Children with ADHD diagnosis often display working memory deficits, as well as reading and mathematical disabilities. Previous studies have demonstrated that computerized working memory training (WMT) is a promising intervention. The present study aimed at exploring the effects of WMT on working memory, scholastic skills and behavioral symptoms in children with ADHD. Thirty-two children, aged 6 to 11, were randomized to WMT or a control condition. WMT consisted of nine tasks taxing working memory with adaptive difficulty level. All children trained in their homes, with their parents acting as supervisors. Children who completed more than 20 days of training in 5-8 weeks (8 in the WMT condition and 13 in the control condition) were considered compliers. Assessments were conducted before and after intervention. Results indicated that WMT lead to significant gains of verbal working memory and arithmetic skills. More research is needed to further investigate the effects of WMT.

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Many learners in South Africa first encounter English when it is used as a medium of instruction at the start of formal schooling. This has ramifications for literacy acquisition and academic performance. Working memory is responsible for distributing cognitive resources among the various processing and storage tasks. It has been pivotal in many cognitive theories linking working memory to academic skills like reading comprehension and mathematics ability. In addition, research indicates that both Short Term Memory (STM) and Working Memory (WM) are instrumental in cognitive processing but that in bilinguals their roles are more complex than they are in monolinguals. This research explored the capacity of WM and the role of WM in reading comprehension and mathematical ability in two South African populations: a monolingual English group (L1) and a bilingual Afrikaans/English group (L2). No significant differences were found in the WM capacity of the two groups. In the second part of the study it was found that both reading comprehension and bilingualism depend on the same verbal domain resources of WM, which act as constraining factors for the L2 group. However, in the L1 group, there appeared to be less competition for verbal domain resources and more for visuospatial resources probably due to the phase of literacy acquisition these learners were in. In terms of WM and mathematical ability it was found that bilinguals exceed their storage capacity (STM) before they run out of processing capacity (WM). STM therefore is a constraining factor for this group. However, for the L1 group, visuospatial processing is the constraining factor. The research concludes that bilinguals use WM both for semantic processing of their nondominant language and for complex cognitive processing. While the WM capacity for monolingual and bilingual learners appears to be equivalent, the way the resources are allocated during cognitive tasks differ.

Rationale : Investigating the relationship between working memory and reading comprehension will lead to an improved understanding of the nature of working memory and will reveal how working memory contributes to reading comprehension failure. A pattern of working memory deficits will determine if ‘signature’ working memory profiles exist which will assist in the diagnosis and treatment of children with reading comprehension difficulties. Aims : (1) To explore the relationship between working memory and reading comprehension to determine if there are ‘signature’ working memory profiles that distinguish subgroups of Grade 5 English language learners with different comprehension capabilities. (2) To determine if a domain-specific or general working memory system is implicated in reading comprehension. (3) To explore the particular role played by the episodic buffer zone in reading comprehension. Method : Eighty Grade 5 English learners were tested on the GORT-4, AWMA and CELF- 4 Recalling Sentences Subtest. Based on their accuracy/decoding and comprehension scores on the GORT-4, participants were assigned to one of four reading ability groups: Skilled Reader Group; Reading Disabled Group; Poor Comprehender Group; or Poor Fluency Group. Comparison of mean standard scores determined how the four reading ability groups fared on the five memory components. Correlation and regression methods investigated the relationships between the five working memory variables and reading comprehension across the four reading ability groups. Results : Working memory plays a role in reading comprehension. The Skilled Reader group displayed intact working memory profiles, whilst the Reading Disabled group performed in the low average range on four working memory variables and below average on the fifth viz. sentence recall. The Poor Comprehender group’s working memory performance resembled that of the Skilled Reader group on two working memory variables. The Poor Fluency group performed below average on visuo-spatial short-term memory. These findings gave evidence of the inter-play between domain-specific and domain-general components of working memory during the complex task of reading comprehension. In addition, the findings highlighted the predictive role of sentence recall, as well as that of verbal working memory in reading comprehension. The episodic buffer was shown to play an important binding function between fluid and crystallised knowledge. The results suggested that reading comprehension was affected by a learner’s working memory capacity, however, working memory alone did not account for variations in performance. Lower-order and higher-order cognitive processes, as well as the interaction between fluid and crystallised knowledge appear essential to authentic reading. This has ramifications for prevention and remediation of reading comprehension deficits and underscores the important role of the speech therapist in literacy promotion.

Phonological awareness, and working memory, as a component of phonological awareness, have been found to be highly correlated, not only with the acquisition of reading skills, but also with each other. Existing data does not address this aspect of emergent literacy in South African children, for whom bilingualism may impact on their levels of phonological awareness, and possibly working memory. This research study was designed and conducted in an attempt to identify the relationship between these two skills in a sample of seventy-nine South African Grade 1 children (mean age 86 months). The sample consisted of two language groups, namely first-language English (EL1), an opaque orthography (n=42) and second-language English with first-language one of the nine official African languages of South Africa (EL2), a transparent orthography (n=37). The primary aim was to examine the relationship between phonological awareness (comprising a sound categorisation task, a phoneme deletion task, and a syllable splitting task) and working memory (comprising a verbal short-term memory task, a visuo-spatial short-term memory task, a verbal working memory task and a visuo-spatial working memory task). A measure of non-verbal intelligence was included as a control. Separate analyses were run for the two language groups in order to draw a comparison between their performance on the tasks. Results generally supported existing literature that showed that the relationship between working memory and phonological awareness appears to be dependent on the depth of analysis of phonological awareness, which determines the level of demand made on working memory, yet the relationship differed between the language groups, indicating that the EL2 children draw more on general or apparently unrelated skills to conduct working memory and phonological awareness tasks. A secondary aim of this study was to explore the predictive power of firstly, the four memory skills on phonological awareness; secondly, the sound categorisation skills on phoneme deletion and finally, non-verbal intelligence on working memory. Results again differed between the language groups, suggesting that a broader range of working memory skills predict performance on phonological awareness tasks in the EL2 group than in the EL1 group. The implications of these results are discussed in detail.

Working memory, which enables the temporary storage of information in an active “online” state, is an exceptionally capacity limited system. Given this capacity limit, irrelevant information in our environment must be filtered out, while relevant representation is maintained. Research has shown that neural oscillations in the alpha frequency range (8-12Hz) are greatly influenced by the number of items in memory. Most work has argued that alpha oscillations primarily support working memory processing by suppressing information that could interfere with items already in memory, as indexed by an increase in alpha power. However, other work has shown that decreases in alpha power, with little evidence of concurrent increases, support the maintenance of working memory representations. In this thesis we show that, in the context of visual working memory, the primary role of alpha oscillations is to maintain distinct working memory representations, rather than to suppress irrelevant information. This is shown in a series of three experiments all indicating that as the number of relevant items increases, the power of alpha oscillations systematically decreases. In the first experiment, we use a whole report and change detection task to examine how the number of items in memory influences alpha oscillations. In the second experiment, we use a cuing (Experiment 2A) and filtering (Experiment 2B) paradigm to demonstrate that alpha power tracks the number of remembered items instead of the number of total items on the screen. Lastly, by presenting items sequentially (Experiment 3A) or in overlapping locations (Experiment 3B), we see evidence that decreases in alpha power are related to the maintenance of relevant spatial locations, instead of the number of items in memory. The results of the experiments suggest that alpha power reflects the maintenance of relevant working memory representations, rather than the suppression of irrelevant external distractors or the inhibition of task-irrelevant neural areas. Furthermore, our last experiment indicates that the alpha frequency band is especially sensitive to the maintenance of spatial information.

During scene viewing, visual working memory (VWM) is used to retain information from recently attended and fixated objects. In the present study, I examined whether and how people can strategically control the content of VWM during scene viewing, prioritizing task-relevant objects for retention even as the eyes are directed to subsequent objects. Participants viewed a set of real-world objects presented serially within a 3-D rendered scene. One object in the sequence was cued by a tone as to-be-remembered. At the end of the sequence, memory for the visual form of one object was tested. Participants exhibited tight control over the content of VWM, implementing prioritization after the encoding of an object into VWM, protecting that item from subsequent interference. Participants also successfully reallocated protection to subsequent objects, regardless of the duration of prioritization of the original item. Such strategic maintenance of objects in VWM is likely to play an important role in real-world visual behavior, especially when object information must be maintained across shifts of attention and the eyes to other objects (such as when comparing two spatially separated objects).

This study explored the relationship between working memory (WM) deficits and reading difficulties using secondary data analysis on data collected from 63 English speaking students in two urban school divisions in Saskatchewan participating in a larger SSHRC funded study (Marche, McIntyre, Claypool, 2013). First, this study addressed whether the WM profiles of individuals with reading difficulties were different from those of individuals without reading difficulties. The results showed that individuals with reading difficulties scored lower than individuals with average reading ability on measures of verbal short-term memory (STM), verbal WM, and visuospatial WM. Second, this study looked at the differential effects of computer-based WM training on the WM profiles of children with and without reading difficulties. The results showed that after WM training, there was a difference between the visuospatial STM scores of individuals with and without difficulties, when reading ability was determined by the combination of a decoding and comprehension task. Furthermore, a difference was also noted between the visuospatial WM scores of individuals with and without word decoding difficulties, and the visuospatial STM, verbal WM, and visuospatial WM scores of individuals with and without reading comprehension difficulties. Additionally, the verbal STM scores of individuals with reading comprehension difficulties were marginally different than the scores of individuals without. No differences were found between individuals who did not participate in WM training. The limitations of the study, as well as the implications for practice and future research, are discussed.

Working memory refers to the ability to retain information for short periods of time to guide future behavior. This type of short-term memory has been shown to play an important role in mental disorders such as schizophrenia and therefore further investigations into the neural basis of this cognitive function may aid in the study of disease states where this cognitive function is defective. A likely neural correlate of working memory has been identified in the persistent neural activity observed during the memory retention intervals of various behavioral tasks. Computational and cellular physiology has suggested that this persistent activity depends on NMDA receptor activation. Indeed, pharmacological studies on both human and animal subjects have reported a significant decrease in working memory task performance following the administration of NMDA-antagonists such as ketamine. However, the task and experimental design of these previous studies have not been ideal, and have therefore only shown equivocal evidence that NMDA-antagonists impair working memory, especially its capacity. Here we aimed to determine the effect of low-dose ketamine injection (0.25-mg/kg and 0.50-mg/kg IM) on the performance of macaque monkeys on a visual sequential comparison task, a task whose performance has minimal influence from other cognitive functions besides working memory. All monkeys showed a detrimental effect of ketamine administration on visual working memory performance, either at higher ketamine doses or with high memory loads. There was also an effect on performance in sessions without a memory component, indicating that the effect of ketamine was no limited to working memory maintenance. Although the effect of ketamine on memory load varied per animal, this study provides solid evidence in support of the hypothesis that working memory maintenance is dependent on NMDA receptor integrity. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2011-05-27 14:56:41.726

Working memory is the ability to store relevant information temporarily to guide future thought and behavior. It is a basic cognitive function instrumental to processes such as learning, reasoning, comprehension and mental arithmetic. Central to mental disorders, such as attention deficit hyperactivity disorder (ADHD), are impairments in cognition including working memory. It is essential to understand working memory, if we want to understand human cognition and mental disorders. A neural correlate of working memory has been identified as selective persistent activity during the retention intervals of tasks that probe working memory. The signal-to-noise ratio of persistent activity can be modulated by catecholamines, neuromodulators that are depleted in many mental disorders, including ADHD. Such modulations should be evident at the level of behavior, particularly as the demands imposed on working memory are increased. To test the contribution of catecholamines to working memory, we opted to administer methylphenidate to three female macaque monkeys. Methylphenidate is a dopamine and norepinephrine reuptake inhibitor that effectively increases their availability in the brain. By having monkeys perform a visual sequential comparison task, which allows the systematic manipulation of working memory load, we tested the hypothesis that increased catecholamine levels modulate task performance in a dose- and memory load-dependent way. Systematic administration of a wide range of doses of methylphenidate (0.1 – 9 mg/kg) did not affect performance on the visual sequential comparison task in either a dose- or memory load-dependent manner. Given these results, we further tested the effects of methylphenidate on overt attention in a visual search task. Again, we did not observe a dose-dependent effect on performance. Nevertheless, methylphenidate was found to generally increase the monkeys’ motivation. We suggest that the positive effect on motivation, elicited by an increased level of catecholamines, might have led to changes in performance observed in previous literature, but not to changes in the ability of retaining visual information per se. These findings question the previously suggested influence that catecholamines exert on cognition, and suggest that the role of catecholamines in working memory should be reevaluated. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2012-05-30 14:04:54.891