Heart rate variability (HRV), the change in the time intervals between adjacent heartbeats, is an emergent property of interdependent regulatory systems that operate on different time scales to adapt to challenges and achieve optimal performance. This article briefly reviews neural regulation of the heart, and its basic anatomy, the cardiac cycle, and the sinoatrial and atrioventricular pacemakers. The cardiovascular regulation center in the medulla integrates sensory information and input from higher brain centers, and afferent cardiovascular system inputs to adjust heart (...) rate and blood pressure via sympathetic and parasympathetic efferent pathways. This article reviews sympathetic and parasympathetic influences on the heart, and examines the interpretation of HRV and the association between reduced HRV, risk of disease and mortality, and the loss of regulatory capacity. This article also discusses the intrinsic cardiac nervous system and the heart-brain connection, through which afferent information can influence activity in the subcortical and frontocortical areas, and motor cortex. It also considers new perspectives on the putative underlying physiological mechanisms and properties of the ultra-low-frequency (ULF), very-low-frequency (VLF), low-frequency (LF), and high-frequency (HF) bands. Additionally, it reviews the most common time and frequency domain measurements as well as standardized data collection protocols. In its final section, this article integrates Porges' polyvagal theory, Thayer and colleagues' neurovisceral integration model, Lehrer et al.'s resonance frequency model, and the Institute of HeartMath's coherence model. The authors conclude that a coherent heart is not a metronome because its rhythms are characterized by both complexity and stability over longer time scales. Future research should expand understanding of how the heart and its intrinsic nervous system influence the brain. (shrink)

A perfectly matched layer (PML) absorbing material composed of a uniaxial anisotropic material is presented for the truncation of finite-difference time-domain (FDTD) lattices. It is shown that the uniaxial PML material formulation is mathematically equivalent to the perfectly matched layer method published by Berenger (see J. Computat. Phys., Oct. 1994). However, unlike Berenger's technique, the uniaxial PML absorbing medium presented in this paper is based on a Maxwellian formulation. Numerical examples demonstrate that the FDTD implementation of the uniaxial PML medium (...) is stable, equal in effectiveness as compared to Berenger's PML medium, while being more computationally efficient. (shrink)

ABSTRACTAccumulating evidence suggests that emotional information is often recognised faster than neutral information. Several studies examined the effects of valence and arousal on word recognition, but yielded partially diverging results. Here, we used two alternative versions of a constructive recognition paradigm in which a target word is hidden by a visual mask that gradually disappears, to investigate whether the emotional properties of words influence their speed of recognition. Participants were instructed either to classify the incrementally appearing word as emotional or (...) non-emotional or to decide whether the appearing letter string is an existing word or not. Results from both tasks revealed faster recognition times for high- compared to low-arousing words, and for positive compared to negative or neutral words. These findings indicate a recognition advantage for emotionally positive and highly arousing stimuli that persists even when visua... (shrink)

Kensinger (2009) and Mather (2007) both argue that intrinsic features of emotional items are remembered better than intrinsic features of non-emotional items. However, Kensinger attributes these effects to negative valence whereas Mather attributes them to arousal. In this paper, we note several reasons why arousal may be the driving factor even when a study reveals more detailed memory for negative items than for positive items. We also reanalyze previous data (Mather & Nesmith, 2008) to show that although both arousal and (...) negative valence were correlated with memory accuracy, enhanced memory accuracy was accounted for by arousal rather than valence. (shrink)

Though emotion conveys memory benefits, it does not enhance memory equally for all aspects of an experience, nor for all types of emotional events. In this review, I outline the behavioral evidence for arousal's focal enhancements of memory and describe the neural processes that may support those focal enhancements. I also present behavioral evidence to suggest that these focal enhancements occur more often for negative experiences than for positive ones. This result appears to arise because of valence-dependent effects on the (...) neural processes recruited during episodic encoding and retrieval, with negative affect associated with increased engagement of sensory processes, and positive affect leading to enhanced recruitment of conceptual processes. (shrink)

How should we measure metacognitive sensitivity, i.e. the efficacy with which observers’ confidence ratings discriminate between their own correct and incorrect stimulus classifications? We argue that currently available methods are inadequate because they are influenced by factors such as response bias and type 1 sensitivity . Extending the signal detection theory approach of Galvin, Podd, Drga, and Whitmore , we propose a method of measuring type 2 sensitivity that is free from these confounds. We call our measure meta-d′, which reflects (...) how much information, in signal-to-noise units, is available for metacognition. Applying this novel method in a 2-interval forced choice visual task, we found that subjects’ metacognitive sensitivity was close to, but significantly below, optimality. We discuss the theoretical implications of these findings, as well as related computational issues of the method. We also provide free Matlab code for implementing the analysis. (shrink)