No description available.

Flexible and goal-driven behaviour requires a process by which the appropriate task-set is selected and maintained in a privileged state of activation. This process can be conceptualised as loading a task-set into a procedural working memory (PWM) buffer. Task switching experiments, which exercise this process, reveal “switch costs”: increased reaction times and error rates when the task changes, compared to when it repeats. The process of loading a task-set into PWM may be one source of these costs. The switch cost is reduced with preparation, suggesting that at least some of the processes involved in a successful change of task can be achieved in advance of the stimulus. The aim of this thesis was to investigate the properties of PWM, and its contribution to task-set control. One account of PWM distinguishes between the level at which recently exercised (but currently irrelevant) task-sets are represented, and the level at which only the currently relevant task-set is maintained in a most active state. To distinguish between these levels of representation, and to assess the extent to which the process of getting a task-set into a most-active state (loading it into the PWM buffer) is subject to a capacity limit at each level, the experiments varied the number of tasks participants switched among (Experiments 1 and 2), and the complexity of individual task-sets (Experiments 3-6) in a task-cueing paradigm. In Experiments 1 and 2, participants switched among three or five tasks, in separate sessions. There was no effect of the number of tasks on the switch cost, or its reduction with preparation, provided that recency and frequency of task usage were matched. When recency and frequency were not matched, there appeared to be a larger switch cost with five tasks at a short preparation interval, suggesting that the time consumed by getting a task-set into a most active state is influenced by its recency and frequency of usage, not the number of alternatives per se. However, Experiment 3 showed that the time required to select an S-R mapping within a task-set does increase as a function of the number of alternatives (even when stimulus frequency and recency are matched), suggesting that representation of the most active task-set in a PWM buffer is subject to a strict capacity limit. Experiments 4-6 further investigated the capacity limit of this PWM buffer, and found that task-set preparation was more effective for task-sets that are less complex (i.e. specified by fewer S-R rules). These findings suggest that only very few S-R rules can be maintained in a most active state in the PWM buffer. Finally, Experiments 7-9 investigated whether S-R rules are represented phonologically for task-set maintenance and preparation, by manipulating the phonological properties of the stimulus terms. But task-cueing performance was not affected by the name length (Experiment 7) or phonological similarity (Experiments 8 and 9) of the stimulus terms. These results suggest that phonological representations of S-R rules do not make a functional contribution to task-set control, possibly because the rules are compiled into a non-linguistic PWM. The results of these experiments are discussed in terms of a procedural working memory which is separate from declarative working memory, and distinguishes between two levels of task-set control: the level of task-sets, which are maintained in a capacity unlimited state of representation, and the level at which the currently relevant task-set is maintained in a most-active but highly capacity limited state of representation.

The research reported was inspired by the Perfect and Maylor (2000) chapter ‘Rejecting the Dull Hypothesis’. This suggested that cognitive ageing research should not focus purely on whether younger adults outperform older adults on a given task. Hartley, Speer, Jonides, Reuter-Lorez and Smith (2001) showed that older adults do not maintain the dissociability of naming identity, visual identity, and spatial location abilities that is seen in younger adults. Away from the ageing literature, Brown, Forbes and McConnell (2006) demonstrated improvement in visual task performance when the availability of verbal coding was increased. The hypothesis that older adults are less likely to use task specific cognitive mechanisms during short-term visual memory tasks was explored. This was carried out by means of a series of 8 experiments (outlined below), which broadly looked at differences in verbal interference effects on visual task performance, differences in Visual Patterns Task performance based on the availability of verbal encoding, and assessed for age-related differences in interference from an executive task in Visual Patterns Task performance. Data was interpreted through the prism of the Scaffolding Theory of Aging (Park & Reuter-Lorenz, 2009), which suggests that compensatory recruitment is employed both young and older adults in response to extrinsic challenges such as task difficulty, and intrinsic challenges, such as declining performance with age. Experiments 1-3 focused on differential effects of articulatory suppression on visual task performance between young (18-25) and older (60-75) adults. Older adults showed negative effects of suppression in short-term maintenance tasks that were not present in younger adults. Both age groups showed negative effects in a mental image rotation task. This suggested a level of verbal activation in visual tasks for both age groups, but that this activation was more common in older adults. Experiments 4-5 assessed differences in Visual Patterns Task performance between both age-groups depending on the availability of verbal encoding. Younger adults displayed the benefit of available verbal encoding with simultaneous but not sequential presentation of information. Older adults showed a benefit of verbal coding in the simultaneous task if the sequential task featured ordered, not randomised presentation pathways. This suggested that older adult task performance may be affected by all conditions within an experiment, not just the current manipulation condition. Experiments 6-7 demonstrated that older adults’ performance in the simultaneous presentation version of the Visual Patterns Task is affected by the availability of verbal encoding in the first task presented to them. Mean performance on subsequent conditions was higher when ‘high verbal coding’ patterns were seen in the first instance. This was not the case for younger adults. The demonstration of a benefit to performance from the ‘high-verbal coding’ pattern set compared to the ‘low-verbal coding’ set was a marker of higher overall performance across all task conditions for younger adults, but not for the older group. This suggested that even if verbal activation during visual task performance was an occurrence for older adults, it was not necessarily a marker for improved performance. Experiment 8 demonstrated that there were no age-related differences in the level of interference from an executive task (Random Month Generation) on Visual Patterns Task performance. This suggested that older adults do not try to actively recruit executive processes during Visual Patterns Task performance to any greater extent than younger adults do. It is suggested that older adults do use specialised task mechanisms to a lesser extent than younger adults in visual memory task performance. It is likely that this is a passive outcome of a decreased inhibition of verbal coding mechanisms, rather than an active attempt to maintain performance through the recruitment of executive cognitive resources. This is seen by the lack of age-group effects from executive interference tasks.

We live in a rich visual world that we experience as a seamless and detailed stream of continuous information. However, we can only attend to and remember a small portion of our visual environment. The visual system is tasked with stitching together snapshots of the world through near constant eye movements, with around three saccades per second. The situation is further complicated with the visual system being contralaterally organized. Each eye movement can bring items in our environment into a different visual hemifield. Despite the many challenges and limitations of attention and the visual system, how does the brain stitch together our experience of our visual environment? One potential mechanism that could contribute to our conscious perception of a continuous visual experience could be visual working memory (VWM) working to maintain representations of items across saccades. Electrophysiological activity using event-related potentials has revealed the contralateral delay activity (CDA), which is a sustained negativity contralateral to the side of the visual field where subjects are attending. However, how does this work if we are constantly moving our eyes? How do we form a stable representation of items across eye movements? Does the representation transfer over to the other side of the brain, constantly shuffling the items between the hemispheres? Or does it stay in the hemisphere contralateral to the visual field where the items were located when we originally created the representation? The consequences of eye movements need to be examined at multiple levels and time points throughout the process. The goal of my doctoral dissertation is to investigate VWM representations throughout the dynamic peri-saccadic window. In Experiment 1, I will first compare VWM representations across shifts of attention and eye position. With the focus on the effect of maintaining attention on items across eye movements, Experiment 2 will also explore eye movements both towards and away from attended visual hemifields. Finally, Experiment 3 is designed to substantiate our use of the CDA as a tool for examining VWM representations across eye movements by confirming that the CDA is indeed established in retinotopic coordinates.

<p>Previous research has shown both positive and negative effects of gaming on academic and cognitive performance. The purpose of this study was to assess the effect of gaming on development of working memory (WM), inattention, reading and math ability using a longitudinal design. A randomly chosen sample of 335 (168 girls) 6–25 year olds performed tests of visuo-spatial and verbal WM, reading and math ability twice, with a two year interval. Gaming and inattention were assed with questionnaires. Time spent gaming did not affect development of any of the variables. However, game category did correlate with development of visuo-spatial WM, with action-gamers having a more favourable development. There was, however, no positive interaction with more time spent gaming for action-gamers. These results suggest that gaming should not be regarded as a damaging leisure activity. There could instead be some positive effects of gaming, but future research should try to identify the aspects of gaming contributing to this effect.</p>

No description available.

Previous research has shown both positive and negative effects of gaming on academic and cognitive performance. The purpose of this study was to assess the effect of gaming on development of working memory (WM), inattention, reading and math ability using a longitudinal design. A randomly chosen sample of 335 (168 girls) 6–25 year olds performed tests of visuo-spatial and verbal WM, reading and math ability twice, with a two year interval. Gaming and inattention were assed with questionnaires. Time spent gaming did not affect development of any of the variables. However, game category did correlate with development of visuo-spatial WM, with action-gamers having a more favourable development. There was, however, no positive interaction with more time spent gaming for action-gamers. These results suggest that gaming should not be regarded as a damaging leisure activity. There could instead be some positive effects of gaming, but future research should try to identify the aspects of gaming contributing to this effect.

No description available.

Background: Gamma oscillations (30-80 Hz) in the dorsolateral prefrontal cortex (DLPFC) are associated with working memory; a process involving the maintenance and manipulation of information on line (Baddeley, 1986). Gamma oscillations are supported by gamma-aminobutyric acid (GABA) inhibitory interneurons in the DLPFC. Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive method in which to stimulate the cortex that has been shown to modify oscillations, cognition and GABAergic mechanisms. Patients with schizophrenia have severe deficits in working memory that may be related to impairments in GABAergic inhibitory neurotransmission underlying gamma oscillations in the DLPFC. Objective: First, to evaluate gamma oscillatory activity in patients with schizophrenia during working memory compared to healthy subjects. Second, to examine the effect of rTMS applied over the DLPFC on gamma oscillations generated during working memory in healthy subjects. Third, to examine the effect of rTMS applied to the DLPFC on gamma oscillations in patients with schizophrenia compared to healthy subjects. Hypotheses: First, it was hypothesized that patients with schizophrenia would exhibit an alteration in gamma oscillatory activity. Second, it was hypothesized that rTMS would be effective in enhancing gamma oscillations in healthy subjects. Third, it was hypothesized that rTMS would be effective in inhibiting gamma oscillations in patients with schizophrenia. Results: The first study found that patients with schizophrenia generate excessive gamma oscillations during working memory compared to healthy subjects. The second experiment found that rTMS over the DLPFC resulted in the potentiation of gamma oscillations in healthy subjects during working memory. The third experiment demonstrated that rTMS inhibited excessive gamma oscillations in patients with schizophrenia while an opposite effect was found in healthy subjects. Conclusions: rTMS applied over the DLPFC modulates frontal gamma oscillatory in healthy subjects and in patients with schizophrenia depending on baseline levels of activity, a finding that may ultimately translate into a better understanding of the mechanisms leading to cognitive improvement in this disorder.

Background: Gamma oscillations (30-80 Hz) in the dorsolateral prefrontal cortex (DLPFC) are associated with working memory; a process involving the maintenance and manipulation of information on line (Baddeley, 1986). Gamma oscillations are supported by gamma-aminobutyric acid (GABA) inhibitory interneurons in the DLPFC. Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive method in which to stimulate the cortex that has been shown to modify oscillations, cognition and GABAergic mechanisms. Patients with schizophrenia have severe deficits in working memory that may be related to impairments in GABAergic inhibitory neurotransmission underlying gamma oscillations in the DLPFC. Objective: First, to evaluate gamma oscillatory activity in patients with schizophrenia during working memory compared to healthy subjects. Second, to examine the effect of rTMS applied over the DLPFC on gamma oscillations generated during working memory in healthy subjects. Third, to examine the effect of rTMS applied to the DLPFC on gamma oscillations in patients with schizophrenia compared to healthy subjects. Hypotheses: First, it was hypothesized that patients with schizophrenia would exhibit an alteration in gamma oscillatory activity. Second, it was hypothesized that rTMS would be effective in enhancing gamma oscillations in healthy subjects. Third, it was hypothesized that rTMS would be effective in inhibiting gamma oscillations in patients with schizophrenia. Results: The first study found that patients with schizophrenia generate excessive gamma oscillations during working memory compared to healthy subjects. The second experiment found that rTMS over the DLPFC resulted in the potentiation of gamma oscillations in healthy subjects during working memory. The third experiment demonstrated that rTMS inhibited excessive gamma oscillations in patients with schizophrenia while an opposite effect was found in healthy subjects. Conclusions: rTMS applied over the DLPFC modulates frontal gamma oscillatory in healthy subjects and in patients with schizophrenia depending on baseline levels of activity, a finding that may ultimately translate into a better understanding of the mechanisms leading to cognitive improvement in this disorder.