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ERPs, specifically the P3, have been proposed as an alternative to traditional polygraphy, with one approach (i.e., Brain Fingerprinting) being promoted as infallible to justify its use on a commercial basis. Concerns have been voiced, however, that such techniques would have to undergo peer-reviewed studies to satisfy validity concerns. Rosenfeld et al. (2004) found, for example, that mental countermeasures were effective in reducing detection rates using an amplitude based, peak-to-peak measure. The present study attempted to replicate and extend Rosenfeld et al.'s study, and to test Brain Fingerprinting's vulnerability to participant manipulation by employing a highly realistic virtual reality crime scenario, multiple countermeasures, and Bayesian and bootstrapping analytic approaches to classify individuals as being guilty or innocent. Participants reported a high degree of realism supporting the external validity of this study and suggesting future uses of virtual environments. Hit rates across statistical methods were significantly lower for standard guilty and innocent participants as compared to previous studies; countermeasures reduced the overall hit rates even further. Brain Fingerprinting was as vulnerable to countermeasures as other statistical measures, and produced a significant number of indeterminate outcomes. Nevertheless, innocent participants remained protected from being falsely accused across statistical methods, consistent with findings of prior studies. Reaction times were determined unsuitable in determining guilt or innocence in this study. Results suggested that ERP based deception detection measures might lack the level of validity required for use in an applied setting.

Brain-Computer Interface (BCI) technology utilizes EEG to measure the electrical activity at the scalp to be used for operating an external device. Therefore, understanding the cognitive responses that can be measured through the EEG to use BCIs is important. BCI systems, such as the P300 Speller, rely on detecting Event-Related Potentials (ERPs). ERPs are time-locked responses to internal or external events. Previous research has indicated that viewing different categories of stimuli activate specific brain structures and produce stimuli specific ERPs. Since the BCI’s ability to detect differences in ERPs is important for operating the system, we have conducted a traditional oddball study to examine the ERPs elicited by two categories of stimuli – images of locations and images of graspable tools. Functional MRI studies have shown that images of familiar locations produce brain responses in the parahippocampal place area (PPA). The PPA is a region of the ventromedial surface of the temporal lobe that responds more strongly to visual scenes (i.e. images of familiar landscapes) than to other presented visual stimuli and is sometimes better known as a “mapping area” of the brain. Conversely, the premotor cortex is an area of motor cortex that lies within the frontal lobe and is used to produce neural impulses that control the implementation of movement. In this instance, logical movement of tools, such as a hammer, can be used as a stimulus for the activation of the premotor cortex. While research has indicated the activation of these different regions, there has not been any research comparing the ERPs that may be produced by these two categories of stimuli. Therefore, our study uses an oddball task to determine if these two types of stimuli can produce distinct ERPs. We hypothesized that images of tools will produce a distinct ERP response, specifically the P300 response, at frontal electrode locations that will significantly differ from ERP responses produced by images of locations. Furthermore, we hypothesized that images of locations will produce distinct ERPs at parietal locations compared to images of tools. Preliminary data collected from 20 participants has indicated a difference in the P300 response at central electrode locations produced by the two types of stimuli. As we continue with data collection, we anticipate observing differences at the frontal and parietal locations. This would indicate that activating these different structures with distal proximity may provide more robust ERP responses that could be used for future P300 Speller BCI operation.

The concept of a unitary cognitive control system has increasingly come under question. Numerous paradigms have emerged that aim to dissect cognitive control into its constituent processes, including task-switching paradigms that require alternation between multiple tasks. A switch in task is associated with increased reaction time (RT) as compared to a repeat in task, which is proposed to at least partially reflect processes associated with reconfiguration of the currently active task-set. Previous event-related brain potential studies show a differential positivity emerging prior to a switch in task that appears to reflect anticipatory task-set reconfiguration. Six experiments were conducted that investigated the behavioural and ERP correlates of task-switching, and in particular, the cognitive control processes involved in anticipatory task-set reconfiguration. Experiment 1 dissociated the effects of passive dissipation of task-set interference from anticipatory task-set reconfiguration. In Experiment 2, it was further verified that the switch-related differential positivity reflects processes associated with anticipatory task-set reconfiguration, particularly initiation of the new task-set. A simplified paradigm was developed in Experiment 3 that maximised engagement in anticipatory task-set reconfiguration, reducing mean RT switch cost. Experiment 4 demonstrated that the RT switch cost and differential positivity in cueing paradigms are associated with task-set reconfiguration rather than a cue repetition benefit. Consistent with previous brain imaging studies, Experiment 5 revealed that anticipatory task-set reconfiguration is associated with increased activation in the prefrontal cortex and parietal lobe. These findings show that task-set reconfiguration processes are activated when switching between tasks and that this consists of multiple components including the active utilisation of cognitive control processes in anticipatory task-set reconfiguration. Task-switching paradigms are thus a useful tool for investigating control processes in healthy populations and as Experiment 6 demonstrates, in clinical populations that have deficits in control processes, such as patients with schizophrenia. / PhD Doctorate

Event-related potentials have been found to be a useful indicator of brain states and brain abnormality. The contingent negative variation, P300 and bereitschafts potential are well researched event-related potentials of particular interest. Many factors have to be considered in the design of measurement systems to record multiple channels of these signals accurately. The correlation between channels must be high and channel noise and distortion must be minimal, whilst the system as a whole must meet the requirements of the medical safety standards. For further research there was found to be a requirement for a dedicated thirty-two channel ERP measurement system that met these criteria. This has been achieved in a PC based system that utilises simultaneous sampling of all channels, and filters that extend to very low frequencies. Software control of the system enables user adjustment of recording parameters and paradigm implementation. Data processing using high level software enables digital signal processing techniques to be applied for further noise removal and signal analysis. The system has been tested using synthetically generated signals and by limited recording of the three ERPs. The results prove that the system is a suitable tool for high accuracy, multi-channel recording of ERPs.

Earlier ages of alcohol initiation have been associated with an increased vulnerability for Alcohol Use Disorder and general risk taking behaviors beyond genetic influence. Reward processes, including reward anticipation (pleasure before receiving alcohol/general reward), reward learning (how quickly one pairs a stimulus with alcohol/general reward), and reward consummation (pleasure when receiving alcohol/general reward), have been implicated as potential mechanisms accounting for this vulnerability. However, no careful bio-behavioral research has been conducted on the effect of age of alcohol initiation on general and alcohol-related reward processes. Using Event Related Potentials (ERPs), the current study addressed this gap in a sample of 123 current alcohol drinkers. The Monetary Incentive Delay-General task and Monetary Incentive Delay-Alcohol task were administered to participants, in which reward learning (quickness of pairing the neutral cue or alcohol cue with monetary feedback), reward anticipation (activity to neutral cue or alcohol cue), and reward consummation (activity to monetary feedback) were examined. Electroencephalography was used to collect ERPs that index reward anticipation (P3) and reward consummation (P3 and Late Positive Potential) during these tasks. Earlier ages of alcohol initiation were associated with increased alcohol-related reward learning and decreased alcohol-related reward consummation (P3 and Late Positive Potential) beyond genetic and environmental covariates. There were no other significant relationships. These findings support and extend alcohol theories by showing that earlier ages of alcohol initiation may foster a greater sensitization in alcohol-specific reward-learning and more pronounced decreases in alcohol-related consummation. Although in need of direct testing, this might explain why earlier ages of alcohol initiation are associated with an increased vulnerability to Alcohol Use Disorder.

The error related negativity (ERN) is an event-related brain potential that is sensitive to errors. It reflects individual differences in the extent to which individuals recruit neural systems involved in monitoring errors and systems for cognitive control that then make adjustments to future behavior. It has been closely linked to anxiety through diverse disorders and symptoms, but recently evidence highlights the role of anxious apprehension as a key individual difference related to error monitoring. Diverse hypotheses have emerged to explain this relationship. While some views emphasize the role of motivation and emotion, others suggest that a transient compensatory control is responsible for this relationship. Although both theories recognize the potential for state anxiety to potentiate the ERN, there is limited literature that allows a comparison of these competing hypotheses. The present study investigated the interaction of state and trait anxiety on the ERN by comparing ERN amplitude before and after a five minute worry induction period that specifically targeted each individual's greatest current worries. Results did not unequivocally support one specific theory, but rather provide some preliminary evidence of how trait and state worry may interact and affect the ERN. Suggestions for future research are provided, including using worry induction paradigms in which the worries increase threat or significance of errors.

Le sommeil est défini comme un état comportemental de repos où nous perdons conscience de notre environnement et notre réactivité aux stimuli extérieurs est drastiquement réduite. Pourtant, lorsque nous dormons, l’appel par notre prénom ou à la sonnerie du réveil peuvent encore nous réveiller, suggérant qu’un certain degré de traitement des stimuli reste possible. Dans ce travail, nous soulevons la question de la profondeur du traitement de l’information extérieure pendant le sommeil. Nous avons enregistré simultanément l’activité cérébrale de sujets sains adultes en électro- et magnéto-encéphalographie (EEG et MEG) en réponse à des stimulations auditives, avant, pendant, et après une courte période de sommeil. Afin de tester la profondeur du traitement de l’information à travers la hiérarchie corticale, nous nous sommes concentrés sur les capacités de codage prédictif hiérarchique, qui permettent au cerveau d’anticiper les évènements futurs à partir d’une connaissance passée. Les prédictions sont faites à de nombreuses si ce n’est toutes les étapes de la hiérarchie corticale. Tester les différents niveaux de prédiction nous permet donc d’évaluer précisément à quel niveau l’intégration de l’information est interrompue. Nous avons d’abord testé les capacités du cerveau à détecter la nouveauté auditive. Nous avons présenté aux sujets des séquences de sons comprenant des régularités temporelles à courte (locale) ou à longue (globale) échelle de temps, et analysé les réponses cérébrales à des sons violant ces régularités. Les réponses cérébrales à ces violations locales ou globales se traduisent respectivement en EEG à l’éveil par l’émergence de deux signaux d’erreur de prédiction : la négativité de mismatch (MMN) et la P300. Notre analyse révèle que la MMN et la P300 disparaissent toutes deux dans le sommeil avec la perte des activations des aires associatives préfrontales et pariétales. Au cours de l’endormissement, la MMN diminue progressivement, tandis que la P300 disparait brutalement avec la perte de conscience des stimuli. Ce comportement tout-ou-rien renforce l’hypothèse que la P300 est un marqueur de la conscience. Malgré tout, nous avons montré que le cerveau détecte toujours les nouveaux sons et peut s’y habituer, mais seulement dans un contexte limité d’adaptation sensorielle de bas niveau. Après avoir démontré la perte des capacités de codage prédictif dans le sommeil dans le cadre de régularités statistiques arbitraires et nouvellement acquises, dans une deuxième série d’expériences nous avons testé la capacité du cerveau endormi à établir des prédictions sur les sons à venir dans le cadre de connaissances sémantiques connues déjà stockées en mémoire à long terme. Nous avons présenté à des sujets endormis des opérations arithmétiques simples, comme “deux plus deux égal neuf”, et nous avons enregistré les réponses cérébrales aux résultats corrects et aux résultats faux. Nous avons découvert que le cerveau était toujours capable de détecter les violations arithmétiques dans le sommeil, avec des activations en partie similaires à celles de l’éveil. Nous suggérons que, bien que le sommeil prévienne tout calcul explicite, il y a conservation des signaux d’erreur de prédiction pour les opérations arithmétiques simple déjà mémorisées. Ce travail clarifie à quel niveau l’intégration de l’information auditive est interrompue pendant le sommeil, et quelles fonctions cognitives persistent ou s’altèrent. La persistance de l’adaptation sensorielle et des capacités de prédiction à partir de connaissances déjà mémorisées sont probablement responsables de la réactivité résiduelle qui peut être observée pendant le sommeil alors que les sujets sont inconscients. Finalement, ces résultats aident aussi à mieux comprendre pourquoi un stimulus donné sera traité ou non dans le sommeil. (...) / Sleep can be defined as a behavioral state of rest in which consciousness of external stimuli vanishes and responsiveness to the environment is drastically reduced. When we sleep, however, we may still react and wake up to our name or to the alarm clock, suggesting that some processing of external stimuli remains. We address in the present work the question of how deeply external information is processed during sleep. We recorded brain activity in adult human subjects simultaneously in electro and magnetoencephalography (EEG and MEG) in response to auditory stimulation, before, during and after a short period of sleep. In order to test information integration through the brain hierarchy, we focused on hierarchical predictive coding capabilities, which enable the brain to anticipate the future from previous knowledge. Predictions occur at many if not all steps of the cortical hierarchy. Testing different levels of predictions enables us to assess the steps at which information integration is disrupted during sleep. We first tested the capacity of the sleeping brain to detect auditory novelty. We analyzed brain responses to violations of local and global temporal regularities, which are respectively reflected in EEG during wakefulness by two successive prediction error signals, the mismatch negativity (MMN) and the P300. Our analysis revealed that both the MMN and the P300 vanish during sleep, along with the loss of activations in prefrontal and parietal associative areas. The MMN gradually decreased in the descent to sleep, whereas the P300 vanished abruptly with the loss of awareness during N1 sleep. This all-or-none behavior strongly reinforces the hypothesis that the P300 is a marker of consciousness. Even so, we showed that sounds still activate sensory cortices, and that the brain remains able to detect new sounds and to habituate to them, but only in the limited context of sensory adaptation. Having demonstrated the disruption of predictive coding for arbitrary and newly acquired statistical regularities, in a second set of experiments we tested the capacity of the sleeping brain to develop predictions of future auditory stimuli for over-learned semantic knowledge stored in long-term memory. We presented sleeping subjects with simple arithmetic facts such as “two plus two is nine” and recorded brain responses to correct or incorrect results. We discovered that the sleeping brain was still able to detect arithmetic violations, with activations in part similar to wakefulness. We suggest that, although sleep disrupts explicit arithmetic computations, there is a preservation of prediction error signals for arithmetic facts stored in long-term memory. The present work clarifies the steps at which auditory information integration is disrupted during sleep, and which cognitive functions remain or vanish. The preservation of low-level sensory adaptation and of predictions from long term memory may account for the residual responsiveness that can be observed during sleep, while subjects are unconscious. Finally, these results also help to better understand why a given stimulus may or may not be processed during sleep. The depth of information integration is function of the ongoing spontaneous oscillations of the sleeping brain, but also of the nature of the stimulus, i.e. its salience, its knowledge, and its relevance.

What are the effects of non-balanced bilingualism on cognitive performance? And how do proficient, non-native speakers acquire and use lexical, syntactic and semantic information during sentence processing? Whilst there is growing research on these topics, there is no firm consensus on how to answer these questions. In the literature on cognitive effects of bilingualism, this lack of consensus has even resulted in radically opposing views and a heated debate. In this thesis, I seek to provide a balanced treatment of the literature and to address the above-mentioned questions by employing behavioral and neurophysiological paradigms. First, using a structural priming paradigm, I examine how proficient, non-native speakers of different native language backgrounds (Romance and Germanic) acquire lexically-specific syntactic restrictions of non-alternating verbs in English. Results from these experiments suggest that, although non-native speakers partially acquire lexically-specific syntactic restrictions, their knowledge is not native-like. Moreover, transfer from the first language does not seem to play a role in the acquisition of the relevant restrictions. Second, using Event-Related Potentials (ERPs) I examine whether proficient non-native Spanish-English speakers draw on different forms of semantic information such as relatedness and animacy incrementally during sentence comprehension. Results of these experiments suggest that, while relatedness facilitates processing (indexed by N400s) in both native and non-native speakers, effects of animacy are smaller in non-native speakers, relative to native speakers. Third, I employ a series of auditory attentional tasks and measures of lexical access and verbal fluency to assess cognitive functions in non-balanced bilinguals with different levels of language proficiency. Results show a bilingual advantage in inhibitory control and a non-significant trend towards bilingual better performance in attentional switching, and the groups exhibit similar performance on verbal fluency. Results of all the studies are discussed in the context of the existing literature on cognitive performance in bilinguals and accounts of language processing in native and non-native speakers and suggestions for future research are provided.

The aim of the current series of experiments was to further explore the boundary conditions of the recognition memory old/new effect in the context of the recognition/associative recall task (Rugg, Schloerscheidt, Doyle, Cox, & Patching, 1996). The study by Rugg et al. was replicated and extended by manipulating both the semantic relatedness between study items and the timing of recall. Eventrelated potentials (ERPs) were recorded from 17 scalp electrode sites during performance of a recognition/associative recall task. Forty participants were visually presented with four blocks of 50 word pairs which were either unrelated (Experiments 1 and 2) or weakly semantically related (Experiments 3 and 4). Participants were instructed to form an association between the members of each word pair. At test, the first members of each pair were visually presented intermixed with a similar number of unstudied items. Participants were required to discriminate (i.e., recognise) previously studied items (old) from new items. Participants were also required to recall the study associate for words judged old, and to provide confidence levels for each recognition decision on a 3-point scale. Recall was either immediate (Experiments 1 and 3) or delayed (Experiments 2 and 4). Relative to ERPs to new items, the ERPs elicited by words correctly recognised and for which the associate was correctly recalled exhibited a positive-going shift between 500-800 ms poststimulus onset. The effect was maximal at posterior temporal-parietal electrode sites (the parietal old/new effect). Although the effect was not lateralised to the left hemisphere, this result may be due to the variability in encoding strategies employed by the participants. Behavioural data consistently indicated that response confidence is confounded with response category. The ERP results also revealed that the old/new effect is not evident following the experimental control of response confidence, and that immediate recall is associated with a negative-going shift at posterior electrode sites between 800-1100 ms poststimulus onset. Manipulating the semantic relatedness between the word pairs did not influence the distribution of the old/new effect. The results are discussed in terms of the view that the parietal old/new effect reflects neural activity associated with the recollection of specific previous experiences, and may reflect retrieval processes supported by the medial temporal lobe memory system (Moscovitch, 1992, 1994; Squire, 1992; Squire, Knowlton, & Musen, 1993). It is suggested that future research extend the current findings by examining the influence of response confidence in alternative recognition memory paradigms.