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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

What limits dual-tasking in working memory? : an investigation of the effect of sub-task demand on maintenance mechanisms employed during dual-tasking

Doherty, Jason Michael January 2016 (has links)
A number of models of working memory have been proposed since the seminal work of Baddeley and Hitch (1974) on the Multiple Component Model (MCM). Subsequent MCM research focussed on developing a theoretical framework based on modality-specific stores that can operate in parallel during dual-tasking. The MCM can be contrasted with theories of working memory that assume an attention-based domain-general shared resource responsible for both short term retention as well as on-line cognition, such as the Time-Based Resource Sharing (TBRS) model (Barrouillet, Bernardin, & Camos, 2004; Barrouillet, Bernardin, Portrat, Vergauwe, & Camos, 2007). The TBRS model assumes that short-term memory is dependent on access to attention, and any diversion of attention results in increased forgetting. The model describes ‘refreshing’ as the process of serially bringing memory items briefly into the focus of attention. Barrouillet and colleagues have demonstrated in numerous studies that memory spans lower as the cognitive demand of the secondary task increases - findings that are incompatible with the MCM. However, Camos, Mora, and Oberauer (2011) found that both sub-vocal rehearsal (the verbal maintenance mechanism described in the MCM) and attention-based refreshing can be selectively employed by participants depending on task demands. Since TBRS methodology compares spans measured under different cognitive load levels that are the same for every participant, we were interested in whether ensuring that secondary task demand was set within each participant’s abilities would avoid ‘over-taxing’ the working memory system and reduce dual-task costs. Our initial investigations re-measured memory and processing spans under dual-task conditions with secondary tasks’ demand titrated according to each individual’s measured ability (Experiments 1 and 2, and Doherty & Logie, 2016). We found that memory span was unaffected when processing demand was titrated, but that processing performance was lower when memory load was set above participants’ span. Subsequent experiments (3-8) investigated the effect of setting memory and processing load ‘below span’, ‘at span’, and ‘above span’ on memory and processing accuracy during dual-tasking. Overall it was found that processing resources can be reallocated to support memory performance but memory resources cannot be reallocated to support processing performance. We interpret the results as evidence for specialised memory resources and rehearsal mechanisms that can be supplemented by attention-based processes once storage capacities are exceeded. Experiments 6-8 aimed to encourage the use of phonological- or attention-based rehearsal mechanisms for verbal short term memory by either introducing articulatory suppression (AS) or shortening available encoding time for memory items. It was found that participants exhibited shared-resource effects when they completed the dual-task under AS, suggesting a shift to attention-based rehearsal. When encoding time was limited participants’ memory performance during dual-tasking was unaffected by concurrent processing load, suggesting the use of a rehearsal method which did not require access to attention. Experiment 9 investigated whether participants could dynamically allocate attention to one task or the other, and found that while ‘priority’ tasks received no benefit, non-priority tasks exhibited a marked decrement in performance. We conclude that the perceived incompatibility between the MCM and attention-based theories of working memory such as the TBRS model may be more apparent than real, and suggest that future research should incorporate procedures and methodological considerations that take into account findings from both literatures.

Effects of hydrotherapy vs land based exercises on dual task postural control in a geriatric population

Turner, Alana Joy 09 August 2019 (has links)
Introduction: The disruption of postural control is one factor that can lead to falls for the geriatric population. Dual tasking can increase the likelihood of a fall for this population. Finding effective ways to lower falls in the geriatric population may increase quality of life. Hydrotherapy is a new therapeutic practice to increase balance performance. Purpose: The purpose is to determine the effectiveness of a six-week hydrotherapy program and its effects on dual-tasking, postural control, and balance in a geriatric population. Methods:11 elderly adults completed static/dynamic balance test with a Stroop Color and Word Test pre/post 6 weeks of dual-tasking balance training either in a land-based (LB) or hydrotherapy (HYDRO) group. Results:Both groups improved in dual tasking responses and overall static and dynamic balance. Conclusions: Both LB and HYDRO may show improvements in static and dynamic balance while under a dual tasking condition. The HYDRO group showed greater improvements in movement time after six weeks.

Dual-tasking while using two languages: Examining the cognitive resource demands of cued and voluntary language production in bilinguals

de Bruin, A., McGarrigle, Ronan 26 April 2023 (has links)
Yes / The way bilinguals switch languages can differ depending on the context. In cued dual-language environments, bilinguals select a language in response to environmental cues (e.g., a monolingual conversation partner). In voluntary dual-language environments, bilinguals communicating with people who speak the same languages can use their languages more freely. The control demands of these types of language-production contexts, and the costs of language switches, have been argued to differ (Adaptive Control Hypothesis). Here, we used a dual-task paradigm to examine how cued and voluntary bilingual production differ in cognitive resources used. Forty Mandarin-English bilinguals completed two language-switching paradigms as the primary task; one in response to cues and one while using two languages freely. At the same time, they also had to respond to the pitch of tones (secondary task). Response times (RTs) on the secondary task, as well as naming times on the primary task, were shorter under the voluntary- than cued-naming condition. Task workload ratings were also higher under the cued- than voluntary-naming condition. This suggests more attentional resources are needed in a cued-naming context to monitor cues and select languages accordingly. However, the costs associated with switching from one language to the other were similar in both voluntary- and cued-naming contexts. Thus, while cued-naming might be more effortful overall, cued and voluntary switching recruited similar levels of cognitive resources.

The type of concurrent task affects dual-task performance in Huntington's disease

Vaportzis, Ria, Georgiou-Karistianis, N., Churchyard, A., Stout, J.C. 17 September 2014 (has links)

Differential Workload Levels for Primary and Secondary Tasks using Virtual Reality

Chandrasekaran, Ritesh 01 January 2022 (has links)
Virtual reality (VR) has modernized the way that training has been done across multiple domains. Combining the benefits of using VR with the ability to measure workload levels from eye tracking data is a promising area of opportunity for all disciplines and jobs that require hands-on training. With VR becoming of increasing interest for optimizing training simulations and protocols for work around the world, this study aims to determine differential workload levels in virtual reality by using objective performance data in a simulation and subjectively assessing workload through the NASA-TLX survey. For this study, a 3x1 repeated measures ANOVA was conducted with one control, primary task only, and two experimental conditions, dual tasking with secondary auditory and visual tasks. 49 particpants were recruited from the local UCF area to study how varying task objectives impacted performance on target identifications, eye fixation counts, and their NASA-TLX survey scores. By doing so, we were able to compare primary task performances that were done concurrently with secondary tasks and measured task interference as a result of workload. Overall, we found that if a secondary task pulls from the same sensory modality (e.g.. visual, auditory) as the primary task, then primary task performance is not significantly impacted. This finding can help future training programs be designed in such a way so that the user is not overburdened and can adequately complete the required tasks. Another key takeaway from the study was that fixation counts may not be a reliable measure of workload as in the dual visual condition, the fixation counts were at the highest but that was not reflected in the workload assessment for the NASA TLX score.

Effects of Two Gait Tasks on Language Complexity in Parkinson's Disease

Marquardt, Betty Ann 01 March 2016 (has links)
The effects of dual tasking in Parkinson's disease (PD) have been studied for a number of years. Previous research has generally focused on changes in gait patterns while another task has been performed concurrently. Very few studies have focused on the impact of a concurrent task on speech or language. Language is key for communication: to express wants and needs, to maintain familial relationships, and for social interaction. Thirty-seven individuals participated in the study: 10 with PD, 14 neurologically healthy older (HO) adults, and 13 healthy younger (HY) adults. The participants were given a list of topics to consider and were invited to select several to talk about during the experiment. Their monologues were recorded as they spoke under three conditions: standing still, walking on a treadmill, and walking over randomly presented obstacles on a treadmill. The monologue recordings were transcribed, marked for processing by Systematic Analysis of Language Transcripts (SALT), and analyzed for subordinate clauses by a language expert. The language variables measured were the mean length of utterance in morphemes (MLUm), relative clauses per utterance, adverbial clauses per utterance, noun clauses per utterance, total clauses per utterance, words per minute, different words per minute, relative clauses per minute, adverbial clauses per minute, noun clauses per minute, total clauses per minutes, and utterances per minute. There were significant changes across the conditions of standing, walking, and obstacle in the language variables of words per minute, different words per minute, noun clauses per minute, total clauses per minute, and utterances per minute. A downward trend was noted for adverbial clauses per minute as the gait task became more demanding. The PD and HO groups had less complex language than the HY group, as reflected by the following language variables: adverbial clauses per minute, noun clauses per minute, and total clauses per minute. These findings suggest that as attentional resources used for the production of language are directed to increasing levels of motoric activity, language complexity will significantly decrease across conditions.

The effects of transcranial direct current stimulation on dual-task walking in Parkinson's disease

Nguyen, Victoria 18 June 2016 (has links)
BACKGROUND: Parkinson’s disease (PD) is a common debilitating disorder that largely effects the aging population. It is associated with a loss of dopamine-producing brain cells, which leads to abnormal brain activity and ultimately, a loss of locomotor control. Transcranial direct current stimulation (tDCS) is a technology that effectively modulates brain excitability by sending low electric current through the scalp. It has been demonstrated to improve working memory, intelligence, learning ability, as well as relieving symptoms of depression, Alzheimer’s and schizophrenia (Kekic, Boysen, Campbell, & Schmidt, 2015; Khedr et al., 2014; Manor et al., 2015). tDCS may thus serve as an effective therapeutic strategy for this vulnerable PD population. OBJECTIVE: The primary purpose of this study was to examine the acute effects of single sessions of tDCS targeting different brain networks on locomotor control metrics and other outcomes in patients with PD. DESIGN: A pilot, double-blinded, sham-controlled study. METHODS: A total of 15 older adults between the ages of 40-85 with a physician diagnosis of PD will be recruited. Participants are screened with questionnaires to determine eligibility. If eligible, participants will undergo a dual task assessment and a freezing of gait (FOG) provoking protocol prior to, as well as immediately after, a 20-minute session of tDCS. The acute effects of each stimulation session will be observed. There will be three different stimulation conditions that each target different areas of the brain: the motor cortex (M1), the motor cortex and the dorsolateral prefrontal cortex (DLPFC), and a sham (i.e., control) condition. Multiple aspects of locomotion (i.e., FOG, gait speed, stride time variability, percent of each walking stride spent with both feet on the ground) and cognition are assessed. RESULTS: This study began enrolling participants on March 3rd, 2016. To date, one participant has been enrolled and completed baseline testing as well as all three tDCS visits. This 42-year-old participant was diagnosed with PD two years ago and symptoms are mild. No side effects were observed during tDCS and the participant was unable to decipher between the M1 and the sham stimulation, but was able to tell the difference between sessions when receiving multi-focal stimulation. DISCUSSION: In this case study, tDCS was well tolerated by the patient and double-blinding procedures were effective. Thus, while tDCS did not induce significant improvements in gait or cognition in this relatively high functioning patient, the developed study protocol and tDCS intervention are highly feasible in the PD population.

Vliv různých typů senzorického a kognitivního souběžného úkolu na stabilitu stoje u sportovců / Effect of various types of sensory and cognitive dual-tasking in high performance athlete's stance stability

Levínská, Kateřina January 2017 (has links)
Bibliographic identification Author's first name and surname: Bc. et Bc. Kateřina Levínská Title of the master thesis: Effect of various types of sensory and cognitive dual-tasking in high performance athlete's stance stability Department: Department of Rehabilitation and Sports Medicine, 2nd faculty of medicine, Charles University and FN Motol Supervisor: PhDr. Ondřej Čakrt, Ph.D. The year of presentation: 2017 Abstract: This study focused on the influence of various types of cognitive and sensory dual- tasking to the stability of stance of the elite floorball players, elite floorbal players with anterior cruciate ligament reconstruction and healthy controls. A total of forty probands were divided into 3 groups according to the sports activity and the history of ACL injuries. Volunteers underwent examination of bipedal and monopedal standing on a stabilometric platform using a foam pad. We chose three types of secondary task, which we tested first at probands in a sitting position. Subsequently, we combined them with a bipedal and monopedal stance on a foam mat. In secondary tests, latency of response and error rate were measured. Our results show that the combination of a postural challenging situation with a secondary task significantly more affects performance in the sensory-cognitive task than the...

Postural stability changes in the elderly during sensory perturbations and dual tasking: the influence of refractive blur

Anand, Vijay, Buckley, John, Scally, Andy J., Elliott, David B. January 2003 (has links)
No / PURPOSE. To determine the influence of refractive blur on postural stability during somatosensory and vestibular system perturbation and dual tasking. METHODS. Fifteen healthy, elderly subjects (mean age, 71 ± 5 years), who had no history of falls and had normal vision, were recruited. Postural stability during standing was assessed using a force platform, and was determined as the root mean square (RMS) of the center of pressure (COP) signal in the anterior-posterior (A-P) and medial-lateral directions collected over a 30-second period. Data were collected under normal standing conditions and with somatosensory and vestibular system perturbations. Measurements were repeated with an additional physical and/or cognitive task. Postural stability was measured under conditions of binocular refractive blur of 0, 1, 2, 4, and 8 D and with eyes closed. The data were analyzed with a population-averaged linear model. RESULTS. The greatest increases in postural instability were due to disruptions of the somatosensory and vestibular systems. Increasing refractive blur caused increasing postural instability, and its effect was greater when the input from the other sensory systems was disrupted. Performing an additional cognitive and physical task increased A-P RMS COP further. All these detrimental effects on postural stability were cumulative. CONCLUSIONS. The findings highlight the multifactorial nature of postural stability and indicate why the elderly, many of whom have poor vision and musculoskeletal and central nervous system degeneration, are at greater risk of falling. The findings also highlight that standing instability in both normal and perturbed conditions was significantly increased with refractive blur. Correcting visual impairment caused by uncorrected refractive error could be a useful intervention strategy to help prevent falls and fall-related injuries in the elderly.

The use of head mounted displays (HMDs) in high angle climbing : implications for the application of wearable computers to emergency response work.

Woodham, Alexander, Timothy January 2015 (has links)
As wearable computers become more ubiquitous in society and work environments, there are concerns that their use could be negatively impactful in some settings. Previous research indicates that mobile phone and wearable computer use can impair walking and driving performance, but as these technologies are adopted into hazardous work environments it is less clear what the impact will be. The current research investigated the effects that head mounted display use has on high angle climbing, a task representative of the extreme physical demands of some hazardous occupations (such as firefighting or search and rescue work). We explored the effect that introducing a secondary word reading and later recall task has on both climbing performance (holds per meter climbed and distance covered), and word reading and recall (dual-task effects). We found a decrease in both climbing performance and word recall under dual task conditions. Further, we examined participant climbing motion around word presentation and non-word presentation times during the climbing traverse. We found that participants slowed around word presentations, relative to periods without word presentation. Finally, we compared our results to those found in previous research using similar dual-tasking paradigms. These comparisons indicated that physical tasks may be more detrimental to word recall than seated tasks, and that visual stimuli might hinder climbing performance more than audible stimuli. This research has important theoretical implications for the dual-tasking paradigm, as well at important practical implications for emergency response operations and other hazardous working environments.

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