These results provide the first evidence that the intake of probiotics may help reduce negative thoughts associated with sad mood. Probiotics supplementation warrants further research as a potential preventive strategy for depression.
Given its non-invasive nature, there is increasing interest in the use of transcutaneous vagus nerve stimulation (tVNS) across basic, translational and clinical research. Contemporaneously, tVNS can be achieved by stimulating either the auricular branch or the cervical bundle of the vagus nerve, referred to as transcutaneous auricular vagus nerve stimulation(VNS) and transcutaneous cervical VNS, respectively. In order to advance the field in a systematic manner, studies using these technologies need to adequately report sufficient methodological detail to enable comparison of results between studies, replication of studies, as well as enhancing study participant safety. We systematically reviewed the existing tVNS literature to evaluate current reporting practices. Based on this review, and consensus among participating authors, we propose a set of minimal reporting items to guide future tVNS studies. The suggested items address specific technical aspects of the device and stimulation parameters. We also cover general recommendations including inclusion and exclusion criteria for participants, outcome parameters and the detailed reporting of side effects. Furthermore, we review strategies used to identify the optimal stimulation parameters for a given research setting and summarize ongoing developments in animal research with potential implications for the application of tVNS in humans. Finally, we discuss the potential of tVNS in future research as well as the associated challenges across several disciplines in research and clinical practice.
The neurovisceral integration model proposes that heart rate variability (HRV) is linked to prefrontal cortex activity via the vagus nerve, which connects the heart and the brain. HRV, an index of cardiac vagal tone, has been found to predict performance on several cognitive control tasks that rely on the prefrontal cortex. However, the link between HRV and the core cognitive control function “shifting” between tasks and mental sets is under-investigated. Therefore, the present study tested the neurovisceral integration model by examining, in 90 participants, the relationship between vagally mediated resting-state HRV and performance in a task-switching paradigm that provides a relatively process-pure measure of cognitive flexibility. As predicted, participants with higher resting-state HRV (indexed both by time domain and frequency domain measures) showed smaller switch costs (i.e., greater flexibility) than individuals with lower resting-state HRV. Our findings support the neurovisceral integration model and indicate that higher levels of vagally mediated resting-state HRV promote cognitive flexibility.
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