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.

Associations between physiological responses to social-evaluative stress and daily functioning in first-episode schizophrenia.

Schizophrenia (SZ) is associated with impaired adaptive functioning, including difficulties managing the demands of independent living, work, school, and interpersonal relationships. Prior studies have linked the physiological stress response with less effective coping in daily life. Differences in stress-response tendencies may also support heterogeneity in daily functioning in SZ. The present study examined two established measures of the stress response in patients with first-episode SZ. Salivary cortisol was included as an index of hypothalamic-pituitary-adrenal response. Vagal suppression (VS), a measure of stress-related reduction in heart rate variability, was used to assess parasympathetic flexibility. Greater cortisol response and VS to social-evaluative stress were predicted to be associated with better functioning in SZ over and above relationships with social cognition and neurocognition, two well-established predictors of functional outcome. Thirty-eight first-episode SZ outpatients and 29 healthy comparison subjects (HC) provided social cognitive, neurocognitive, and physiological measurements before and after the Trier Social Stress Test (TSST). Although SZ and HC did not differ on VS to the TSST, patients exhibited significant associations between VS and functioning across all four domains of the Role Functioning Scale. Furthermore, greater VS predicted more effective functioning with friends, beyond the contributions associated with social cognition and neurocognition, and strengthened the positive effects of higher levels of social cognition on independent living/self-care. VS elicited by social-evaluative stress in the laboratory may reflect stress-response tendencies in daily life that are relevant for daily functioning in first-episode SZ.

Schizophrenia, smoking status, and performance on the matrics Cognitive Consensus Battery.

Cognitive deficits and high rates of nicotine dependence are consistently documented in the schizophrenia literature. However, there is currently no consensus about how regular smoking influences cognition in schizophrenia or which cognitive domains are most affected by chronic smoking. Previous studies have also failed to disambiguate the effects of chronic nicotine from those of acute exposure. The current study uses a novel approach to testing nicotine addicted patients at a time-point between acute enhancement and withdrawal and implements the MATRICS Cognitive Consensus Battery (MCCB) to compare the overall cognitive performance of regular smokers (n=40) and nonsmokers (n=36) with schizophrenia. Controlling for age, gender, and education, smokers with schizophrenia were significantly more impaired on a visual learning task, the Brief Visuospatial Memory Test-Revised (BVMT-R), than their nonsmoking peers. Among smokers, smoking behavior (i.e., exhaled carbon monoxide levels of smokers) predicted BVMT-R T score; greater smoking was associated with more impaired visual learning. Negative symptom severity was not predictive of greater visual learning deficits in smokers or nonsmokers. Future longitudinal research will be required to determine if there is a dose-response relationship between chronic nicotine and visual learning impairment in patients at various stages of psychotic illness.