Correction: Intensive longitudinal modelling predicts diurnal activity of salivary alpha-amylase.

[This corrects the article DOI: 10.1371/journal.pone.0209475.].

Association between Salivary Alpha-Amylase and Executive Functioning in Healthy Children.

The main aim of this study was to confirm the relationship between executive performance and salivary alpha-amylase (SAA) activity in a sample of 64 healthy children (39 boys), and compare it to the association of SAA output and salivary flow rate (SFR). Executive functioning was assessed via fluency, trail-making, rings and inhibition tasks from the Batería de Evaluación Neuropsicológica de la Función Ejecutiva en Niños [Battery of Neuropsychological Assessment for Executive Function in Children] (ENFEN), merged into an ENFEN total score. SAA activity, output, and SFR were measured at baseline, one minute before, and one minute after the end of a neuropsychological testing session. Our results confirmed a direct, linear and significant association between SAA activity and executive functioning, r(64) = .351, p < .05, and extended it to SAA output, r(64) =.431, p < .05. The mean level of SAA output was the best predictor of executive functioning (ß = .431, p < .05) and explained 18.2 % of the variance in ENFEN total score. In sum, and compared to SAA activity, measuring SAA output may be a more precise and indirect marker to assess executive functioning in children.

Autonomic reactivity in blood-injection-injury and snake phobia.

OBJECTIVE: This research aimed to study the salivary flow and other autonomic reactions -heart rate (HR) and skin conductance response (SCR)- in blood-injection-injury (BII) phobia and snake phobia participants, under the assumption that exposure to blood-related pictures in BII phobia will provoke an increase in parasympathetic activity that, in turn, will lead to a greater saliva production than other affective contents. METHODS: We selected 18 BII phobia and 14 snake phobia participants along with 22 non-phobia individuals. All participants were exposed to 3 blocks of pictures (12 pictures per block) depicting either mutilations, snakes or neutral, household objects. Saliva samples were taken in the 2-min interval before and after each block. RESULTS: In comparison to other contents, blood-related pictures provoked an increase in salivary flow in BII phobia participants, as well as an increase in the number of SCRs. In the snake phobia group, snake pictures provoked HR acceleration, but the SCRs they elicited did not differ from the SCRs provoked by the blood-related pictures. CONCLUSION: BII phobia individuals react to their phobic object with a series of physiological changes resulting from a sympathetic-parasympathetic co-activation. This is in contrast with other specific phobias (e.g., small animal phobias) that usually show a sympathetically mediated, defensive reactivity when exposed to their disorder-relevant stimuli. These data support the use of therapeutic interventions in BII phobia that may differ in some respect from those used in other specific phobias.

Salivary alpha-amylase changes promoted by sustained exposure to affective pictures.

We studied the changes in salivary alpha-amylase (sAA) and other psychophysiological indices (heart rate, skin conductance, and corrugator supercilii activity) elicited by sustained exposure to affective pictures. Thirty-nine subjects viewed five blocks of pictures depicting mutilations, human attack, neutral scenes, sport/adventure, and erotica. Each block comprised 12 pictures of the same content. Saliva samples were collected before and after each block of pictures. The results showed that mutilation pictures promoted the greatest increase in sAA activity and output, as well as greater corrugator supercilii activity than pleasant pictures. Skin conductance response did not differ among high arousal picture contents. Changes in sAA varied with the affective valence but not with the arousal ratings of the pictures. Our results point to sAA as an index directly related to the unpleasantness elicited by sustained exposure to affective stimuli.

Salivary cortisol response to a psychosocial stressor on children diagnosed with attention-deficit/hyperactivity disorder: differences between diagnostic subtypes.

The purpose of the present study was to compare the reactivity of the HPA-axis in children diagnosed with different subtypes of ADHD against a healthy control group. This study included a total of 66 children: 33 children with ADHD diagnoses (10 with prevalent inattentive symptoms, 9 with prevalent hyperactive-impulsive symptoms and 14 with the combined subtype) and 33 healthy controls. The Trier Stress Social Test for Children (TSST-C) was employed as stressor. This test included two main stressors: first, completing a story initiated by an interviewer, and second, executing a timed cognitive task. Saliva samples were then obtained at -1, and +1, +10, +20 and +30 minutes with respect to the stress-inducing task. While the repeated-measures ANOVA showed a statistically significant time effect, the expected cortisol stress-response was not observed in any group. A difference was observed in the response from the hyperactive-impulsive group that was also observed in the AUC(G) comparisons with the subgroups. The ADHD group with prevalent hyperactivity-impulsive symptoms showed more significantly reduced cortisol levels than the control group and other experimental subgroup with prevalent inattentive symptoms.

Subjective Sleep Quality and hormonal modulation in long-term yoga practitioners.

Yoga represents a fascinating mind-body approach, wherein body movements (asana), breathing exercises (pranayama) and meditation are integrated into a single multidimensional practice. Numerous beneficial mental and physical effects have been classically ascribed to this holistic ancient method. The purpose of the present study has been to examine the effects of long-term yoga practice on Subjective Sleep Quality (SSQ) and on several hormonal parameters of the hypothalamus-pituitary-adrenal (HPA) axis. Twenty-six subjects (16 experimental and 10 controls) were recruited to be part of the study. Experimental subjects were regular yoga practitioners with a minimum of 3 years of practice. Blood samples for the quantification of adrenocorticotropic hormone (ACTH), cortisol and dehydroepiandrosterone sulphate (DHEA-S) were drawn from all subjects. Likewise, the Pittsburgh Sleep Quality Index (PSQI) was employed to assess SSQ. As statistical analysis, Mann-Whitney U-test was performed. The yoga group displayed lower PSQI scores and higher blood cortisol levels than control subjects. Therefore, it can be concluded that long-term yoga practice is associated with significant psycho-biological differences, including better sleep quality as well as a modulatory action on the levels of cortisol. These preliminary results suggest interesting clinical implications which should be further researched.

Cognitive performance and morning levels of salivary cortisol and alpha-amylase in children reporting high vs. low daily stress perception.

The aim of the present study was to assess the effects of daily stress perception on cognitive performance and morning basal salivary cortisol and alpha-amylase levels in healthy children aged 9-12. Participants were classified by whether they had low daily perceived stress (LPS, n = 27) or a high daily perceived stress (HPS, n = 26) using the Children Daily Stress Inventory (CDSI). Salivary cortisol and alpha-amylase were measured at awakening and 30 minutes later. Cognitive performance was assessed using the Cognitive Drug Research assessment system. The HPS group exhibited significantly poorer scores on speed of memory (p < .05) and continuity of attention (p < .05) relative to the LPS group. The HPS group also showed significantly lower morning cortisol levels at awakening and at +30 minutes measures in comparison with the LPS group (p < .05), and mean morning cortisol levels were negatively correlated with speed of memory (p < .05) in the 53 participants. No significant differences were observed between both groups in alpha-amylase levels. These findings suggest that daily perceived stress in children may impoverish cognitive performance via its modulating effects on the HPA axis activity.

Biochemical changes after a qigong program: lipids, serum enzymes, urea, and creatinine in healthy subjects.

BACKGROUND: The aim of the present study was to analyze the effects of a qigong training program on blood biochemical parameters. MATERIAL/METHODS: Twenty-nine healthy subjects participated in the study of whom 16 were randomly assigned to the experimental group and 13 to the control. The experimental subjects underwent daily qigong training for one month. Blood samples for the quantification of biochemical parameters (total cholesterol, HDL, LDL, triglycerides, phospholipids, GOT, GPT, GGT, urea, creatinine) were taken before and after the training program. As statistical analysis, ANCOVA was performed. RESULTS: Statistically significant differences were found showing that the experimental group had lower serum levels of GOT (glutamic-oxaloacetic transaminase), GPT (glutamic-pyruvic transaminase), and urea and that there was a trend towards significance in GGT (gamma-glutamyltransferase). CONCLUSIONS: This study demonstrates that after practicing qigong for the short period of one month, noteworthy changes in several blood biochemical parameters were induced. While it is tempting to speculate on the relevance and implications of these biochemical variations, further investigation is needed to elucidate the scope of these findings.

The psychosocial stress-induced increase in salivary alpha-amylase is independent of saliva flow rate.

The stress response of salivary alpha-amylase (sAA) has been suggested as an index for sympathetic nervous system activation. However, concurrent inhibition of the parasympathetic nervous system is discussed as a confounder due to suppression of saliva flow rate. Here we set out to test the influence of stress-induced changes in flow rate on sAA secretion. Twenty-six subjects underwent the Trier Social Stress Test and a control condition. Saliva was sampled by passive drooling or salivettes. Saliva flow rate, sAA levels and output, salivary cortisol, and heart rate variability were measured. Flow rate increased only when sampled by passive drooling. Stress-induced increases in amylase levels were correlated with increases of amylase output but not with flow rate. Results indicate that flow rate is not a confounder of stress-induced sAA activation and suggest that valid measurements of sAA can be obtained by salivettes without the need for assessment of flow rate.

Assessment of immunological parameters following a qigong training program.

BACKGROUND: Qigong is a type of Chinese psychosomatic exercise that integrates meditation, slow physical movements, and breathing, and to which numerous physical as well as mental benefits have been classically ascribed. The aim of the present study was to analyze the effects of a qigong program on various immunological parameters. MATERIAL/METHODS: 29 naive subjects participated in the study, of whom 16 were allocated to the experimental group and the rest to the control group. The experimental subjects underwent a qigong training program, conducted by a qualified instructor, consisting of half an hour of daily practice for one month. The day before the experiment commenced and the day after it finished, blood samples were drawn from all subjects for the quantification of immunological parameters (leukocytes, immunoglobulins, and complement). As statistical analysis, analysis of covariance (ANCOVA) was carried out. RESULTS: Statistically significant differences were found between the control and experimental groups, with the experimental group showing lower numbers of total leukocytes and eosinophils, number and percentage of monocytes, as well as complement C3 concentration. In addition, a similar result with a trend towards significance was observed in the number of eosinophils. CONCLUSIONS: These findings demonstrate that after one month of practicing qigong, significant immunological changes occurred between the experimental and control groups, with a consistently lower and broadly significant profile of these measures within the qigong practitioner group.