Modality-specific effects of mental fatigue in multitasking

The mechanisms underlying increased dual-task costs in the comparison of modality compatible stimulus-response mappings (e.g., visual-manual, auditory-vocal) and modality incompatible mappings (e.g., visual-vocal, auditory-manual) remain elusive. To investigate whether additional control mechanisms are at work in simultaneously processing two modality incompatible mappings, we applied a transfer logic between both types of dual-task mappings in the context of a mental fatigue induction. We expected an increase in dual-task costs for both modality mappings after a fatigue induction with modality compatible tasks. In contrast, we expected an additional, selective increase in modality incompatible dual-task costs after a fatigue induction with modality incompatible tasks. We tested a group of 45young individuals (19–30 years) in an online pre-post design, in which participants were assigned to one of three groups. The two fatigue groups completed a 90-min time-on-task intervention with a dual task comprising either compatible or incompatible modality mappings. The third group paused for 90 min as a passive control group. Pre and post-session contained single and dual tasks in both modality mappings for all participants. In addition to behavioral performance measurements, seven subjective items (effort, focus, subjective fatigue, motivation, frustration, mental and physical capacity) were analyzed. Mean dual-task performance during and after the intervention indicated a practice effect instead of the presumed fatigue effect for all three groups. The modality incompatible intervention group showed a selective performance improvement for the modality incompatible mapping but no transfer to the modality compatible dual task. In contrast, the compatible intervention group showed moderately improved performance in both modality mappings. Still, participants reported increased subjective fatigue and reduced motivation after the fatigue intervention. This dynamic interplay of training and fatigue effects suggests that high control demands were involved in the prolonged performance of a modality incompatible dual task, which are separable from modality compatible dual-task demands

Effects of aerobic fitness on dual task walking in older adults

Having higher aerobic fitness levels leads to better cognitive performance and increases in the oxygenation of the prefrontal cortex (PFC) (i.e., increase in PFC activation patterns). Unfortunately, it is unknown how aerobic fitness levels can affect these measures while dual-task walking. Additionally, the relationship between aerobic fitness levels and cognitive motor interference (CMI), which is a direct of measure of dual-task performance related to falls in older adults, has not been examined. It is important to understand these relationships because falls related to dual-task walking is very common in older adults and causes major consequences that negatively affect their quality of life. Thus, the objective of this dissertation was to examine the encompassing effects of aerobic fitness on dual-task walking in older adults by examining cognitive motor interference, cognitive performance, and changes in PFC activation patterns. For the studies included in the dissertation, depending on the study design, the sample size differed (i.e., 24 vs 34 participants) and different tasks were incorporated (i.e., single task walking, dual-task standing, or dual-task walking). All studies involved assessing aerobic fitness levels with the Rockport 1 mile walk test and performing the Modified Stroop Color Word Test on a self-instrumented treadmill. Gait speed dual-task cost was used to measure CMI and the Stroop Interference was used as the measure for cognitive performance. Chapter 1 found that lower fit individuals exhibited higher dual-task cost than the higher fit individuals when going from single-task walking to dual-task walking. Furthermore, when compared to the easiest dual-task Stroop condition, all participants exhibited decreases in dual-task cost during the other dual-task walking conditions with increasing difficulty. Chapter 2 found that individuals with lower estimated VO2max scores exhibited lower cognitive performance (i.e., greater SI) while dual-task walking when compared to individuals with higher estimated VO2max scores and dual-task standing in a moderately difficult Stroop condition. Additionally, during the most difficult Stroop condition, individuals with lower estimated VO2max scores exhibited greater SI while both dual-task walking and dual-task standing. Chapter 3 found that lower fit individuals exhibited greater decrements in recruitment of PFC activation (i.e., greater changes in PFC when going from single-task walking to dual-task walking) during the most difficult Stroop condition when compared to higher fit individuals and the easiest Stroop condition. Additionally, the fitness level groups only differed in PFC activation patterns while dual-task standing with a moderately difficult Stroop condition. Overall, the findings from this study indicated that while dual-task walking, individuals with lower fitness levels or low estimated VO2max scores exhibited greater decrements in physical and cognitive dual-task performance and greater recruitment of attentional resources which is consistent with the neural efficiency model. As a whole, these study’s findings add to the current literature establishing the beneficial effects of aerobic fitness for dual-task walking. While this study was the first to examine the overall effects of aerobic fitness on measures directly and indirectly related to dual-tasking, no causal relationships can be formed. Thus, it is recommended for research to examine the effects of an aerobic intervention program on these measures in older adults. Such findings will elucidate the importance of aerobic fitness in older adults to improve dual-tasking ability and decrease the risk of falls

A field study of mental workload: conventional bus drivers versus bus rapid transit drivers

Editing Services Awareness English-speaking Publish your Policy Brief rapidly today and inspire change for tomorrow. Banner advert for Australian Journal of Psychology, now open access Full Article Figures & data References Citations Metrics Reprints & Permissions Get access Abstract Road traffic accidents are increasing worldwide and cause a high number of fatalities and injuries. Mental Work Load (MWL) is a contributing factor in road safety. The primary aim of this work was to study important MWL factors and then compare conventional and BRT (Bus Rapid Transit) drivers' MWL. This study evaluated bus drivers' MWL using the Driving Activity Load Index (DALI) questionnaire conducted with 123 bus drivers in Tehran. The results revealed significant differences between conventional and BRT drivers' mental workload. Moreover, data modelling showed that some organisational and environmental factors such as bus type, working hours per day, road maze, and route traffic volume contribute to drivers' mental workload. These findings suggest some essential customised factors that may help measure and offer practical solutions for decreasing the level of bus drivers' MWL in real-world road driving. Practitioner summary Mental workload is affected by several contributing factors. Depending on the working context, some of these contributing factors have a more significant influence on the level of the experienced MWL. Therefore, the main factors influencing the MWL of BRT and conventional bus drivers were assessed in their real-life environment. Abbreviations: MWL: mental work load; BRT: bus rapid transit; CB: conventional bus; DALI: driving activity load index; NASA-TLX: NASA task load index; SWAT: subjective workload assessment technique; EEG: electroencephalography electrocardiogram; fNIRS: functional magnetic resonance imaging; ITS: intelligent transportation systems; AVL: automated vehicle locatio

The effect of perturbation warning on attention switching abilities during dual-task performance in young and older adults

This study examined whether providing an auditory warning would facilitate attention switching abilities in older adults during dual-tasking. Fifteen young and 16 older adults performed a tracking task while recovering their balance from a support surface translation. For half of the trials, an auditory warning was presented to inform participants of the upcoming translation. Performance was quantified through electromyographic (EMG) recordings of the lower limb muscles, while the ability to switch attention between tasks was determined by tracking task error. Providing warning of an upcoming loss of balance resulted in both young and older adults increasing their leg EMG activity by 10-165% (p<0.05) in preparation for the upcoming translation. However, no differences in the timing of attention switching were observed with or without the warning (p=0.424). Together, these findings suggest that providing a perturbation warning has minimal benefits in improving attention switching abilities for balance recovery in healthy older adults

Modulation exekutiver Funktionen durch transkranielle Gleichstromstimulation

Hintergrund: Versuchen wir zwei Reize gleichzeitig zu verarbeiten und auf sie zu reagieren, sind wir in der Regel langsamer in unseren Reaktionen und machen mehr Fehler. Im experimentellen Rahmen wird ein solcher Zusammenhang mit dem Doppelaufgabenparadigma untersucht. Bei der Bewältigung dieser Doppelaufgaben spielen exekutive Funktionen eine Rolle und sind in bildgebenden Studien mit einer Aktivierung im inferioren frontalen Kreuzungsareal (engl. inferior frontal junction, IFJ) im Bereich des lateralen präfrontalen Cortex assoziiert. Dabei zeigten sich unterschiedliche Aktivierungsmuster zwischen linker und rechter Hemisphäre. Durch ein nicht-invasives Hirnstimulationsverfahren, der sog. transkraniellen Gleichstromstimulation (engl. transcranial direct current stimulation, tDCS), lassen sich neuronale Aktivitäten stimulierter Areale modulieren und entsprechende Verhaltenseffekte messen. Hierüber lassen sich kausale Zusammenhänge zwischen Hirnarealen und kognitiven Funktionen aufstellen. Vorangegangene Arbeiten zeigten, dass die Applikation von tDCS über der linken IFJ Leistungen in Doppelaufgaben verbessert. Erstmalig untersuchten wir in der vorliegenden Studie die Rolle der rechten IFJ in der Bewältigung von Doppelaufgaben. Methoden: In einer placebokontrollierten Studie an 30 jungen, gesunden Probanden untersuchten wir den Effekt von tDCS über der rechten IFJ in gemixten Doppelaufgaben. Die Doppelaufgaben waren kombinierte Wahlreaktionsaufgaben mit je einem visuellen und einem auditorischen Reiz, welche in ihrer Reihenfolge und ihrem Zeitabstand (200ms/400ms) variierten. Während der Aufgabendurchführung applizierten wir in zwei getrennten Sitzungen jeweils anodale tDCS (1mA, 20min) bzw. Placebostimulation (1mA, 30s) über der rechten IFJ. Reaktionszeiten und Fehlerraten wurden mittels mehrfaktorieller Varianzanalysen mit Messwiederholungen evaluiert. Ergebnisse: Unter dem Einfluss anodaler tDCS zeigten sich im Vergleich zur Placebostimulation signifikant niedrigere Fehlerraten in gemixten Doppelaufgaben (p<.05). Die Effekte traten jedoch nur unter Bedingungen gleichbleibender Reizreihenfolge und kurzen zeitlichen Reizabständen auf. Ein Stimulationseffekt auf die Reaktionszeiten war nicht festzustellen. Der leistungssteigernde Effekt auf die Fehlerraten war umso größer, je schlechter die Ausgangsperformanz vor Stimulationsbeginn war (p<.01). Schlussfolgerung: Die signifikant niedrigere Fehlerrate unter dem Einfluss anodaler tDCS über der rechten IFJ deutet auf einen kausalen Zusammenhang dieses Hirnareals und exekutiven Funktionen in Doppelaufgaben hin. Dass die Probanden mit der schlechtesten Ausgangsperformanz am meisten von der Stimulation profitierten, ist vereinbar mit der in vielen Studien bestätigten Annahme, dass tDCS Effekte positiv mit dem Schwierigkeitslevel der Aufgabe korrelieren. Die Leistungsverbesserung könnte durch gesteigerte Koordinations- oder Arbeitsgedächtnisprozesse bedingt sein. Welche kognitiven Prozesse moduliert wurden, um die beobachteten Verhaltenseffekte hervorzurufen, lässt sich aus dieser Untersuchung nicht schließen. Zukünftige Studien sollten spezifischere Doppelaufgabenparadigmen anwenden, um einzelne kognitive Funktionen gezielter zu untersuchen.Background: Processing and reacting to two stimuli simultaneously makes our reactions slower and more prone to errors. In an experimental design this phenomenon is investigated in dual-task paradigms. Executive functions are essential when processing dual tasks. Functional imaging studies show a related activation in the lateral prefrontal cortex, especially of the inferior frontal junction (IFJ), revealing different activation patterns between the left and right hemisphere. Transcranial direct current stimulation (tDCS), a non-invasive brain stimulation technique, modulates neuronal activities of stimulated brain areas. The evaluation of tDCS-induced behavioral effects facilitates conclusions about causal relations between stimulated brain areas and cognitive functions. Previous studies have reported that tDCS over the left IFJ improves performance in dual-task situations. In the present study, we investigated the functional role of the right IFJ in dual-task processing for the first time. Methods: In a placebo-controlled trial with 30 young, healthy patients we evaluated the effects of tDCS over the right IFJ in dual tasks with a random task order. The dual tasks were combined choice reaction tasks consisting of a visual and an auditory stimulus, which varied in their task order and time interval (200ms/400ms). In two separate sessions subjects received anodal tDCS (1mA, 20min) in contrast to placebo stimulation (1mA, 30s) during task execution. Reaction times and error rates were evaluated in multifactorial analyses of variance with repeated measurements. Results: Anodal tDCS reduced error rates significantly in random order dual tasks in comparison to placebo stimulation (p<.05). However, the effects occurred exclusively in trials with repeated task order and a short time interval (200ms) between stimuli. No effect on reaction times could be observed. The baseline performance correlated with tDCS-induced performance improvement in error rates (p<.01). Conclusions: Anodal tDCS over the right IFJ reduced error rates significantly implicating its causal relation to executive functioning in dual-task processing. The fact that the subjects with the worst initial performance benefited most from the stimulation is consistent with the findings of precedent studies that the level of task difficulty correlates with tDCS-induced effects positively. The performance improvement could be due to coordination or working memory processes. It is not possible to determine exactly which cognitive processes lead to the observed behavioral effects. Future studies should apply more specific dual-task paradigms to investigate separate cognitive functions in a more targeted manner

A comparison of behavioural and functional neuroanatomical correlates of executive functions in multitasking and working memory

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonThis thesis aims to explore the role of executive functions in multitasking. Research has shown that severe performance decrements often arise in dual-task performance, also called multitasking, as compared to single task performance. This reflects a limitation in processing temporally overlapping information. Interference between tasks arises due to a bottleneck process limited to processing only one task at a time. It has been proposed that this interference is resolved by executive functions. However, the dual-task paradigm employed in this thesis, Psychological Refractory Period (PRP) paradigm, (Pashler, 1994) is typically investigated in the field of human action performance, and the exact concept of executive functions remains underspecified. However, while underspecified in the area of action performance, executive functions have been investigated in detail in the field of memory research, more specifically in the context of working memory (WM). Therefore, the aim of this thesis was to investigate whether the executive functions in PRP are related to the executive functions as discussed in the context of WM. To test this question, we combined the PRP paradigm with a WM task, creating a complex WM span task. If the executive functions of WM and PRP are indeed related, then an interaction between the two tasks should be evident. Participants were presented with a sequence of letters to remember, followed by a processing block in which they had to perform either a single task or a dual-task, and finally were asked to recall the letters. Results (Chapter 2) showed that recall performance decreased when performing a dual-task as compared to performing a single task. This supports the assumption that PRP dual-tasks demand executive functions of WM. Following this, two other experiments were performed each with a different parametric modulation of the processing demands of the PRP dual task; response order (fixed vs random; Chapter 3) and stimulus onset asynchrony (SOA, short vs long; Chapter 4) of the component tasks. Recall performance was lower after a more difficult dual-task compared to an easier dual-task, which again indicates that demands on executive functions are increased in the dual-task. While previous neuroscientific research indeed showed that dual-tasks as well as WM tasks rely on lateral-prefrontal cortices (LPFC), it remains unknown whether both tasks activate the same areas or different sub-areas of the LPFC. Therefore, this study (Chapter 6) investigated how the neuroanatomical correlates of both dual-task and WM compare to each other. The brain activation for the PRP and WM tasks showed considerable overlap as well as some differentiation. Both tasks activated, among other areas, the inferior frontal junction. With respect to differences, the PRP task activated more the inferior middle frontal gyrus (MFG) whilst the WM component activated more the superior MFG. Thus, results support the assumption that PRP dual-tasks demand the executive functions of WM. This will allow us to inform theoretical models of cognition and to get a better understanding of human cognition. Future studies can build on this in order to create a more consolidated conceptualisation of the relationship between WM and multitasking

Executive function abilities, cognitive ageing, and cognitive decline

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonDecline in cognitive abilities is a predominant feature of cognitive ageing and neuropathological conditions, which is attributed to the decline of executive functions (EFs). Four EFs are suggested to be particularly important, dual-tasking (DT), inhibition, shifting, and working memory (WM) updating. As part of the research completed in this thesis, two studies sought to determine the age-associated trajectory of decline of these abilities as this has not been extensively researched. An initial literature review (Chapter 2) evaluated how these abilities have previously been examined in cognitively healthy and pathological impaired older adults. A cross-sectional behavioural study (Chapter 3) conducted between young and older adults where each EF was assessed with a pair of tasks, showed age-associated decline in some measures. Results further demonstrated that inhibition, shifting, and updating declined at a comparable high rate, whereas DT declined independently at a lower rate. A following correlation analysis (Chapter 4) between task pair measures of each EF in both age groups, found a significant positive correlation in DT in the older adults. Confirmatory factor analysis (Chapter 4) of these task measures revealed the older adults showed a better common EF factor loading than the young adults. Furthermore, correlation loading analysis between the EFs showed a weakly correlated four-factor model in the young adults, and three- and two-factor models in the older adults, indicating age-related structural change of EFs due to dedifferentiation (Koen & Rugg, 2019; La Fleur et al., 2018). Lastly, a voxel-based morphometry study (Chapter 6), using secondary imaging data from the OASIS-3 database (LaMontagne et al., 2019) of participants ranging from cognitive healthy to advance Alzheimer’s disease, identified substantial atrophy in the medial temporal lobes but not in the prefrontal cortex, the region primarily associated with EF processing. Nevertheless, atrophy in midbrain structures which are important for EF processing seemed to be associated with performance in the EF tasks employed. The findings of this thesis illustrate that cognitive ageing is not a unitary process, therefore, further research into how the trajectory of the four EFs differs in neuropathological conditions would aid in understanding cognitive impairment greatly