Oscillatory Coupling Between Neural and Cardiac Rhythms.

Oscillations serve a critical role in organizing biological systems. In the brain, oscillatory coupling is a fundamental mechanism of communication. The possibility that neural oscillations interact directly with slower physiological rhythms (e.g., heart rate, respiration) is largely unexplored and may have important implications for psychological functioning. Oscillations in heart rate, an aspect of heart rate variability (HRV), show remarkably robust associations with psychological health. Mather and Thayer proposed coupling between high-frequency HRV (HF-HRV) and neural oscillations as a mechanism that partially accounts for such relationships. We tested this hypothesis by measuring phase-amplitude coupling between HF-HRV and neural oscillations in 37 healthy adults at rest. Robust coupling was detected in all frequency bands. Granger causality analyses indicated stronger heart-to-brain than brain-to-heart effects in all frequency bands except gamma. These findings suggest that cardiac rhythms play a causal role in modulating neural oscillations, which may have important implications for mental health.

Task-based default mode network connectivity predicts cognitive impairment and negative symptoms in first-episode schizophrenia.

Individuals diagnosed with schizophrenia (SZ) demonstrate difficulty distinguishing between internally and externally generated stimuli. These aberrations in "source monitoring" have been theorized as contributing to symptoms of the disorder, including hallucinations and delusions. Altered connectivity within the default mode network (DMN) of the brain has been proposed as a mechanism through which discrimination between self-generated and externally generated events is disrupted. Source monitoring abnormalities in SZ have additionally been linked to impairments in selective attention and inhibitory processing, which are reliably observed via the N100 component of the event-related brain potential elicited during an auditory paired-stimulus paradigm. Given overlapping constructs associated with DMN connectivity and N100 in SZ, the present investigation evaluated relationships between these measures of disorder-related dysfunction and sought to clarify the nature of task-based DMN function in SZ. DMN connectivity and N100 measures were assessed using EEG recorded from SZ during their first episode of illness (N = 52) and demographically matched healthy comparison participants (N = 25). SZ demonstrated less evoked theta-band connectivity within DMN following presentation of pairs of identical auditory stimuli than HC. Greater DMN connectivity among SZ was associated with better performance on measures of sustained attention (p = .03) and working memory (p = .09), as well as lower severity of negative symptoms, though it was not predictive of N100 measures. Together, present findings provide EEG evidence of lower task-based connectivity among first-episode SZ, reflecting disruptions of DMN functions that support cognitive processes. Attentional processes captured by N100 appear to be supported by different neural mechanisms.

Impact of hormonal contraceptives on sex differences in fear conditioning and fear extinction in PTSD.

Sex differences in the neurobiological mechanisms involved in fear conditioning and extinction have been suggested to contribute to differential vulnerability for the development of posttraumatic stress disorder (PTSD) in women compared with men. Reproductive hormones, such as estradiol, have been shown to facilitate fear conditioning and extinction learning and may explain some of these differences. However, the effect of commonly used hormonal contraceptives on the neurobiological mechanisms of fear conditioning and extinction is poorly understood. A laboratory study was conducted in trauma-exposed men and women with and without full or partial PTSD to examine effects of sex and use of hormonal birth control on fear conditioning, fear extinction learning, and extinction retention. Participants underwent fear conditioning with stimuli that were paired (CS+) or unpaired (CS-) with shock. Extinction learning occurred 72 h later, and extinction retention was tested 1 wk after extinction. Women on hormonal contraceptives (HCs) demonstrated enhanced acquisition of fear conditioning and enhanced extinction of fear as compared with women off hormonal birth control and men. While clinical implications have yet to be determined, these results suggest that hormonal contraceptives may facilitate learning during both fear acquisition and extinction. Understanding the impact of sex and hormones on fear conditioning and extinction processes may lead to new insights into the pathophysiology of PTSD and result in advancements in treatment that may vary by sex.

Reconfiguration of brain networks supporting inhibition of emotional challenge.

Reacting to the salient emotional features of a stimulus is adaptive unless the information is irrelevant or interferes with goal-directed behavior. The ability to ignore salient but otherwise extraneous information involves restructuring of brain networks and is a key impairment in several psychological disorders. Despite the importance of understanding inhibitory control of emotional response, the associated brain network mechanisms remain unknown. Utilizing functional magnetic resonance imaging (fMRI) data obtained from 103 participants performing an emotion-word Stroop (EWS) task, the present study applied graph-theory analysis to identify how brain regions subserving emotion processing and cognitive control are integrated within the global brain network to promote more specialized and efficient processing during successful inhibition of response to emotional distractors. The present study identified two sub-networks associated with emotion inhibition, one involving hyper-connectivity to prefrontal cortex and one involving hyper-connectivity to thalamus. Brain regions typically associated with identifying emotion salience were more densely connected with the thalamic hub, consistent with thalamic amplification of prefrontal cortex control of these regions. Additionally, stimuli high in emotional arousal prompted restructuring of the global network to increase clustered processing and overall communication efficiency. These results provide evidence that inhibition of emotion relies on interactions between cognitive control and emotion salience sub-networks.

Inhibitory control of emotional processing: Theoretical and empirical considerations.

Although inhibitory control appears to support successful emotion regulation (ER; Joorman and Gotlib, 2010; McCabe et al., 2010), few emotion inhibition studies position themselves in the literature on ER, and even fewer ER studies reference the role of emotion inhibition. Perhaps contributing to this, the ER literature is frequently divided into implicit or "automatic" (which subsumes emotion inhibition) and explicit or "effortful" control (Braunstein et al., 2017; Gyurak et al., 2011). The present paper evaluates relationships among constructs of inhibitory control, emotion inhibition, and ER to assess neural evidence for and against distinctions between implicit and explicit ER. We argue that, whereas the distinction between implicit and explicit ER may appear organizationally or conceptually helpful, such categorical distinctions are not supported by available research and in fact contribute to imbalances in the research literature.

Explaining interpersonal difficulty via implicit and explicit personality correlates of mania risk.

BACKGROUND: Mania is associated with social conflict, reduced social support, and reduced social interaction quality (Breyer et al., 2003; Coryell et al., 1998; Morriss et al., 2007). Chronic stress in interpersonal relationships is related to the worsening of mood symptoms (Kim et al., 2007), suggesting the importance of characterizing the mechanism of interpersonal relationship disruption in bipolar disorder. The current study was designed to investigate exaggerated dominance tendencies present in at-risk individuals (Gardner, 1982; Wilson and Price, 2006), which may represent one such mechanism. METHODS: Sixty-nine University undergraduate participants (50.7% female, 22 categorized as high mania risk) completed an implicit measure of power motivation and series of self-report questionnaires designed to assess dominance-relevant traits. RESULTS: Risk for mania was related to a tendency to experience contempt, and an implicit index of dominance tendencies, and also to trait-like tendencies to experience pride, perceptions of being more powerful and influential across relationships,. LIMITATIONS: Use of an undergraduate population and a dimensional measure of mania risk (rather than diagnosed individuals) are limitations. CONCLUSIONS: Mania risk is tied not only to the pursuit of dominance, but also to beliefs and actions consistent with a sense of power. Current findings provide evidence that the dominance system profile observed in those at risk for mania could be one source of interpersonal problems.

Nonverbal dominance behavior among individuals at risk for mania.

BACKGROUND: Research suggests that people with bipolar disorder may be highly motivated to attain dominance and may over-estimate their social power (Johnson and Carver, 2012). This manic temperament may provide an adaptive advantage in the pursuit of dominance and leadership (Akiskal and Akiskal, 1992). It was hypothesized that people at high risk for bipolar disorder, as defined by the Hypomanic Personality Scale (HPS), would fail to assume a submissive role when it was appropriate to do so. METHOD: Participants (81 undergraduates) completed an image description task with a confederate. Participants were randomly assigned to interact with a confederate who assumed one of three nonverbal postures: dominant (expanded), neutral, or submissive (constricted). Nonverbal dominance behavior was defined as the rate at which participants expanded their body span during the task. RESULTS: Consistent with hypotheses, an ANOVA indicated an interaction of Mania risk x Dominance condition on body expansion. Whereas participants with low mania risk (HPS scores) adapted complementary behavior in response to the confederate, participants with high mania risk demonstrated a consistently dominant (expanded) nonverbal posture. LIMITATIONS: A major limitation of this study is the use of an analog measure of mania risk in place of clinical diagnoses. CONCLUSIONS: In this experiment, participants at high risk for mania maintained a dominant posture even when submissiveness would have been more appropriate. It is argued that persistent dominance behavior may play an important role in the interpersonal interactions of individuals at risk for bipolar disorder.