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This thesis considers the contribution of semantic cognition to verbal short-term memory (STM) in three groups of brain damaged patients. It directly compares patient groups that are typically studied separately. Patients with semantic dementia (SD) suffer a loss of core semantic representations and make phonological errors in STM tasks, suggesting that semantic knowledge binds phonological information.

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In 1972, Endel Tulving coined the term "episodic memory", with reference to the process used to link the many different types of infonuation constituting an event into a spatio-temporal context, which can be retrieved later. In this thesis I investigate what type of information is encoded in episodic memory while performing selective attention and action tasks. Over seven experiments, I look at the impact of various experimental conditions on the recall accuracy (free, recognition and cue) of episodic memory that includes object identity, spatial and temporal recall, since only very few studies have considered these three components together. My approach is novel as most other studies have used traditional attention experimental tasks to understand how infonuation is selected, Specifically, I use episodic-like memory tests to dissociate the impact of active and passive encoding states on memory, which in turn allows me to observe the phenomenon of distractor suppression encountered during the retrieval of previously encoded information. In general, results across several experimental conditions strongly indicate that memory superiority under passive 1110de could be related to the incidental encoding of irrelevant information. This effect is mostly found when memory is immediately tested and disappears some time later following a retroactive interference task. Distractors competing for an action receive a stronger suppression than those, which are not. The results are in agreement with selective attention studies, which suggest that distractors prevent from becoming the target of the action. The results highlight the role of action on epikodic encoding, demonstrating that using an active state of encoding does not increase the amount of information to encode (enhancement of targets), but reduces the numbers of non- relevant information stored in this trace (suppression of distractors).

"An object of primary memory is not thus brought back; it never was lost; its date was never cut off in consciousness from that of the immediately present moment. In fact, it comes to us as belonging to the rearward portion of the present space of time, and not to the genuine past," (James, 1890, p. 609). Since William James's seminal work on 'primary' memory, the notion that a short term memory store, now termed short term memory (STM) or working memory (WM) is a key part of human consciousness has become commonplace. This memory store is known to be subject to limitations in the amount and quality of information it can represent at any time, but is a crucial part of the cognitive toolkit humans use to navigate the physical and social world. Given these capacity limitations, there is a clear evolutionary imperative for efficient selection into and retention within WM of items of high utility over those of less importance to survival.

Clinical experience suggests that it is common for older adults to experience anxiety when undergoing assessment at memory clinic, and that this anxiety may impair performance during neuropsychological testing. The aim of this study was to understand more about this phenomenon. There is a good evidence base which offers theoretical models of how such a relationship between anxiety and cognitive performance may occur. However, empirical evidence is limited, particularly for this population. A cross sectional study was designed to examine the relationship between anxiety and cognitive performance in this specific clinical context. Eighty-nine participants were recruited to the study from patients referred to memory clinics. They each completed two measures of anxiety in addition to their routine neuropsychological assessment. Data from each assessment were also collected. Correlational analyses including multiple regression were used to investigate the relationship between anxiety and performance on measures of divided attention and working memory. The findings did not replicate results from previous research. No relationship was found between any form of anxiety and performance on the neuropsychological tests investigated. Likewise, there was no relationship between anxiety and cognitive status. No effects were found for age. However, depression was not controlled for, which is one of the limitations of this research. Other limitations are also discussed, such as generalisability of the findings which are limited by the non- normal distribution of data. The relationships between anxiety and cognitive performance have important clinical implications which are explored.

BACKGROUND: Prospective memory difficulties are one of the most common deficits following acquired brain injury. The application of smartphones as a compensatory aid to these difficulties has shown promising results. This study looked to investigate these benefits further. OBJECTIVE: The aims of this study were to investigate whether receipt of reminder prompts through ones smartphone improved completion of pre-planned tasks, in addition to whether it also had secondary implications for participant's wellbeing, confidence, independent functioning, and whether it had any impact on caregiver strain levels. METHOD: This study used an ABAB case series design with mild to moderate acquired brain injury. Task completion rates were monitored across four phases (prompts vs. no prompts). Quantitative questionnaires were administered pre, post and at three months follow up to assess coping with memory difficulties. A qualitative questionnaire explored the perceived impact of the smartphone reminders on everyday functioning, in addition to a 3 month follow up measure assessing attrition rates in smartphone use. RESULTS: Visual inspection analysis suggested greater task completion when reminders were provided. The quantitative questionnaires showed increased use of a Smartphone as reminder device post intervention and at follow up. A basic thematic analysis highlighted a perception that the smartphone system increased task completion, confidence in coping with memory demands, supported emotional wellbeing and reduced dependence on others. As a memory aid it was also less stigmatising and promoted dignity. The three month follow up questionnaire highlighted that all participants continued to use their smartphone as a memory aid. CONCLUSIONS: Use of a smartphone as a memory compensation aid may improve completion of pre-set tasks. Secondary benefits may include increased confidence in coping with memory demands, reduced dependence on others for help, and reduced anxiety or frustration around forgetting.

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The dissertation explores the effect of the knowledge base on the acquisition of memory strategies. It is postulated that 'salient' categories - highly elaborated categorial structures in the knowledge base - facilitate memory performance so that elevated levels of clustering and recall, and an emergent organisational strategy, can be expected in young children's memory performance with such categories. Two multitrial, free-recall experiments were conducted to test the hypothesis. The first experiment analysed the memory performance of preschool children and adults on category type (salient versus nonsalient categories). The second experiment analysed the effect of category saliency on memory search processes. The experiments yielded evidence suggesting that highly salient items in the knowledge base are easily activated during the course of memory retrieval, resulting in enhanced levels of recall with such items, and the early manifestation of an organisational strategy. / Psychology / M.A. (Psychology)

It is an unresolved question whether the mental representations that enable visual/haptic crossmodal memoory for objects are modality-specific - either visual (Zhang et al., 2004) and/or haptic (Reed et al., 2004); modality-independent - either abstract (Easton et al., 1997) or structural but still in some way abstract (Reales & Ballesteros, 1999); or dual code - visual for unfamiliar objects but visual and verbal for familiar objects (Johnson et al., 1989). The thesis argues that dual-code representation can be parsimoniously reduced to visual representation, with verbal processes relegated to strategic roled, and that visual representation can be reduced to spatial representation. Spatial representation can be defined as containing information about size, shape and the arrangement of different object parts and features relative to each other, and is a novel hypothesis in visual/haptic crossmodal memory. Seven experiments tested existing theories and the novel hypothesis primarily through the innovative use of interference techniques. These experiments showed that there was no evidence for strictly abstract representation or for the main predictions of the dual-code account. There was no effect of interference on familiar objects and it is suggested that these are either resistant to interference because they involce deep long-term memory representations or that they are represented through an associative network of different representations. The novel hypothesis of spatial representation was supported in experiments that contrasted visual and haptic, spatial and non-spatial interference. These showed strongly that the modality of the interference was irrelevant and that spatiality was the key factor. Whether itoccured during encoding or retrieval, spatial interference disrupted performance regardless of its modality and also disrupted the visual-haptic and haptic-visual conditions equally. The thesis concludes that visual/haptic crossmodal memory is enabled by modality-indeopendent spatial representation. This new finding is an original and theoretically important contribution because it specifies the format of a modality-independent representation and solves two of the three main task constraints: how any kind of object can be re[presented via both vision and touch. It is also a generative source of hypotheses about the third constraint: why error is systematically greater in the haptic-visual condition than the visual-haptic condition.