Event-related potentials and the study of memory retrieval: A critical review

Altered hierarchical auditory predictive processing after lesions to the orbitofrontal cortex

Orbitofrontal cortex (OFC) is classically linked to inhibitory control, emotion regulation, and reward processing. Recent perspectives propose that the OFC also generates predictions about perceptual events, actions, and their outcomes. We tested the role of the OFC in detecting violations of prediction at two levels of abstraction (i.e., hierarchical predictive processing) by studying the event-related potentials (ERPs) of patients with focal OFC lesions (n = 12) and healthy controls (n = 14) while they detected deviant sequences of tones in a local-global paradigm. The structural regularities of the tones were controlled at two hierarchical levels by rules defined at a local (i.e., between tones within sequences) and at a global (i.e., between sequences) level. In OFC patients, ERPs elicited by standard tones were unaffected at both local and global levels compared to controls. However, patients showed an attenuated mismatch negativity (MMN) and P3a to local prediction violation, as well as a diminished MMN followed by a delayed P3a to the combined local and global level prediction violation. The subsequent P3b component to conditions involving violations of prediction at the level of global rules was preserved in the OFC group. Comparable effects were absent in patients with lesions restricted to the lateral PFC, which lends a degree of anatomical specificity to the altered predictive processing resulting from OFC lesion. Overall, the altered magnitudes and time courses of MMN/P3a responses after lesions to the OFC indicate that the neural correlates of detection of auditory regularity violation are impacted at two hierarchical levels of rule abstraction.

Evaluation of classification approaches for distinguishing brain states predictive of episodic memory performance from electroencephalography: Abbreviated Title: Evaluating methods of classifying memory states from EEG

Previous studies have attempted to separate single trial neural responses for events a person is likely to remember from those they are likely to forget using machine learning classification methods. Successful single trial classification holds potential for translation into the clinical realm for real-time detection of memory and other cognitive states to provide real-time interventions (i.e., brain-computer interfaces). However, most of these studies-and classification analyses in general- do not make clear if the chosen methodology is optimally suited for the classification of memory-related brain states. To address this problem, we systematically compared different methods for every step of classification (i.e., feature extraction, feature selection, classifier selection) to investigate which methods work best for decoding episodic memory brain states-the first analysis of its kind. Using an adult lifespan sample EEG dataset collected during performance of an episodic context encoding and retrieval task, we found that no specific feature type (including Common Spatial Pattern (CSP)-based features, mean, variance, correlation, features based on AR model, entropy, phase, and phase synchronization) outperformed others consistently in distinguishing different memory classes. However, extracting all of these feature types consistently outperformed extracting only one type of feature. Additionally, the combination of filtering and sequential forward selection was the optimal method to select the effective features compared to filtering alone or performing no feature selection at all. Moreover, although all classifiers performed at a fairly similar level, LASSO was consistently the highest performing classifier compared to other commonly used options (i.e., naïve Bayes, SVM, and logistic regression) while naïve Bayes was the fastest classifier. Lastly, for multiclass classification (i.e., levels of context memory confidence and context feature perception), generalizing the binary classification using the binary decision tree performed better than the voting or one versus rest method. These methods were shown to outperform alternative approaches for three orthogonal datasets (i.e., EEG working memory, EEG motor imagery, and MEG working memory), supporting their generalizability. Our results provide an optimized methodological process for classifying single-trial neural data and provide important insight and recommendations for a cognitive neuroscientist's ability to make informed choices at all stages of the classification process for predicting memory and other cognitive states.

Memória de Reconhecimento: Modelos de Processamento Simples versus Duplo

Resumo O processo de reconhecimento de memórias consiste em discriminar informações previamente encontradas de informações novas. Duas abordagens teóricas divergentes buscam explicar esse fenômeno. A primeira propõe que o reconhecimento se baseia essencialmente na sensação de familiaridade gerada por cada estímulo. A segunda propõe que além da intensidade da familiaridade, a evocação de aspectos qualitativos e contextuais dos eventos memorizados possui um papel fundamental no processo de reconhecimento. Aspectos teóricos e metodológicos inerentes às duas linhas teóricas são criticamente discutidos no presente artigo, sendo que o resultado dessa discussão se apresenta favorável à segunda perspectiva teórica.

Cognição e eletrofisiologia: uma revisão crítica das perspectivas nacionais

A técnica eletrofisiológica Potenciais Relacionados ao Evento (PRE) vem sendo amplamente utilizada para o estudo da atividade cerebral correspondente a processos cognitivos específicos. O presente artigo apresenta uma revisão crítica dos estudos empregando PRE desenvolvidos em universidades brasileiras, enfatizando especialmente seus objetivos principais e abordagens metodológicas. Os estudos examinados investigaram efeitos eletrofisiológicos tradicionalmente reportados na literatura em PRE, como os efeitos denominados P300, N400 e MMN, proporcionando resultados relevantes teoricamente, bem como demonstrando a utilidade do PRE para a investigação de diversos temas de pesquisa. Possibilidades referentes a abordagens metodológicas alternativas para a análise dos PREs, assim como o emprego desta técnica no estudo de diversos processos psicológicos, são examinados e discutidos.