From randomness to stability

The present study describes how the association between randomly chosen variables changes at the successive steps of temporal processes to converge into stable values as suggested by I. Prigogine. To generalize the results to any specific area so results may be applied to concrete problems in different sciences, randomly chosen matrices of random numbers were successively multiplied to generate temporal sequences that before reaching stability had different number of steps. Our results indicate that the obtained poliphasic stability is irreversible.     

Chimpanzees (Pan troglodytes) can wait,when they choose to: a study with the hybrid delay task

Self-control has been studied in nonhuman animals using a variety of tasks. The inter-temporal choice (ITC) task presents choices between smaller–sooner (SS) and larger–later (LL) options. Using food amounts as rewards, this presents two problems: (a) choices of the LL option could either reflect self-control or instead result from animals’ difficulty with pointing to smaller amounts of food; (b) there is no way to verify whether the subjects would not revert their choice for the LL option, if given the opportunity to do so during the ensuing delay. To address these problems, we have recently introduced a new protocol, the hybrid delay task, which combines an initial ITC with a subsequent accumulation phase in which selection of the SS option leads to its immediate delivery, but choice of the LL option then leads to one-by-one presentation of those items that continues only as long as the subject does not eat any of the accumulated items. The choice of the LL option therefore only reflects self-control when the number of items obtained from LL choices during the accumulation phase is higher than what could be received in the SS option. Previous research with capuchin monkeys demonstrated that their apparent self-control responses in the ITC task may have overestimated their general self-control abilities, given their poor performance in the hybrid delay task. Here, chimpanzees instead demonstrated that their choices for the LL option in the ITC phase of the hybrid delay task were confirmed by their ability to sustain long delays during accumulation of LL rewards.     

Paralimbic Gray Matter Reductions in Incarcerated Adolescent Females with Psychopathic Traits

Psychopathy-related paralimbic and limbic structural brain abnormalities have been implicated in incarcerated adult and adolescent male samples. However, there have been few neuroimaging studies of psychopathic traits in females in general and no studies from incarcerated female youth in particular. Here we present the first study to examine the relationship between brain gray matter volumes and psychopathic traits (assessed using the Psychopathy Checklist-Youth Version [PCL-YV]) in a sample of maximum-security incarcerated female adolescents (N?=?39; mean age?=?17.6 years). Consistent with male samples, regional gray matter volumes were negatively related to psychopathic traits in female youth offenders in limbic and paralimbic areas, including orbitofrontal cortex, parahippocampal cortex, temporal poles, and left hippocampus. These results provide evidence that psychopathic traits manifest similar neural abnormalities across sex and age.     

EEG theta/beta ratio as a potential biomarker for attentional control and resilience against deleterious effects of stress on attention

Anxious stress compromises cognitive executive performance. This occurs, for instance, in cognitive performance anxiety (CPA), in which anxiety about one’s cognitive performance causes that performance to actually deteriorate (e.g., test anxiety). This is thought to result from a prefrontal cortically (PFC) mediated failure of top-down attentional control over stress-induced automatic processing of threat-related information. In addition, stress-induced increased catecholamine influx into the PFC may directly compromise attentional function. Previous research has suggested that the ratio between resting state electroencephalographic (EEG) low- and high-frequency power (the theta/beta ratio) is related to trait attentional control, which might moderate these effects of stress on attentional function. The goals of the present study were to test the novel prediction that theta/beta ratio moderates the deleterious effects of CPA-like anxious stress on state attentional control and to replicate a previous finding that the theta/beta ratio is related to self-reported trait attentional control. After recording of baseline frontal EEG signals, 77 participants performed a stress induction or a control procedure. Trait attentional control was assessed with the Attentional Control Scale, whereas stress-induced changes in attentional control and anxiety were measured with self-report visual analogue scales. The hypothesized moderating influence of theta/beta ratio on the effects of stress on state attentional control was confirmed. Theta/beta ratio explained 28% of the variance in stress-induced deterioration of self-reported attentional control. The negative relationship between theta/beta ratio and trait attentional control was replicated (r = –.33). The theta/beta ratio reflects, likely prefrontally mediated, attentional control, and should be a useful biomarker for the study of CPA and other anxiety–cognition interactions.