Comparison of Pupil Dilation Responses to Unexpected Sounds in Monkeys and Humans

Pupil dilation in response to unexpected stimuli has been well documented in human as well as in non-human primates; however, this phenomenon has not been systematically compared between the species. This analogy is also crucial for the role of non-human primates as an animal model to investigate neural mechanisms underlying the processing of unexpected stimuli and their evoked pupil dilation response. To assess this qualitatively, we used an auditory oddball paradigm in which we presented subjects a sequence of the same sounds followed by occasional deviants while we measured their evoked pupil dilation response (PDR). We used deviants (a frequency deviant, a pink noise burst, a monkey vocalization and a whistle sound) which differed in the spectral composition and in their ability to induce arousal from the standard. Most deviants elicited a significant pupil dilation in both species with decreased peak latency and increased peak amplitude in monkeys compared to humans. A temporal Principal Component Analysis (PCA) revealed two components underlying the PDRs in both species. The early component is likely associated to the parasympathetic nervous system and the late component to the sympathetic nervous system, respectively. Taken together, the present study demonstrates a qualitative similarity between PDRs to unexpected auditory stimuli in macaque and human subjects suggesting that macaques can be a suitable model for investigating the neuronal bases of pupil dilation. However, the quantitative differences in PDRs between species need to be investigated in further comparative studies.

Some psychophysiological parameters of a person during a passive orthostatic test

The study involved 14 volunteer students. Situational anxiety was determined, tests were carried out to determine simple and complex sensorimotor reactions, the cardiac rhythm of the subjects was recorded. Oxygen saturation was determined using an oximeter. Dynamic parameters were recorded: lying in a state of functional rest (background 1), vertical at 65-70° (vertical), lying after verticalization (horizontal), lying in a state of functional rest (background 2). The analysis of the data obtained was carried out using the Excel and StatPlus Pro programs. It was revealed that during verticalization, changes in the regulation of the heart activity of the subjects are carried out mainly due to the central mechanisms of regulation through the sympathetic nervous system. The transfer from a vertical to a horizontal state is accompanied by a restructuring of the regulatory system towards the activation of subcortical nerve centers and a shift in the balance of the SNS/PSNS towards the parasympathetic nervous system. Key words: passive orthostatic test, cardiac rhythm, simple sensorimotor reaction.

Exhaled Methane is Associated with a Lower Heart Rate

Background: In humans, methane (CH4) is exclusively produced by the intestinal microbiota and has been implicated in several conditions including cardiovascular disease. After microbial production of CH4 in the gut, it steadily crosses into the systemic circulation and reaches the lungs where it can be detected in the exhaled breath, as a surrogate measure for intestinal CH4 production. Recent reports have shown an association between CH4 and vagal dysfunction as well as the inhibition of CH4 activity on ileal contractions with atropine, suggesting its action on the parasympathetic nervous system. Given these findings we hypothesized that CH4 may be affecting resting heart rate based on the potential effect of CH4 on the vagus nerve. Objectives: Given its possible role in the parasympathetic nervous system, we aimed to study the relationship between breath CH4 and resting heart rate (HR) in humans. Additionally, we performed a longitudinal study analyzing the change in HR and its association to breath CH4 over time. Methods: First, we reviewed 1,126 subjects and compared HR in subjects with detectable and undetectable breath CH4. Second, we performed a post-hoc analysis of a randomized control trial to compare the change in HR for those who had an increase in breath CH4 vs those that had a decrease in breath CH4 over 14 weeks. Lastly, we assessed whether a larger decrease in CH4 is associated with a larger increase in HR over time. Results: In the retrospective cohort, subjects with detectable CH4 had a lower HR compared to those with undetectable CH4 (73.0±0.83 vs 76.0±0.44 beats/min; p=0.01). In the post-hoc analysis, a decrease in CH4 over time was associated with an increase in heart rate (median ∆ = 6.5 ± 8.32 beats/min, p=0.0006). Lastly, we demonstrated a biological gradient whereby a larger drop in CH4 is associated with a greater increase in heart rate (R= -0.31, p=0.03). Conclusion: Our findings suggest a potential role for the microbiome (and specifically CH4 from methanogens) to regulate heart rate. Considering these findings, mechanistic studies are warranted to further investigate this potential novel microbiome-neurocardiac axis.

Nervous system disorders in a patient with Adie syndrome (a clinical case)

Holmes-Adie syndrome, or tonic pupil syndrome, is a condition characterized by a triad of main symptoms: unilateral tonic pupil dilation, accommodative paresis without or with a significant reduction in pupillary light reflex, and decreased tendon reflexes. The disease is based on dysfunction of the parasympathetic nervous system. The syndrome results from damage to the ciliary ganglion, which carries parasympathetic innervation to the m.sphincter pupillae, cornea, and eyeball. Often the condition is accompanied by dysfunction of the spinal ganglia and, as a consequence, autonomic dysfunction in the form of sweating disorders, usually on one side of the body, rarely — by heart rhythm disorders, lability of blood pressure. A frequent sign of Adie syndrome is the absence or reduction in patellar, rarely Achilles, reflexes. The etiology of the disease is not definitively determined, bacterial or viral factors are not excluded. The diagnosis of Adie syndrome is mainly based on a clinical comparison of the symptoms of the disease, as well as on a thorough and comprehensive examination by a neuroophthalmologist with mandatory testing of pupillary responses with low doses of pilocarpine (narrowing of the pupil is characteristic). Despite the positive prognosis for the patient’s life and his ability to work, the condition belongs to the group of difficult-to-treat ones, and the management consists in symptomatic vision correction.

Assessment of cardiovascular sympathetic function tests in premenstrual syndrome patients visiting tertiary care hospital: A case–control study

Background: Premenstrual syndrome (PMS) is a stress-induced disorder and is showing a rising prevalence but its etiopathogenesis is not yet understood. Stress disturbs the balance of the sympathetic and parasympathetic nervous system. Alteration in heart rate and blood pressure is the most important physiological response following stress-induced sympathetic changes. Aims and Objectives: The present study was designed to test the hypothesis of an association between sympathetic functions and PMS and to observe the degree of changes (if any) in these sympathetic functions. The study also aims to provide timely interventions to prevent the development of cardiovascular complications and improve lifestyle. Materials and Methods: A Menstrual Distress Questionnaire was used to evaluate physical, emotional, and behavioral symptoms accompanying the menstrual cycle of the subjects who fulfilled the inclusion criteria. Based on the scores obtained by their questionnaire, subjects with the higher scores formed the PMS group, while the age-matched females with low score served as controls. Cardiovascular sympathetic functions were assessed by standardized, simple, non-invasive tests which included Handgrip test and orthostatic hypotension test. Unpaired Student’s t-test was used for statistical analysis. Results: The results revealed that the sympathetic reactivity is insignificantly higher in PMS group during the follicular phase. During the luteal phase, sympathetic activity is significantly increased. Conclusion: PMS involves psychoneuroendocrinal turmoil, thus early screening of high-risk groups and interventions such as relaxation techniques and lifestyle modification can prevent further cardiovascular complications in patients of high sympathetic responses.

Head Massage Therapy More Efficacious Than Mechanical Helmet Massager to Stimulate Parasympathetic Cardiac Tone: A Randomized Cross-Over Trial

HMT shows a stronger effect on the parasympathetic nervous system as expressed by increase in HFnu with decrease in HR, diastolic blood pressure and body tension, compared with RR and also MHM. More studies are needed to understand how different relaxing interventions may modulate the autonomic nervous system

Angiotensin II and the Cardiac Parasympathetic Nervous System in Hypertension

The renin–angiotensin–aldosterone system (RAAS) impacts cardiovascular homeostasis via direct actions on peripheral blood vessels and via modulation of the autonomic nervous system. To date, research has primarily focused on the actions of the RAAS on the sympathetic nervous system. Here, we review the critical role of the RAAS on parasympathetic nerve function during normal physiology and its role in cardiovascular disease, focusing on hypertension. Angiotensin (Ang) II receptors are present throughout the parasympathetic nerves and can modulate vagal activity via actions at the level of the nerve endings as well as via the circumventricular organs and as a neuromodulator acting within brain regions. There is tonic inhibition of cardiac vagal tone by endogenous Ang II. We review the actions of Ang II via peripheral nerve endings as well as via central actions on brain regions. We review the evidence that Ang II modulates arterial baroreflex function and examine the pathways via which Ang II can modulate baroreflex control of cardiac vagal drive. Although there is evidence that Ang II can modulate parasympathetic activity and has the potential to contribute to impaired baseline levels and impaired baroreflex control during hypertension, the exact central regions where Ang II acts need further investigation. The beneficial actions of angiotensin receptor blockers in hypertension may be mediated in part via actions on the parasympathetic nervous system. We highlight important unknown questions about the interaction between the RAAS and the parasympathetic nervous system and conclude that this remains an important area where future research is needed.

fMRI Acoustic Noise Enhances Parasympathetic Activity in Humans

Background: Functional magnetic resonance imaging (fMRI) is one of the most important neuroimaging techniques; nevertheless, the acoustic noise of the MR scanner is unavoidably linked to the process of data acquisition. We hypothesized that the auditory noise of the scanner has an effect on autonomic activity. Methods: We measured heart rate variability (HRV) while exposing 30 healthy subjects to fMRI noise. In doing so, we demonstrated an increase in parasympathetic nervous system (PNS) activity compared to silence and white noise and a decrease in sympathetic nervous system (SNS) activity compared to white noise. Conclusions: The influence of MR scanner noise on the autonomic nervous system should be taken into account when performing fMRI experiments.