The long-term memory system for what is conscious and can be verbalized – declarative memory- is often separated into memory for general facts and memory for personal events (Squire, 2009; Tulving, 2002). Personal semantics share elements of both semantic memory (i.e., they are facts that can be known) and episodic memory (i.e., they are self-related and idiosyncratic; Renoult, Davidson, Palombo, Moscovitch, & Levine, 2012). According to the taxonomy of personal semantics (Renoult et al., 2012), they vary in proximity to either semantic or episodic memory. Towards one end of the continuum, memory for autobiographical facts such as jobs and names of friends were hypothesized to be closer to general facts. Towards the other end of the continuum, repeated events are summaries of the core elements of similar events that happened more than once (e.g., getting coffee at a coffee shop), and they were hypothesized to be closer to episodic memory (i.e., the recollection of a unique event). Self-knowledge involves self-reflection about one’s own personality traits and preferences; it was thought to be the most distinct from semantic and episodic memory. However, little research had compared personal semantics to both semantic and episodic memory, or to one another, and these proposals needed to be tested experimentally. In this thesis, I compared the neural correlates of three types of personal semantics to semantic memory (study 1, 2, 3) and episodic memory (study 1, 2), and to one another (study 1) using functional magnetic resonance imaging (fMRI; study 1) and event related potentials (ERPs; study 2, 3). Moreover, I examined whether temporal orientation modified the personal semantics’ relationship to the typically atemporal semantic memory (study 2, 3) and to the typically past-oriented episodic memory (study 2). In study 1, general facts, autobiographical facts, repeated events, and unique events were compared using fMRI, in a follow-up to an ERP study (Renoult et al., 2016). In our analyses of the hippocampus (HPC) and posterior medial network (Ritchey, Libby, & Ranganath, 2015), general semantics and autobiographical facts were often not significantly different from one another (except for the left posterior HPC), and repeated events and unique events did not differ from one another in any comparison. I observed a small graded increase of brain activity from general facts to autobiographical facts to repeated events and unique events (with a significant linear trend) in the left posterior HPC. In contrast, no memory type differed in the anterior temporal network (Ritchey et al., 2015). In study 2 and 3, self-knowledge was operationalized as the knowledge of one’s own traits, and could concern past (study 2), present (study 2, 3) and future selves (study 2, 3). A neural correlate of recollection, the Late Positive Component (LPC), had a larger mean amplitude for thinking about the self than others (study 2, 3), and thinking about a past and/or future self than the present self (on average for study 2, and significant for study 3). The amplitude of the LPC for thinking about the past and future selves did not differ from an episodic recognition memory task (or present self-knowledge; study 2). Further, the temporal orientation effect was smaller and not significant when we compared thinking about the present and the future traits of others (study 3). The operationalization of the “other” as a close friend or a group of people did not modify this result (study 3). Together, in addition to Renoult et al. (2016), these findings suggest that: the neural correlates of autobiographical facts, repeated events, and self-knowledge do not overlap perfectly with semantic or episodic memory. Moreover, the temporal orientation of the knowledge is one factor that can influence the proximity of the neural correlates of personal semantics to either semantic or episodic memory.

The present study sought to investigate the effects of meditation practice on the neural mechanisms of attention and self-monitoring by comparing a group of experienced meditators to matched controls. Self-report measures of mindfulness and self-compassion were assessed to examine whether meditation-related improvements in attention and self-monitoring were linked to increases in these qualities. Thus, differences between groups (meditator versus control) on all variables and relationships among variables (attention, self-monitoring, self-compassion, and mindfulness) were explored. Results indicate that individuals with meditation experience showed enhancement in neural networks related to selective attention and attentional allocation, as evidenced by larger P1/N1 and P3b amplitudes, relative to controls. Meditators also showed improved self-monitoring of their errors, as indexed by enhanced Pe amplitudes, when compared to controls. Importantly, greater number of years of meditation experience was linked to larger Pe amplitudes, providing evidence that more practice with meditation was associated with greater error awareness. At the same time, meditators showed greater levels of mindfulness and self-compassion when compared to controls. Importantly, each of the neural indices was linked to greater levels of mindfulness and self-compassion. Specifically, self-kindness was correlated with each of these ERP components and to percentage of alpha power during meditation, and the mindfulness facet of observing fully mediated the relationship between meditation experience and P1 amplitudes. These findings suggest that the qualities that are enhanced with meditation are associated with enhancements in attentional control and awareness of errors. This study is an exciting step toward future intervention studies that combine multiple sources of information (self-report, neural measures, and behavior) to clarify the nature of the associations among these variables so that the mechanisms of mindfulness can be more fully understood.

No description available.

No description available.

La reconnaissance experte de l'expression faciale est cruciale pour l'interaction et la communication sociale. Le comportement, les potentiels évoqués (ERP), et les techniques d’oculométrie peuvent être utilisés pour étudier les mécanismes cérébraux qui participent au traitement visuel automatique. La reconnaissance d'expressions faciales implique non seulement l'extraction d'informations à partir de caractéristiques faciales diagnostiques, stratégie qualifiée de traitement local, mais aussi l'intégration d'informations globales impliquant des traitements configuraux. Des nombreuses recherches concernant le traitement des informations faciales émotionnelles il apparaît que l’interaction des traitements locaux et configuraux pour la reconnaissance des émotions est mal comprise. La complexité inhérente à l'intégration de l'information faciale est mise en lumière lorsque l'on compare la performance de sujets sains et d’individus atteints de schizophrénie, car ces derniers ont tendance à s’attarder sur quelques éléments locaux, parfois peu informatifs. Les différentes façons d'examiner les visages peuvent avoir un impact sur la capacité socio-cognitive de reconnaître les émotions. Pour ces raisons, cette thèse étudie le rôle des caractéristiques diagnostiques et configurales dans la reconnaissance de l'expression faciale. En plus des aspects comportementaux, nous avons donc examiné la dynamique spatiale et temporelle des fixations à l’aide de mesures oculométriques, ainsi que l’activité électrophysiologique précoce considérant plus particulièrement les composantes P100 et N170. Nous avons créé de nouveaux stimuli des esquisses par une transformation numérique de portraits photos en esquisses, pour des visages exprimant colère, tristesse, peur, joie ou neutralité, issus de la base Radboud Faces Database, en supprimant les informations de texture du visage et ne conservant que les caractéristiques diagnostiques (yeux et sourcils, nez, bouche). Ces esquisses altèrent le traitement configural en comparaison avec les visages photographiques, ce qui augmente le traitement des caractéristiques diagnostiques par traitement élémentaire, en contrepartie. La comparaison directe des mesures neurocognitives entre les esquisses et les visages photographiques exprimant des émotions de base n'a jamais été testée, à notre connaissance. Dans cette thèse, nous avons examiné (i) les fixations oculaires en fonction du type de stimulus, (ii) la réponse électrique aux manipulations expérimentales telles que l'inversion et la déconfiguration du visage. Concernant, les résultats comportementaux montrent que les esquisses de visage transmettent suffisamment d'information expressive (compte tenu de la présence des caractéristiques diagnostiques) pour la reconnaissance des émotions en comparaison des visages photographiques. Notons que, comme attendu, il y avait un net avantage de la reconnaissance des émotions pour les expressions heureuses par rapport aux autres émotions. En revanche, reconnaître des visages tristes et en colère était plus difficile. Ayant analysé séparément les fixations successives, les résultats indiquent que les participants ont adopté un traitement plus local des visages croqués et photographiés lors de la deuxième fixation. Néanmoins, l'extraction de l'information des yeux est nécessaire lorsque l'expression transmet des informations émotionnelles plus complexes et lorsque les stimuli sont simplifiés comme dans les esquisses. Les résultats de l’électroencéphalographie suggèrent également que les esquisses ont engendré plus de traitement basé sur les parties. Les éléments transmis par les traits diagnostiques pourraient avoir fait l'objet d'un traitement précoce, probablement dû à des informations de bas niveau durant la fenêtre temporelle de la P100, suivi d'un décodage ultérieur de la structure faciale dans la fenêtre temporelle de la N170. / Proficient recognition of facial expression is crucial for social interaction. Behaviour, event-related potentials (ERPs), and eye-tracking techniques can be used to investigate the underlying brain mechanisms supporting this seemingly effortless processing of facial expression. Facial expression recognition involves not only the extraction of expressive information from diagnostic facial features, known as part-based processing, but also the integration of featural information, known as configural processing. Despite the critical role of diagnostic features in emotion recognition and extensive research in this area, it is still not known how the brain decodes configural information in terms of emotion recognition. The complexity of facial information integration becomes evident when comparing performance between healthy subjects and individuals with schizophrenia because those patients tend to process featural information on emotional faces. The different ways in examining faces possibly impact on social-cognitive ability in recognizing emotions. Therefore, this thesis investigates the role of diagnostic features and face configuration in the recognition of facial expression. In addition to behavior, we examined both the spatiotemporal dynamics of fixations using eye-tracking, and early neurocognitive sensitivity to face as indexed by the P100 and N170 ERP components. In order to address the questions, we built a new set of sketch face stimuli by transforming photographed faces from the Radboud Faces Database through the removal of facial texture and retaining only the diagnostic features (e.g., eyes, nose, mouth) with neutral and four facial expressions - anger, sadness, fear, happiness. Sketch faces supposedly impair configural processing in comparison with photographed faces, resulting in increased sensitivity to diagnostic features through part-based processing. The direct comparison of neurocognitive measures between sketch and photographed faces expressing basic emotions has never been tested. In this thesis, we examined (i) eye fixations as a function of stimulus type, and (ii) neuroelectric response to experimental manipulations such face inversion and deconfiguration. The use of these methods aimed to reveal which face processing drives emotion recognition and to establish neurocognitive markers of emotional sketch and photographed faces processing. Overall, the behavioral results showed that sketch faces convey sufficient expressive information (content of diagnostic features) as in photographed faces for emotion recognition. There was a clear emotion recognition advantage for happy expressions as compared to other emotions. In contrast, recognizing sad and angry faces was more difficult. Concomitantly, results of eye-tracking showed that participants employed more part-based processing on sketch and photographed faces during second fixation. The extracting information from the eyes is needed when the expression conveys more complex emotional information and when stimuli are impoverished (e.g., sketch). Using electroencephalographic (EEG), the P100 and N170 components are used to study the effect of stimulus type (sketch, photographed), orientation (inverted, upright), and deconfiguration, and possible interactions. Results also suggest that sketch faces evoked more part-based processing. The cues conveyed by diagnostic features might have been subjected to early processing, likely driven by low-level information during P100 time window, followed by a later decoding of facial structure and its emotional content in the N170 time window. In sum, this thesis helped elucidate elements of the debate about configural and part-based face processing for emotion recognition, and extend our current understanding of the role of diagnostic features and configural information during neurocognitive processing of facial expressions of emotion.

Nous proposons d'explorer électrophysiologiquement la question de l'accès au sens. Pour cela, nous nous intéressons particulièrement à deux ERPs. La composante N400 est classiquement associée à la prise en compte d'un contexte sémantique. La composante P600, moins explorée, est retrouvée lors de tâches syntaxiques, sémantiques ou non spécifiquement linguistiques. Nous avons décrit trois études électrophysiologiques en conditions naturelles de langage. La première étude nous a permis de valider l'usage de ce matériel original dans une population contrôle. Puis nous avons proposé le transfert clinique de ce protocole en conditions naturelles de langage auprès de patients souffrant de TAB (deuxième étude) et de schizophrénie (troisième étude, en cours). Nous avons retrouvé une composante N400 préservée dans les TAB, alors que les patients souffrant de schizophrénie présentent un profil ERP altéré, avec une compréhension perturbée des mots comme congruents au contexte sémantique. Après nous être interrogés sur la notion de transfert clinique, et la prudence nécessaire à l'interprétation de ces résultats en pratique clinique quotidienne, nous avons envisagé deux autres approches relatives à l'accès au sens. D'une part, nous avons repris un modèle linguistique issu des perspectives phénoménologique, structuraliste et morphodynamique, pour détailler un protocole expérimental en cours de réalisation, ainsi que des premiers résultats exploratoires obtenus en population contrôle. D'autre part, les données en première personne après entretien d'explicitation apportent une illustration subjective des phénomènes d'accès au sens mis en jeu dans les deux protocoles utilisés. / The aim of our projectwas to examine semantic access from an electrophysiological view. We specifically explored two Event-related Potentials (ERPs): N400, associated to semantic processing, and P600, associated to syntactic, semantic and non linguistic and general processes. In the first part of our project, we have explored these ERPs among healthy participants and psychiatric patients. People with schizophrenia exhibit thought and language disorders. In spite of common clinical manifestations with schizophrenia, patients with bipolar disorders (BDs) have rarely been assessed using neurolinguistic ERPs. We have conducted three electrophysiological studies in natural speech conditions. In the first study, we validated our original linguistic material among healthy participants. Then, in a clinical transfer perspective, we assessed manic patients suffering from BDs (second study) and patients with schizophrenia (third study, in preparation) using the same linguistic material. Our results support the hypothesis of a preserved N400 component in patients with BDs. On the contrary, preliminary results showed a disturbed N400 associated to congruent sentences among patients with schizophrenia.After discussing the limitations of the notion of clinical transfer and of our experimental studies, we also presented two alternative perspectives on speech comprehension. One the one hand, we described a linguistic model inherited from phenomenology, structuralism and morphodynamics. On the other hand, we reported first person data obtained through elicitation techniques. These experiential data enable us to better grasp semantic phenomena involved in our both experiments.

H προβολή υποσυνείδητων μηνυμάτων είναι η διαδικασία έκθεσης ερεθισμάτων κάτω από το κατώφλι της συνειδητοποίησης. Με τον τρόπο αυτό μπορεί να επηρεαστούν οι σκέψεις, τα συναισθήματα και ενέργειες του ανθρώπου. Η υποσυνείδητη αντίληψη συμβαίνει όταν οι πληροφορίες αποθηκεύονται στο ανθρώπινο μυαλό, χωρίς ο δέκτης να έχει συνειδητά επίγνωση του προβλήματος. Οι πληροφορίες φτάνουν στο μυαλό, γιατί ενώ δεν είναι συνειδητά αντιληπτές, γίνονται αντιληπτές από το υποσυνείδητο κομμάτι του εγκεφάλου. Αντικείμενο της παρούσας διπλωματικής εργασίας είναι η αποτίμηση των πιθανών διαφορών στις καταγραφές ηλεκτροεγκεφαλογραφήματος (ΕΕG) και προκλητών δυναμικών (ERPs) κατά την υποβολή ενός ατόμου σε οπτικά υποσυνείδητα ερεθίσματα σε σύγκριση με καταγραφές χωρίς ερέθισμα. Στην εργασία χρησιμοποιήθηκε ένα ερευνητικό πρωτόκολλο το οποίο εξετάζει το πώς επηρεάζουν τα υποσυνείδητα ερεθίσματα τη λήψη αποφάσεων και την εγκεφαλική λειτουργία. Στο πρώτο μέρος της εργασίας (κεφάλαια 1 και 2) γίνεται μια συνοπτική αναφορά στις κυριότερες μεθόδους απεικόνισης εγκεφάλου, όπως το ηλεκτροεγκεφαλογράφημα και την λειτουργική απεικόνιση Μαγνητικού Συντονισμού καθώς και στον συνδυασμό τους για πιο ικανοποιητικά αποτελέσματα. Το κεφάλαιο 3 αναφέρεται κυρίως σε θέματα σχετικά τα προκλητά δυναμικά, καθώς και την υποσυνείδητη αντίληψη. Στο κεφάλαιο 4 περιγράφεται η πειραματική διαδικασία και η μετρητική διάταξη που χρησιμοποιήθηκε καθώς και η παρουσίαση της επεξεργασίας των μετρήσεων μέσω του eeglab. Τέλος, στο κεφάλαιο 5 παρουσιάζονται τα αποτελέσματα της επεξεργασίας σε διαγράμματα προκλητών δυναμικών και φασματικής ισχύος καθώς επίσης και τα συμπεράσματα της εργασίας αυτής. / The display of subliminal messages is the process of stimuli exposure below the threshold of awareness. Through this procedure the thoughts, feelings and actions of a human can be influenced. The subliminal perception occurs when information stored in the human mind without the receiver being consciously aware of it. The information reaching the brain is perceived by the subconscious part of the brain. The object of this diploma thesis is to assess the possible differences in electroencephalogram (EEG) and event - related potentials (ERPs) recordings during the presentation of visual subliminal stimuli compared to non – subliminal conditions. A protocol that examines how subliminal stimuli influence the decision making and the cerebral operation is used. In the first part of the thesis (chapters 1 and 2) there is a brief review of the main brain imaging methods such as EEG and fMRI as well as the combination of them. Chapter 3 reveals issues about event - related potentials and mostly about subliminal perception. In chapter 4, the experiment and the measuring devices used are described, and there is also a presentation of the analysis by using the eeglab. Finally, chapter 5 includes the results of analysis on event - related potential and spectral power graphs, as well as the conclusions of this work.

[pt] A perda de insight nas próprias habilidades cognitivas pode ser uma característica de uma ampla gama de distúrbios neurológicos e pode ser relevante para os resultados clínicos e a eficácia da reabilitação. Além disso, pesquisas recentes têm mostrado que alterações na metacognição também podem caracterizar o envelhecimento saudável e interferir nas atividades da vida cotidiana, aumentando a incidência de um conjunto de comportamentos que afetam a saúde e a tomada de decisões. Considerando a natureza subjetiva da autoconsciência e a falta de consenso sobre instrumentos de avaliação para medir habilidades metacognitivas, é importante elucidar a neuroarquitetura da consciência metacognitiva e identificar biomarcadores de funções metacognitivas. A presente tese explora este tema através de quatro artigos. De acordo com o Modelo de Consciência Cognitiva (CAM), diferentes tipos de comprometimento da autoconsciência dependem de diferentes perfis de disfunções neurocognitivas, como anosognosia mnemônica e executiva. O primeiro é discutido no Artigo 1, que se concentra nos mecanismos subjacentes à autoconsciência prejudicada na doença de Alzheimer. Especificamente, as evidências sugerem que os pacientes com Alzheimer dependem de informações desatualizadas sobre si mesmos e são incapazes de consolidar novas informações como consequência da amnésia anterógrada e retrógrada. Além disso, achados de neuroimagem mostram que a degeneração fronto-cingulada e temporal estão implicadas em deficiências de autoconsciência. O Artigo 2, por sua vez, concentrou-se nos mecanismos neurais subjacentes à anosognosia executiva. Foi realizada uma revisão sistemática de estudos potenciais relacionados a eventos que investigam o automonitoramento em distúrbios neurológicos foi realizada para entender a contribuição de diferentes estruturas cerebrais para o monitoramento de erros. Especificamente, o estudo concentrou-se na negatividade relacionada ao erro (ERN) e na positividade do erro (Pe), que indexam a detecção de erros e a consciência do erro, respectivamente. Os achados sugerem a presença de processamento de domínio geral de detecção de erros com base em áreas cingulo-operculares e gânglios da base, mas também foi levantada a hipótese de que lesões fora da rede de monitoramento fronto-basal podem levar a déficits específicos de domínio. Para testar a hipótese de especificidade de domínio, foi realizado um estudo de potencial relacionado a eventos (Artigo 3). Um grupo de adultos jovens e idosos completou uma tarefa de flanker perceptual e de memória, e os resultados demonstraram que é possível diferenciar processos de automonitoramento em domínios cognitivos. Além disso, os achados de Pe demonstraram um declínio global da consciência de erro no envelhecimento. Curiosamente, apenas em adultos mais velhos, o aumento de Pe dentro da tarefa foi específico para o domínio da memória, sugerindo a presença de efeitos de aprendizagem para a memória, mas não para as decisões perceptivas. Foi levantada a hipótese de que as deficiências na percepção do erro podem estar associadas ao declínio sensorial no envelhecimento. Assim, o Artigo 4 investigou a associação entre Pe e potenciais bloqueados por estímulo em adultos jovens e idosos durante o desempenho da tarefa flanker de memória, a fim de entender a contribuição dos processos sensoriais ou de memória para mudanças relacionadas à idade na consciência de erro. Os resultados mostraram que a lembrança eficiente de estímulos foi associada a uma maior consciência de erro em adultos jovens e mais velhos e que a redução da consciência de erro em adultos mais velhos foi associada a deficiências no processamento perceptivo de estímulos. No geral, este trabalho contribui para nossa compreensão dos processos neurocognitivos subjacentes à consciência metacognitiva e correlatos neurais de diferentes tipos de anosognosia e apóia a conceituação multidimensional da consciência metacognitiva delineada pelo CAM. Os resultados do estudo oferecem novos insights sobre marcadores neurais de processos metacognitivos que podem servir para avaliação clínica e desenvolvimento de treinamento e reabilitação cognitiva. / [en] Loss of insight in own s cognitive abilities can be a feature of a wide range of neurological disorders and can be relevant for clinical outcomes and rehabilitation effectiveness. Furthermore, recent research has shown that changes in metacognition can also characterize healthy aging and interfere with everyday life activity, increasing the incidence of a set of behaviours affecting health and decision making. Considering the subjective nature of self-awareness and the lack of consensus on assessment instruments to measure metacognitive abilities, it is important to elucidate the neuroarchitecture of metacognitive awareness and identify biomarkers of metacognitive functions. The current thesis explores this topic through four articles. According to the Cognitive Awareness Model (CAM), different type of self-awareness impairments depends on different profiles of neurocognitive dysfunctions, such as mnemonic and executive anosognosia. The former is discussed in Article 1, which focuses on mechanisms underlying impaired self-awareness in Alzheimer s disease. Specifically, the evidence suggests that Alzheimer s patients rely on outdated information about the self and are unable to consolidate new information as consequence of anterograde and retrograde amnesia. Moreover, neuroimaging findings show that fronto-cingulate and temporal degeneration are implicated in self-awareness impairments. Article 2 focused instead on neural mechanisms underlying executive anosognosia. A systematic review of event-related potential studies investigating self-monitoring in neurological disorders was conducted to understand the contribution of different brain structures to error monitoring. Specifically, the study focused on the error-related negativity (ERN) and the error positivity (Pe), which index error detection and error awareness, respectively. The findings suggest the presence of domain-general processing of error detection relying on cingulo-opercular areas and basal ganglia, but it was also hypothesized that lesions outside the fronto-basal monitoring network may lead to domain-specific deficits. To test the domain- specificity hypothesis, an event-related potential study was conducted (Article 3). A group of young and older adults completed a perceptual and a memory flanker task and the findings demonstrated that it is possible to differentiate self-monitoring processes across cognitive domains. Moreover, Pe findings demonstrated a global decline of error awareness in aging. Interestingly, in older adults only, within-task increase in Pe was specific to the memory domain, suggesting the presence of learning effects for memory but not for perceptual decisions. It was hypothesized that error awareness impairments may be associated with sensory decline in aging. Thus, Article 4 investigated the association between Pe and stimulus-locked potentials in young and older adults during memory flanker task performance, in order to understand the contribution of sensory or memory processes to age-related changes in error awareness. The findings showed that efficient stimulus recollection was associated with higher error awareness in both young and older adults and that reduced error awareness in older adults was associated with impairments in perceptual processing of stimuli. Overall, this work contributes to our understanding of neurocognitive processes underlying metacognitive awareness and neural correlates of different types of anosognosia and supports the multidimensional conceptualization of metacognitive awareness delineated by the CAM. The study s results offer novel insights into neural markers of metacognitive processes that can serve clinical assessment and the development of cognitive training and rehabilitation.

The electroencephalogram (EEG) reflects summated, slow post-synaptic potentials of cortical neurons. Sensory, motor or cognitive events (such as a fast-rising sensory stimulus, a brisk self-paced movement or a stimulus-triggered cognitive task) can elicit transient changes in the ongoing human EEG, called event-related potentials (ERPs). ERPs are widely used in clinical practice, and believed to reflect the activity of the sensory system activated by the stimulus (for example, laser-evoked potentials are used to substantiate the neuropathic nature of clinical pain conditions). When ERPs are elicited by pairs or trains of stimuli delivered at short inter-stimulus intervals (ISIs), the magnitude of the ERP elicited by the repeated stimuli is markedly reduced, a phenomenon known as response decrement. While the interval between two consecutive stimuli becomes longer, the reduced response is recovered. Thus, this phenomenon has been traditionally interpreted in terms of neural refractoriness of generators of ERPs ("neural refractoriness hypothesis"). This thesis, however, challenges this neural refractoriness hypothesis by describing the results of manipulating the preceding events of the eliciting stimulus. The first study examined the effect of variable and short ISIs on sensory ERPs, delivering trains of auditory and electrical stimuli with random ISIs ranging from 100 to 1000ms. In the second study, pairs of laser stimuli were presented in two comparable conditions. In the constant condition, the ISI was identical across trials in each block, while in the variable condition, the ISI was variable across trials. By directly comparing ERPs elicited by laser stimulation, this study aimed to explore whether lack of saliency in the eliciting stimulus could explain the response decrement during stimulus repetition. Finally, the third study tested the hypothesis that the reduced eliciting ERPs would recover if saliency were introduced by changing the modality of the preceding event. Thus, trains of three stimuli (S1-S2-S3) with 1s ISI were presented; S2 was either same or different in modality as S1 and S3 in each block. Results from these three experiments demonstrate that this "refractoriness hypothesis" does not hold, and suggest that the magnitude of ERPs is only partly related to the magnitude of the incoming sensory input, and instead largely reflects neural activities triggered by salient events in the sensory environment. These results are important for the correct interpretation of ERPs in both physiological and clinical studies.

Recognition memory is thought to rely upon both recollection and familiarity. When people recall an episode from the past it is generally considered to reflect the memory process of recollection. Therefore, if people can successfully recall an item, they should be able to recognize it. However, in cued recall paradigms of memory research, participants sometimes correctly recall a studied target word in the presence of a strong semantic cue but then fail to recognize that word as actually having been studied. This paradox and underlying cognitive processes have been minimally studied by scientists, leaving this phenomenon poorly understood. Extant research has investigated some of the conditions necessary to produce these conditions but not the underlying neural correlates that drive them. The present study builds upon earlier studies using Electroencephalogram (EEG) to investigate the neural processes that underlie recognition failures of successfully recalled words. In the present experiment, participants studied words one at a time, and then later were asked to verbally recall these previously studied words as cued by their semantic associates. Following the participant’s verbal response, their recognition memory was tested for the recalled word. The current study aimed to use physiological measures (EEG) to investigate the explicit and implicit cognitive processes that may be involved in the recognition failure of recalled words. The data indicate that successfully recalled words that are recognized are driven by recollection at recall and a combination of recollection and familiarity at recognition, whereas successfully recalled words that are not recognized are instead driven by semantic priming at recall and at recognition, are driven by negative-going ERP effects reflecting implicit processes such as repetition fluency.