Dissertations / Theses on the topic 'Potential correlates'

There is a need for outcome measurement tools which are able to provide accurate and reliable information regarding the efficiency and efficacy of therapeutic intervention of soft tissue injury e.g. ligament tear. Electrical activity within the body tissues has been shown to be influenced by the tissue state, and following injury, bioelectric changes have been demonstrated for example in bone healing and nerve regeneration. This project considers the relationship between the electrical potentials recorded from the skin surface and clinical recovery following a soft tissue lesion. The measurement of the skin potential is not new but the application and approach used is novel in that a non invasive differential skin surface potential is used instead of the traditional and invasive transcutaneous potential. The differential potential was initially investigated in non injured subjects in order to gain an understanding of its character and behaviour. Simultaneous monitoring of environmental, physiological and psychological factors enabled evaluation of their influence on the generation mechanisms. In order to carry out the work, specialist instrumentation was designed and computer software developed. Injured subjects were recruited during two test series and the results compared with those obtained from the non-injured subjects. Differences in potential profiles were marked on occasions. However a significant percentage of injured subjects presented a profile which was very similar to the non injured subject potentials. The failure to demonstrate consistent differences between potentials from the groups may reflect the lability of tissue potentials or that their behaviour is not purely related to local tissue state. Psychological factors were shown to exert influences on the potentials and differences in environmental and physiological conditions may also be responsible for the variations seen. The refinement of the test apparatus and protocol which is discussed may facilitate more discriminative data collection.

Object recognition memory (ORM) refers to both recognition of an object and the memory of having seen it before. In humans, ORM has been investigated using functional neuroimaging and electrophysiological techniques with tests of episodic memory retrieval involving recollection of previously studied items. Processes involved in the maintenance of a mental state adopted for the performance of a retrieval task (retrieval mode) appear to involve right frontal neural regions. More transient processes occurring at the time of item recollection (retrieval success) have shown scalp activity over parietal and right frontal regions. This activity is thought to originate in the medial temporal lobes and the underlying right frontal cortex respectively. The aforementioned findings have been derived mainly from studies using verbal stimuli. It is uncertain whether the same neural regions are involved in object recollection. It is also uncertain whether sustained modal and transient item-related activity involve the same or different right frontal regions. In this study, steady-state probe topography (SSPT) was used to investigate both sustained and transient processes involved in the retrieval of abstract pictorial objects from memory. The ability to vary the evaluation period of the steady-state visually evoked potential (SSVEP) allows investigation of cognitive processes occurring over different time scales. Neural regions involved in sustained modal processes were identified by examining the SSVEP values averaged over the duration of a memory retrieval task. Sustained SSVEP effects were observed over right fronto-temporal regions. Neural regions involved in transient retrieval success processes were identified by comparing the transient SSVEP responses to tasks with different memory loads. Comparison of a higher with a lower memory load condition showed SSVEP effects over parieto-temporal and right inferior frontal regions. Larger differences between memory loads gave effects that were larger and more right lateralized. Retrieval mode and retrieval success processes showed SSVEP effects over different right frontal regions. It was also found that, in contrast to the left lateralized parietal ERP response to recollected verbal stimuli, the SSVEP effects produced with abstract pictorial shapes showed a more bilateral pattern. This was considered to reflect the relatively non-verbalizable pictorial nature of the stimuli.

Theory of mind (ToM) is the knowledge that other people have minds, thoughts, beliefs and values different from our own. Patients with schizophrenia are generally thought to be impaired at tasks requiring this ability. Frith (1992) has proposed that specific signs and symptoms of schizophrenia are associated with dysfunction in ToM ability. The purpose of the present study was to investigate the role of thought disorder in theory of mind and to tease out the electrophysiological correlates of this phenomenon. Participants partook in an intention attribution task, during which event-related potentials (ERPs) were recorded. Patients with high ratings of thought disorder performed worse than those with low thought disorder and significantly worse than normal subjects. ERP results were unexpected as no differences were detected for ERPs on frontal sites. A significant difference in the P600 component was observed on Pz. Possible explanations for parietal activation are discussed.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2009.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
"February 2009."
Includes bibliographical references.
The visually evoked potential (VEP) is a local field potential (LFP) evoked in visual cortex in response to visual stimuli. Unlike extracellular single unit recordings, which allow us to probe the function of single spiking cells acutely, the chronic VEP technique gives us insight into ensemble synaptic activity. However, while action potentials are easily interpreted as the output of the recorded neuron, LFPs are difficult to interpret because they may reflect the sum of activity occurring at or beyond the site of recording. The goal of this study was to use the current source density (CSD) method to derive information about synaptic activity occurring at the site of recording and to determine how this activity relates to the concurrent LFP. The mouse has recently become a widely-used experimental model for studying the mechanisms of plasticity and there has been an increase in the use of VEP recordings to study experience-dependent changes in mouse primary visual cortex (V1). These studies typically focus on changes occurring in the layer 4 VEP after a variable period of visual deprivation. Layer 4 of mouse V1 receives heavy direct input from the lateral geniculate nucleus. This initial input is followed by strict hierarchical connectivity from cortical layer 4 to superficial layers 2/3 and from 2/3 to deep layers 5/6. Using a method for silencing cortical activity without affecting geniculate input activity in conjunction with CSD analyses, we found that the laminar flow of activity in mouse V1 in response to various grating stimuli was consistent with the anatomical connectivity going from layer 4 ?? 2/3 ?? 5/6. To determine if the layer 4 VEP is indeed reflecting synaptic activity occurring in layer 4, we applied the CSD method to field potentials recorded from mouse V1. Our results indicate that changes in the layer 4 VEP strongly and significantly covaries with changes in layer 4 current sink activity suggesting that the layer 4 VEP is indeed reflecting local layer 4 synaptic activity.
(cont.) This layer 4 activity is likely due to direct geniculate input since it persisted after intracortical activity was blocked. If the layer 4 VEP reflects synaptic activity due to direct geniculo-cortical input and if this input is carrying information about the visual world then we would expect the VEP to change as the parameters of the stimuli vary. Indeed the binocular-driven VEP broadened in shape as we increased the spatial frequency (SF) of grating stimuli. Using CSD analyses, we were able to trace the transformations of the layer 4 VEP waveform to changes happening in layer 4 current sinks and layer 4 current sinks were in turn affected by events in deep layers. Specifically, increasing SF of the grating stimuli led to a reduction of current sink activity in deep layers and this unmasked prolonged current sink activity in layer 4. This prolonged layer 4 current sink activity persisted after cortical silencing suggesting that it is likely due to late-onset direct geniculate input. We suggest that late-onset activity from the ipsilateral-eye may be unmasked with increasing SF. VEPs have been used extensively in the clinical and laboratory setting to determine visual acuity in humans as well as anaesthetized animals. If the layer 4 VEP is to be a useful measure of visual function in awake head-fixed mice, VEP-assessed visual acuity and contrast sensitivity should be consistent with behaviorally-assessed measures. We found that VEP-assessed visual acuity agreed with previous behaviorally-assessed acuity; however, VEP-assessed contrast-sensitivity values were slightly higher. One of the reasons why inbred laboratory mice are becoming increasingly useful in Neuroscience is because individual mice are genetically identical and any behavioral variability should be experience-driven. While this is true for mice within a given strain, it is not true between strains since strains are genetically different. Therefore, it is crucial to understand how strain differences in genes affects neural activity before comparing results from different strains.
(cont.) To this end, we compared the VEP response of two commonly used laboratory mouse strains: C57BL/6 and 129/Sv and found important differences in the VEP waveform which may translate into differences in visual function. Specifically, our data suggest that 129/Sv mice may have better acuity than C57BL/6 mice. The advent of molecular engineering tools is another reason why the mouse has become the preferred model system for studying the cellular and molecular mechanisms underlying behavioral and physiological phenomena. Genetically modified mice are routinely screened for behavioral deficits using tasks such as the Morris watermaze -- test for spatial navigation which assumes that the mice have functional vision. In order to remove the experimental confound of vision, the layer 4 VEP can be used to assay the visual function of mice prior to behavioral experimentation. Using the VEP technique, we determined the visual function of Shank1-/- mice to be normal in response to low SF gratings but impaired in response to high SF gratings. Shank1-/- mice were not impaired in the eight-arm radial maze task - another test of spatial navigation suggesting that low SF vision may be sufficient for performing this task. Taken together, this study demonstrates that the VEP is an interpretable and useful recording technique which can be combined with CSD analysis to determine the laminar activity patterns which underlie visual function in the awake mouse.
by Rahmat Muhammad.
Ph.D.

Despite the controversy surrounding Affirmative Action (AA), relatively little research has appeared about attitudes towards these programs. In this research, an exploratory approach is implemented to assess the support of personnel managers for the theory of AA as well as the mechanisms designed to carry it out. Also, the relationship to Supreme Court decisions, relevant legislation, and numerous demographic, attitudinal, and organizational variables are examined for their impact on Affirmative Action attitudes. A questionnaire was utilized to assess support for AA and its correlates. The majority of personnel managers indicate support for both AA in theory and the mechanisms required to carry these programs out. This research indicates either very small or no differences exist between support for AA concepts versus AA mechanisms, support for gender -based versus race-based AA, or support reported by private sector versus public sector personnel managers for AA. How personnel managers perceive the impact of Court Decisions and the 1991 Civil Rights Act on AA implementation, although small, was found to be a significant correlate of AA attitudes. The race of the respondent was found to be the most significant determinant of AA attitudes. Although minorities were found to be more supportive than nonminorities, both were found to register support for these programs.

The aim of this PhD thesis was to explore the way in which recognition memory changes over time. Of particular interest was how forgetting and systems level consolidation processes alter the qualitative nature of recognition judgments and the impact this has on event related potentials (ERPs) recorded during recognition. An emerging body of fMRI and animal work has started to suggest that changes to the neural basis of memory can be observed after intervals in the order of days and weeks. Although much research has examined the ERP correlates of recent recognition, there has been little attempt to compare this to remote recognition. This gap in the literature is investigated in the present PhD thesis over five ERP and two behavioural experiments. The first set of experiments investigated recognition success i.e. the subjective awareness that a stimulus has been encountered before. Previous work has associated familiarity-based recognition with an early midfrontal ERP effect whereas recollection-based recognition has been linked to a later onsetting parietal ERP effect. These effects were compared for recently studied stimuli and stimuli studied 1 week earlier. Results revealed an attenuation of the late parietal effect. This quantitative difference suggests that the neural networks underlying the ERPs for recent and remote recollection remain the same after a 1 week delay but may be less active after a period of forgetting. Behavioural work linked this to a drop in strength and episodic detail for remote recollection. Examining the midfrontal effect over time produced a more complex pattern of results. The effect was not reliable in Experiment 1 for remote familiarity judgments. In follow up experiments, however, midfrontal effects were reliable for week old memories but were not modulated by either delay or memory strength manipulations. These findings do not permit strong conclusions regarding the way familiarity memory and midfrontal ERPs vary over time, other than to say that the midfrontal effect is not a short lived correlate of recognition memory. A second set of experiments investigated how the length of the delay between study and test impacts on retrieval orientation and retrieval effort. Retrieval orientation refers to the way in which participants strategically alter how a memory cue is processed based on current task demands. Results showed ERP differences when remote memories were cued compared to when recent memories were cued. However, these differences were eliminated when recent and remote memory was matched for performance. This finding indicated that effort required at retrieval rather than memory age per se influenced differential cue processing. A follow up experiment supported this claim but found that participants may utilise delay information during recognition in a very general sense. In this experiment, ERPs indicated different cue processing when participants knew the age of the memories they were trying to retrieve compared to when they did not. Taken together, the results suggest that memory age does not influence the ERP correlates of recognition in a direct manner. More important are the indirect changes occurring over time, such as reduced memory strength, reduced episodic detail, slower reaction times and increased effort at retrieval. These variables, and possibly a range of others, should be controlled as far as possible in studies aiming to explore neural changes driven by systems consolidation. Prospective studies, where the learning phase can be controlled makes this aim feasible, as some of the experiments in this thesis have shown. Future work might benefit from focusing more on variations at encoding, rather than large differences in the length of the retention interval, as has been the traditional approach to this issue.

Neural correlates of consciousness (NCCs) represent the physiological processes related to consciousness and awareness. Consciousness is theorized as a recurrent process of integration between separate but specialized brain areas. Previous research has used electroencephalography (EEG) to locate NCCs of sensory awareness in vision through event-related potentials (ERPs). Two ERP components thought to represent visual awareness are the visual awareness negativity (VAN) and late positivity (LP). VAN and LP have been extensively studied, yet little research has been conducted in other sensory modalities. In this study, the presence of an auditory awareness negativity (AAN) and associated LP is investigated in 23 subjects using EEG. To avoid false positives in data analysis, two research hypotheses were preregistered. The results indicate that auditory LP does occur, but that AAN does not, in hypothesized intervals. However, the data suggest that AAN may occur at a later interval. Possible attributes of the later interval are discussed. In sum, the data provide results consistent with recurrent theories of sensory awareness.

Scalp-recorded ERPs were employed in four experiments to explore the strategic control of recollection in a recognition exclusion task. For each experiment, the study phase comprised two study lists. The test required the endorsement of 'targets' from study list 2 and the rejection of 'non-targets' from study list 1 and 'new' items. Experiments 1-3 showed that the ERP signature for recollection, the 'left parietal old/new effect', was elicited by correctly rejected non-targets only when memory for targets was poor (cf. Herron & Rugg, 2003a). These findings support the proposal that, when there is good memory for targets, the adoption of a 'retrieval orientation' allows test cues to selectively probe memory for target source information. However, when target and non-target study tasks were identical (Experiment 4), left parietal effects were additionally found for non-targets despite high target accuracy. This indicates that the degree of similarity between target and non-target study contexts moderates the extent to which it is possible to focus retrieval attempts exclusively on target memories. However, when target and non-target study contexts were partially distinct (Experiment 4), a late posterior negativity was seen to attenuate an emerging left parietal effect for non-targets suggesting that non-target recollection was not completely precluded in this condition. Furthermore, the magnitude of the late posterior negativity was observed to correlate with the amount of contextual information associated with each item type that was irrelevant to the task demands. It was proposed that this negativity reflects processes acting upon a mismatch between the targeted memory representation and the contextual details that are actually retrieved. When such mismatches occur, an additional strategic control process, 'attentional suppression', may provide an account of how target memories can be successfully isolated from among competing alternatives.

Natural intelligences appear to represent the world in ways which filter out irrelevant information and allow them to function in a challenging environment. Episodic memory is thought to be mediated by control processes that facilitate the retrieval of task-relevant information at the expense of irrelevant information. Six event-related potential (ERP) experiments were conducted to explore the factors facilitating this strategic recollection. All of the experiments employed a variant of the exclusion task first used by Jennings & Jacoby (1997), in which studied words (targets) are endorsed on one response key, whereas new words and new words which repeat after an intervening lag of 7–9 items (non-targets) are rejected on another key. In all of the experiments correct responses to targets and non-targets elicited reliable left-parietal ERP old/new effects. However, when target accuracy was high (experiments 4 and 5) the effect for non-targets was significantly attenuated. This pattern of data is consistent with previous suggestions that, when the likelihood of recollecting information about targets is high, participants use the success or failure of an attempt to recollect information about targets as the basis for distinguishing between targets and all other classes of test word. Importantly, the findings generalise those obtained in previous experiments to circumstances under which one class of 'old' test items comprises items repeated during the exclusion test phases. The findings in this set of experiments also highlight important considerations when employing exclusion task data in order to make estimates of the relative contributions of memory processes to task performance. Furthermore, an exploratory magnetoencephalography (MEG) experiment found likely functional correlates of ERP memory effects, as well an event-related field (ERF) to which there is no comparable modulation within the electrical record, therefore, highlighting the possible benefits for the use of MEG in the study of human recognition memory.

Exposure to interparental conflict has been implicated in children's development. Research suggests that underlying mechanisms, such as neuropsychological indicators of cognitive processes, may shed light on how exposure to interparental conflict differentially influences children's outcomes over time. Event-related potentials (ERP), extracted from electroencephalogram data, allow for examination of neuropsychological markers of cognition based on precise timing and scalp topography of electrical activity in the brain. For example, the late positive potential (LPP) ERP component has been implicated in the timing and magnitude of sustained attention and emotion regulation processes elicited in response to emotionally salient stimuli. LPP amplitudes and peak latencies were compared for a community sample of 23 children (9-11 years of age, 12 females) during an oddball task, which used images of couples looking angry, happy, and neutral toward each other. Linear mixed models were used to analyze whether children's perceptions of interparental conflict, and whether they were from high- compared to low-conflict homes, influenced their level of neuropsychological resources directed toward angry compared to happy emotionally-charged interpersonal images. Significant results were found for when children were directed to respond to angry images. Differences emerged in LPP amplitudes for all children in the sample, with the greatest amplitudes produced for happy images compared to neutral and angry images. Regarding conflict exposure and perceptions of conflict, children from homes with greater levels of conflict and children who blamed themselves for conflicts they witnessed between parents produced greater LPP amplitudes when happy trials were presented compared to neutral trials. Finally, females reached their maximum LPP amplitude faster than males for neutral trials compared to angry trials. Results are discussed in terms of the implications for children's processing of interpersonal emotions as it is related to underlying neuropsychological mechanisms for sustained attention and emotion regulation.

Two influential theories of consciousness disagree about if consciousness initially arises along the occipitotemporal cortex to later engage frontoparietal regions and attentional mechanisms, or if it necessarily requires the latter. Consequently, different predictions are made about the temporal emergence of consciousness. The event-related potential (ERP) technique can be used to resolve the issue. It can temporally track neural activity of consciously perceived stimuli relative to stimuli bypassing consciousness. This essay describes the two theories and reviews ERP studies on visual consciousness and its relationship to attention. Three ERP correlates of consciousness have been proposed. The question is if they should be interpreted as supporting the one or the other theory. Most plausibly, visual consciousness arises along occipitotemporal regions and later incorporates frontal areas engaging higher cognitive functions. Importantly it seems that consciousness cannot arise without spatial attention/parietal regions.

The works presented in this thesis examine the neural effects of treatment on different features of depression, such as affective biases, working memory impairments and dysfunctional thinking. The thesis opens with a review of longitudinal studies that examined the effects of antidepressants and psychological therapies on the neural correlates of affective and cognitive processing. Motivated by the paucity in the number of fMRI studies that examined psychotherapy in depression, Chapter 2 examines the effects of Cognitive Behavioural Therapy (CBT) on dysfunctional thinking in depression. In Chapter 3, the effects of a dual acting serotonin norepinephrine reuptake inhibitor, duloxetine, on affective biases are examined using implicit affective paradigms comprising happy and sad facial expressions. Chapter 4 investigates the neural effects of duloxetine on working memory in depression utilizing a modified version of the Sternberg Working Memory Task. Another key focus in the thesis is to examine the potential of structural neuroimaging data to identify depression and predict clinical remission using machine learning algorithms in a sample of wide ethnic diversity from the community. Findings from this study are presented in Chapter 5. Overall, the results showed antidepressant treatment related increases in posterior cingulate during sad facial effect processing, consistent with preliminary findings that show increases in this region with antidepressants that potentiate the noradrenergic systems. The neural correlates of working memory, on the other hand, showed a significant group by time interaction during the rehearsal phase, such that there was a tendency for reductions in brain activations at the follow up scan compared to baseline in healthy controls in a network of brain areas extending from the prefrontal, to the cingulate, temporal and cerebellar regions, while no change was observed in patients. The tendency for decreased activations in controls in the follow up scan is perhaps indicative of less recruitment of these regions with increased familiarity with the task, while no change in activation in patients may reflect persistent recruitment of regions associated with working memory to maintain task performance. In the CBT study, an interaction effect was found in the left parahippocampal gyrus, which showed less attenuation in patients relative to controls at the follow up scan, perhaps reflecting an improvement in dysfunctional thinking with CBT with some persistent vulnerability. Investigation of neuroimagingbased biomarkers in depression indicated that structural neuroanatomy combining white and grey matter distinguished patients from controls at the highest accuracy of 81% with the most stable pattern being at around 70%. In contrast, the whole brain structural correlates of depression showed limited potential as a prognostic marker. These findings suggest some distinct neural effects of treatment on cognitive and affective processing and provide preliminary evidence to indicate that identification of depression is possible within a multi-ethnic group from the general community.

The research reported in this thesis examines some aspects of upward influence behaviours at work, and in particular, the relationship between type of influence behaviours used and a number of potential correlates, including sex of agent, sex of target, sex-role identity, locus of control, job level, job type (secretarial worker or not) and educational level of agent. To examine these relationships. 64 male and 173 female white-collar workers (at AS01 to AS06 levels, or equivalent) in three large organisations in Canberra (A.C.T.) were surveyed, with a questionnaire containing measures of influence behaviours, attitudes to influencing upwards at work, a measure of sex-role identity, and a measure of locus of control beliefs, as well as demographic information. The data gathered from this survey was analysed using univariate, bivariate. and multivariate methods. Results showed limited support for stereotypical differences between males and females in influence behaviours used, and no support for hypotheses involving sex of target, sex-role identity, or secretarial workers. Influence behaviours previously identified as having positive outcomes for the agent were found in this study to be significantly associated with job level and educational level; influence behaviours previously identified as having negative outcomes for the agent were significantly associated with the tendency to explain outcomes in terms of control by powerful others, and with a sex-role identity characterised by negative masculinity traits. These findings suggest the importance of both structural and personal factors in choice of upward influence strategies at work. Suggestions for further research are provided.

This dissertation consists of a review of the N2 component of the ERP and five experiments investigating the role of complex visual object categorization in modulating the N2 and two other ERP components: the P300, and a late prefrontal positivity. In the review, we focus on paradigms that elicit N2 components with an anterior scalp distribution, namely cognitive control, novelty, and sequential matching, arguing that the anterior N2 should be divided into separate control- and mismatch-related subcomponents. The experiments manipulated categorical typicality and the presence of conflicting information as participants categorized multi-featured artificial animals. In Experiments 1 and 2, rule-irrelevant features were correlated with particular categories during training. During transfer, participants applied a one- dimensional rule to stimuli with category-congruent, category-incongruent, or novel rule-irrelevant features. Category-incongruent and novel features delayed RT and P300 latency, but had no effect on the N2. Experiment 3 used a two-dimensional rule to create conflict between rule-relevant features. Conflict resulted in prolonged RTs, P300 latency, and larger amplitudes of a prefrontal positive component, but had no impact on the N2. Novel features did enhance the N2 relative to frequent features. In Experiments 4 and 5, participants categorized stimuli using a more complex three dimensional rule. Conflicting stimuli shared two features with one prototype and one feature with a second prototype while prototypes contained no conflicting information. A third category contained stimuli with either common or novel features. Again, perceptual novelty, but not conflict, increased the amplitude of the N2. Compared to prototypes, stimuli with conflicting information slowed reaction times but had no effect on P300 latency, instead enhancing a late prefrontal positive component. These results suggest limitations on the generality of the N2's sensitivity to conflicting information, while confirming its sensitivity to attended visual novelty. We suggest that, while P300 latency tracks stimulus evaluation time, application of a complex categorization rule requires a later stage of evaluation involving prefrontal cortex. In very complex rules, computations indexed by the P3 may be terminated early in favor of computations in PFC.

The aim of this thesis was to refine current models of memory in Autism Spectrum Disorder (ASD) and elucidate similarities and differences between memory in ASD and that of Typically Developing (TD) individuals. This thesis built upon recently established behavioural patterns of preserved semantic and diminished episodic memory in ASD, by linking these with established patterns of electrophysiological activity in different cortical regions of the brain in TD individuals. Event-Related Potential (ERP) Old-New effects (enhanced positivity in the brain for correctly recognised Old stimuli compared to correctly rejected New stimuli) were recorded for episodic and semantic memory judgments (the parietal Old-New effect 400-800 ms, and the mid-frontal Old-New effect 300-500 ms respectively) in ASD, and were compared to TD individuals in terms of (1) temporal and (2) topographical similarities and differences. A series of five experimental studies were conducted using nameable line drawings, non-nameable kaleidoscope images and words as stimuli. A combination of two experimental paradigms were used; the Remember/Know paradigm and the Inclusion/Exclusion paradigm. The current thesis demonstrates that recognition memory Old-New effects are attenuated in ASD for word stimuli and nameable line drawings, but that the topography remains comparable between groups. The current findings suggest that although episodic memory is quantitatively diminished in ASD during behavioural tests, residual episodic memory judgements are phenomenologically similar to TD individuals. Despite demonstrating quantitatively preserved semantic memory, different patterns of neurophysiology are observed for these judgements in ASD, suggesting that different processes are engaged in this group. Finally, although individuals with ASD demonstrated diminished Old-New effects for nameable line drawing and word stimuli compared to TD individuals, enhanced Old-New effects were observed for non-nameable and novel kaleidoscope images in ASD. These findings have important implications for our understanding of verbal mediation and its relation to thought in ASD. The findings are interpreted within a theoretical account of diminished episodic memory and verbal processing difficulties in ASD.

Little research has examined the nature of attitudes towards parents with learning disabilities directly. The 'Parenting Interactional Model' (Feldman, 2002) proposes a link between social factors, such as discrimination and stigmatisation, the extent and nature of social support and parental well-being of those with learning disabilities. This study involved the investigation of the psychometric properties of a scale designed to measure attitudes towards parenting by those with learning disabilities (ATPLD). It also examined the potential relationship between a variety of demographic variables and experiences of contact with people with learning disabilities and responses on this scale. The ATDP-R (Slevin and Sines, 1996) was used as a comparison to measure general attitudes towards those with learning disabilities. A number of 'open questions' asked participants opinions about the problems faced by parents with learning disabilities and asked them to attribute causes for these. 278 participants completed the measures in the study and were grouped according to four categories, specialist learning disability staff, general health-care staff, students on health-related courses and lay people. The ATPLD demonstrated a good level of internal reliability, test-retest reliability and concurrent validity with the ATDP-R. However, it appeared to be measuring a construct labelled 'willingness to accept whether people with learning disabilities should have babies' rather than 'attitudes towards parenting by people with learning disabilities'. Women and specialist learning disability staff scored significantly more positively than men, lay people and general health-care staff on both attitude scales. The ATPLD was significantly correlated with measures of overall contact, contact in a work setting and contact with parents with learning disabilities, but not contact in a social setting.

While signatures of attention can be observed in widespread areas within and outside of cortex, the control of attention is thought to be regulated by higher cognitive brain areas, such as the prefrontal cortex. In their recent study on mice Kim et al. could show that successful allocation of attention is characterized by increased spiking of a specific type of inhibitory interneurons, the parvalbumin neurons, and higher oscillatory activity in the gamma band in the local prefrontal network. It was recently demonstrated that encoding of working memory in prefrontal areas is linked to bursts of gamma oscillations, a discontinuous network process characterized by short periods of intense power in the gamma band. The relationship between attention and working memory is unclear, and it is possible that these two cognitive processes share encoding principles. To address this gap, the electrophysiological data collected in the Carlén Lab have been analyzed with advanced spatio-temporal approaches. In particular, we have analyzed bursting gamma activity in medial prefrontal cortex during attentional processing and investigated the similarities to gamma bursting observed during working memory. Gamma-band bursts during attention were reliably detected with several methods. We have characterized several features of the bursts, including the occurrence, duration and amplitude. The neuronal firing rates during and outside of bursts have also been computed. We investigated the correlation between different criteria characterizing the gamma burst and successful vs failed allocation of attention. Control data were generated to discuss the obtained results. The aim of the study was to explore the hypothesis that the medial prefrontal cortex encodes attention trough gamma bursts, which could reveal some similarities and differences in coding of central cognitive processes. No clear difference was found in the characterization between successful and failed allocation of attention. In addition, results were very similar in control set and original data. No underlying mechanism could be identified from this analysis. Therefore, as the bursts occurring in the gamma band in the prefrontal cortex (PFC) were not discriminative with respect to the different tested conditions, they do not seem to encode information related to attention.
Även fast flera olika hjärnområdens aktivitet kan korreleras med uppmärksamhet, anses kontrollen av uppmärksamhet regleras av högre kognitiva hjärnområden, såsom främre hjärnbarken. I en nyligen publicerad artikel studerade Kim et al. hjärnaktiviteten hos möss och kunde visa att en framgångsrik uppmärksamhet kännetecknas av en ökad aktivitet av en specifik typ av inhiberande nervceller, parvalbumin celler, och högre oscillerande aktivitet i gammafrekvens i främre hjärnbarkens lokala nätverk. Det har nyligen visats att kodning av arbetsminne i främre hjärnbarken är kopplat till utbrott av gamma-oscillationer, en diskontinuerlig nätverksprocess som kännetecknas av korta perioder av intensiva oscillationer av det lokala nätverket i gammafrekvens . Relationen mellan uppmärksamhet och arbetsminne är oklar, och det är möjligt att dessa två kognitiva processer delar kodningsprinciper. För att minska detta gap av kunskap har den elektrofysiologiska datan som samlats in i Carlén Lab analyserats med avancerade spatio-temporala tillvägagångssätt. I synnerhet har vi analyserat utbrott i gammaaktivitet i främre hjärnbarken under uppmärksamhet och undersökt likheterna med gamma- utbrott observerade under arbetsminne. Gamma-bandutbrott under uppmärksamhet påvisades på ett tillförlitligt sätt med flera metoder. Vi har karaktäriserat flera funktioner hos utbrotten, inklusive förekomsten, varaktigheten och amplituden. De enskilda cellernas aktivitet undersöktes även under och utanför utprotten av gamma-oscillationer. Vi undersökte sambandet mellan de olika kriterier som karakteriserar gamma-utbrott under framgångsrik mot misslyckad allokering av uppmärksamhet. Kontrolldata genererades för att diskutera de erhållna resultaten. Syftet med studien var att utforska hypotesen att den främre hjärnbarken kodar uppmärksamhet genom gamma-utbrott, vilket kan avslöja vissa likheter och skillnader i kodning av centrala kognitiva processer. Ingen klar skillnad hittades i karaktäriseringen mellan framgångsrik och misslyckad allokering av uppmärksamhet. Dessutom var resultaten mycket likartade i kontrolluppsättningen och den ursprungliga datan. Ingen underliggande mekanism kunde identifieras ur denna analys. Eftersom de utbrott som uppstod i gamma-bandet i främre hjärnbarken inte var unika med hänsyn till de olika testade förhållandena, tycks de därför inte koda information relaterad till uppmärksamhet.

Because event-related potentials (ERPs) can reflect individual differences in intellectual ability, individual differences in college grade-point average (GPA) may be associated with specific individual ERP waves, such as the P300. However, P300 amplitude is higher in women than in men and varies across the menstrual cycle, factors that could confound the association between GPA and ERPs. In this regard, our objective was to determine whether differences in GPA are reflected in ERPs while standardling for sex and menstrual phase. After participants provided informed consent, we obtained GPAs from 22 right-handed college students (11 male, age range 22 to 26 and 10 female, age range 17 to 24) at a university with high admission and retention standards. We assessed menstrual phase by measuring luteinizing hormone levels across the cycle. We then obtained ERPs for each male participant and ERPs during each phase of the menstrual cycle for each female participant in an object-recognition visual pop-out protocol using Net Station Software (Electrical Geodesics, Inc., Eugene, Oregon) and E-prime Software (Psychology Software Tools, Inc., Sharpsburg, Pennsylvania). Males had larger P300s than females. The male and female high GPA was significantly different from the low GPA male and female groups. High GPA in females and males were associated with a positive peak at approximately 689 ms that was not present in the low-GPA male group and was significantly diminished in low-GPA females. Electro-cortical processing of cognitive stimuli differs between college students with high and low GPAs.

Thesis (Ph. D.)--University of Oregon, 1999.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 95-97). Also available for download via the World Wide Web; free to University of Oregon users. Address:http://wwwlib.umi.com/cr/uoregon/fullcit?p9957570.

Single-particle Green's function method is a direct way of calculating electron binding energy, which relies on expanding the Fock subspace in a finite single-particle basis. However, these methods suffer from slow asymptotic decay of basis set incompleteness error. An energy-dependent explicitly correlated (F12) formalism for Green's function is presented that achieves faster convergence to the basis set limit. The renormalized second-order Green's function method (NR2-F12) scales as iterative N^5 where N is the system size. These methods are tested on a set of small (O21) and medium-sized (OAM24) organic molecules. The basis set incompleteness error in ionization potential (IP) obtained from the NR2-F12 method and aug-cc-pVDZ basis for OAM24 is 0.033 eV compared to 0.067 eV for NR2 method and aug-cc-pVQZ basis. Hence, accurate electron binding energies can be calculated at a lower cost using NR2-F12 method. For aug-cc-pVDZ basis, the electron binding energies obtained from NR2-F12 are comparable to EOM-IP-CCSD method that uses a CCSD reference and scales as iterative N^6.
Master of Science

Natural sounds are characterized by the distribution of acoustic power over different frequency regions and/or time. This is termed spectral, temporal or spectro-temporal modulation. The auditory system is equipped with banks of filters tuned to different spectral, temporal and spectro-temporal modulation frequencies (SM, TM, STM). The sensitivity of the peripheral system to these modulations can be measured by undertaking a linear systems approach. In addition to understanding the psychophysical sensitivity, studying the neural patterns of their processing is also critical. The current study is an attempt to understand the relationship between the behavioral and neural correlates of spectral, temporal and spectro-temporal processing in ten normal hearing subjects (age range 21-27 years; mean = 23.7 years). In the behavioral experiment, sensitivity to SM, TM and STM frequencies was estimated using a 3-interval, 3-alternative, forced-choice paradigm with a 3-down-1-up tracking algorithm. In the electrophysiological experiment, Electroencephalographs (EEGs) were recorded in a change-detection paradigm in response to the same set of modulation stimuli used in the behavioral experiment presented at 20 dB sensation level (SL). The EEG data were analyzed to determine the global field power and latencies of the N1and P2 components and the amplitude of the N1-P2 complex. Although an overall parietal dominance was observed for all of the components, the N1-P2 complex was strongly lateralized to the right hemisphere in the frontal region, but the hemispheric asymmetry decreased at central and parietal regions. A highly significant but weak to moderate negative correlation between individual behavioral thresholds and N1-P2 amplitudes was observed, and this relationship also was observed when behavioral spectro-temporal transfer functions and N1-P2 amplitude transfer functions were examined together. Thus the current project reveals that a relationship exists between the behavioral measures and neural correlates and gives us hope to work towards establishing this relationship.

Thesis (Ph. D.)--University of Oregon, 2004.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 432-460). Also available for download via the World Wide Web; free to University of Oregon users.

Dans cette thèse, nous étudions les propriétés des bosons unidimensionnels dans divers types de systèmes, en nous concentrant sur les transitions de phase ou les croisements entre différents régimes de dégénérescence quantique. En combinant la méthode de Monte Carlo quantique avec d'autres techniques standard telles que la diagonalisation exacte et l’ansatz de Bethe thermique, nous pouvons calculer le comportement des bosons à une dimension dans différents cas où les résultats font encore défaut. Tout d'abord, dans le cas de bosons continus piégés de manière harmonique, nous fournissons une caractérisation complète d'une quantité appelée contact de Tan. En calculant la fonction d'échelle universelle de cette quantité, nous identifions le comportement du contact dans différents régimes de dégénérescence pour les bosons 1D. Nous montrons que le contact présente un maximum en fonction de la température et qu’il s’agit d’une signature de la fermionisation du gaz dans le régime de forte interaction. Ensuite, nous étudions la localisation et les propriétés fractales des gaz idéaux 1D dans des potentiels quasi-périodiques peu profonds. Le système quasi-périodique constitue un intermédiaire intéressant entre les systèmes ordonnés à longue distance et les véritables systèmes désordonnés aux propriétés critiques inhabituelles. Alors que le modèle d'Aubry-André (AA) à liaison étroite a été largement étudié, le cas du réseau peu profond se comporte différemment. Nous déterminons les propriétés critiques de localisation du système, le potentiel critique, les bords de mobilité et les exposants critiques qui sont universels. De plus, nous calculons la dimension fractale du spectre d'énergie et nous constatons qu'elle est non universelle mais toujours inférieure à l'unité, ce qui montre que le spectre n'est dense nulle part. Enfin, nous passons à l'étude avec les interactions. Avec les calculs quantiques de Monte Carlo, nous calculons le diagramme de phase des bosons de Lieb-Liniger en potentiels quasi-périodiques peu profonds. On trouve un verre de Bose, entouré de phases superfluides et de Mott. À température finie, nous montrons que la fusion des lobes de Mott est caractéristique d'une structure fractale et constatons que le verre de Bose est robuste contre les fluctuations thermiques jusqu'à des températures accessibles dans les expériences
In this thesis, we investigate the properties of one-dimensional bosons in various types of systems, focusing on the phase transitions or crossovers between different quantum degeneracy regimes. Combining quantum Monte Carlo with other standard techniques such as exact diagonalization and thermal Bethe ansatz, we can compute the behavior of 1D bosons in different cases where the results are still lacking. First, in the case of harmonically trapped continuous bosons, we provide a full characterization of a quantity called Tan's contact. By computing the universal scaling function of it, we identify the behavior of the contact in various regimes of degeneracy for 1D bosons. We show that the contact exhibits a maximum versus temperature and that it is a signature of the crossover to fermionization in the strongly-interacting regime. Secondly, we study the localization and fractal properties of 1D ideal gases in shallow quasiperiodic potentials. The quasiperiodic system provides an appealing intermediate between long-range ordered and genuine disordered systems with unusual critical properties. While the tight-binding Aubry-Andr'e (AA) model has been widely studied, the shallow lattice case behaves differently. We determine the critical localization properties of the system, the critical potential, mobility edges and critical exponents which are universal. Moreover, we calculate the fractal dimension of the energy spectrum and find it is non-universal but always smaller than unity, which shows the spectrum is nowhere dense. Finally, we move to the study of the interacting case. With the quantum Monte Carlo calculations, we compute the phase diagram of Lieb-Liniger bosons in shallow quasiperiodic potentials. A Bose glass, surrounded by superfluid and Mott phases, is found. At finite temperature, we show that the melting of the Mott lobes is characteristic of a fractal structure and find that the Bose glass is robust against thermal fluctuations up to temperatures accessible in experiments

The purpose of this study was to examine language organization in the brain by using a series of three tasks concurrent with event-related potentials (ERPs) to investigate both hemispheric differences and interhemispheric reactions. Overall, the findings from this study support a relative rather than absolute hemispheric specialization for language processing. Despite an overall RVF (LH) advantage, both hemispheres were capable of performing the tasks and benefited from semantic priming.

he use of evoked potentials to evaluate the functional integrity of neuronal pathways has become a useful and accepted practice in clinical medicine. The use of visual evoked potentials for assisting in the diagnosis of such diseases as optic neuritis and multiple sclerosis is also well recognized. However, the visual evoked potential, unlike the auditory evoked potentials, lacks a well defined electrophysiological to neuroanatomical correlation; especially that of a significant non-cortical component. Currently, visual evoked potentials rely principally on the measurement of a cortical (occipital) positive peak of activity at 100ms (P100), recorded with a single channel electrode system, to evaluate pathway integrity. In this study, visual evoked potentials were recorded using a three-channel, orthogonal co-ordinate system which we have designated "vector" visual evoked potentials (VVEP). This method allows the generated evoked response to be plotted on a three dimensional co-ordinate system with respect to time. Through the use of pattern reversal of a checkerboard pattern, in full and hemi retinal field stimulation, reproducible activity both prior to and afier the P100 wave was demonstrated. In particular, activity found at approximately 55ms is believed to be generated from the Lateral Geniculate Body. Furthermore, because this method summarizes the activity of the entire brain for a given time, as opposed to the single channel recording, a great deal of information about the entire visual pathway can be suggested. Finally, anatomical correlates to discrete activities identified by this method can be made.

Processos de recuperação de memórias são frequentemente investigados através de técnicas de monitoração da atividade cerebral. Na presente tese, é desenvolvido inicialmente um exame sobre a utilização no Brasil de uma ferramenta chamada Potenciais Relacionados ao Evento (PRE). Em seguida, são descritos dois estudos que investigaram processos de recuperação de items neutros associados a contextos emocionais versus contextos neutros. Em ambos os PREs foram extraídos. Através do estudo de revisão sobre PRE no Brasil, constatou-se que esta abordagem de pesquisa ainda é pouco desenvolvida neste país. Através dos outros dois estudos, demonstrou-se a presença de dois efeitos emocionais: um efeito de início rápido (200 ms) e um tardío (iniciando entre 500 e 800 ms). Estes efeitos sugerem que o cérebro responde a items associados a contextos emocionais antes de realizar um processo de recuperação envolvendo a consciência, e indicam que os processos pós-recuperação são modulados pela propriedade emocional dos items.
Memory retrieval processes are frequently investigated by brain monitoring techniques. In the present dissertation, a review on the state of the art of Event-related potentials (ERP) research in Brazil is initially conducted. It is followed by the report of two ERP studies investigating the retrieval processes of neutral items associated to emotional versus neutral contexts. The exam of the Brazilian ERP research demonstrated that this approach still needs to be properly developed in this country. Both ERP studies demonstrated the presence of two main emotional ERP effects: an early onset effect (200 ms) and a late onset effect (onsetting between 500 and 800 ms). These effects suggest that the brain reacts to items associated to emotional contexts before the onset of conscious retrieval processes. They also indicate that post-retrieval processes are modulated by the emotional properties acquired by the items.

The critical bandwidth (CBW) is an auditory phenomenon that has been used to study various aspects of auditory processing, including auditory masking, complex tone processing, and loudness perception. Although the psychoacoustic aspects of the CBW have been well studied, the underlying neurophysiology of the CBW has not been as thoroughly examined. The current study examined the neurophysiology of the CBW in young adults, as well as loudness perception in response to the CBW. Auditory stimuli consisting of complex tones of varying bandwidths were presented to 12 individuals (6 male and 6 female, ages 18-26 years). Complex tones were presented around center frequencies (CFs) of 250, 500, 1000, and 3000 Hz at bandwidths of 2, 5, 8, 10, 20, 50, 100, 200, 500, 1000, and 2000 Hz. Participants made loudness perception judgments while electroencephalography measured and recorded components of the event related potentials (ERPs) in response to the acoustic stimuli. Reaction time (RT) was recorded for each behavioral response, and the latencies of the N1, P2, C3, and C4 components of the ERPs were obtained. The results showed that RT increased with increasing bandwidth followed by a decrease in RT corresponding approximately with the CBW. This indicated that participants perceived a change in loudness at bandwidths greater than the CBW. Significant differences, p < .05, in RT were observed in bandwidths of 5 Hz and greater, although there was not complete consistency in this observation across all CFs and bandwidths. No significant critical band-like behavior amongst ERP latencies was observed. The results indicated that responses to acoustic stimuli originating in the superior temporal gyrus progressed to areas of higher neural function in the mid-temporal lobe. It was observed that each response must be processed temporally and independently to determine if a frequency difference is present for each stimulus. This observation is significant because this type of processing had not been identified prior to the current study.

Two decades of event-related potential (ERP) research have established that the most consistent correlates of the onset of visual consciousness are the early visual awareness negativity (VAN), a negative component in the N2 time range over posterior electrode sites, and the late positivity (LP), a positive component in the P3 time range over fronto-parietal electrode sites. A review by Koivisto & Revonsuo (2010) had looked at 39 studies and concluded that the VAN is the earliest and most reliable correlate of visual phenomenal consciousness, whereas the LP probably reflects later processes associated with reflective/access consciousness. However, an “early” vs. “late” debate still persists. This thesis provides an update to that earlier review. All ERP and MEG studies that have appeared since 2010 and directly compared ERPs of aware and unaware conditions are considered. The result corroborates the view that VAN is the earliest and most consistent signature of visual phenomenal consciousness, and casts further doubt on the LP as an ERP correlate of consciousness. Important new methodological, empirical, and theoretical developments in the field are described, and the empirical results are related to the theoretical background debates.

The thesis is composed for four articles, where is studied either as relationships between body condition and energetic mobilization in rabbits and as the effect of selection for litter size variability in body condition and energetic mobilization, such as welfare biomarkers, and in litter size and its components after seven generation of selection. The first article examines the relationships between measures of body condition and energetic mobilization on primiparous rabbit at mating, delivery and 10 d after delivery, using principal component analysis. Body condition was measured as body weight and perirenal fat thickness. Energetic mobilization was measured as non-esterified fatty acid concentration in blood, before (NEFAb) and after lipolysis stimulation by isoproterenol (NEFAr). All body weights and perirenal fat thickness were located on the first principal component, exhibiting high correlations between them both at the same or different times (from 0.51 to 0.83). All NEFA measurements were located on the second component, showing low correlations with body condition measurements. Both NEFAs showed high positive correlations when measured at the same time (0.65 at mating, 0.72 at delivery and 0.69 at 10 d after delivery), but low correlations when measured at different times (from 0.09 to 0.20). The second article analyses the correlated response in body condition and fat reserves mobilization. The perirenal fat thickness and the increase in NEFAs from basal until adrenergic stimulation by isoproterenol were measured at second mating, at delivery and at 10 d after delivery. Perirenal fat thickness was similar in both lines at mating. However, the high line showed lower fat thickness than the low line at delivery (-0.16 mm, P=0.86), and this difference remained at 10 d after delivery (-0.17 mm, P=0.86). Moreover, this line exhibited 30% more concentration in NEFAs at delivery than the low one (P=0.96). The third and fourth articles study the correlated responses to selection in litter size and its components. A laparoscopy was performed 12 d of the second gestation, in order to estimate ovulation rate and number of implanted embryos. The litter size was recorded at the second parity. In the last gestation, the embryonic development was analysed at 28, 48 and 72 hours of gestation. The ovulation rate was similar in both lines. The line selected to reduce variability in litter size showed a higher number of implanted embryos (1.23, P=1.00) than the high line. Also, this line showed a more advanced development of the embryos from 48 hours of gestation, exhibiting a lower percentage of early morulae both at 48 hours (53.32% vs 79.90%, P=0.93) and at 72 hours (3.88% Vs. 21.04%, P=0.93). More advanced embryo development is related to higher embryo survival (0.85 vs 0.78, P=1.00). A higher uterine overcrowding of embryos in the low line did not penalise fetal survival, and as a result, this line continued showing a greater number of kits born at birth (0.98, P=0.96). In conclusion, body weight and perirenal fat thickness are good predictors of body reserves and both measurements could be used to estimate energy changes in the mid-long term, while NEFA measurements should be used in the short term. A decrease in litter size variability has a favourable effect on body condition, fat reserve mobilization, embryonic development and survival, and litter size.
La tesis se compone de cuatro artículos, donde se estudia tanto la relación entre la condición corporal y la movilización de energía en la coneja como el efecto de la selección divergente por variabilidad del tamaño de camada en la condición corporal y movilización de reservas energéticas, como biomarcadores del bienestar del animal, y en el tamaño de camada y sus componentes después de siete generaciones de selección. El primer artículo examina las relaciones entre las medidas de la condición corporal y la movilización de energía en conejas primíparas a la monta, al parto y a los 10 días tras el parto, a través de un análisis de componentes principales. La condición corporal se midió como el peso corporal y el espesor de grasa perirenal. La movilización de energía se midió como la concentración de ácidos grasos no esterificados en sangre, antes (NEFAb) y después de la estimulación lipolítica con isoproterenol (NEFAr). Todos los pesos y espesores de grasa perirenal se situaron sobre la primera componente principal, exhibiendo altas correlaciones entre ellos independientemente del estado fisiológico donde se midieron (de 0.51 a 0.83). Todas las medidas de NEFAs se localizaron sobre la segunda componente principal, mostrando una baja correlación con las medidas de la condición corporal. Los NEFAb y NEFAr mostraron elevadas correlaciones entre ellos cuando se midieron en el mismo momento (0.65 a la monta, 0.72 al parto y 0.69 a los 10 días tras el parto), pero bajas correlaciones cuando se midieron en diferentes momentos (de 0.09 a 0.20). El segundo artículo analiza la respuesta correlacionada sobre la condición corporal y la movilización de reservas grasas. El espesor de la grasa perirenal y el incremento de los niveles basales de NEFAs después de su estimulación adrenérgica con isoproterenol fueron medidos a la segunda monta, al parto y a los 10 días tras el parto. El espesor de la grasa perirenal fue similar en ambas líneas a la monta. Sin embargo la línea de alta mostró un menor espesor de grasa que la línea de baja al parto (-0.16 mm, P=0.86), y esta diferencia se mantuvo a los 10 días después del parto (-0.17 mm, P=0.86). Por otro lado, esta línea exhibió un 30% menos de NEFAs al parto que la línea de baja (P=0.96). El tercer y cuarto artículo estudian la respuesta correlacionada sobre el tamaño de camada y sus componentes. Se realizó una laparoscopía a los 12 días de la segunda gestación para estimar la tasa de ovulación y el número de embriones implantados. Se contabilizó el tamaño de camada al segundo parto. En la última gestación se analizó el desarrollo embrionario a 28, 48 y 72 horas de gestación. La tasa de ovulación fue similar en ambas líneas. La línea seleccionada para reducir la variabilidad en tamaño de camada mostró un mayor número de embriones implantados (1.23, P=1.00) que la línea de alta. También, esta línea mostró un desarrollo de los embriones más avanzado a partir de las 48 horas de gestación, exhibiendo un menor porcentaje de mórulas tempranas tanto a 48 horas (53.32% vs 79.90%, P=0.93) como a 72 horas (3.88% vs 21.04%, P=0.93). Un desarrollo más avanzado del embrión está relacionado con una mayor supervivencia de éste (0.85 vs 0.78, P=1.00). Por otro lado, un mayor atestamiento de embriones en el útero de la línea de baja variabilidad no penalizó la supervivencia fetal, y como resultado, esta línea continuó mostrando un mayor número gazapos al parto (0.98, P=0.96). En conclusión, el peso y el espesor de grasa perirenal son buenos predictores de las reservas corporales, ambas medidas podrían usarse para estimar los cambios energéticos a medio plazo, mientras que las medidas de NEFAs se deberían usar a corto plazo. La disminución de la variabilidad del tamaño de camada tiene un efecto favorable sobre la condición corporal, la movilización de reservas grasas, el desarrollo y supervivencia embrionaria y el tam
La tesi es compon de quatre articles, on s'estudia tant la relació entre la condició corporal i la mobilització d'energia en la conilla com l'efecte de la selecció divergent per variabilitat de la grandària de ventrada en la condició corporal i mobilització de reserves energètiques, com biomarcadores del benestar de l'animal, i en la grandària de ventrada i els seus components després de set generacions de selecció. El primer article examina les relacions entre les mesures de la condició corporal i la mobilització d'energia en conilles primípares a la muntada, al part i als 10 dies després del part, a través d'una anàlisi de components principals. La condició corporal es va mesurar com el pes corporal i la grossària de greix perirenal. La mobilització d'energia es va mesurar com la concentració d'àcids grassos no esterificats en sang, abans (NEFAb) i després de l'estimulació lipolítica amb isoproterenol (NEFAr) . Tots els pesos i grossàries de greix perirenal es van situar sobre la primera component principal, exhibint altes correlacions entre ells independentment de l'estat fisiològic on es van mesurar (de 0.51 a 0.83) . Totes les mesures de NEFAs es van localitzar sobre la segona component principal, mostrant una baixa correlació amb les mesures de la condició corporal. Els NEFAb i NEFAr van mostrar elevades correlacions entre ells quan es van mesurar en el mateix moment (0.65 a la muntada, 0.72 al part i 0.69 als 10 dies després del part) , però baixes correlacions quan es van mesurar en diferents moments (de 0.09 a 0.20). El segon article analitza la resposta correlacionada sobre la condició corporal i la mobilització de reserves greixos. La grossària del greix perirenal i l'increment dels nivells basals de NEFAs després de la seua estimulació adrenérgica amb isoproterenol van ser mesurats a la segona muntada, al part i als 10 dies després del part. La grossària del greix perirenal va ser semblant en ambdós línies a la muntada. No obstant això la línia d'alta va mostrar una menor grossària de greix que la línia de baixa al part (-0.16 mm, P=0.86) , i esta diferència es va mantindre als 10 dies després del part (-0.17 mm, P=0.86) . D'altra banda, esta línia va exhibir un 30% menys de NEFAs al part que la línia de baixa (P=0.96). El tercer i quart article estudien la resposta correlacionada sobre la grandària de ventrada i els seus components. Es va realitzar una laparoscopía als 12 dies de la segona gestació per a estimar la taxa d'ovulació i el nombre d'embrions implantats. Es va comptabilitzar la grandària de ventrada al segon part. En l'última gestació es va analitzar el desenrotllament embrionari a 28, 48 i 72 hores de gestació. La taxa d'ovulació va ser semblant en ambdós línies. La línia seleccionada per a reduir la variabilitat en grandària de ventrada va mostrar un nombre més gran d'embrions implantats (1.23, P=1.00) que la línia d'alta. També, esta línia va mostrar un desenrotllament dels embrions més avançat a partir de les 48 hores de gestació, exhibint un menor percentatge de mórulas primerenques tant a 48 hores (53.32% vs 79.90%, P=0.93) com a 72 hores (3.88% vs 21.04%, P=0.93). Un desenrotllament més avançat de l'embrió està relacionat amb una major supervivència d'este (0.85 vs 0.78, P=1.00). D'altra banda, un major atapeïment d'embrions en l'úter de la línia de baixa variabilitat no va penalitzar la supervivència fetal, i com resultat, esta línia va continuar mostrant un nombre més gran errors al part (0.98, P=0.96). En conclusió, el pes i la grossària de greix perirenal són bons predictors de les reserves corporals, ambdós mesures podrien usar-se per a estimar els canvis energètics a mitjà termini, mentres que les mesures de NEFAs s'haurien d'usar a curt termini. La disminució de la variabilitat de la grandària de ventrada té un efecte favorable sobre la condició corporal, la mobilització de reserves greixos, el dese
Calle Ayma, EW. (2017). CORRELATED RESPONSE TO SELECTION FOR LITTER SIZE RESIDUAL VARIANCE IN RABBITS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/81021
TESIS

Abstract Objective: The aim of the present study was to investigate mechanisms of real-time language production of adults who stutter. Method: Data were analyzed for 19 typically fluent young adults (TFA) and 19 young adults who stutter (AWS). Participants performed a masked picture priming task where priming stimuli consisted of two conditions 1) Identity- a masked printed prime word identical to the picture target label, and 2) Unrelated- a masked printed prime word unrelated to the picture target label. Brain event-related potentials (ERPs), time-locked to pictures eliciting spontaneous naming, were recorded, as well as naming accuracy and reaction times. Results: Masked priming effects on ERP components were compared between groups. Priming modulated N400 amplitude in TFA while, at the same latency, priming modulated P300 amplitude in AWS. N400 is attributed to processing of meaningful stimuli, and P300 is a measure of effortful control. An even later priming effect generalized to both groups. Conclusion: Results suggest that post-lexical processing was similar in AWS and TFA, while lexical-semantic processing operated differently. Whereas TFA evidenced automaticity in activation and selection of target picture labels, AWS evidenced enhanced attentional control during lexical selection. We propose that AWS recruited a compensatory attentional mechanism to stabilize activation of target words on the path to naming. These conclusions suggest that clinically, AWS may benefit from vocabulary enrichment and attentional control treatment.

Judgments of Learning (JOLs) are judgments of the likelihood of remembering recently studied material on a future test. Although JOLs have been extensively studied, particularly due to their important applications in education, relatively little is known about the cognitive and neural processes supporting JOLs and how these processes relate to actual memory processing. Direct access theories describe JOLs as outputs following direct readings of memory traces and hence predict that JOLs cannot be distinguished from objective memory encoding operations. Inferential theories, by contrast, claim JOLs are products of the evaluation of a number of cues, perceived by learners to carry predictive value. This alternative account argues that JOLs are made on the basis of multiple underlying processes, which do not necessarily overlap with memory encoding. In this thesis, the neural and cognitive bases of JOLs were examined in a series of four ERP experiments. Across experiments the study phase ERP data showed that JOLs produce neural activity that is partly overlapping with, but also partly distinct from, the activity that predicts successful memory encoding. Furthermore, the neural correlates of successful memory encoding appear sensitive to the requirements to make a JOL, emphasising the close interaction between subjective and objective measures of memory encoding. Finally, the neural correlates of both JOLs and successful memory encoding were found to vary depending on the nature of the stimulus materials, suggesting that both phenomena are supported by multiple cognitive and neural systems. Although the primary focus was on the study phase ERP data, the thesis also contains two additional chapters reporting the ERP data acquired during the test phases of three of the original experiments. These data, which examined the relative engagements of retrieval processes for low and high JOL items, suggest that encoding processes specifically resulting in later recollection (as opposed to familiarity) form one reliable basis for making JOLs. Overall, the evidence collected in this series of ERP experiments suggests that JOLs are not pure products of objective memory processes, as suggested by direct access theories, but are supported by neural systems that are at least partly distinct from those supporting successful memory encoding. These observations are compatible with inferential theories claiming that JOLs are supported by multiple processes that can be differentially engaged across stimulus contents.

L’activité psychologique spontanée contribue de façons importantes à notre expérience du monde qui nous entoure. Cette thèse s’intéresse à l’atténuation spontanée des mécanismes sensoriels cérébraux, qui constitue un important déterminant du découplage attentionnel, menant à une expérience de « mind-wandering » (vagabondage/errance de la pensée). Cet état de mind-wandering se caractérise par une augmentation spontanée de pensées sans lien avec la tâche en cours de réalisation, qui vont varier au cours du temps et interférer avec les processus cognitives. Certain processus de découplage sensoriel apparaissent très précocement après une stimulation, alors que d’autres, comme l’attention sélective, apparaissent plus tardivement. La recherche s’est principalement intéressée aux effets du mind-wandering sur les processus cognitifs, mais nous ne savons que peu de chose sur les processus sensoriels précoces au cours du mind-wandering et sur leur dynamique temporelle. Dans cette thèse, nous nous intéresserons principalement au développement temporel précoce de l’atténuation sensorielle qui précède un état de mind-wandering. Nous chercherons, plus particulièrement, à déterminer si cette atténuation sensorielle est un processus qui se développe progressivement ou s’il s’agit d’un évènement de découplage soudain, qui déclenche alors à un changement cognitif global amenant à un état de mind-wandering. Nous avons développé une nouvelle approche expérimentale, inspiré de la tâche classique de SART (Sustained Attention to Response Task), et basée sur la mesure de l’évaluation en continue de performance psychophysique individuelle. Ceci était réalisé en sondant les participants par une question, lorsque leurs temps de réponse (RT) dépassaient de plus ou moins deux fois la déviation standard (SD) de leur temps de réponse moyen. Les résultats montrent que l’état de mind-wandering est généralement précédé par des temps de réponses plus court, en comparaison aux essais dans lesquels le sujet est focalisé sur la tâche. Plus particulièrement, il est possible de prédire de façons fiables les épisodes de mind-wandering à partir de la différence de temps de réponse entre les deux derniers essaies précédent la question. Ainsi, l’état de mind-wandering suit une augmentation de courte durée de la variabilité comportementale avec une durée comprise entre 2,5 et 10 secondes. Dans une seconde étude, nous avons exploré les corrélats electrophysiologiques de la dynamique de l’atténuation sensorielle précédent les phases de mind-wandering au cours d’une version modifiée de la tâche de SART. Nous avons décrit les modulations de l’activité cérébrale dans plusieurs régions du cortex visuel pendant les épisodes de mind-wandering. Les résultats montrent une modulation de composantes associées au traitement sensoriel précoce (augmentation de P1 et diminution de N1) juste avant le report par les participants d’épisodes de mind-wandering. Ce résultat suggère une diminution des ressources neuronales associées aux traitements visuels précoces du stimulus visuel. Le mind-wandering augmente également l’amplitude d’une composante plus tardive, entre 300 et 500ms, suggérant une augmentation de la préparation à la réponse. Cette thèse apporte ainsi, pour la première fois, une description de l’organisation temporelle précoce du découplage sensoriel précédent l’experience de mind-wandering. En effet, le mind-wandering apparait comme étant fortement associé à une atténuation précoce et abrupte des processus sensoriels. Ainsi, le cours découplage sensoriel (quelques centaines de ms) peut alors entrainer un long et dramatique état de conscience tel que le mind-wandering
Spontaneous psychological activity substantially contributes to our everyday experience of the external world. This thesis focuses on spontaneous attenuation of sensory processing in the human brain, an important determinant of attentional decoupling, which results in mind-wandering experience. Mind wandering is characterized by the spontaneous rise of thoughts unrelated with the ongoing task, which varies over time and interferes with the current cognitive processes. Some sensory decoupling processes arise very early after an event, whereas others, such as selective attention processes, take place later on. Previous research mainly focused on the general effects of mind-wandering on cognitive processing, but little is known about the early sensory processes during mind wandering and about their temporal dynamics. This thesis focuses on the study of the temporal development of early sensory attenuation previous to mind-wandering experiences. Specifically, we addressed whether this sensory attenuation is a process that develops gradually or whether it is an abrupt decoupling event that consequently triggers a global cognitive change towards a mind-wandering experience. We developed a new experimental approach, inspired by the classic sustained attention to response task (SART), based on the continuous, online assessment of individual psychophysical performance. Probe questions were asked whenever response times (RTs) exceeded 2 SD from the participant’s average RT. Results showed that mind-wandering reports were generally preceded by slower RTs, as compared to trials preceding on-task reports. Specifically, we could reliably predict mind-wandering episodes based on the response time difference between the last and the second-to-last trials. Thus, mind-wandering follow an abrupt increase in behavioral variability, lasting between 2.5 and 10 seconds. In a second study, we addressed the electrophysiological correlates of the dynamics of the sensory attenuation prior to mind-wandering experiences during the performance of a modified version of the RT task. We described the modulation of the brain activity in different regions of the visual cortex during mind-wandering episodes. We found modulations of components related to early sensory processing (increase of P1 and decrease of N1), shortly before participants reported mind-wandering episodes. This suggests a decrease of neural resources related with the early visual processing of the sensory input. Mind wandering also increased the amplitude of a late component peaking around 300-500 ms, perhaps because of increased preparation of response. Overall, this thesis provides for the first time a clear description of the early temporal organization of the sensory decoupling prior to mind-wandering experiences. In particular, mind wandering appears to be strongly linked to early, abrupt sensory attenuation. Thus, short-lasting sensory decoupling (a few hundreds ms) can thus determine a prolonged and dramatic consciousness state such as mind wandering

Orientador: Prof. Dr. André Mascioli Cravo
Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Neurociência e Cognição, 2016.
Uma série de estudos tem mostrado que saber onde determinado alvo será apresentado facilita seu processamento. Em muitos desses trabalhos, uma pista simbólica (como uma seta) é utilizada para guiar a orientação da atenção espacial. Entretanto, os mecanismos que regem o aprendizado e a atualização de pistas simbólicas visuoespaciais ainda são amplamente desconhecidos. Para esclarecermos melhor estes mecanismos, investigamos: (1) os padrões comportamentais da aprendizagem e atualização de pistas simbólicas e (2) os mecanismos neurais subjacentes a estes processos. Foi utilizada uma versão modificada do paradigma de orientação de atenção espacial de Posner juntamente com registro eletroencefalográfico. Nessa tarefa, os participantes deviam aprender a cada bloco qual das cores em um anel de cores servia de pista simbólica e utilizá-la para orientar a atenção e fazer a discriminação de um alvo. A tarefa incluía uma condição rara de pista inválida. Os resultados apontaram rápida aprendizagem da pista simbólica, porém a interpretação dos correlatos eletrofisiológicos ficou prejudicada por aparente contaminação das tentativas válidas pelas inválidas. Um novo experimento foi feito sem pistas inválidas e com a utilização de um distrator em metade dos blocos. Novamente, efeitos da aprendizagem da pista foram observados após uma única exposição, com ganhos em tempo de reação e acurácia. A presença do distrator limitou o benefício da pista. Como correlatos eletrofisiológicos foram identificados dois componentes no período entre pista e alvo: um componente semelhante à negatividade precoce de direcionamento atencional (EDAN) e uma negatividade tardia. Esses potenciais se intensificavam ao longo do bloco. Também foi observada tendência de dessincronização contralateral na banda alfa em eletrodos parieto-occipitais com intensificação com o avanço do bloco. Esses resultados sugerem que alguns correlatos eletrofisiológicos típicos da utilização de pistas simbólicas não se estabelecem imediatamente com sua aprendizagem, estando ausentes nas primeiras utilizações componentes como a negatividade anterior de direcionamento atencional (ADAN) e a positividade tardia de direcionamento atencional (LDAP), enquanto outros (EDAN e dessincronização contralateral de alfa) já são identificáveis. Adicionalmente, o padrão dos correlatos eletrofisiológicos permite levantar a hipótese de que nessa etapa inicial haja um papel preponderante da memória operacional para utilização das pistas simbólicas ainda não estabelecidas completamente.
Several studies have shown that knowing where a target will be presented facilitates its processing. Many of these works use symbolic cues (for instance, arrows) to guide spatial attention orienting. However, the mechanisms that rule the learning and updating of symbolic visuospatial cues are still unknown. To clarify these mechanisms, we investigated: (1) behavioral patterns of learning and updating symbolic cues and (2) neural mechanisms underlying these processes. A modified version of Posner¿s paradigm of attention orienting was used, along with eletroencephalografic recording. Participants had to learn which color from a colorwheel was the cue on each experimental block and use it to guide attention to facilitate the discrimination of a target. The task included a rare condition of invalid cues. Results showed fast learning of symbolic cues, however the interpretation of eletrphysiological correlates was impaired by an apparent contamination of the valid condition by the invalid one. A new experiment was done without invalid cues and including a distractor on half of the blocks. Once again, effects of cue learning were present after a single exposition, with gains in reaction time and accuracy. Distractor presence limited cueing benefits. As neural correlates, two components in the period between cue and target were identified: a component similar to the early directing attention negativity (EDAN) and a late negativity. These potentials were enhanced throughout the block. A tendency of contralateral desyncronization on parieto-occipital electrodes, increasing along the block, was also present. These results suggest that some typical eletrophysiological correlates of symbolic cueing in visuospatial attention are not immediately established with learning, since the anterior directing attention negativity (ADAN) and the late directing attention positivity (LDAP) are absent, while others (EDAN and alpha desynchronization) are already identifiable. Additionally, the pattern of eletrophysiological correlates found allows us to hypothesize that, in this initial stage, there is a heavy role for working memory in using symbolic cues that are not completely established.

At northern midlatitudes over the 1979–2002 time period, column ozone trends are observed to have maximum negative amplitudes in February and March. Here, the portion of the observed ozone interannual variability and trends during these months that can be attributed to two specific dynamical transport processes is estimated using correlative and regression methods. In approximate agreement with a recent independent study, 18%–25% of the observed maximum negative trend is estimated to be due to long-term changes in the diabatic (Brewer–Dobson) circulation driven by global-scale changes in planetary wave [Eliassen–Palm (EP) flux] forcing. In addition, 27%–31% of the observed maximum midlatitude trend during these months is estimated to be due to long-term changes in local nonlinear synoptic wave forcing as deduced from correlated interannual variations of zonal mean ozone and Ertel’s potential vorticity. Like long-term decreases in the Brewer–Dobson circulation, this trend component reflects an overall net increase in the polar vortex strength, which is associated with increased numbers of anticyclonic, poleward-breaking Rossby waves at northern midlatitudes. Together, these components can explain approximately 50% of the observed maximum negative column ozone trend and interannual variance at northern midlatitudes in February and March. The combined empirical model also approximately simulates a leveling off or slight increase in column ozone anomalies that has been observed for some months and latitudes since the mid-1990s.

Comparing data from different subfields of research may help in understanding emerging patterns and refining interpretations. This is especially true in neuroscience because brain functions can be studied at multiple levels of analysis, spatially and temporally, and with a variety of complementary measurement techniques. Within the ERP domain, several subfields of research have evolved over time, typically reflecting the specific time-window of interest and brain function investigated. The current investigation focused on three widely studied ERP effects reflecting a variety of key brain functions: the N400 effect, the P3b effect and the Left Parietal effect. The N400 effect has attracted researchers interested in language processing, the P3b effect researchers interested in attentional processes and the Left Parietal effect researchers focused on episodic recollection. Even though the ERP technology constitutes a common thread across these subfields, there is often a lack of communication across groups of researchers. The literatures on the N400 effect, P3b effect and Left Parietal effect have been written by relatively non-overlapping groups of researchers, and as such the kind of analysis carried out in the current thesis is not a common one, as it compares effects investigated within different subfields. Specifically, the approach taken in the current thesis involves assessment of the comparative reliability of the three effects of interest, and at the same time allowing refining their validity. Results showed that all three effects were found to be reliable at the group level and the N400 effect and the P3b effect were also found to be reliable at the single participant level. A correlational analysis involving all three effects yielded a significant correlation between the P3b and the Left Parietal effect but not between the P3b and the N400, or between the Left Parietal effect and the N400. Following up on the significant correlation, suggesting a convergence between the P3b effect and the Left Parietal effect, a probability manipulation of the Left Parietal effect was carried out to investigate if the old/new effect is sensitive to probability changes similarly to the P3b. The size of the Left Parietal effect was found to be sensitive to the relative probability of old and new items, in a manner consistent with the P3b effect‟s sensitivity to probability manipulations. The results pointing to a relationship between the P3b effect and the Left Parietal effect suggest that attentional processes sensitive to probability may temporally overlap and confound memory processes as indexed by the Left Parietal effect. The N400 effect, in the initial correlational study, was found to be independent from attentional processes as reflected by the P3b, and from episodic recollection as indexed by the Left Parietal effect. The validity of the N400 effect as a measure of semantic processing was then assessed by manipulating associative relationships while keeping constant semantic relationships, with results showing that the effect can be clearly modulated by associative changes when semantic relatedness is kept constant. The same association norms were then used in an old/new recognition experiment to assess if the Bilateral-Frontal old/new effect behaves in reaction to association relationships similarly or differently from the N400, in the attempt of assessing if the N400 is only a measure of associative relationships or also a measure of the process of familiarity. The observed pattern suggests independence between the N400 and the Bilateral Frontal effect. Overall, the N400 effect was found to be independent from memory processes occurring in the same time window, but, contrary to the dominant interpretation of the effect, the effect was modulated by changes in association strength while keeping semantic relatedness constant, suggesting that the N400 effect may be sensitive to a contiguity-based associative learning process not constrained to the linguistic domain.

Submitted by Isabella Bonamigo da Silva (bonamiga.isabella@gmail.com) on 2018-06-29T00:21:52Z No. of bitstreams: 1 dissertacao_final_isabella 24.06.pdf: 1619807 bytes, checksum: 8e0f5202f6630e66364e97951bac7cdf (MD5)
Approved for entry into archive by Satie Tagara (satie@marilia.unesp.br) on 2018-06-29T16:53:33Z (GMT) No. of bitstreams: 1 silva_ib_me_mar.pdf: 1619807 bytes, checksum: 8e0f5202f6630e66364e97951bac7cdf (MD5)
Made available in DSpace on 2018-06-29T16:53:33Z (GMT). No. of bitstreams: 1 silva_ib_me_mar.pdf: 1619807 bytes, checksum: 8e0f5202f6630e66364e97951bac7cdf (MD5) Previous issue date: 2018-05-29
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A prematuridade é considerada um fator de risco para o desenvolvimento motor, social, cognitivo e de linguagem. Pesquisadores têm utilizado instrumentos nacionais e internacionais para a avaliação da linguagem falada nesta população, destacando a necessidade desta investigação em diferentes aspectos. Uma técnica que tem sido utilizada como ferramenta para a investigação de elementos do processamento da linguagem falada é a eletroencefalografia (EEG) e suas medidas de Event Related Potentials (ERPs). Posto isso, o objetivo deste estudo foi investigar o desempenho da linguagem falada e achados eletrosifiológicos em crianças pré-escolares nascidas prematuras e compará-los aos de crianças nascidas a termo com desenvolvimento típico de linguagem. Para compor o Grupo Amostral I (GAI), participaram 20 crianças nascidas prematuras moderadas de 4 e 5 anos de idade cronológica, e para o Grupo Comparativo I (GCI), 40 crianças nascidas a termo pareadas a seus pares por sexo e idade cronológica. Para esses grupos, foi utilizado o instrumento Preeschool Language Assessment - Second Edition (PLAI-2) para a avaliação da linguagem falada. Como um recorte do GAI, o Grupo Amotral II (GAII) foi composto por oito crianças participantes do GAI, e para o Grupo Comparativo II (GCII), oito crianças participantes do GCI, pareadas ao GAII por gênero e idade cronológica. Para a avaliação eletrofisiológica de GAII e GCII, utilizou-se uma tarefa de julgamento semântico, na qual frases de finais congruentes e incongruentes foram apresentadas de forma passiva e os registros eletrofisiológicos foram captados a partir de um capacete geodésico de 128 canais. O resultado, de forma geral, indicou que o grupo de crianças nascidas prematuras apresentou desempenho inferior nos itens (i.e, recepção; expressão e habilidade comunicativa) e subitens (i.e, escolha, análise, síntese, análise perceptual) da linguagem falada, com exceção apenas para o subitem “raciocínio”. Os resultados da avaliação eletrofisiológica mostraram diferenças no padrão de ativação eletrofisiológico (i.e, amplitude e latência das ondas), quando os grupos foram comparados. Como conclusões, destaca-se que crianças pré-escolares nascidas prematuras apresentaram desempenho inferior nas habilidades de linguagem falada na maioria das habilidades avaliadas pelo PLAI-2 e diferenças no padrão eletrofisiológico, quando comparadas a seus pares nascidos a termo. Os dados indicaram a necessidade de investigação e diagnóstico precoce das possíveis alterações de linguagem falada em pré-escolares prematuros, considerando que diferenças importantes podem já se manifestar na investigação eletrofisiológica (i.e captação da informação em nível cerebral).
Prematurity is considered a risk factor for motor, social, cognitive and language development. Researchers have used national and international instruments for the evaluation of spoken language in this population, highlighting the need for this research in different aspects. One technique that has been used as a tool for the investigation of elements of speech processing is electroencephalography (EEG) and its measures of Event Related Potentials (ERPs). Therefore, the aim of this study was to investigate the performance of spoken language and eletrophysiological findings of preschool children born prematurely and compare to that of full-term children with typical language development. Twenty preterm infants born at the age of 4 and 5 years of age were included in Amostral Group (AGI), and for Comparative Group I (CGI) 40 children born at term were matched to their peers by sex and chronological age. For these groups the Preschool Language Assessment - Second Edition (PLAI-2) instrument was used for the evaluation of spoken language. As a AGI cut, Amotral II Group (AGII) was composed of 8 children participating in the AGI and for Comparative Group II (CGII), 8 children participating in the CGI, matched to AGII by gender and chronological age. For the electrophysiological evaluation of AGII and CGII, a semantic judgment task was used, where congruent and incongruent sentences were presented passively and the electrophysiological records were captured from a 128-channel geodetic helmet. The result, in general, indicated that the group of children born premature presented inferior performance in the items (ie, reception, expression and communicative ability) and subitens (i.e., choice, synthesis analysis, and perceptual analysis) of spoken language, with the exception of for the subitem "reasoning". The results of the electrophysiological evaluation showed differences in the pattern of electrophysiological activation (i.e., wave amplitude and latency), when the groups were compared. As a conclusion, it should be pointed out that preschool children born prematurely presented lower performance in spoken language skills in most abilities assessed by PLAI-2 and differences in the electrophysiological pattern when compared to their full-term pairs. The data indicated the need for investigation and early diagnosis of possible changes in spoken language in preterm infants, considering that important differences may already be manifested in electrophysiological investigation (i.e., information capture at the brain level).

The studies presented in this thesis investigated the neural correlates of attention in touch. In particular, the electrophysiology of exogenous tactile processing and inhibition of return (IOR) - an area previously unexplored. In all studies a variation of the Posner cue-target paradigm was used. Typically, a cue was presented to the left or right hand. Following a stimulus onset asynchrony of 800 ms, a target would appear at the same or opposite hand. Behavioural results consistently demonstrated IOR when employing a simple target detection task, showing that IOR is a reliable phenomenon in touch. The concurrently recorded event related potentials (ERPs) demonstrated an early attention modulation of the N80 in all studies presented in this thesis, regardless of the presence or absence of IOR. This early component likely reflects processing of the exogenous lateralized cues. Following the N80, the attention modulations varied across studies. The conclusion to be drawn from this thesis is that not one particular ERP component is directly associated with IOR. Analysis of endogenous tactile attention (Chapter V) demonstrated modulations at the N140 and Nd components. Moreover, correlation analysis showed that larger ERP attention modulation was associated with a larger behavioural effect, demonstrating a novel relationship between ERP modulations and response time effects. Analysis of the cue-target interval has previously only been investigated during endogenous orienting. Here, and for the first time, an anterior directing attention negativity (ADAN) was demonstrated during exogenous orienting. This ADAN was unaffected by varying posture suggesting exogenous tactile attention and IOR are somatotopically coded. Indications of an external frame of reference were only demonstrated during shifts of endogenous attention, as indicated by the presence of a late directing attention positivity (LDAP) (endogenous counter-predictive task presented in Chapter V). The final study of this thesis (Chapter VI) demonstrated that varying visual perceptual load influenced tactile processing. Specifically, high perceptual load led to elimination of IOR. Moreover, the P100 for irrelevant tactile stimuli was significantly reduced in high versus low load condition. This suggests perceptual load may suppress irrelevant tactile stimuli relatively early (around 100 ms post stimuli onset) during tactile processing. Taken together, this thesis presents a series of experiments which map out effects of endogenous and exogenous attention and how these mechanisms interact, both through behaviour and underlying neural correlates.