Event-related brain potentials reflect traces of echoic memory in humans

In sequences of identical auditory stimuli, infrequent deviant stimuli elicit an event-related brain potential component called mismatch negativity (MMN). MMN is presumed to reflect the existence of a memory trace of the frequent stimulus at the moment of presentation of the infrequent stimulus. This hypothesis was tested by applying the recognition-masking paradigm of cognitive psychology. In this paradigm, a masking sound presented shortly before or after a test stimulus diminishes the recognition memory of this stimulus, the more so the shorter the interval between the test and masking stimuli. This interval was varied in the present study. It was found that the MMN amplitude strongly correlated with the subject’s ability to discriminate between frequent and infrequent stimuli. This result strongly suggests that MMN providesa measure for a trace of sensory memory, and further, that with MMN, this memory can be studied without performance-related distortions.     

When does the brain distinguish between genuine and ambiguous smiles? An ERP study

Event-related brain potentials (ERPs) were recorded to assess the processing time course of ambiguous facial expressions with a smiling mouth but neutral, fearful, or angry eyes, in comparison with genuinely happy faces (a smile and happy eyes) and non-happy faces (neutral, fearful, or angry mouth and eyes). Participants judged whether the faces looked truly happy or not. Electroencephalographic recordings were made from 64 scalp electrodes to generate ERPs. The neural activation patterns showed early P200 sensitivity (differences between negative and positive or neutral expressions) and EPN sensitivity (differences between positive and neutral expressions) to emotional valence. In contrast, sensitivity to ambiguity (differences between genuine and ambiguous expressions) emerged only in later LPP components. Discrimination of emotional vs. neutral affect occurs between 180 and 430 ms from stimulus onset, whereas the detection and resolution of ambiguity takes place between 470 and 720 ms. In addition, while blended expressions involving a smile with angry eyes can be identified as not happy in the P200 (175–240 ms) component, smiles with fearful or neutral eyes produce the same ERP pattern as genuinely happy faces, thus revealing poor discrimination.     

Emotional distraction in boys with ADHD: Neural and behavioral correlates

Although, in everyday life, patients with attention deficit hyperactivity disorder (ADHD) are frequently distracted by goal-irrelevant affective stimuli, little is known about the neural and behavioral substrates underlying this emotional distractibility. Because some of the most important brain responses associated with the sudden onset of an emotional distracter are characterized by their early latency onset and short duration, we addressed this issue by using a temporally agile neural signal capable of detecting and distinguishing them. Specifically, scalp event-related potentials (ERPs) were recorded while 20 boys with ADHD combined type and 20 healthy comparison subjects performed a digit categorization task during the presentation of three types of irrelevant, distracting stimuli: arousing negative (A−), neutral (N) and arousing positive (A+). Behavioral data showed that emotional distracters (both A− and A+) were associated with longer reaction times than neutral ones in the ADHD group, whereas no differences were found in the control group. ERP data revealed that, compared with control subjects, boys with ADHD showed larger anterior N2 amplitudes for emotional than for neutral distracters. Furthermore, regression analyses between ERP data and subjects’ emotional ratings of distracting stimuli showed that only in the ADHD group, emotional arousal (ranging from calming to arousing) was associated with anterior N2: its amplitude increased as the arousal content of the visual distracter increased. These results suggest that boys with ADHD are more vulnerable to the distracting effects of irrelevant emotional stimuli than control subjects. The present study provides first data on the neural substrates underlying emotional distractibility in ADHD.     

The semantic organization of the animal category: evidence from semantic verbal fluency and network theory

Semantic memory is the subsystem of human memory that stores knowledge of concepts or meanings, as opposed to life-specific experiences. How humans organize semantic information remains poorly understood. In an effort to better understand this issue, we conducted a verbal fluency experiment on 200 participants with the aim of inferring and representing the conceptual storage structure of the natural category of animals as a network. This was done by formulating a statistical framework for co-occurring concepts that aims to infer significant concept-concept associations and represent them as a graph. The resulting network was analyzed and enriched by means of a missing links recovery criterion based on modularity. Both network models were compared to a thresholded co-occurrence approach. They were evaluated using a random subset of verbal fluency tests and comparing the network outcomes (linked pairs are clustering transitions and disconnected pairs are switching transitions) to the outcomes of two expert human raters. Results show that the network models proposed in this study overcome a thresholded co-occurrence approach, and their outcomes are in high agreement with human evaluations. Finally, the interplay between conceptual structure and retrieval mechanisms is discussed.     

The relationships between Internet addiction, subjective vitality, and subjective happiness

The aim of the present study is to examine the relationships between Internet addiction, subjective vitality, and subjective happiness. The participants were 328 university students who completed a questionnaire package that included the Online Cognition Scale, the Subjective Vitality Scale, and the Subjective Happiness Scale. According to the results, subjective vitality and subjective happiness were negatively predicted by Internet addiction. On the other hand, subjective happiness was positively predicted by subjective vitality. In addition, subjective vitality mediated the relationship between Internet addiction and subjective happiness. Results were discussed in light of the literature.     

MMPI-A performance of African and Mexican American adolescent first-time offenders

54 African and Mexican American adolescent first-time offenders were examined with the MMPI-A to evaluate ethnic differences. Multivariate analyses by ethnicity and MMPI-A scales (validity, clinical, content, and supplementary scales) were not significant; however, there was a significant univariate difference where African American adolescents scored significantly higher on the Repression scale than the Mexican American group. A greater percentage of within-normal-limits profiles were African American (50%) than Mexican American (25%). Research and clinical implications for using the MMPI-A with these groups are discussed.     

Maintaining global coherence in reading: The role of sentence boundaries

In four experiments, we examined the reinstatement of backgrounded information in locally coherent passages, investigating the influence of syntactic boundaries, such as periods, on the time course of this process. In Experiment 1, using a line-by-line reading paradigm, readers were delayed in noticing a contradiction on a target line when the sentence continued onto a posttarget line. Consistent with this, in Experiments 2A and 2B, the results of a recognition probe demonstrated that relevant concepts from long-term memory were not integrated immediately unless the contradiction was followed by a period. Experiment 3 demonstrated that sentence boundaries are sufficient to facilitate the integration of related background information but are not necessary; additional time served the same purpose. Consistent with a memory-based text-processing framework, it appears that the reactivation of related information is initiated automatically but that an integration stage is influenced by such factors as syntactic boundaries.     

Qualitative differences between implicit and explicit sequence learning

Four experiments investigate the differences between implicit and explicit sequence learning concerning their resilience to structural and superficial task changes. A superficial change that embedded the SRT task in the context of a selection task, while maintaining the sequence, did selectively hinder the expression of implicit learning. In contrast, a manipulation that maintained the task surface, but decreased the sequence validity, affected the expression of learning specifically when it was explicit. These results are discussed in the context of a dynamic framework (Cleeremans & Jiménez, 2002), which assumes that implicit knowledge is specially affected by contextual factors and that, as knowledge becomes explicit, it allows for the development of relevant metaknowledge that modulates the expression of explicit knowledge.     

Amitriptyline administered after consolidation of inhibitory avoidance does not affect memory retrieval

In Experiment 1, the effect of the administration of the antidepressant amitriptyline (30 mg/kg) for 21 days on the acquisition and consolidation of the inhibitory avoidance task was studied in male and female mice. In Experiment 2, it was evaluated whether amitriptyline administered after the consolidation of this task would block the memory retrieval. Anxiety and spontaneous activity in the elevated plus maze were also assessed. When amitriptyline was given before the training phase of inhibitory avoidance it blocked learning in males and there was a tendency in the same direction in females. However, the drug administered between training and test phases did not affect conditioning. These effects of amitriptyline seem to be independent of its actions on anxiety and locomotor activity. It may be that the effects observed are related to the therapeutic effects of antidepressants.     

Relationship between dispositional optimism/pessimism and stress coping strategies

Recent studies confirm that dispositional pessimism is related with a worse state of physical health, in comparison with dispositional optimism . The efficacy of stress coping strategies has been considered as a mediating mechanism in this relationship. The aim of the present study is to analyze in a sample of university students (n = 200) the association between dispositional optimism/pessimism and different categories of self-reported somatic symptoms , and evaluate the possible mediation of the stress coping strategies in this relationship. The results indicate that: 1) pessimism is positively related with the report of physical symptoms, whereas optimism is negatively associated to somatic complaints; and 2) this relationship can be mainly explained by the differential utilization of the coping strategy denominated self-criticism (characteristic of pessimism).