit a common store with different activation states corresponding to STM and LTM (Cowan, 1995; McElree, 1996; Oberauer, 2002). In this paper, we will focus on state-based accounts of STM. First, we will consider several theoretical models that postulate, based on considerable behavioral evidence, that information in STM can exist in multiple representational states. We will then consider how neural data from recent studies of STM can inform and constrain these theoretical models. In the process we will highlight the inferential advantage of multivariate, information-based analyses of neuroimaging data (fMRI and electroencephalography (EEG)) over conventional activation-based analysis approaches (Postle, in press). We will conclude by addressing lingering questions regarding the fractionation of STM, highlighting differences between the attention to information vs. the retention of information during brief memory delays.

Complex working memory span in cochlear implanted and normal hearing teenagers.

The individual’s capacity to maintain attention and process new information in the face of distraction is known in the literature as working memory (WM). Short term memory (STM) is used to encode and retain information for a short period of time. WM tasks are functionally distinct from STM tasks because they require not only information encoding, storage and rehearsal, but also include a processing/manipulation component requiring a dual task load, such as judging semantic acceptability of a sentence. STM tasks, such as word span or digit span, may be considered a subset of WM. STM requires simple storage, whereas WM requires a storage component as well as an active attention and control process. WM tasks have been found to differ from simple span tasks in their predictive validity, measuring variance that is unique from STM 1. The current model of working memory developed by Baddeley and his colleagues consists of four components2, (1) a domain-general central executive that controls attention and processing activities and regulates the flow of information in the processing system, (2) the phonological loop that is used for the temporary storage of verbal phonological memory codes, (3) the visual-spatial sketchpad that maintains and processes visual and spatial representations, and (4) the episodic buffer that is used to integrate and bind memory codes from different processing domains into larger chunks of information. The complex reading span task developed by Daneman & Carpenter 3 is among the most widely used tools for measuring the central executive function. The reading span task requires the participant to perform two operations at once: 1) read a series of sentences aloud and make a semantic acceptability judgment about the sentence and 2) keep track of the last word of each sentence so that the words can be recalled later. Reading span tasks have been found to have good reliability (i.e., .70 to .90) across a number of studies. Furthermore, performance on reading span tasks has been found to predict complex cognitive processes such as comprehension, problem solving and reasoning – all tasks that require “executive attention” 1. Reading span is thought to measure the capacity of the central executive because it requires simultaneous storage and processing of phonological and lexical information. Verbal storage uses a phonological loop, composed of a short-term phonological store subject to rapid decay plus a subvocal rehearsal process that can be used to refresh decaying representations within the store. Individuals with normal hearing perform similarly whether the task is presented through listening or through reading 3. However, WM estimates might be expected to differ considerably for reading and listening tasks in populations with significant hearing loss. Memory skills in Children with Hearing Loss Memory studies of children with hearing loss have primarily used STM tasks. Stiles et al, 4 compared performance of 6-9 year olds with mild to moderate HL with NH age mates on both phonological and visuospatial STM tasks. Although articulation rate and vocabulary were lower in children with hearing loss than in age-mates with normal hearing, there was no significant effect of hearing loss on memory performance,. This stands in contrast to results for children with greater hearing losses who use CIs. Watson, et al, 5 found a marked impairment on digit span and non-word repetition measures for children with CIs compared to NH children. Similar results were reported by Pisoni6 for digit span results obtained in CI users tested in both elementary grades and high school. When WM processes rely on verbal rehearsal and serial scanning of phonological information in STM, early severe-profound auditory deprivation seems to impair normal development. Reinstatement of auditory sensation in children with CIs was not sufficient to enable adequate development. Further evidence of this impairment is provided by examining the relationship between mismatch negativity activation and memory span. Connections between pre-attentive auditory sensory memory and “higher language functions” were apparent in NH children but not in age-matched CI users 5.

Short-term memory, working memory, and syntactic comprehension in aphasia

Sixty-one people with aphasia were tested on 10 tests of short-term memory (STM) and for the ability to use syntactic structure to determine the meanings of 11 types of sentences in three tasks—object manipulation, picture matching, and picture matching with self-paced listening. Multilevel models showed relationships between measures of the ability to retain and manipulate item and order information in STM and accuracy and reaction time (RT), and a greater relationship between these STM measures and accuracy and RT for several more complex sentence types in individual tasks. There were no effects of measures of STM that reflect the use of phonological codes or rehearsal on comprehension. There was only one effect of STM measures on self-paced listening times. There were double dissociations between performance on STM and individual comprehension tasks, indicating that normal STM is not necessary to perform normally on these tasks. The results are most easily related to the view that STM plays a facilitatory role in supporting the use of the products of the comprehension process to accomplish operations related to tasks.

Parallel Processing of Appetitive Short- and Long-Term Memories In Drosophila

It is broadly accepted that long-term memory (LTM) is formed sequentially after learning and short-term memory (STM) formation, but the nature of the relationship between early and late memory traces remains heavily debated [1-5]. To shed light on this issue, we used an olfactory appetitive conditioning in Drosophila, wherein starved flies learned to associate an odor with the presence of sugar [6]. We took advantage of the fact that both STM and LTM are generated after a unique conditioning cycle [7, 8] to demonstrate that appetitive LTM is able to form independently of STM. More specifically, we show that (1) STM retrieval involves output from γ neurons of the mushroom body (MB), i.e., the olfactory memory center [9, 10], whereas LTM retrieval involves output from αβ MB neurons; (2) STM information is not transferred from γ neurons to αβ neurons for LTM formation; and (3) the adenylyl cyclase RUT, which is thought to operate as a coincidence detector between the olfactory stimulus and the sugar stimulus [11-14], is required independently in γ neurons to form appetitive STM and in αβ neurons to form LTM. Taken together, these results demonstrate that appetitive short- and long-term memories are formed and processed in parallel.

Dissociable contributions of prefrontal cortex and the hippocampus to short-term memory: Evidence for a 3-state model of memory

Behavioral research has yielded conflicting results regarding the architecture of short-term memory (STM). Whereas a consensus has emerged that within STM a single chunk within the focus of attention (FA) has a privileged status, it is unclear whether further distinctions exist. One proposal is that outside of FA, memory is all of one sort with a continuous progression from STM to long-term memory (LTM). On the other hand, sharp performance drop-offs when STM is loaded with more than 4±1 items suggest distinctions between STM and LTM. We use functional magnetic resonance imaging (fMRI) to adjudicate between these theories. A neural triple dissociation provided evidence for a 3-state model of memory. Critically, prefrontal cortex was selectively enhanced to retrieval from activated portions of LTM whereas the hippocampus was associated with retrieval of items within putative 4±1 capacity limits. We hypothesize that the associative properties of the hippocampus serve to inter-relate information actively maintained in STM which not only promotes strong STM, but also lays the foundations for subsequent LTM. By contrast, information not actively maintained in mind requires top-down retrieval processes mediated by the prefrontal cortex. These data provide key insights into the architecture of STM and its relationship to LTM.

Processing spatial–temporal information in recent-onset schizophrenia: The study of short-term memory and its susceptibility to distraction

Memory impairment is a core feature in schizophrenia (SZ). The aim of this study was to investigate short-term memory (STM) and its sensitivity to distraction with visual–spatial material. This study comprised 23 recent-onset SZ patients and 23 healthy controls. The degree of disruption upon recall from interleaving irrelevant items within a sequence of to-be-remembered items—the sandwich effect [Hitch, G. J. (1975). The role of attention in visual and auditory suffix effects. Memory and Cognition, 3, 501–505]—was examined. STM performance, whether in the presence or absence of distraction, was poorer and markedly more vulnerable to disruption in SZ. Our results suggest that processing spatial information in STM is susceptible to interference in SZ.

The role of dorsolateral prefrontal cortex in the preparation of forthcoming actions: an fMRI study.

The dorsolateral prefrontal cortex (DLPFC) plays a key role in working memory (WM). Yet its precise contribution (the storage, manipulation and/or utilization of information for the forthcoming response) remains to be determined. To test the hypothesis that the DLPFC is more involved in the preparation of actions than in the maintenance of information in short-term memory (STM), we undertook a functional magnetic resonance imaging investigation in normal subjects performing two delayed response tasks (matching and reproduction tasks) in a visuospatial task sequence (presentation, delay, response). In the two tasks, the presentation and delay phases were similar, but the expected response was different: in the matching task, subjects had to indicate whether a visuospatial sequence matched the sequence presented before the delay period; in the reproduction task, subjects had to reproduce the sequence and, therefore, to mentally organize their response during the delay. Using a fMRI paradigm focusing on the delay period, we observed a significant DLPFC activation when subjects were required to mentally prepare a sequential action based on the information stored in STM. When subjects had only to maintain a visuospatial stimulus in STM, no DLPFC activation was found. These results suggest that a parietal-premotor network is sufficient to store visuospatial information in STM whereas the DLPFC is involved when it is necessary to mentally prepare a forthcoming sequential action based on the information stored in STM.

Working memory impairments in multiple sclerosis: Evidence from a dual-task paradigm.

The aim of this study was to investigate working memory in multiple sclerosis (MS) patients. To test the hypothesis that the central executive system (CES) of working memory is impaired, 36 MS patients were administered a dual-task paradigm in which a judgment of line orientation measure was performed concurrently with finger tapping, humming a melody, or reciting the alphabet. MS patients exhibited a significantly greater decrement in performance than controls during the more demanding dual-task conditions (concurrent humming or alphabet recitation) as compared with the single-task condition. Dual-task performance in MS patients correlated with performance on the Paced Auditory Serial Addition Test but not with other cognitive or clinical measures. The authors conclude that MS patients have a working memory deficit reflecting an impaired central executive system. Moreover, impairments in speed of information processing in MS patients are associated with this CES deficit. Memory dysfunction is the most common cognitive impairment observed in patients with multiple sclerosis (MS). A long-term memory deficit in these patients is well documented (Grafman, Rao, & Litvan, 1990), but most early studies of MS patients have concluded that short-term memory (STM) is intact. Support for this claim was derived from the observation of a normal digit span, as well as an intact recency effect on supraspan list learning, measures commonly used to assess STM (Caine, Bamford, Schiffer, Shoulson, & Levy, 1986; Rao, Hammeke, McQuillen, Khatri, & Lloyd, 1984). Although most studies continue to focus on the long-term memory impairments in MS patients (Rao, Leo, & Aubin-Faubert, 1989), evidence is accumulating that STM deficits may also exist (Grigsby, Ayarbe, Kravcism, & Busenbark, 1994; Rao et al., 1993). However, the nature of these deficits remain unclear. The purpose of this study was to further investigate STM processing in MS patients. Several experimental tasks have been useful for identifying impairment in various aspects of STM in MS patients. One experimental measure, the Brown-Peterson task (Peterson & Peterson, 1959), measures consolidation of information in STM and the effect of interference on temporarily stored information. With this task, two groups of investigators (Beatty, Goodkin, Monson, Beatty, & Hertsgaard, 1988; Grant,

Short-Term Retention of Pitch Sequence

This research focused on short-term memory (STM) and the extent to which pitch sequence length and pitch position within a sequence affect the amount of pitch information losi between offset of the stimulus and the time of perceptual report. Loss of pitch information in STM was shown as a result of increased time before recall, the position of a pitch within a sequence (recency > primacy > center), and the increased length of a sequence. It was also demonstrated that loss of pitch information due to an increased number of pitch items stored in STM was dependent upon the amount of time before report. Moreover, time was shown to be a selective function depending upon the pitch position in a melodic sequence. Implications were indicated for research design in several areas. These included music perception, pedagogical and measurement techniques in eartraining instruction, and programed instruction design in melodic dictation and sight-singing.