A comparative study of slow and fast suryanamaskar on physiological function

Background: Numerous scientific studies have reported beneficial physiological changes after short- and long-term yoga training. Suryanamaskar (SN) is an integral part of modern yoga training and may be performed either in a slow or rapid manner. As there are few studies on SN, we conducted this study to determine the differential effect of 6 months training in the fast and slow versions. Materials and Methods: 42 school children in the age group of 12-16 years were randomly divided into two groups of 21 each. Group I and Group II received 6 months training in performance of slow suryanamaskar (SSN) and fast suryanamaskar (FSN), respectively. Results: Training in SSN produced a significant decrease in diastolic pressure. In contrast, training in FSN produced a significant increase in systolic pressure. Although there was a highly significant increase in isometric hand grip (IHG) strength and hand grip endurance (HGE) in both the groups, the increase in HGE in FSN group was significantly more than in SSN group. Pulmonary function tests showed improvements in both the groups though intergroup comparison showed no significance difference. Maximum inspiratory pressure (MIP) and maximum expiratory pressure increased significantly in both the groups with increase of MIP in FSN group being more significant than in SSN. Conclusion: The present study reports that SN has positive physiological benefits as evidenced by improvement of pulmonary function, respiratory pressures, hand grip strength and endurance, and resting cardiovascular parameters. It also demonstrates the differences between SN training when performed in a slow and fast manner, concluding that the effects of FSN are similar to physical aerobic exercises, whereas the effects of SSN are similar to those of yoga training

Investigation of Autonomic Dysfunction in Alzheimer’s Disease—A Computational Model-Based Approach

(1) Background and Objective: Alzheimer’s disease (AD) is commonly accompanied by autonomic dysfunction. Investigating autonomic dysfunction’s occurrence patterns and severity may aid in making a distinction between different dementia subtypes, as cardiac autonomic dysfunction and AD severity are correlated. Heart rate variability (HRV) allows for a non-invasive assessment of the autonomic nervous system (ANS). AD is characterized by cholinergic depletion. A computational model of ANS based on the kinetics of acetylcholine and norepinephrine is used to simulate HRV for various autonomic states. The model has the flexibility to suitably modulate the concentration of acetylcholine corresponding to different autonomic states. (2) Methods: Twenty clinically plausible AD patients are compared to 20 age- and gender-matched healthy controls using HRV measures. Statistical analysis is performed to identify the HRV parameters that vary significantly in AD. By modulating the acetylcholine concentration in a controlled manner, different autonomic states of Alzheimer’s disease are simulated using the ANS model. (3) Results: In patients with AD, there is a significant decrease in vagal activity, sympathovagal imbalance with a dominant sympathetic activity, and change in the time domain, frequency domain, and nonlinear HRV characteristics. Simulated HRV features corresponding to 10 progressive states of AD are presented. (4) Conclusions: There is a significant difference in the HRV features during AD. As cholinergic depletion and autonomic dysfunction have a common neurological basis, autonomic function assessment can help in diagnosis and assessment of AD. Quantitative models may help in better comprehending the pathophysiology of the disease and assessment of its progress

Modulation of cardiac autonomic functions in patients with major depression treated with repetitive transcranial magnetic stimulation

Background: Sub clinical cardiac autonomic imbalance is associated with depression. Clinical improvement produced by antidepressant therapy might alter this autonomic balance. Objectives: To investigate the effect of repetitive transcranial magnetic stimulation (rTMS) therapy on autonomic functions measured by heart rate variability (HRV) in depression patients and compare it with selective serotonin re-up-take inhibitors (SSRI) therapy. Methods: Consecutive drug-naive patients of major depression based on DSM-IV-TR were recruited in this study (n=67). Basal Hamilton depression-rating scale (HDRS) and measures of cardiac autonomic function were recorded and compared with those after two weeks of therapy with rTMS (n=27) and one month after SSRI therapy (n=25). Results: Both therapies produced comparable and significant reduction in HDRS scores. HRV measures indicated that rTMS produced significantly greater reduction in the sympathetic: parasympathetic ratio suggesting improvement in sympathovagal balance. Conventional cardiac autonomic function tests did not differentiate the two therapy effects. Conclusions: rTMS not only produced antidepressant effects but also "corrected" the autonomic imbalance. SSRI was systemically administered and hence by direct cardiac effect, may have masked cardiac effects that would have occurred by the improvement in depression. Alternatively, the neurophysiological "correction" with drug therapy may have longer latency, just as with the therapeutic effects

Alteration of cardiac autonomic functions in patients with major depression: a study using heart rate variability measures

Background: Depression is associated with greater cardiac morbidity and mortality. One of the contributory factors for this may be altered cardiac autonomic activity in depression. However, cardiac autonomic involvement in depression remains controversial because of methodological issues. In this study, alteration of cardiac autonomic functions was studied in drug-naive patients with major depression without co-morbidity. Heart rate variability, a sensitive measure of neurocardiac autonomic regulation was used in addition to conventional methods of measuring cardiac autonomic functions. Methods: We recruited 40 patients suffering from major depression, diagnosed based on DSM-IV-TR criteria. Their cardiac autonomic functions were measured using both conventional and heart rate variability measures. These were compared with those of age- and gender-matched healthy controls. Results: Patients with major depression showed significantly lesser Valsalva ratio, maximum/minimum ratio and greater sympathovagal balance than healthy controls indicating decreased parasympathetic and increased sympathetic activity. Conclusions: Depression is associated with alteration of cardiac autonomic tone towards decreased parasympathetic activity and an increased sympathetic activity. It is possible that a common neurobiological dysfunction contributes to both depression and cardiac autonomic changes in the illness

The perturbational map of low frequency repetitive transcranial magnetic stimulation of primary motor cortex in movement disorders

Background: Repetitive transcranial magnetic stimulation (rTMS) is applied to the primary motor cortex (M1) for the treatment of different movement disorders like Writer's Cramp (WC), Essential tremor (ET), and Spinocerebellar ataxia (SCA). However, the benefits vary, ranging from no effect to significant improvement in tremor. The variation in the benefits obtained from rTMS might be due to the difference in the spread of the stimuli across the brain areas associated with tremor. The spread of stimuli can be evaluated by combining rTMS with resting state functional magnetic resonance imaging (rsfMRI). Aim: To determine the spread of low frequency rTMS for WC, ET and SCA after stimulation of M1. Method: The rsfMRI was collected from the participants with WC (n = 27), ET (n = 30) and SCA (n = 28) at two time points, i.e., before and after the delivery of 1 Hz rTMS. Two measures from dynamic systems theory were calculated to understand how the system interacts with exogenously applied input (rTMS), namely entropy and frustration. While entropy measures the disorder from the rsfMRI time series, frustration quantifies it by assessing the change in sign (positive to negative, and vice-versa) of the functional connections.  The two quantities outlined the spread of perturbation due to rTMS. Result: For WC, a dense architecture of functional connections facilitated the spread across the bilateral areas of the five regions namely- the frontal cortex (frontal-Mid and Sup), motor cortex (supplemental motor area, precentral- and postcentral gyrus), parietal cortex (precuneus), subcortical regions (caudate, thalamus, posterior and mid-cingulate cortex) and the cerebellum (Crus-I and II, Cerebellum III and VI, and Vermis VI). For ET, though the areas belong to the above-mentioned 5 regions, the spread was narrower (i.e., lesser areas in the region). For SCA, the sparse connection between the areas led to minimal spread with no propagation of rTMS perturbation to the cerebellar regions. Interestingly for the three disorders, rTMS reduced the disorderliness (frustration and entropy) of the neural circuit (motor, subcortical and cerebellar regions) but increased the disorderliness in the default mode network (frontal and parietal regions). Conclusion: The spread of perturbation (due to TMS on M1) in the functional circuit varies in the three movement disorders. The current rTMS protocol achieves a wider spread for WC but not for ET and SCA. Findings from the present study suggest that pathology-specific stimulation protocols are required in movement disorders

Focality-Oriented Selection of Current Dose for Transcranial Direct Current Stimulation

Background: In transcranial direct current stimulation (tDCS), the injected current becomes distributed across the brain areas. The objective is to stimulate the target region of interest (ROI) while minimizing the current in non-target ROIs (the ‘focality’ of tDCS). For this purpose, determining the appropriate current dose for an individual is difficult. Aim: To introduce a dose–target determination index (DTDI) to quantify the focality of tDCS and examine the dose–focality relationship in three different populations. Method: Here, we extended our previous toolbox i-SATA to the MNI reference space. After a tDCS montage is simulated for a current dose, the i-SATA(MNI) computes the average (over voxels) current density for every region in the brain. DTDI is the ratio of the average current density at the target ROI to the ROI with a maximum value (the peak region). Ideally, target ROI should be the peak region, so DTDI shall range from 0 to 1. The higher the value, the better the dose. We estimated the variation of DTDI within and across individuals using T1-weighted brain images of 45 males and females distributed equally across three age groups: (a) young adults (20 ≤ x ˂ 40 years), (b) mid adults (40 ≤ x ˂ 60 years), and (c) older adults (60 ≤ x ˂ 80 years). DTDI’s were evaluated for the frontal montage with electrodes at F3 and the right supraorbital for three current doses of 1 mA, 2 mA, and 3 mA, with the target ROI at the left middle frontal gyrus. Result: As the dose is incremented, DTDI may show (a) increase, (b) decrease, and (c) no change across the individuals depending on the relationship (nonlinear or linear) between the injected tDCS current and the distribution of current density in the target ROI. The nonlinearity is predominant in older adults with a decrease in focality. The decline is stronger in males. Higher current dose at older age can enhance the focality of stimulation. Conclusion: DTDI provides information on which tDCS current dose will optimize the focality of stimulation. The recommended DTDI dose should be prioritized based on the age (>40 years) and sex (especially for males) of an individual. The toolbox i-SATA(MNI) is freely available