Photoplethysmography (PPG) is a simple and low-cost optical technique that can be used to detect blood volume changes in the microvascular bed of tissue. It is often used non-invasively to make ...measurements at the skin surface. The PPG waveform comprises a pulsatile ('AC') physiological waveform attributed to cardiac synchronous changes in the blood volume with each heart beat, and is superimposed on a slowly varying ('DC') baseline with various lower frequency components attributed to respiration, sympathetic nervous system activity and thermoregulation. Although the origins of the components of the PPG signal are not fully understood, it is generally accepted that they can provide valuable information about the cardiovascular system. There has been a resurgence of interest in the technique in recent years, driven by the demand for low cost, simple and portable technology for the primary care and community based clinical settings, the wide availability of low cost and small semiconductor components, and the advancement of computer-based pulse wave analysis techniques. The PPG technology has been used in a wide range of commercially available medical devices for measuring oxygen saturation, blood pressure and cardiac output, assessing autonomic function and also detecting peripheral vascular disease. The introductory sections of the topical review describe the basic principle of operation and interaction of light with tissue, early and recent history of PPG, instrumentation, measurement protocol, and pulse wave analysis. The review then focuses on the applications of PPG in clinical physiological measurements, including clinical physiological monitoring, vascular assessment and autonomic function.
Chloroplasts and mitochondria are subcellular bioenergetic organelles with their own genomes and genetic systems. DNA replication and transmission to daughter organelles produces cytoplasmic ...inheritance of characters associated with primary events in photosynthesis and respiration. The prokaryotic ancestors of chloroplasts and mitochondria were endosymbionts whose genes became copied to the genomes of their cellular hosts. These copies gave rise to nuclear chromosomal genes that encode cytosolic proteins and precursor proteins that are synthesized in the cytosol for import into the organelle into which the endosymbiont evolved. What accounts for the retention of genes for the complete synthesis within chloroplasts and mitochondria of a tiny minority of their protein subunits? One hypothesis is that expression of genes for protein subunits of energy-transducing enzymes must respond to physical environmental change by means of a direct and unconditional regulatory control—control exerted by change in the redox state of the corresponding gene product. This hypothesis proposes that, to preserve function, an entire redox regulatory system has to be retained within its original membrane-bound compartment. Colocation of gene and gene product for redox regulation of gene expression (CoRR) is a hypothesis in agreement with the results of a variety of experiments designed to test it and which seem to have no other satisfactory explanation. Here, I review evidence relating to CoRR and discuss its development, conclusions, and implications. This overview also identifies predictions concerning the results of experiments that may yet prove the hypothesis to be incorrect.
We present evidence that a multitude of mid‐frontal event‐related potential (ERP) components partially reflect a common theta band oscillatory process. Specifically, mid‐frontal ERP components in the ...N2 time range and error‐related negativity time range are parsimoniously characterized as reflections of theta band activities. Forty participants completed three different tasks with varying stimulus–response demands. Permutation tests were used to identify the dominant time–frequency responses of stimulus‐ and response‐locked conditions as well as the enhanced responses to novelty, conflict, punishment, and error. A dominant theta band feature was found in all conditions, and both ERP component amplitudes and theta power measures were similarly modulated by novelty, conflict, punishment, and error. The findings support the hypothesis that generic and reactive medial prefrontal cortex processes are parsimoniously reflected by theta band activities.
For over 35 years, research has examined frontal alpha EEG asymmetry, discussed in terms of relative left frontal activity (rLFA) in the present review, as a concurrent and prospective marker of ...affective processing and psychopathology. Because rLFA may index (a) neural correlates of frontal asymmetry, or (b) psychological constructs to which frontal asymmetry relates, rLFA can advance our understanding of both neural and psychological models of emotion and psychopathology. In order to improve such understanding, the specific role of rLFA in extending or challenging existing theory must be clear to researchers and readers alike. In particular, in 2004, Coan and Allen argued that examination of rLFA as a mediator or moderator may improve our theoretical understanding of rLFA. Despite being a commonly cited paper in the field, most rLFA research today still fails to acknowledge the statistical role of rLFA in the research. The aim of the present paper is to (a) convince the reader of the importance of distinguishing rLFA as a predictor, outcome, mediator, or moderator in order to conduct theory‐driven research, and (b) highlight some of the major advances in rLFA literature since the review by Coan and Allen (2004) in the framework of mediators and moderators. We selected a broad range of search terms to capture relevant rLFA research and included only those studies utilizing established methods for rLFA measurement.
Error-related activity in the medial prefrontal cortex (mPFC) is thought to work in conjunction with lateral prefrontal cortex (lPFC) as a part of an action-monitoring network, where errors signal ...the need for increased cognitive control. The neural mechanism by which this mPFC-lPFC interaction occurs remains unknown. We hypothesized that transient synchronous oscillations in the theta range reflect a mechanism by which these structures interact. To test this hypothesis, we extracted oscillatory phase and power from current-source-density-transformed electroencephalographic data recorded during a Flanker task. Theta power in the mPFC was diminished on the trial preceding an error and increased immediately after an error, consistent with predictions of an action-monitoring system. These power dynamics appeared to take place over a response-related background of oscillatory theta phase coherence. Theta phase synchronization between FCz (mPFC) and F5/6 (lPFC) sites was robustly increased during error trials. The degree of mPFC-lPFC oscillatory synchronization predicted the degree of mPFC power on error trials, and both of these dynamics predicted the degree of posterror reaction time slowing. Oscillatory dynamics in the theta band may in part underlie a mechanism of communication between networks involved in action monitoring and cognitive control.
Frontal electroencephalographic (EEG) alpha asymmetry is widely researched in studies of emotion, motivation, and psychopathology, yet it is a metric that has been quantified and analyzed using ...diverse procedures, and diversity in procedures muddles cross-study interpretation. The aim of this article is to provide an updated tutorial for EEG alpha asymmetry recording, processing, analysis, and interpretation, with an eye towards improving consistency of results across studies. First, a brief background in alpha asymmetry findings is provided. Then, some guidelines for recording, processing, and analyzing alpha asymmetry are presented with an emphasis on the creation of asymmetry scores, referencing choices, and artifact removal. Processing steps are explained in detail, and references to MATLAB-based toolboxes that are helpful for creating and investigating alpha asymmetry are noted. Then, conceptual challenges and interpretative issues are reviewed, including a discussion of alpha asymmetry as a mediator/moderator of emotion and psychopathology. Finally, the effects of two automated component-based artifact correction algorithms—MARA and ADJUST—on frontal alpha asymmetry are evaluated.
•Frontal EEG asymmetry is widely but inconsistently quantified and analyzed.•This review overviews of data acquisition and processing procedures.•Spatial transformations will enhance recording of frontal activity specifically.•A special focus is provided on ICA-based artifact correction procedures.•Statistical and conceptual models are reviewed.
Transcranial focused ultrasound (tFUS) is an emerging method for non-invasive neuromodulation akin to transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS). tFUS ...offers several advantages over electromagnetic methods including high spatial resolution and the ability to reach deep brain targets. Here we describe two experiments assessing whether tFUS could modulate mood in healthy human volunteers by targeting the right inferior frontal gyrus (rIFG), an area implicated in mood and emotional regulation. In a randomized, placebo-controlled, double-blind study, participants received 30 s of 500 kHz tFUS or a placebo control. Visual Analog Mood Scales (VAMS) assessed mood four times within an hour (baseline and three times after tFUS). Participants who received tFUS reported an overall increase in Global Affect (GA), an aggregate score from the VAMS scale, indicating a positive shift in mood. Experiment 2 examined resting-state functional (FC) connectivity using functional magnetic resonance imaging (fMRI) following 2 min of 500 kHz tFUS at the rIFG. As in Experiment 1, tFUS enhanced self-reported mood states and also decreased FC in resting state networks related to emotion and mood regulation. These results suggest that tFUS can be used to modulate mood and emotional regulation networks in the prefrontal cortex.
Abstract Background We tested the hypothesis that subgenual anterior cingulate cortex (sgACC) participates in concurrently regulating shifts in both affective state and cardiac vagal control. Methods ...Eleven healthy adults and 8 depressed subjects performed the Emotional Counting Stroop task in alternating 15-second blocks of emotion words and neutral words while undergoing functional magnetic resonance imaging (fMRI) and electrocardiography (ECG). We measured the absolute value of change between adjacent 15-second blocks in both cardiac vagal control and the BOLD signal in specific regions of interest. Results Strong positive correlations were observed in healthy control participants between changes in cardiac vagal control and changes in BOLD signal intensity in sgACC (BA25) (right: r =.67, p <.02; left r =.69, p <.02), as well as other key structures in the medial visceromotor network. Depressed subjects showed no significant correlations between cardiac vagal control and BOLD signal intensity within BA25 or any other brain region examined. During the transition from depression-specific emotion blocks to neutral blocks, the correlation between BOLD signal change in BA25 and cardiac vagal control change was significantly greater in controls than in depressed subjects ( p <.04). Conclusions Findings in healthy volunteers suggest that sgACC participates in affective state shifting. The latter function appears to be altered in depressed individuals, and may have implications for the unvarying mood and vagal dysfunction associated with depression. Limitations Limitations include a small sample size, an inability to disentangle afferent versus efferent contributions to the results, and the lack of a whole-brain analysis.
Investigations into action monitoring have consistently detailed a frontocentral voltage deflection in the event-related potential (ERP) following the presentation of negatively valenced feedback, ...sometimes termed the feedback-related negativity (FRN). The FRN has been proposed to reflect a neural response to prediction errors during reinforcement learning, yet the single-trial relationship between neural activity and the quanta of expectation violation remains untested. Although ERP methods are not well suited to single-trial analyses, the FRN has been associated with theta band oscillatory perturbations in the medial prefrontal cortex. Mediofrontal theta oscillations have been previously associated with expectation violation and behavioral adaptation and are well suited to single-trial analysis. Here, we recorded EEG activity during a probabilistic reinforcement learning task and fit the performance data to an abstract computational model (Q-learning) for calculation of single-trial reward prediction errors. Single-trial theta oscillatory activities following feedback were investigated within the context of expectation (prediction error) and adaptation (subsequent reaction time change). Results indicate that interactive medial and lateral frontal theta activities reflect the degree of negative and positive reward prediction error in the service of behavioral adaptation. These different brain areas use prediction error calculations for different behavioral adaptations, with medial frontal theta reflecting the utilization of prediction errors for reaction time slowing (specifically following errors), but lateral frontal theta reflecting prediction errors leading to working memory-related reaction time speeding for the correct choice.
It is unclear at present whether psychopathic tendencies are associated with lower or higher levels of emotional awareness (EA). Given that psychopathy includes a proficiency for manipulating others, ...one might expect an elevated ability to identify and use information about others' emotions. On the other hand, empathic deficits in psychopathy could arise from reduced emotional awareness. Further, heterogeneity in psychopathy may also play a role, wherein 'secondary' psychopathy is associated with early adversity and high negative affect, while 'primary' psychopathy is not. In this paper, we tested the relationship between EA and psychopathic tendencies in 177 undergraduate students (40 males) who completed the levels of emotional awareness scale (LEAS), the triarchic psychopathy measure (TPM), the affective (empathy-related) subscales of the interpersonal reactivity index (IRI), and two measures of early adversity: the childhood experiences of care and abuse questionnaire (CECA) and the childhood trauma questionnaire (CTQ). We found that lower LEAS scores were associated with higher TPM and lower IRI empathy scores, but these relationships were primarily present in those with early adversity and high negative affect. This suggests that lower EA may be selectively associated with higher levels of secondary psychopathy, while those with higher levels of primary psychopathy remain capable of higher EA.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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