Dissertations / Theses on the topic 'Attention – Physiological aspects'
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Wong, Ting-ting Natalie. "Sustained attention in schizophrenia." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B29727686.
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Johnson, Jennifer Adrienne. "The behavioral and neural correlates of bimodal selective and divided attention to incongruent audiovisual events /." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111851.
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Humans live in a world rich in multisensory information. Often information reaching one sense is completely unrelated to information reaching another sense; that is, they are spatially and temporally incongruent. The goal of the research presented in this thesis was to elucidate the behavioral and neural bases of attention to incongruent audiovisual information. Five issues were addressed: (1) developing an appropriate behavioral paradigm to test bimodal attention, (2) understanding the role of crossmodal suppression in unimodal attention, (3) exploring the interaction of auditory and visual sensory cortex during bimodal selective attention, (4) exploring the role of fronto-parietal networks in bimodal selective attention, and (5) exploring the neural correlates of bimodal divided attention. Two different behavioral paradigms demonstrated that attended information was remembered better than unattended information. Functional magnetic resonance imaging (fMRI) revealed that crossmodal suppression of sensory cortex subserving a non-presented modality occurred consistently during unimodal attention tasks, and increased with attentional demand. During bimodal selective attention, activity was often enhanced in sensory cortex subserving an attended modality and suppressed in sensory cortex subserving an unattended modality, both compared to a bimodal passive baseline. This interaction depended in part on attentional demand and the nature of the stimulus information. No prefrontal regions were consistently activated by bimodal selective attention; however, dorsolateral prefrontal cortex (DLPFC) was recruited during one of the bimodal divided attention paradigms. Furthermore, temporary inactivation of the DLPFC using transcranial magnetic stimulation (TMS) led to decreased bimodal divided attention performance using the same paradigm. However, using a different bimodal divided attention paradigm, DLPFC was not recruited and instead ventrolateral prefrontal cortex (VLPFC) showed task-induced deactivation. This divergence is explained by the unique requirements of the two bimodal divided attention paradigms. Overall, these findings provide improved understanding of how humans process and attend to multisensory information, and raise several questions for further investigation.
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Siegle, Greg Jeremy. "Cognitive and physiological aspects of attention to personally relevant negative information in depression /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1999. http://wwwlib.umi.com/cr/ucsd/fullcit?p9935457.
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De, Gray Birch Casey. "The effects of sustained attention, workload and task-related fatigue on physiological measures and performance during a tracking task." Thesis, Rhodes University, 2012. http://hdl.handle.net/10962/d1005198.
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Despite extensive research into the concept of mental fatigue there is as yet no “gold standard” definition or measurement technique available. Because of this a large amount of fatigue-related errors are still seen in the workplace. The complexity of the problem lies with the inability to directly measure mental processes as well as the various endogenous and exogenous factors that interact to produce the experienced fatigue. Fatigue has been divided into sleep-related and task-related fatigue; however the task-related aspect is evident both during normal waking hours as well as during periods of sleep deprivation, therefore this aspect is considered important in the understanding of fatigue in general. The concept of task-related fatigue has further been divided into active and passive fatigue states; however differentiation between the two requires careful consideration. Various physiological measures have been employed in an attempt to gain a better understanding of the mechanisms involved in the generation of fatigue, however often studies have produced dissociating results. The current study considered the task-related fatigue elicited by a tracking task requiring sustained attention, in order to evaluate the usefulness of various cardiovascular and oculomotor measures as indicators of fatigue. A secondary aim was to determine whether the behavioural and physiological parameter responses could be used to infer the type of fatigue incurred (i.e. an active versus passive fatigue state) as well as the energetical mechanisms involved during task performance. A simple driving simulator task was used as the main tracking task, requiring constant attention and concentration. This task was performed for approximately two hours. Three experimental groups (consisting of 14 subjects each) were used: a control group that performed the tracking task only, a group that performed a five minute auditory memory span task concurrently with the driving task after every 20 minutes of pure driving, and a group that performed a visual choice reaction task for five minutes following every 20 minute driving period. The secondary tasks were employed in order to evaluate the extent of resource allocation as well as arousal level. Performance measures included various driving performance parameters, as well as secondary task performance. Physiological measures included heart rate frequency (HR) and various time- and frequency-domain heart rate variability (HRV)parameters, pupil dilation, blink frequency and duration, fixations, and saccadic parameters as well as critical flicker fusion frequency (CFFF). The Borg CR-10 scale was used to evaluate subjective fatigue during the task, and the NASA-TLX was completed following the task. A decline in driving performance over time was supplemented by measures such as HR, HRV and pupil dilation indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Longer and faster saccades were also evident over time, coupled with shorter fixations. With regards to the secondary task influence, the choice RT task did not affect any behavioural or physiological parameters, thereby contesting the active fatigue theory of resource depletion, as well as implying that the increase in demand for the same resources used by the primary task was insufficient to affect the state of the subjects. The increased load elicited by the memory span task improved driving performance and increased measures of HR, HRV, pupil dilation and blink frequency. Some of these measures produced opposite effects to what was expected; an attempt to explain the dissociation of the various physiological parameters was expressed in terms of arousal, effort and resource theories. Overall, the results indicate that the fatigue and/or reduced arousal accompanying a monotonous sustained attention task can, to some degree, be alleviated through intermittent performance of a secondary task engaging mental resources other than the ones used for the primary task. The degree to which such a task is beneficial, however, requires careful consideration as while an immediate increase in arousal and primary task performance is noted, the impact of the task on general attentional resources may be detrimental in the case of reacting should an emergency situation occur.
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Berman, Tamara. "Effects of methylphenidate on complex cognitive : processing in attention-deficit hyperactivity disorder." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0023/NQ50112.pdf.
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Joshi, Aditi A. "Effects of meditation training on attentional networks: A randomized controlled trial examining psychometric and electro-physiological (EEG) measures." Thesis, University of Oregon, 2007. http://hdl.handle.net/1794/8452.
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x, 133 p. ; ill. (some col.) A print copy of this title is available through the UO Libraries under the call number: SCIENCE QP405 .J67 2007Meditation has been defined as a "group of practices that self-regulate the body and mind, thereby affecting mental events by engaging a specific attentional set" (Cahn & Polich, 2006). We conducted a randomized, longitudinal trial to examine the effects of concentrative meditation training (40 min/day, 5 days/week for 8 weeks) on top-down, voluntary control of attention with a progressive muscle relaxation training group as a control. To determine if training produced changes in attentional network efficiency we compared, pre- and post-training, mean validity effect scores (difference between invalid cue and center cue reaction time) in the contingent capture paradigm (Folk et al., 1992). The meditation group showed a trend towards improvement of top-down attention while the relaxation group did not. Using EEG we assessed the changes in amplitudes of wavelets during periods of mind-wandering and meditation. Periods in which subjects were on- vs. off-focus during the meditation task were identified by asking subjects to make button presses whenever the mind wandered and also at probe tones, if they were off-focus. After training, the episodes of mind-wandering were significantly lower in the meditation group as compared to the relaxation group. Increased amplitudes of alpha and theta EEG frequencies in the occipital and right parietal areas were seen during the meditation task for the meditation but not the relaxation group as an effect of training. A baseline EEG trait effect of reduced mental activity was seen (meditation training: occipital and right parietal areas; relaxation training: only occipital areas). Within a given meditation session, prior to training, alpha and theta activity was lower in on-focus conditions (occurring immediately after subjects discovered they were off-focus and returned to active focus on the breath/syllable) compared to meditative focus segments. After training, we found higher alpha amplitude in periods of meditative focus as compared to periods of mind wandering for both groups. However, the meditation group showed significantly higher theta amplitude than the relaxation group during the meditative state segments.
Adviser: Marjorie Woollacott
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Stanislaus-Carter, Rudi. "Behavioural examination of the role of the thalamic reticular nucleus in attention." Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/16298.
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The ability to selectively attend to aspects of the environment which signal opportunity or danger, while marginalising irrelevant stimuli is critical to an animal's survival. With finite cognitive resources, the brain must dedicate resources to only those stimuli that are biologically significant. Incoming thalamic information must therefore be filtered. The thalamic reticular nucleus has long been considered critically involved in modulating thalamic sensory processing. Sharing connections with both the thalamus and cortex, it is ideally located to modulate the transfer of pertinent incoming sensory information. This thesis sought to determine the functional role of the thalamic reticular nucleus in attentional processes by combining lesion techniques and well established behavioural paradigms. Chapter 3 examined the role of visual thalamic reticular nucleus lesions on performance in a two-alternative forced choice reaction time task when auditory distractors were presented. No effect of the lesion was found. Chapter 4 examined excitotoxic lesions of thalamic retlcular nucleus on performance in the 7-stage attentional set shifting task. No effect of lesion on performance was found. Chapter 5 examined mediodorsal thalamus and rostral thalamic reticular nucleus lesions on performance in the attentional set shifting task. Despite strong connectivity with prefrontal regions known to be involved in this task, there was no effect of either lesion. Finally, chapter 6 examined the effects of reducing dopamine input into the thalamic reticular nucleus on a two alternative forced choice reaction time task. Following bilateral lesions the animals were impaired in the re-orientation of attention – suggesting a critical role for both the thalamic reticular nucleus and dopamine in attentional processes. Taken together, these results suggest that while the thalamic reticular nucleus is involved in attention, it is not involved in every aspect.
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Petrof, Iraklis. "Behavioural investigation of the role of caudal thalamic reticular nucleus in attention." Thesis, University of St Andrews, 2007. http://hdl.handle.net/10023/373.
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The thalamic reticular nucleus (TRN), and especially its caudal, sensory-related, half (cTRN), has been hypothesised for years to be at the very heart of thalamic sensory processing modulation, and attentional processes in particular. Very limited behavioural evidence is available, nonetheless, in support of such a functional attribution. In this thesis we carried out a series of investigations, combining immunocytochemical and lesion techniques with tests of behaviour, in order to examine the potential role of cTRN in attention and identify the attentional processes, if any, that it is more likely to contribute to. In chapter II, we looked at the Fos activation levels within modality-specific sectors of cTRN following attentive behaviours to stimulation of different modalities. We observed a selective activation of the visual sector of cTRN in visually attentive animals but not in tactilely attentive, yet visually stimulated, animals, thus demonstrating an involvement of that area in processes of visual attention. In chapter III we looked at the role of cTRN in cross-modal expressions of divided attention. We found that its removal, through neurotoxic lesioning, did not result in any behavioural costs with regard to the division of attention. Detriments in response accuracy, however, suggested that cTRN may be involved in stimulus processing enhancement operations, unrelated with the division of attention. Finally, in chapters IV and V, we looked at the effects of lesions of the visual sector of cTRN (TRNvis) on the ability to orient attention covertly within visual space. We found that the removal of TRNvis did not affect visual covert orienting behaviour, both when this is triggered by exogenous and endogenous means. Overall our results suggest that even though cTRN appears to be involved in some aspects of attention, it does not represent a necessary structure for the generation and operation of certain other forms of attention.
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Lee, Kangsoo, and 李岡洙. "Using EEG methodology to examine the effect of exercise induced fatigue on the direction of attention during motor skill performance." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206744.
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Exercise induced fatigue can have a negative impact on motor skill performance. While part of the decline is attributable to physiological factors that directly influence the coordination of movement, psychological factors may also contribute. Typically, motor learning environments encourage the accumulation of task-relevant declarative knowledge, which can be depended on to consciously support performance. The literature suggests that skills learnt in this way are vulnerable to demanding performance environments, including those in which the performer is fatigued. Recent empirical work has demonstrated that ‘implicit’ motor learning environments, devised to limit declarative knowledge buildup and/or dependence on working memory, promote resilient skill performance even after exhaustive fatigue protocols. Such findings imply that dependence on declarative knowledge to support motor skill execution may be a limiting factor under physiologically fatigue. However, it remains unclear the effect fatigue has on attentional resources, such as working memory.
Using established experimental paradigms and EEG methodology, a research project was designed to investigate. Two explanations were considered: (1) fatigue distracts attention away from the control of movement or (2) fatigue directs attention to the skill, which interferes with automated control of the movement. In this study novice participants were allowed to freely accumulate declarative knowledge before completing a targeted muscle-fatigue protocol. A probe response paradigm assessed participants’ ability to recall the position of movement at the time a tone sounded, under the assumption that better recall reflects skill-focused attention. Neural activity was monitored by wireless EEG technology. Neural co-activation (or coherence) between brain regions associated with motor planning (Fz or F3) and with verbal-analytical processing (T3) has been suggested to reflect conscious control of motor skills. Therefore, a fatigue induced increase in T3-F3 coherence can be interpreted as increased conscious involvement in movement control, whereas, a decrease suggests a shift of attention away from movement control. The data collected suggests that to some extent fatigue raises visual-spatial and verbal-analytical contributions to motor control, but highlights methodological issues and limitations of the work.published_or_final_version
Human Performance
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Master of Philosophy
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Shue, Karen L. "Attention deficit hyperactivity disorder and the frontal lobe syndrome." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74239.
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The usefulness of frontal lobe (FL) dysfunction as a conceptual model for Attention Deficit Hyperactivity Disorder (ADHD) was investigated. Twenty-four ADHD and 24 normal control (NC) children were tested using tasks sensitive to FL deficits in motor control and problem solving skills and memory tasks sensitive to temporal lobe (TL) dysfunction. ADHD children differed significantly from NCs on measures of FL function, but not on tests of TL functions. Wherever norms were available for normal children on the same FL tests, ADHD subjects performed like 6 to 7 year olds, in spite of their mean age of 10 years and minimum age of 8 years. The differential performance of ADHD children on tasks sensitive to FL and TL damage supports the conceptualization of ADHD deficits as analogous to FL dysfunction and implies that deficits are not explained by reference to generalized impairment.
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Russell, William David. "The effects of a dissociative strategy of attention on ratings of perceived exertion during physical exercise." Virtual Press, 1992. http://liblink.bsu.edu/uhtbin/catkey/834509.
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The purpose of this investigation was to compare associative and dissociative psychological strategies of attentional focus for their effects on self - report ratings of perceived exertion (RPE), and heart rate during endurance exercise. Trained cyclists (n = 7) performed three 60 minute experimental rides on a bicycle ergometer which consisted of an association ride (attention focused on heart rate feedback), a dissociation ride (attention focused on responding to a cue word on a videotape), and a control condition ride in which focus of attention was not purposely manipulated. Results indicated that the deliberate application of a cognitive strategy designed to encourage an individual to associate or dissociate did not differentially effect either actual efficiency (heart rate) or perception of exercise intensity (RPE scores). Overall, it was concluded that there was a trend for the dissociation condition to result in higher RPE scores than the association condition or control condition.School of Physical Education
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Glauert, Rebecca. "Body dissatisfaction and its relationship with the perceptual effects of exposure to bodies and attentional biases toward bodies." University of Western Australia. School of Psychology, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0220.
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[Truncated abstract] Socio-cultural processes are often cited as one of the main causes of body dissatisfaction amongst women. Numerous studies have found that exposure to thin, idealized images in the media increases women's body dissatisfaction. The central aims of this thesis are to investigate how exposure to thin and fat bodies alters womens perceptions of body normality and body ideals, whether body dissatisfaction is related to these changes, and whether body dissatisfaction is associated with an attentional bias toward thin bodies. In Chapter 1 I review the main theories dominating body dissatisfaction research. In Chapter 2 I present two studies which investigate how exposure to thin and fat bodies influences perceptions of body normality and ideal body size. Women who varied on a measure of body dissatisfaction (Experiment 1 & 2) and awareness and acceptance of societal standards of beauty (Experiment 2) rated a range of computer generated bodies, varying in simulated BMI, for how normal (Experiment 1 & 2) and ideal they looked (Experiment 2). They were then exposed to either thin or fat bodies, and they re-rated the bodies. Increased levels of body dissatisfaction and internalisation of societal standards of beauty were related to a thinner most normal and ideal rated body, before any exposure, as well as a greater discrepancy between the most normal and ideal rated bodies. Both Experiments 1 & 2 revealed that brief exposure to thin or fat bodies altered women's perceptions of body normality and body ideal, where exposure to fat bodies made womens perceptions of a normal and ideal body fatter, and exposure to thin bodies, made perceptions of the most normal and ideal rated body thinner. ... In Chapter 5 I present normative data for the Body Shape Questionnaire-34 (a measure of dissatisfaction with body weight and shape) (Cooper et al, 1987) from an Australian university sample. Many researchers use university samples iv when investigating body dissatisfaction, so it is useful to have normative data for such a sample. One thousand and fifty two women aged between 16 and 30 completed the BSQ-34. A mean score of 94.4 (SD = 34.5) was found, with a range of 34-203. My scores are comparable with those found in an American undergraduate sample, and are significantly higher than those found in community, undergraduate and clinical samples in the UK and Italy. Results indicate that levels of body dissatisfaction may be higher in Australia than in the UK and Italy. Together, these studies provide some important new findings. 1) Body dissatisfaction and internalisation of societal standards of beauty are related to thinner body norms and ideals. 2) Women's perceptions of normal and ideal female body sizes can be readily altered by exposure to thin and fat bodies, and 3) women selectively attend to thin bodies, but the more dissatisfied she is with her own body, the less she attends to thin bodies. Potential implications of these results for the treatment of body dissatisfaction may include the incorporation of treatment programs which target not only unnaturally slim body ideals, but perceptions of what constitutes a normal body, as well as trying to alter selective attention toward thin bodies in the environment. The results may also highlight to the media that consistently showing ultra slim models will very likely affect women's perceptions of normal and ideal female body sizes.
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Cleaveland, Bonnie L. "An attention allocation model for the effects of alcohol on aggression." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-10102009-020232/.
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Rogers, Jeffrey Michael. "Electrophysiological and neuropsychological assessment of automatic and controlled processing aspects of attention after mild traumatic brain injury." University of Western Australia. School of Psychology, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0191.
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[Truncated abstract] Controlled and automatic processing are broad categories, and how best to measure these constructs and their impact on functioning after mild traumatic brain injury (TBI) remains uncertain. The purpose of this thesis was to examine automatic and controlled processing aspects of attention after mild TBI using the Paced Auditory Serial Addition Task (PASAT) and event-related potentials (ERPs). The PASAT is one of the most frequently used tests to evaluate attentional functioning. It has been demonstrated to be a measure sensitive to both acute and longer-term effects of mild TBI, presumably due to demands for rapid processing and executive attentional control. ERPs provide a noninvasive neurophysiological index of sensory processing and cognitive functions and have demonstrated sensitivity to even minor cognitive dysfunction. The parameters provided by this functional technique may be those most likely to distinguish individuals with mild TBI from controls. Initially, it was hypothesized that successful novice PASAT performance requires the engagement of executive attention to establish novel controlled information processing strategies. Ten individuals who had suffered a mild TBI an average of 15.20 months previously were therefore expected to demonstrate processing abnormalities on the PASAT, relative to 10 healthy matched controls. Although the mild TBI group reported significant intensification of subjective symptoms since their injury, compared to controls, the mild TBI group provided a similar amount of correct PASAT responses. ... In the first experiment a visual search task consisting of an automatic detection and a controlled search condition was developed. In the second experiment the search task was performed concurrently with the PASAT task in a dual-task paradigm. In the mild TBI group, prior failure to establish more efficient forms of information processing with practice was found to significantly interfere with simultaneous performance of the PASAT task and the attention demanding condition of the search task. The pattern of impaired performance was considered to reflect a reduction in processing resources rather than a deficit in resource allocation. Dual-task performance in the control group was not associated with a large interference effect. In general, the results of this thesis suggest that individuals with mild TBI are impaired in their ability to progress from the stage of effortful controlled information processing to a stage of more efficient, automatic processing, and thus suffer a subtle attentional deficit. Following mild TBI, performance levels equivalent to controls may only be achieved with an abnormal expenditure of cognitive effort. As a result of the neuropathologic consequences of injury, individuals who have sustained a mild TBI are less able to benefit from practice, experience difficulty coping with simultaneous performance of secondary task, and are susceptible to distressing subjective symptomatology.
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Chaplin, Caley. "The factors affecting self-regulation through the analysis of physiological, psychological and behavioural measures during task-switching." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1006027.
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Individuals are required to manage multiple tasks which require strategic allocation of time and effort to ensure goals are reached efficiently. By providing the worker with autonomy over their work, performance and worker well-being have improved. This increased control allows individuals to organize work according to the needs of the body, which prevents fatigue leading to improved productivity. When given the option, humans tend to switch between tasks frequently. This behaviour can be used to determine the change in self-regulation strategies. An understanding of human task-switching behaviour is important for the design of job rotation systems. However, there is a lack of evidence explaining the factors motivating the need to switch between tasks. This study aims to use physiological, subjective and behavioural measures to explain the factors influencing selfregulation through the act of task-switching. Three primary hypotheses were developed to explain the factors underlying taskswitching behaviour. It was hypothesized that the degree of boredom experienced, the effort required to perform the task and the resource usage induced by the task are factors responsible in deciding task switching behaviour. Participants (17 males and 17 females) switched freely between five different information-processing tasks for the 45 minutes. Participants were allowed to switch back and forth between tasks and did not have to conduct all five tasks. The following measures were recorded during the experiment: subjective measures of boredom, mental effort, task frustration and perceived performance of the tasks; energy consumption and physiological measures of effort (HR, HRV and body temperature) and behavioural measures, including duration and frequency of task. Perceived boredom was found to differ among the tasks and before and after the experiment. The average boredom rating at each task transition for all tasks exceeded a score of 2.5 out of a possible 4. There were no significant changes in physiological measures between the beginning and end of the task trials. However, changes in physiological measures showed a decrease in effort investment following task transition. Heart rate variability was lower for externally-paced tasks than for self-paced tasks, despite the differences in cognitive demands. The most frequent task-switch combination occurred between tasks of high and low cognitive demand. The least frequent task-switching combination occurred between tasks of similar characteristics, which produced no differences in physiological responses. Task-switching behaviour was influenced by the degree of boredom, and therefore more time was spent on less monotonous tasks. The level of physiological effort required for the task affected task-switching behaviour. Task switches were made before any changes in effort took place in an attempt to maintain task efficiency. It appears plausible that a task switch was made to reduce effort investment and activation levels. The type of information processing resources used by different tasks affected the task-switching combinations. Individuals tended to switch between tasks of differing resources so that those in limited supply were able to replenish. Therefore the findings from this study can potentially be used to improve the design of job rotation systems. Such improvements may enhance productivity and worker well-being by inhibiting the onset of down regulation and fatigue processes. This study showed that autonomy is necessary for individuals to regulate behaviour to suit human needs.Microsoft� Office Word 2007
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Kedzior, Karina Karolina. "Chronic cannabis use and attention-modulated prepulse inhibition of the startle reflex in humans." University of Western Australia. School of Medicine and Pharmacology, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0027.
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Background. Various studies show that cannabis use alters attention and cognitive functioning in healthy humans and may contribute to development of schizophrenia or worsening of pre-existing psychosis. However, the impact of cannabis use on brain function in humans is not well understood. Schizophrenia is associated with a deficit in prepulse inhibition (PPI), the normal inhibition of the startle reflex by a non-startling stimulus (prepulse), presented before the startle stimulus at short time intervals (lead-time intervals). Such PPI deficit is thought to reflect a sensorimotor gating dysfunction in schizophrenia. PPI is also modulated by attention and PPI reduction in schizophrenia is observed when patients are asked to attend to, not ignore, the stimuli producing PPI. The aim of the current study was to investigate the association between self-reported chronic cannabis use and attentional modulation of PPI in healthy controls and in patients with schizophrenia. Furthermore, the association between cannabis use and other startle reflex modulators, including prepulse facilitation (PPF) of the startle reflex magnitude at long lead-time intervals, prepulse facilitation of the startle reflex onset latency and habituation of the startle reflex magnitude, were examined. Method. Auditory-evoked electromyographic signals were recorded from orbicularis oculi muscles in chronic cannabis users (29 healthy controls and 5 schizophrenia patients) and non-users (22 controls and 14 patients). The data for 36 participants (12 non-user controls, 16 healthy cannabis users, and eight non-user patients) were used in the final analyses and the patient data were used as a pilot study, because relatively few participants met the rigorous exclusionary criteria. Participants were instructed to attend to or to ignore either the startle stimuli alone (70 100 dB) or prepulse (70 dB) and startle stimuli (100 dB) separated by short lead-time intervals (20 200 ms) and long lead-time intervals (1600 ms). In order to ignore the auditory stimuli the participants played a visually guided hand-held computer game. A pilot study showed that the response component of playing the game had no effects on attentional modulation of the startle reflex magnitude and onset latency. Results. Relative to controls, cannabis use in healthy humans was associated with a reduction in PPI similar to that observed in schizophrenia while attending to stimuli, and with an attention-dependent dysfunction in the startle reflex magnitude habituation. While ignoring the stimuli there were no statistical differences in PPI between cannabis users and controls, although PPI in cannabis users tended to differ from that of the patients. The reduction in PPI in cannabis users was correlated with the increased duration of cannabis use, in years, but not with the concentration of cannabinoid metabolites in urine or with the recency of cannabis use in the preceding 24 hours. Furthermore, cannabis use was not associated with any differences in PPF, onset latency facilitation, and startle reflex magnitude in the absence of prepulses. The accuracy of self-reports of substance use was also investigated in this study and was found to be excellent. In addition, the study examined the validity of the substance use module of the diagnostic interview, CIDI-Auto 2.1, which was found to be acceptable for cannabis misuse diagnoses (abuse and/or dependence). Finally, cannabis dependence was found to be associated with more diagnoses of mental illness other than schizophrenia (mainly depression). Conclusions. The results of the current study suggest that chronic cannabis use is associated with schizophrenia-like deficit in PPI in otherwise healthy humans. This PPI reduction is associated with attentional impairment rather than a global sensorimotor gating deficit in healthy cannabis users.
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Tau, Sethunya Harriet Hlobisa. "An analysis of regulatory mechanisms during sustained task execution in cognitive, motor and sensory tasks." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1006806.
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Fatigue is a state that, although researched for many years, is still not completely understood. Alongside this lack of a general understanding of fatigue is a lack of knowledge on the processes involved in the regulation of fatigue. The existing theories relating to regulation are focussed on mental effort regulation, suggesting that performance outcomes are co-ordinated by effort regulation that functions by making alterations to physiological processes and strategic adjustments at a cognitive level in response to cognitive demands and goals. Since fatigue is a multi-dimensional construct with psychological, physiological, and behavioural effects that respond to endogenous and exogenous variables, it follows then that fatigue assessment techniques ought to include multi-dimensional measures to acquire a holistic depiction of the fatigue symptom. This study aimed to assess whether or not a mechanism that regulated fatigue during sustained task execution could be identified and whether this mechanism resulted in regulation patterns that were distinct to a specific task. An additional aim of the study was on assessing whether the manner in which performance, psychophysical and subjective variables were modified over time followed a similar regulation pattern. The research design was aimed at inducing task-related fatigue twice on two different occasions in the same participants and evaluating the resultant changes in fatigue manifestation. This was done to assess the ability of participants to cope with fatigue as a result of previous experience. The research protocol included three tasks executed for an hour aimed at targeting and taxing the sensory, cognitive, motor resources, each task performed twice. 60 participants were recruited to participate in the current study, with 20 participants – 10 males and 10 females – randomly assigned to each of the three tasks. The cognitive resource task consisted of a memory recall task relying on working memory intended to evaluate the extent of reductions in memory and attention. The sensory resource task consisted of a reading task measuring visual scanning and perception designed to evaluate the extent of reduced vigilance. The motor resource task consisted of a modified Fitts’ stimulus response task targeted at monitoring the extent of movement timing disruption. Performance measures comprised of: response delay and the number of correctly identified digits during the cognitive resource task, the amount of correctly identified errors and reading speed during the sensory resource task, response time during the motor resource task, and responses to simple auditory reaction time tests (RTT) initiated at intervals during the task and then again at the end of each task. Physiological measures included ear temperature, eye blink frequency and duration, heart rate (HR), and heart rate variability (HRV). Subjective measures included the use of the Ratings of Perceived Exertion Category Ratio 10 scale (RPE CR 10) to measure cognitive exertion and the NASA-Task Load Index (NASA-TLX) to index mental workload. Eye blink frequency and duration, HR and HRV were sensitive to the type of task executed, showing differing response patterns both over the different tasks and over the two test sessions. The subjective measures indicated increasing RPE ratings over time in all tasks while the NASA-TLX indicated that each task elicited different workloads. Differing task performance responses were measured between the 1st test session and the 2nd test session during all tasks; while performance was found to improve during the 2nd test session for the motor and sensory tasks, it declined during the cognitive task. The findings of this research indicate that there was a regulatory mechanism for fatigue that altered the manner in which performance, psychophysical and subjective variables were modified over time, initiating a unique fatigue regulation pattern for each variable and each task. This regulation mechanism is understood to be a proactive and protective mechanism that functions through reducing a person’s ability to be vigilant, attentive, to exercise discernment, and to direct their level of responsiveness, essentially impacting how the body adapts to and copes with fatigue. The noted overall findings have industry implications; industries should consider accounting for the effects of this regulatory mechanism in their fatigue management interventions, specifically when designing job rotation and work/rest schedules because each cognitive task, having elicited a unique fatigue regulation pattern, ought to also have a different management program.Microsoft� Office Word 2007
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Zhang, Wujie. "Network Models of the Lateral Intraparietal Area." Thesis, 2016. https://doi.org/10.7916/D8MS3SP5.
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The monkey lateral intraparietal area (LIP) is involved in visual attention and eye movements. It has traditionally been studied using extracellular recording, where often a single neuron is recorded at a time. Thus we have a wealth of correlational knowledge of what LIP neurons do, but not how or why, i.e. we do not know the circuit mechanisms and functions of the observed LIP activity. In this thesis, we have aimed to uncover the circuit mechanisms underlying LIP activity by building tightly constrained computational models.
In Part 1, we found that during two versions of a delayed-saccade task, beneath similar population average firing patterns across time lie radically different network dynamics. When neurons are not influenced by stimuli outside their receptive fields (RFs), dynamics of the high-dimensional LIP network lie predominantly in one multi-neuronal dimension, as predicted by an earlier model. However, when activity is suppressed by stimuli outside the RF, LIP dynamics markedly deviate from a single dimension. The conflicting results can be reconciled if two LIP local networks, each dominated by a single multi-neuronal activity pattern, are suppressively coupled to each other. These results demonstrate the low dimensionality of LIP local dynamics and suggest active involvement of LIP recurrent circuitry in surround suppression and, more generally, in processing attentional and movement priority and in related cognitive functions.
In Part 2, we examine the mechanisms of learning in LIP. When monkeys learn to group visual stimuli into arbitrary categories, LIP neurons become category-selective. Surprisingly, the representations of learned categories are overwhelmingly biased: while different categories are behaviorally equivalent, nearly all LIP neurons in a given animal prefer the same category. We propose that Hebbian plasticity, at the synapses to LIP from prefrontal cortex and from lower sensory areas, could lead to the development of biased representations. In our model, LIP category selectivity arises due to competition between inputs encoding different categories, and bias develops due to excitatory lateral interactions among LIP neurons. This model reproduces the different levels of category selectivity and bias observed in multiple experiments. Our results suggest that the connectivity of LIP allows it to learn the behavioral importance of stimuli in order to guide attention.
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Van, Doren Jon Jay. "Remediation of sustained attention following traumatic brain injury: vigilance task training and the generalization of its effects." Thesis, 1991. https://dspace.library.uvic.ca//handle/1828/9567.
Full textAbstract:
Studies of sustained-attention retraining following brain injury are reviewed, and found to have produced inconclusive results. The reason for this, it is suggested, is that a standard operational analysis of attention has not been applied, as evidenced by considerable inconsistency in the dependent measures and treatment methods used from study to study. The present study addresses this concern by applying well established principles of operant conditioning to the analysis and remediation of attention deficits. After briefly reviewing the variety of task parameters in the attention literature, noting ambiguities inherent in the various conceptualizations of attention, it is decided to train vigilance task performance, a relatively unambiguous and uncontroversial operational definition of sustained attention. Both the principle of immediacy, of reinforcement (feedback of correct and incorrect on each trial) and shaping (gradual increase of speed demands contingent on increased performance accuracy) are employed. The issue of generalization is deemed central to concerns of treatment efficacy, and is explored by administration of alternate versions of the same basic vigilance task. Results show that training with immediate reinforcement and speed-shaping produced better acquisition of the trained task than delayed feedback and invariant speed of stimulus presentation. Furthermore, gains resulting from training were essentially limited to the task on which training was conducted, with little evidence for generalization to like tasks employing different stimuli. These results are discussed in terms of the applicability of the construct of sustained attention to head injury rehabilitation.Graduate
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Perrier, Erica Taylor. "Spinal reflex control in healthy and ACL-injured women during a distracting task." Thesis, 2011. http://hdl.handle.net/1957/23655.
Full textAbstract:
Female athletes exhibit three- to six-fold greater incidence of noncontact anterior cruciate ligament (ACL) injury relative to their male counterparts. The increased risk appears to stem from interactions between several risk factors, that can roughly be categorized as anatomic, biomechanical, hormonal, and neuromuscular. Neuromuscular risk factors have recently gained a greater focus, and include differences in the timing and magnitude of activation of lower extremity and trunk musculature. In addition to neuromuscular risk factors, the incidence of ACL injury is not evenly distributed across the menstrual cycle, suggesting that hormonal fluctuations may influence neuromuscular control. Finally, it is known that even well-trained athletes experience decrements in performance and postural control when forced to attend to multiple sensory stimuli, which is common in many sports. PURPOSE: To explore neuromuscular differences in the ways healthy and ACL-injured women respond to a secondary task requiring fine motor control and sustained mental focus (typing task). Our investigation encompassed three broad aims. First, we sought to determine whether ACL-injured individuals demonstrated similar reflex profiles to healthy individuals, as well as to determine whether the ACL-involved limb was similar to its uninvolved counterpart. Our second aim was to determine whether the typing task resulted in attenuated Hoffmann (H) reflex amplitudes, and to investigate whether any observed changes were similar in healthy and ACL-injured groups. Finally, our third broad aim was to utilize more complex H reflex analysis techniques to determine whether differences in spinal excitability existed at different points in the menstrual cycle. METHODS: Thirty nine recreationally active women (20 with prior unilateral noncontact ACL injury: 24.0 ± 4.5 years; 23.8 ± 4.5 kg•m⁻²; 4.1 ± 2.6 years post-injury; 19 with no history of knee injury: 23.8 ± 4.5 years; 23.1 ± 2.3 kg•m⁻²) agreed to participate, and were tested during days 2-5 (follicular phase) of the menstrual cycle. A sub-set of this original group (n=8; 24.0 ± 4.8 years; 22.0 ± 2.1 kg•m⁻²) also agreed to return for a second testing session 24-96 hours after ovulation (early luteal phase), in order to assess H reflex differences across the menstrual cycle. During each testing session, H reflex testing was used to explore spinal-level control mechanisms of the lower extremity musculature under both Rest and Task conditions. In the control group, the dominant limb was tested (CON-D) while in the ACL group, both the uninvolved (ACL-UN) and involved (ACL-INV) limbs were assessed. Differences between groups (Control vs. ACL) and within-groups (ACL-UN vs. ACL-INV) were explored. RESULTS: At rest, H reflex parameters in ACL-INV were generally similar to ACL-UN and to CON-D. However, differences in presynaptic inhibition were apparent in ACL-INV that imply reduced reflex plasticity. During the typing task, both the Control and ACL groups experienced attenuated H reflex parameters. In the sub-set of participants who were tested twice during the menstrual cycle, a significant increase in presynaptic inhibition was observed during the early luteal phase compared to the follicular phase. CONCLUSION: While individuals with prior ACL injury display similar H reflex profiles to healthy individuals, the ACL-involved limb may demonstrate less reflex plasticity in response to environmental changes. This lack of plasticity may potentially increase the risk of re-injury. In addition, an upper extremity task requiring fine motor control and sustained mental focus attenuates the H reflex in both groups. This attenuation has implications for lower-extremity neuromuscular control in dual-task environments. Finally, the increase in presynaptic inhibition observed during the early luteal phase may provide insight into why ACL injuries are not evenly distributed across the menstrual cycle.Graduation date: 2012
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Bauer, Tanja. "System response times in a simulated driving task : effects on performance, visual attention, subjective state and time estimation." Diss., 2009. http://hdl.handle.net/10500/2610.
Full textAbstract:
The utilisation of navigation systems in cars has given rise to road safety concerns, and the design and functionality of such systems must therefore be adjusted to the users’ needs, since they have to divide their attention between driving and the operation of the navigation system. The study was aimed at finding the optimum system response time (SRT) which would enable a driver to focus as much as possible on the road while attaining an efficient task completion time using an electronic navigational system. The research project consists of two separate experiments and was completed by 10 subjects. Experiment 1 included a temporal reproduction task and a secondary memory task. The subjects had to memorise two symbols and then reproduce six time spans ranging from 1 to 30 s to provide a baseline measurement of their time estimation abilities. Experiment 2 consisted of a simulated automobile driving task. While driving in the simulator the subjects completed a memorising task displayed on a touch screen. The task was presented with seven different system response times (SRTs) ranging from 0 to 30 s. The effects of different SRTs on the eye movement from road to monitor, regarding the duration of fixation and the frequency of change were evaluated. The distribution of gazes to the secondary task was analysed to provide information about the time estimation performance in the driving simulator. Other dependent variables tested were the accuracy of selected items, memory game performance, drive performance and the subjective state of the test person. The results of this study can be employed to find the optimum duration of inter-task delays for in-vehicle technical devices.Psychology
M.A. (Psychology)
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Coskunpinar, Ayca. "The relationship between trait impulsivity and alcohol related attentional biases." Thesis, 2015. http://hdl.handle.net/1805/7904.
Full textAbstract:
Indiana University-Purdue University Indianapolis (IUPUI)Harmful alcohol use is a global concern, which has made research in this area a prime public health interest. Previous research has identified alcohol-related attentional biases (Cox et al., 2002, 2007; Marissen et al., 2006; Streeter et al., 2008) and impulsivity (see Acton, 2003; Dick et al., 2010; Mulder, 2002) as two important predictors that affect alcohol use, seeking, and relapse (Cox et al., 2002; Robbins & Ehrman, 2004). Recent review of the literature has also revealed that there is a significant relationship between these two constructs (Coskunpinar & Cyders, 2013). The current study used college undergraduate social drinkers (at least 3 drinks per week) (n = 42, mean age = 23.27 (SD = 5.21), female: 69.2%) to examine the relationship between specific trait impulsivity facets and alcohol-related attentional biases and to examine how this relationship is affected by measurement type (eye movement, reaction time measures), attentional bias constructs (initial orientation, delayed disengagement), and environmental cues (specifically mood and alcohol olfactory cues). Participants had alcohol-related attentional bias as measured by reaction time (areas of interest: p < .05) and eye-movement data (areas of interest: p < .05), which was not affected by mood, odor, or urgency.
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Karyadi, Kenny. "The effects of alcohol odor cues on food and alcohol attentional bias, cravings, and consumption." Thesis, 2015. http://hdl.handle.net/1805/7986.
Full textAbstract:
Indiana University-Purdue University Indianapolis (IUPUI)In order to elucidate the role of classical conditioning in food and alcohol co-consumption, the present study examined: (1) the effects of alcohol odor cues on alcohol and food cravings and attentional bias (bias in selective attention toward either food or alcohol pictures relative to neutral pictures); and (2) the role of alcohol odor cue elicited cravings and attentional biases on subsequent consumption. Participants (n = 77; mean age = 30.84, SD = 9.46; 51.9% female, 83.1% Caucasian) first completed the lab portion of the study. In this portion, they were exposed to alcohol and neutral odorants, after which their food and alcohol cravings and attentional bias were assessed. Participants then received an online survey the next day, on which they reported their level of food and alcohol consumption following the lab portion of the study. Using repeated measures analysis of covariance, alcohol odor cues were differentially effective in increasing food and alcohol attentional bias and cravings (Fs= 0.06 to 2.72, ps= 0.03 to 0.81). Using logistic and multiple regressions, alcohol odor cue elicited alcohol attentional bias, food attentional bias, and food cravings were associated with later alcohol consumption, but not with later food consumption or concurrent consumption (βs = -0.28 to 0.48, ps = 0.02 to 0.99; Exp(B)s = 0.95 to 1.83, ps = 0.33 to 0.91). Overall, alcohol odor cues can become conditioned stimuli that elicit conditioned food-related and alcohol-related responses, both of which persist long enough to motivate later alcohol consumption; however, these conditioned responses might not persist long enough to motivate later food or concurrent consumption. These findings serve as a first step in clarifying the role of classical conditioning in concurrent consumption. In particular, they suggest that additional empirical investigations are needed to: (1) clarify the classical conditioning mechanisms underlying concurrent consumption; and (2) examine whether interventions targeting classical conditioning mechanisms are effective for reducing alcohol use.