Is EEG Entropy a Useful Measure for Alzheimer's Disease?

BACKGROUND: The number of individuals diagnosed with Alzheimer's disease (AD) has increased, and it is estimated to continue rising in the coming years. The diagnosis of this disease is challenging due to variations in onset and course, its diverse clinical manifestations, and the indications for measuring deposit biomarkers. Hence, there is a need to develop more precise and less invasive diagnostic tools. Multiple studies have considered using electroencephalography (EEG) entropy measures as an indicator of the onset and course of AD. Entropy is deemed suitable as a potential indicator based on the discovery that variations in its complexity can be associated with specific pathologies such as AD. METHODOLOGY: Following PRISMA guidelines, a literature search was conducted in 4 scientific databases, and 40 articles were analyzed after discarding and filtering. RESULTS: There is a diversity in entropy measures; however, Sample Entropy (SampEn) and Multiscale Entropy (MSE) are the most widely used (21/40). In general, it is found that when comparing patients with controls, patients exhibit lower entropy (20/40) in various areas. Findings of correlation with the level of cognitive decline are less consistent, and with neuropsychiatric symptoms (2/40) or treatment response less explored (2/40), although most studies show lower entropy with greater severity. Machine learning-based studies show good discrimination capacity. CONCLUSIONS: There is significant difficulty in comparing multiple studies due to their heterogeneity; however, changes in Multiscale Entropy (MSE) scales or a decrease in entropy levels are considered useful for determining the presence of AD and measuring its severity.

Association of polymorphisms rs4680 of the Catechol-O-Methyltransferase gene and rs6265 of the brain derived neurotrophic factor gene with the behavioral inhibition and behavioral activation systems.

Background: The Behavioral Inhibition System (BIS) comprises limbic circuitry implicated in avoidance behaviors. Its increased activation has been identified as a risk factor for anxiety and depressive disorders. In addition, both Catechol-O-Methyltransferase (COMT) and Brain Derived Neurotrophic Factor (BDNF) have been postulated as candidate genes that constitute a vulnerability for the onset of anxiety and depressive disorders. The aim of this study was to evaluate the possible association between the rs4680 polymorphism of the COMT gene and the rs6265 polymorphism of the BDNF gene with the BIS and the Behavioral Activation System (BAS) in a population sample from Colombia. Methods: Genetic information was obtained by extracting DNA from blood samples of 80 participants and using Taqman probes designed for each polymorphism. In addition, participants completed a BIS/BAS scale in order to establish a neuropsychological classification. Results: The frequency of the Met allele of the BDNF gene was greater in the group with BIS sensitivity compared to the group with BAS sensitivity. On the contrary, the frequency of the Met allele of the COMT gen did not show a significant association with the BIS. Conclusions: The rs6265 polymorphism of BDNF gene is associated with the BIS which in turn constitutes a risk factor for anxiety and depression.

The effect of information seeking behaviors in fear control.

BACKGROUND AND OBJECTIVES: Individuals experiencing conditioned fear reactions often resort to avoidance and escape behaviors as attempts to decrease fear. Nevertheless, these strategies are not always available. In such cases, people seek information to mitigate aversive events. This study aimed at evaluating the effect of information seeking behaviors on self-reported fear, predictability, and physiological responses. METHODS: Participants were randomly assigned to two groups. In group one, individuals were given the choice to perform an instrumental behavior which provided information about the occurrence of either an aversive or a neutral event (100% contingency). In group two, individuals were also allowed to perform an instrumental behavior. However, such behavior provided partial information (50% contingency). RESULTS: Individuals in group one presented lower levels of fear compared to individuals assigned to group two. LIMITATIONS: The generalizability of the results may be restricted to undergraduate students. CONCLUSIONS: The results suggests that when avoidance and escape are not available, individuals seek information that provides control over fear. Clinical implications are discussed.

Work Intensification and Psychological Detachment: The Mediating Role of Job Resources in Health Service Workers.

Psychological detachment is the central experience of recovery from work-related stress that allows individuals to reduce burnout symptoms. The stressor-detachment model (SDM) contends that job resources moderate the relationship between job stressors and psychological detachment. We designed an instrument to measure job resources from a multidimensional perspective. A sample of n = 394 individuals from the health service industry participated in the study. Data indicate that job resources comprise a four-factor structure underlying a formative model. Consistent with the SDM, a partial least squares structural equation modeling (PLS-SEM) analysis suggests a moderating effect of job resources (e.g., control over working conditions, leaders' emotional support), between work intensification and psychological detachment. In addition; results indicate that workers who perceive high levels of support from their organization achieved higher levels of detachment compared with those who perceived low levels of support. Theoretical as well as practical implications for stress management practices, occupational health, and well-being are discussed.

The role of safety signals in fear extinction: An analogue study.

BACKGROUND AND OBJECTIVES: Safety signals are conditioned inhibitory stimuli that indicate the absence of unconditioned stimuli. It is not clear whether the presence of safety signals is detrimental or beneficial in extinction-based interventions. The purpose of this study was to evaluate the effect of safety signals on autonomic and expectancy fear-related responses. METHODS: Following the conditional discrimination paradigm (AX +, BX-), undergraduate students (N = 48) underwent an aversive conditioning procedure, while safety signals were experimentally created. Participants were randomly assigned to one of two conditions during extinction: presence or absence of safety signals. RESULTS: Significant reductions of fear-related responses were found in both groups. Expectancy measures showed that the presence of safety signals did not interfere with reduction of fear related responses at follow-up. LIMITATIONS: The analogue nature of the study affects its ecological validity. There are some methodological issues. CONCLUSIONS: Safety signals did not interfere with extinction learning. Attention may be a mechanism associated with the maintenance of fear responses.

Intervención sobre el mecanismo de reconsolidación / Intervention on the Reconsolidation Mechanism

En la actualidad, existen tratamientos eficaces para reducir los síntomas de ansiedad y el malestar asociado. Sin embargo, se observa con frecuencia que las respuestas de ansiedad, después de haberse extinguido, se recuperan, sin que esté claro el mecanismo que subyace a dicha recuperación. Desde hace décadas, se considera la posibilidad de un mecanismo de reconsolidación que colaboraría en el proceso de almacenar nuevamente los recuerdos que han sido evocados. Algunas investigaciones recientes revelan que la intervención sobre el mecanismo de reconsolidación aparentemente previene la recuperación de respuestas de ansiedad que han sido previamente extinguidas. Si esto es así, podría ser una alternativa a los tratamientos actuales de los trastornos de ansiedad basados en la exposición. El objetivo del presente trabajo es revisar la evidencia sobre los efectos de actuar sobre el mecanismo de reconsolidación para la reducción de las respuestas de ansiedad. Finalmente se discuten las posibles implicaciones clínicas.

At the present, effective treatments are available to reduce anxiety symptoms and their associated distress. Nevertheless, it is frequently observed that anxiety responses are recovered after extinction, without being clear the responsible mechanism of such phenomenon. For decades, it has been presumed the existence of a reconsolidation mechanism. Such mechanism is thought to participate in the re-storage of memories that have been evoked. Recent research apparently reveals that intervention on reconsolidation mechanisms prevents the recovery of anxiety responses that have been previously extinguished. Intervention on these mechanisms could represent an alternative to current psychological treatments for anxiety disorders based on exposure procedures. The objective of the present work is to review the evidence on reconsolidation mechanisms and its effects on the reduction of anxiety responses. Finally some clinical implications will be discussed.