The Integrative Neuropsychological Theory of Executive-Related Abilities and Component Transactions (INTERACT; Garcia-Barrera, 2011) is a novel perspective on executive function(s), and the functional interactions among those neural systems thought to underlie them. INTERACT was examined in this validation study using structural equation modeling. A novel battery of computerized tasks was implemented in a sample of 218 healthy, adult, university students. Each of the derived indicator variables represented a specific aspect of performance, and corresponded with one of the five distinct executive components of INTERACT. After eliminating tasks that demonstrated poor psychometric properties, overall model fit was excellent, χ2 = 36.38, df = 44, p = .786; CFI = 1.00; RMSEA = .000. Further, INTERACT was superior to six alternative measurement models, which were theoretically-based. Although the structural model of INTERACT was too complex to be tested here, a novel analysis of the data was introduced to test the interactions among INTERACT’s components. This analysis demonstrated the significant utility of INTERACT’s fundamental theoretical predictions. Given the outcome of this initial validation study, the predictive power of INTERACT should continue to be exploited in future studies of executive function(s), and should be extended to explore executive systems in unique populations. / Graduate

Olfaction is one of the most important senses by which insects obtain information about their environment. In the early stages of olfactory perception in insects, odour molecules are carried across the sensillum lymph by small soluble Odorant Binding Proteins (OBPs). This is followed by activation of the appropriate olfactory receptor, resulting in an electrical impulse, and subsequent degradation of the initial signal. OBPs have been studied in a range of insect orders including Lepidoptera, Diptera and Orthoptera, and this study reports the cloning and characterisation of cDNAs with a potential olfactory role in the vetch aphid, Megoura viciae (Buckton, Homoptera: Aphididiae). Construction and sequencing of antennal cDNA libraries identified two cDNAs, MvicOBP1 and Mv164, which were approximately 0.8kb and 1kb respectively. The amino acid sequence of MvicOBP1 has the spacing pattern of six cysteine residues that is characteristic of insect OBPs, and Mv164 shows similarity to insect cytochrome P450 enzymes. RT-PCR showed that these cDNAs have specific or enhanced expression in the chemosensory tissues of M. viciae, and parallel expression patterns suggest a "linked" function. Related sequences are present and expressed in other aphid species, and sequencing of genomic fragments allowed the partial elucidation of the intron/exon organisation of these genes. Subtracted antennal cDNA libraries identified two cDNAs encoding proteins with significant similarity to insect chemosensory proteins (CSPs), cDNAs encoding Juvenile Hormone Binding Proteins (JHBPs), and a tissue-specific cDNA with a potential carrier role. These, coupled with the OBPs, add evidence to the suggestion that there is an insect superfamily of binding proteins. A PBP from Bombyx mori (BmorPBP1) was used as a model system for in vitro expression of an insect OBP and subsequent characterisation of the recombinant protein. Four forms of this protein, identified through their interaction with an anti-BmorPBP antibody, were resolved by isoelectric focusing.

The primary goal of the empirical research outlined in this thesis was to examine a number of the factors contributing to the design of more ergonomic multisensory warning signals, that is, signals that elicit efficient and effective responses from interface operators under demanding conditions. To achieve this goal, a series of experiments was conducted in order to examine the nature and consequences of the crossmodal links inherent in spatial attention between various different sensory modalities, such as audition, vision, and touch, in an applied setting. In particular, a laboratory-based simulated driving task was used to investigate the effectiveness of various different auditory and vibrotactile cues in orienting a driver's attention to potential emergency driving events seen through the front windscreen or rearview mirror. The results of the first set of auditory spatial cuing experiments highlighted a significant performance advantage when the target driving events occurred in the cued, rather than the uncued, direction, with the biggest benefits being seen following spatially-predictive auditory or verbal cues. The second set of vibrotactile spatial cuing experiments demonstrated the potential utility of vibrotactile warning signals for presenting spatial information to car drivers, and the results were successfully replicated in a study using a high-fidelity driving simulator. The third set of experiments, incorporating an orthogonal task design, were conducted in order to examine the mechanisms responsible for the advantageous spatial cuing effects reported in the earlier experiments. Taken together, the results demonstrated that while directional congruency between a warning signal and target driving event may be sufficient to facilitate performance due to the priming of the appropriate response, attentional facilitation (i.e., perceptual enhancement) typically requires the co-location of the cue and target within the same functional region of space. In sum, this thesis demonstrates the potential value of approaching the design of effective multisensory warning signals for human operators by studying the information processing mechanisms in the human brain. The findings outlined here add to the literature concerning the brain's differential representation of stimuli presented in peripersonal as opposed to extrapersonal space. Further experimental chapters detail experiments that examined verbal directional cuing, olfactory cuing, and crossmodal interactions in virtual haptic environments.

Current models of face perception suggest independent processing of identity and expression, though this distinction is still unclear. Using converging methods of psychophysics and functional magnetic resonance imaging (fMRI) in healthy and patient populations we assessed the relationship between these two perceptual processes. First, using perceptual aftereffects, we explored the neural representations underlying identity and expression. The expression aftereffect only partially transferred across different identities, suggesting adaptation within identity-invariant and identity-dependent expression representations. Contrarily, the identity aftereffect fully transferred across different expressions. This asymmetry cannot be explained through low-level adaptation. The identity-dependent component of the expression aftereffect relies on adaptation to a coherent expression, not low-level features, in the adapting face. Thus adaptation generating the expression aftereffect must occur within high-level representations of facial expression. Second, using fMRI adaptation, we examined identity and expression sensitivity in healthy controls. The fusiform face area and posterior superior temporal sulcus showed sensitivity for both identity and expression changes. Independent sensitivity for identity and expression changes was observed in the precuneus and middle superior temporal sulcus respectively. Finally, we explored identity and expression perception in a neuropsychological population. Selective identity impairments were associated with inferior occipitotemporal damage, not necessarily affecting the occipital or fusiform face areas. Impaired expression perception was associated with superior temporal sulcus damage, and also with deficits in the integration of identity and expression. In summary, psychophysics, neuroimaging and neuropsychological methods all provide converging evidence for the independent processing of identity and expression within the face network. However, these same methods also supply converging evidence for a partial dependence of these two perceptual processes: in the expression aftereffect, the functional sensitivities of the FFA and pSTS, and identity deficits observed in a patient with primarily impaired expression perception and a spared inferotemporal cortex. Thus, future models of face perception must incorporate representations or regions which independently process identity or expression as well as those which are involved in the perception of both identity and expression.

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The marked heterogeneity between individuals diagnosed as experiencing schizophrenia has troubled nosologists since the very coining of the term. Catalysed by Crows (1980) hypothesis of independent positive, and negative syndromes, which led to substantial breakthroughs in our comprehension of schizophrenia, the last two decades have seen a resurgence of interest in the characterisation of symptom dimensions to resolve the issue of heterogeneity. A three dimensional model, comprising 'psychotic', 'negative', 'disorganised' syndromes has received considerable research attention and has been proposed for inclusion in the Diagnostic and Statistical Manual of Mental Disorders. Similarly, a five-dimensional model, adding syndromes of 'affective disturbance'and 'excitement', has also attracted an increasing profile of literature. Mounting evidence suggests, however, that these models do not adequately reflect the diversity of symptoms seen among those with a diagnosis of schizophrenia, and that they may emerge as an artefact of lossy factor-analytic techniques applied to measurement models biased or inadequate in their coverage of symptoms. To overcome such limitations, in the present study one hundred in- and out- patients diagnosed with schizophrenia were assessed for completed a battery of neuropsychological tests tapping five aspects of attention, and smooth pursuit eye tracking was also recorded. Using cluster analyses to examine correlations between symptoms, eleven groups of symptoms were identified: 'hostility', 'conceptual disorganisation', 'bizarre behaviour', 'grandiosity', 'auditory hallucinations', 'loss of boundary delusions', 'paranoia', 'anxious intropunitiveness', 'cognitive dysfunction', 'negative signs' and 'social dysfunctions'. All groupings were internally consistent, largely independent of others, and supported by other symptom models proposed in the literature. Several of the symptom groupings were validated by demonstration of independent relationships with neuropsychological variables or aspects of eye movements, and the more complex symptom model was equivalent or superior in the prediction of neuropsychological performance than the three- and five- factor symptom models. Implicit in dimensional approaches to conceptualising schizophrenia is the notion that the identified groupings may reflect the functioning of distinct brain systems. This thesis has demonstrated that the 'syndromes' defined by the three- and five- dimensional models of schizophrenia are actually heterogeneous groupings of poorly correlated symptoms. This, in turn, obscures the relationships between symptoms and underlying pathology. Dimensional approaches to psychopathology hold great promise for unravelling the nature of psychosis. However, the existing facile descriptions may actively constrain the potential for research progress. The rigorously developed description of symptomatology presented here represents a compact and useful representation of the spectrum of symptoms experienced in schizophrenia, and has demonstrated an advantage over existing conceptions that demands implementation and vigorous research attention.