Working Memory System Research Articles

A Basal Ganglia Network Centric Reinforcement Learning Model and Its Application in Unmanned Aerial Vehicle

Reinforcement learning brings flexibility and generality for machine learning, while most of them are mathematical optimization driven approaches, and lack of cognitive and neural evidence. In order to provide a more cognitive and neural mechanisms driven foundation and validate its applicability in complex task, we develop a basal ganglia (BG) network centric reinforcement learning model. Compared to existing work on modeling BG, this paper is unique from the following perspectives: 1) the orbitofrontal cortex (OFC) is taken into consideration. OFC is critical in decision making because of its responsibility for reward representation and is critical in controlling the learning process, while most of the BG centric models do not include OFC; 2) to compensate the inaccurate memory of numeric values, precise encoding is proposed to enable working memory system remember important values during the learning process. The method combines vector convolution and the idea of storage by digit bit and is efficient for accurate value storage; and 3) for information coding, the Hodgkin-Huxley model is used to obtain a more biological plausible description of action potential with plenty of ionic activities. To validate the effectiveness of the proposed model, we apply the model to the unmanned aerial vehicle (UAV) autonomous learning process in a 3-D environment. Experimental results show that our model is able to give the UAV the ability of free exploration in the environment and has comparable learning speed as the Q learning algorithm, while the major advances for our model is that it is with solid cognitive and neural basis.

Vorhersage von modalitätsspezifischen Arbeitsgedächtnisleistungen im Kindergartenalter

Working memory (WM) as a central cognitive construct is a fundamental prerequisite for learning and provides a marker of developmental disorders. It has received considerable attention in recent years. Here, multivariate regression analyses using generalized linear models were conducted to determine predictor variables for phonological and visuospatial WM. The phonological WM was investigated by repetition of non-words (subtest PGN of the German SETK 3-5) and number recall (K-ABC-subtest), the visuospatial WM by the imitation of a sequence hand movements (K-ABC-subtest hand movements). The estimation of intelligence was operationalized by the performance in the K-ABC-scale "Simultaneous Processing". Kindergarten kids (N = 169; 49 % boys; 51 % girls), mostly with migration background and German as second language (mean age: 45.9; SD 6.2; min 36, max 61 months). They visited the kindergarten at the time of testing for 9.9 (SD 6.9) months, on average and had an average intelligence. Independent variables were chronological age, gender, kindergarten attendance until the test examination, intelligence, migration background. Both phonological and visuospatial working WM performance were on average not reduced. Chronological age and simultaneous processing were found to be significant predictors for the performance in all WM tests. In the age from 36 to 61 months both working memory systems can be described as a congenital, maturity-dependent and rather gender non-specific mechanism.

A More Rigorous Examination of the Effects of Mindfulness Meditation on Working Memory Capacity

Working memory is a core cognitive system that is thought to support many forms of complex cognition. Mindfulness meditation has shown promise in improving the functioning of the working memory system, but no study has thoroughly tested its benefits by using a well-controlled study design (i.e., using multiple, valid outcome measures and an active, adaptive control group). The main goal of the current study was to more rigorously examine the effects of mindfulness meditation on working memory capacity. This was done by comparing 2 weeks of focused attention mindfulness meditation training to active, adaptive cognitive training regarding improvement on multiple, valid indicators of working memory capacity that were different from the tasks participants trained on. The results of the present experiment suggest that 2 weeks of focused attention mindfulness meditation training does not improve working memory capacity when controlling for non-specific effects. Future interventions using similar well-controlled study designs can consider using longer duration, more frequent, or alternative styles of mindfulness meditation training to potentially enhance working memory capacity.

A preliminary psychometric evaluation of the eight-item cognitive load scale

AimThe aim of this article is to report the psychometric properties of the eight-item cognitive load scale. BackgroundAccording to cognitive load theory, the formatting and delivery of healthcare education influences the degree to which patients and/or family members can engage their working memory systems for learning. However, despite its relevance, cognitive load has not yet been evaluated among surrogate decision makers exposed to electronic decision support for healthcare decisions. To date, no psychometric analyses of instruments evaluating cognitive load have been reported within healthcare settings. MethodsA convenience sample of 62 surrogate decision makers for critically ill patients were exposed to one of two healthcare decision support interventions were recruited from four intensive care units at a tertiary medical center in Northeast Ohio. Participants were administered a battery of psychosocial instruments and the eight-item cognitive load scale (CLS). ResultsThe CLS demonstrated a bidimensional factor structure with acceptable discriminant validity and internal consistency reliability (Cronbach's α = 0.75 and 0.89). ConclusionsThe CLS is a psychometrically sound instrument that may be used in the evaluation of decision support among surrogate decision makers of the critically ill. The authors recommend application of the cognitive load scale in the evaluation and development of healthcare education and interventions.

How context features modulate the involvement of the working memory system during discourse comprehension

Using functional magnetic resonance imaging (fMRI), we investigated the effects of context features on the involvement of the working memory (WM) system during discourse comprehension. During the fMRI scan, participants were asked to read two-sentence discourses in which the topic of the second sentence was either maintained, or was shifted from, the topic of the first. Changes in the level of coherence between the two sentences as well as context length were also investigated across discourse items. The WM system was identified with a verbal N-back task. Analysis of the reading comprehension task revealed that within the WM system, stronger activation in the left inferior frontal gyrus corresponded with increased bridging coherence demands between sentences, while greater activation in the left inferior and middle frontal gyri, bilateral superior frontal gyri, and bilateral inferior parietal lobules corresponded with increased context length. Topic variation showed no effect on activation of the WM system. These results provide new insights into understanding how different levels of context features modulate activation of the subcomponents of the WM system and indicate a role for the left inferior frontal gyrus as a core component of the WM system supporting discourse processing.

Critical care nurses' knowledge and practice regarding life-threatening ventricular dysrhythmias

Working memory is widely discussed in competitive sports. Researchers have systematically investigated the working memory system in the field of sports which was mainly based on papers publishing in English. Therefore, it is essential, in our opinion, to provide an overview of papers focusing on working memory and its relevance in sport psychology which were published in other languages, like Chinese. The China National Knowledge Infrastructure (CNKI) database was searched in November 2017, with no date restrictions, chose the theme as index item and index words were athlete and working memory (index mode was specific match). Studies were included if they were empirical research which used quantification index to demonstrate their results (investigated the relation of working memory and athlete), contained a population of athlete, involved in working memory task, published on normal domestic journals or the thesis of master or doctor. In total, 41 citations were identified, 13 of which were retrieved for full-text indexed and then conducted a quantitative analysis. There was little amount of studies in this field and most of which used scales and experimental research design methods. The studies contained the effect of working memory on athlete cognition and performance, the detriment of working memory because of combat sports as well as the impact factors on athlete working memory. Research of working memory and athlete in China gets some achievements. Inter-disciplinary research and working memory training will be trends of this field in the future.

Giving A Hand To Pilots With Animated Alarms Based On Mirror System Functioning

Controlled Flight Into Terrain (CFIT) accidents are among the most frequent and deadly accidents in aviation (IATA, 2016). Pilots have sometimes only a few seconds to react to the ‘Pull-Up’ alarm that indicates an imminent collision with the ground. The auditory modality of the alarm can generate stress, which can disrupt cognitive processes (Porcelli et al., 2008) and negatively impact the ability to take timely and appropriate actions (Scholz et al., 2009). While in general humans are less sensitive to auditory stimuli than to visual stimuli (Mrugalska et al. 2016), the auditory component of the ‘Pull-Up’ alarm is loud and prominent whereas its visual component is more discreet (i.e., small text). Consequently, a first step to enhance the efficiency of this alarm would be to increase the conspicuity of its visual component by enlarging the ‘Pull-Up’ text size and to increase its salience by displacing it from the artificial horizon to the bottom of the Primary Flight Display (PFD). However, enlarging the inscription may not be sufficient to cope with the loss of cognitive performance due to stress (BEA, 2009). Previous researched found that watching an action activates premotor cortex and pre-initiates the gesture imitation through the mirror neuron system (Ocampo & Kritikos, 2011). Therefore, presenting a video of the gesture to perform (i.e., a hand pulling the sidestick), in case of imminent impact with the ground, should pre-activate the motor reaction to the alarm and then improve the pilots’ performance in terms of reaction time. The present experiment aimed at assessing whether these ‘Pull-Up’ video better performance than more conventional ‘Pull-Up’ alarms. Both behavioral and electroencephalographic (EEG) results were used to assess the best alarm design.

Working memory network alterations in high-functioning adolescents with an autism spectrum disorder.

People with autism spectrum disorder (ASD) typically have deficits in the working memory (WM) system. WM is found to be an essential chain in successfully navigating in the social world. We hypothesize that brain networks for WM have an altered network integrity in ASD compared to controls. Thirteen adolescents (one female) with autistic disorder (n = 1), Asperger's disorder (n = 7), or pervasive developmental disorder not otherwise specified (n = 5), and 13 typically developing healthy control adolescents (one female) participated in this study. Functional magnetic resonance imaging (MRI) was performed using an n-back task and in resting state. The analysis of the behavioral data revealed deficits in WM performance in ASD, but only when tested to the limit. Adolescents with ASD showed lower binary global efficiency in the WM network than the healthy control group with n-back and resting-state data. This correlated with diagnostic scores for total problems, reciprocity, and language. Adolescents with higher-functioning autism have difficulty with the WM system, which is typically compensated. Functional MRI markers of brain network organization in ASD are related to characteristics of autism as represented in diagnostic scores. Therefore, functional MRI provides neuronal correlates for memory difficulties in adolescents with ASD.

Commentary on Pierce, Genesee, Delcenserie, and Morgan

Early linguistic experiences are intimately tied to later language learning outcomes (e.g., Chilosi et al., 2013; Kaushanskaya & Marian, 2009b). The underlying neural and cognitive processes mediating this relationship remain unclear. Pierce, Genesee, Delcenserie, and Morgan (2017) propose that the phonological working memory (PWM) system is the critical component responsible for linking early linguistic experiences to later language development. Their argument arises from research demonstrating that exposure to linguistic input early in life shapes the kinds of phonological representations that are formed about the sounds within one's native language (Kuhl, 2004; Majerus et al., 2005; Mody, Schwartz, Gravel, & Ruben, 1999; Nittrouer & Burton, 2005). These phonological representations, which the authors believe to be created and stored using the PWM system (Gathercole & Baddeley, 1989), are highly predictive of later language outcomes (Bernhardt, Kemp, & Werker, 2007; Kuhl, 2010; Molfese & Molfese, 1985; Tsao, Liu, & Kuhl, 2004). Explaining language development via memory processes has many benefits. For instance, drawing on a large extant literature on memory-related processes allows researchers to make novel predictions about language learning, especially in regard to its connections to other kinds of learning (e.g., Gathercole, 2006). Identifying PWM as a key driver to language development is a useful insight likely to generate much further research, but it may not go far enough in tying language acquisition to more domain-general aspects of the human cognitive architecture. We believe that a complete account of language will require consideration of additional aspects of the human cognitive architecture working alongside the PWM system.

Novel Measures to Assess the Effects of Partial Sleep Deprivation on Sensory, Working, and Permanent Memory.

Sleepiness has repeatedly been demonstrated to affect performance on a variety of cognitive tasks. While the effects of total sleep deprivation (TSD) have been extensively studied, acute partial sleep deprivation (PSD), a more frequent form of sleep loss, has been studied much less often. The present study examined the effects of sleep deprivation on novel tasks involving classic sensory, working, and permanent memory systems. While the tasks did implicate different memory systems, they shared a need for effortful, sustained attention to maintain successful performance. Because of the novelty of the tasks, an initial study of the effects of TSD was carried out. The effects of PSD were subsequently examined in a second study, in which subjects were permitted only 4 h of sleep. A general detrimental effect of both total and PSD on accuracy of detection was observed and to a lesser extent, a slowing of the speed of responding on the different tasks. This overall effect is best explained by the often-reported inability to sustain attention following sleep loss. Specific effects on distinct cognitive processes were also observed, and these were more apparent following total than PSD.

Considering the (separable) influences of phonological sensitivity and working memory on language learning outcomes

In their keynote article examining links between early experience, phonological working memory, and language outcomes, Pierce, Genessee, Delcenserie, and Morgan (2017) present, what I argue, is a two-pronged hypothesis. In brief, the thesis is that the timing of language exposure and the quality and quantity of language input during an early sensitive period of phonological development shape the quality of phonological representations later used by the phonological working memory system to support short- and long-term language learning. The hypothesis is two-pronged because it hinges on (a) qualitative differences in the development of phonological representations, resulting in (b) variations in the efficiency of working memory as the key constraint on language learning. In this commentary, I examine support for these two prongs in detail.

Are Episodic Buffer Processes Intact in ADHD? Experimental Evidence and Linkage with Hyperactive Behavior.

Working memory deficits are present in a substantial proportion of children with ADHD, and converging evidence links these deficits with ADHD-related behavioral and functional impairments. At the same time, working memory is not a unitary construct, and evidence is lacking regarding the role of several components of this system in ADHD. Preclinical behavioral studies are needed to fractionate the multicomponent working memory system, determine which specific subcomponent(s) are impaired in ADHD, and more importantly link these subcomponent(s) with specific ADHD-related behavioral symptoms/functional impairments. The current study reflects one piece of that puzzle, and focuses on the episodic buffer component of working memory. Across multiple testing days, a well-characterized sample of 86 children ages 8-13 (M=10.52, SD=1.54; 34 girls; 64% Caucasian/Non-Hispanic) with ADHD (n=49) and without ADHD (n=37) completed three counterbalanced working memory tests that were identical in all aspects except the key subcomponent process (phonological, visuospatial, episodic buffer). Gross motor movement during these and control tasks were measured using 4 high-precision actigraphs. There was no evidence of group differences in gender, age, SES, or IQ. Bayesian mixed-model ANOVAs indicated that the ADHD group performed significantly worse on all three working memory tests (d=1.17-1.44) and was significantly more hyperactive than controls (d=0.66-1.05) during the visuospatial and episodic buffer tests. In contrast, the ADHD and Non-ADHD groups were equivalent with regard to effects of episodic buffer demands on performance and hyperactive behavior. The most parsimonious conclusion is that the episodic buffer is likely intact in ADHD, and unrelated to ADHD hyperactivity symptoms.

A neuronal retuning hypothesis of sentence-specificity in Broca's area.

It is clear that the left inferior frontal gyrus (LIFG) contributes in some fashion to sentence processing. While neuroimaging and neuropsychological evidence support a domain-general working memory function, recent neuroimaging data show that particular subregions of the LIFG, particularly the pars triangularis (pTri), show selective activation for sentences relative to verbal working memory and cognitive control tasks. These data suggest a language-specific function rather than a domain-general one. To resolve this apparent conflict, I propose separating claims ofdomain-generality and specificity independently for computations and representations-a given brain region may respond to a specific representation while performing a general computation over that representation, one shared with other systems. I hypothesize that the pTri underlies a language-specific working memory system, comprised of general memory retrieval/attention operations specialized for syntactic representations. There is a parallelism of top-down retrieval function among the phonological and semantic levels, localized to the pars opercularis and pars orbitalis, respectively. I further explore the idea of how such a system emerges in the human brain through the framework of neuronal retuning: the "borrowing" of domain-general mechanisms for language, either in evolution or development. The empirical data appear to tentativelysupport a developmental account of language-specificity in the pTri, possibly through connections to the posterior superior temporal sulcus (pSTS), a region that is both anatomically distinct for humans and functionally essential for language. Evidence of representational response specificity obtained from neuroimaging studies is useful in understanding how cognition is implemented in the brain. However, understanding the shared computations across domains and neural systems is necessary for a fuller understanding of this problem, providing potential answers to questions of how specialized systems, such as language, are implemented in the brain.

Monkeys and humans take local uncertainty into account when localizing a change

Since sensory measurements are noisy, an observer is rarely certain about the identity of a stimulus. In visual perception tasks, observers generally take their uncertainty about a stimulus into account when doing so helps task performance. Whether the same holds in visual working memory tasks is largely unknown. Ten human and two monkey subjects localized a single change in orientation between a sample display containing three ellipses and a test display containing two ellipses. To manipulate uncertainty, we varied the reliability of orientation information by making each ellipse more or less elongated (two levels); reliability was independent across the stimuli. In both species, a variable-precision encoding model equipped with an “uncertainty–indifferent” decision rule, which uses only the noisy memories, fitted the data poorly. In both species, a much better fit was provided by a model in which the observer also takes the levels of reliability-driven uncertainty associated with the memories into account. In particular, a measured change in a low-reliability stimulus was given lower weight than the same change in a high-reliability stimulus. We did not find strong evidence that observers took reliability-independent variations in uncertainty into account. Our results illustrate the importance of studying the decision stage in comparison tasks and provide further evidence for evolutionary continuity of working memory systems between monkeys and humans.

Suppression of irrelevant sounds during auditory working memory

Auditory working memory (WM) processing in everyday acoustic environments depends on our ability to maintain relevant information online in our minds, and to suppress interference caused by competing incoming stimuli. A challenge in communication settings is that the relevant content and irrelevant inputs may emanate from a common source, such as a talkative conversationalist. An open question is how the WM system deals with such interference. Will the distracters become inadvertently filtered before processing for meaning because the primary WM operations deplete all available processing resources? Or are they suppressed post perceptually, through an active control process? We tested these alternative hypotheses by measuring magnetoencephalography (MEG), EEG, and functional MRI (fMRI) during a phonetic auditory continuous performance task. Contextual WM maintenance load was manipulated by adjusting the number of “filler” letter sounds in-between cue and target letter sounds. Trial-to-trial variability of pre- and post-stimulus activations in fMRI-informed cortical MEG/EEG estimates was analyzed within and across 14 subjects using generalized linear mixed effect (GLME) models. High contextual WM maintenance load suppressed left auditory cortex (AC) activations around 250–300 ms after the onset of irrelevant phonetic sounds. This effect coincided with increased 10–14 Hz alpha-range oscillatory functional connectivity between the left dorsolateral prefrontal cortex (DLPFC) and left AC. Suppression of AC responses to irrelevant sounds during active maintenance of the task context also correlated with increased pre-stimulus 7–15 Hz alpha power. Our results suggest that under high auditory WM load, irrelevant sounds are suppressed through a “late” active suppression mechanism, which prevents short-term consolidation of irrelevant information without affecting the initial screening of potentially meaningful stimuli. The results also suggest that AC alpha oscillations play an inhibitory role during auditory WM processing.

Differences in brain morphology and working memory capacity across childhood.

Working memory (WM) skills are closely associated with learning progress in key areas such as reading and mathematics across childhood. As yet, however, little is known about how the brain systems underpinning WM develop over this critical developmental period. The current study investigated whether and how structural brain correlates of components of the working memory system change over development. Verbal and visuospatial short‐term and working memory were assessed in 153 children between 5.58 and 15.92 years, and latent components of the working memory system were derived. Fractional anisotropy and cortical thickness maps were derived from T1‐weighted and diffusion‐weighted MRI and processed using eigenanatomy decomposition. There was a greater involvement of the corpus callosum and posterior temporal white matter in younger children for performance associated with the executive part of the working memory system. For older children, this was more closely linked with the thickness of the occipitotemporal cortex. These findings suggest that increasing specialization leads to shifts in the contribution of neural substrates over childhood, moving from an early dependence on a distributed system supported by long‐range connections to later reliance on specialized local circuitry. Our findings demonstrate that despite the component factor structure being stable across childhood, the underlying brain systems supporting working memory change. Taking the age of the child into account, and not just their overall score, is likely to be critical for understanding the nature of the limitations on their working memory capacity.

Limitations of working memory capacity: The cognitive and social consequences

This paper aimed to explore, from the perspective of cognitive psychology, the natural limitations of human cognition that determine our capabilities to deal with information overflow. These limitations are related mainly to the working memory system. This system is conceived to be composed of the storage components, which are responsible for active maintenance, and executive control that supervises the storage units. People differ in their working memory capacities, and because virtually every complex cognitive activity requires the temporal availability of a certain amount of cognitive representations, these differences are predictive of many outcomes. In the area of ‘cold’ cognition, these outcomes include intelligence and verbal reasoning, multitasking, language comprehension and verbal fluency, whereas in the area of ‘hot’ cognition, they include mentalising, stereotyping and self-control. Natural limitations in working memory capacity may be overcome (to some extent) through the training of working memory skills or the application of processing strategies (e.g. task simplification, using external environment as in situated or distributed cognition, changing a code of mental representation).

Clear evidence for item limits in visual working memory

There is a consensus that visual working memory (WM) resources are sharply limited, but debate persists regarding the simple question of whether there is a limit to the total number of items that can be stored concurrently. Zhang and Luck (2008) advanced this debate with an analytic procedure that provided strong evidence for random guessing responses, but their findings can also be described by models that deny guessing while asserting a high prevalence of low precision memories. Here, we used a whole report memory procedure in which subjects reported all items in each trial and indicated whether they were guessing with each response. Critically, this procedure allowed us to measure memory performance for all items in each trial. When subjects were asked to remember 6 items, the response error distributions for about 3 out of the 6 items were best fit by a parameter-free guessing model (i.e. a uniform distribution). In addition, subjects’ self-reports of guessing precisely tracked the guessing rate estimated with a mixture model. Control experiments determined that guessing behavior was not due to output interference, and that there was still a high prevalence of guessing when subjects were instructed not to guess. Our novel approach yielded evidence that guesses, not low-precision representations, best explain limitations in working memory. These guesses also corroborate a capacity-limited working memory system – we found evidence that subjects are able to report non-zero information for only 3–4 items. Thus, WM capacity is constrained by an item limit that precludes the storage of more than 3–4 individuated feature values.

Verbal and visual-spatial working memory: What develops over a life span?

This study investigates whether age-related changes in the structure of 5 complex working memory (WM) tasks (a) reflect a general or domain specific system, (b) follows a similar trajectory across different age spans, and (c) contribute domain general or domain specific resources to achievement measures. The study parsed the sample (N = 2,471) into 11 age groups (mean ages of 6, 7, 8, 9, 11, 13, 15, 18, 26, 41, and 66 years), and compared their performances on verbal and visuospatial WM measures. Three important findings emerged: (a) a confirmatory factor analysis and Schmid-Leiman transformation to a high-order model solution supported a domain general factor model for the total sample as well as separately for children and adults, (b) performance on visual-spatial WM tasks as a function of age decreased at a faster rate than verbal WM tasks, and (c) both verbal and visual-spatial WM measures in concert with each other uniquely predicted reading and math measures, suggesting that a domain general WM system contributed to performance on achievement measures. The results support the notion that (a) complex WM tasks function as a domain general system and (b) the factor structure for children and adults on complex WM tasks was highly similar, even though there was evidence of differentiation among verbal and visual-spatial WM measures at certain age groups. (PsycINFO Database Record

Semantic and Syntactic Interference in Sentence Comprehension: A Comparison of Working Memory Models.

This study investigated the nature of the underlying working memory system supporting sentence processing through examining individual differences in sensitivity to retrieval interference effects during sentence comprehension. Interference effects occur when readers incorrectly retrieve sentence constituents which are similar to those required during integrative processes. We examined interference arising from a partial match between distracting constituents and syntactic and semantic cues, and related these interference effects to performance on working memory, short-term memory (STM), vocabulary, and executive function tasks. For online sentence comprehension, as measured by self-paced reading, the magnitude of individuals' syntactic interference effects was predicted by general WM capacity and the relation remained significant when partialling out vocabulary, indicating that the effects were not due to verbal knowledge. For offline sentence comprehension, as measured by responses to comprehension questions, both general WM capacity and vocabulary knowledge interacted with semantic interference for comprehension accuracy, suggesting that both general WM capacity and the quality of semantic representations played a role in determining how well interference was resolved offline. For comprehension question reaction times, a measure of semantic STM capacity interacted with semantic but not syntactic interference. However, a measure of phonological capacity (digit span) and a general measure of resistance to response interference (Stroop effect) did not predict individuals' interference resolution abilities in either online or offline sentence comprehension. The results are discussed in relation to the multiple capacities account of working memory (e.g., Martin and Romani, 1994; Martin and He, 2004), and the cue-based retrieval parsing approach (e.g., Lewis et al., 2006; Van Dyke et al., 2014). While neither approach was fully supported, a possible means of reconciling the two approaches and directions for future research are proposed.