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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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.

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.

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.

[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.

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 2007 / Meditation 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

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.

Working memory (WM) is a process that allows for the temporary and limited storage of information for an immediate goal or to be stored into a more permanent system. A large number of studies have led to the widely accepted view that WM is mediated by the frontoparietal network (FPN), consisting of areas in the prefrontal cortex (PFC) and posterior parietal cortex (PPC). Current evidence suggests that task specific patterns of neuronal oscillatory activity within the FPN play a fundamental role in WM, and yet specific spatio-temporal properties of this activity are not well characterized. This study utilized multisite local field potential (LFP) data recorded from PFC and PPC sites in two macaque monkeys trained to perform a rule-based, Oculomotor Delayed Match-to-Sample task. The animals were required to learn which of two rules determined the correct match (Location matching or Identity matching). Following a 500 ms fixation period, a sample stimulus was presented for 500 ms, followed by a randomized delay lasting 800-1200 ms in which no stimulus was present. At the end of the delay period, a match stimulus was presented, consisting of two of three possible objects presented at two of three possible locations. When the match stimulus appeared, the monkey made a saccadic eye movement to the target. The rule in effect determined which object served as the target. Time-frequency plots of three spectral measures (power, coherence, and Wiener Granger Causality (WGC) were computed from MultiVariate AutoRegressive LFP time-series models estimated in a 100-ms window that was slid across each of three analysis epochs (fixation, sample, and delay). Low (25- 55 Hz) and high gamma (65- 100 Hz) activity were investigated separately due to evidence that they may be functionally distinct. Within each epoch, recording sites in the PPC and PFC were classified into groups according to the similarity of their power t-f plots derived by a K-means clustering algorithm. From the power-based site groups, the corresponding coherence and WGC were analyzed. This classification procedure uncovered spatial, temporal, and frequency dynamics of FPN involvement in WM and other co-occurring processes, such as sensory and target related processes. These processes were distinguishable by rule and performance accuracy across all three spectral measures- power, coherence, and WGC. Location and Identity rule were distinguishable by the low and high-gamma range. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

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