To use or not to use? Compulsive behavior and its role in smartphone addiction.

Global smartphone penetration has led to unprecedented addictive behaviors. To develop a smartphone use/non-use pattern by mobile application (App) in order to identify problematic smartphone use, a total of 79 college students were monitored by the App for 1 month. The App-generated parameters included the daily use/non-use frequency, the total duration and the daily median of the duration per epoch. We introduced two other parameters, the root mean square of the successive differences (RMSSD) and the Similarity Index, in order to explore the similarity in use and non-use between participants. The non-use frequency, non-use duration and non-use-median parameters were able to significantly predict problematic smartphone use. A lower value for the RMSSD and Similarity Index, which represent a higher use/non-use similarity, were also associated with the problematic smartphone use. The use/non-use similarity is able to predict problematic smartphone use and reach beyond just determining whether a person shows excessive use.

The high-frequency component of heart rate variability during extended wakefulness is closely associated with the depth of the ensuing sleep in C57BL6 mice.

This study aimed to test the hypothesis that, during extended wakefulness, parasympathetic activity is associated with the depth of the subsequent recovery sleep in mice. Fourteen male C57BL/6 mice were implanted with electrodes for sleep recording. Continuous spectral analysis was performed on the electroencephalogram (EEG) to obtain theta power (6-9Hz) and delta power (0-4Hz), as well as the R-R interval signals in order to quantify the high-frequency power (HF) and normalized low-frequency power (LF%) that are used to assess parasympathetic and sympathetic activity, respectively. All animals underwent a sleep deprivation experiment and a control experiment (6-h intervention and 1-h recovery period) on two separate days. During sleep deprivation, HF and theta power during wakefulness were significantly higher than during the control wakefulness after the second hour and first hour, respectively. During recovery non-rapid eye movement sleep, there was a rebound in sleep time and delta power as well as an elevation in HF relative to control post-intervention sleep. Both the rise in HF and theta power during extended wakefulness were found to be positively correlated with the delta power rebound. Furthermore, the HF change during extended wakefulness was also correlated with the amount of sleep loss and the enhancement of waking theta power. Our finding suggests that waking parasympathetic activity intimately reflects the cumulative sleep pressure, suggesting a potential role to be an autonomic marker for sleep propensity.

The Effects of Antidepressants and Quetiapine on Heart Rate Variability.

Introduction: The autonomic effects of antidepressants and quetiapine on heart rate variability (HRV) are inconsistent based on past studies. The aim of this study was to explore their influence on the HRV of psychiatric patients without psychotic symptoms. Methods: A total of 94 patients with depression, anxiety, or somatic symptoms, were recruited into this study. Based on their medication, 4 groups were identified: the no antidepressant group (n=19), the SSRI group (using sertraline or escitalopram, n=53), the other antidepressants group (using venlafaxine or mirtazapine, n=9), and the augmentation group (AG, using an antidepressant+quetiapine, n=13). The HRV of the 4 groups were compared. The correlations between HRV and the medication(s) used were clarified. Results: Among the 4 groups, the AG had the lowest HRV with its total power (TP), very low frequency power (VLF) and low frequency power (LF) of HRV being significantly different from those of the other groups. Age and using quetiapine were found to be negatively correlated with TP, VLF and LF. With this study group, the autonomic effects of antidepressants were found not to be significant. Discussion: Among psychiatric patients without psychotic symptoms, quetiapine causes an overt decrease in HRV.

Differential changes and interactions of autonomic functioning and sleep architecture before and after 50 years of age.

We hypothesize that the time when age-related changes in autonomic functioning and in sleep structure occur are different and that autonomic functioning modulates sleep architecture differently before and after 50 years of age. Sixty-eight healthy subjects (aged 20 to 79 years old, 49 of them women) were enrolled. Correlation analysis revealed that wake after sleep onset, the absolute and relative value of stage 1 (S1; S1%), and relative value of stage 2 (S2) were positively correlated with age; however, sleep efficiency, stage 3 (S3), S3%, and rapid-eye-movement latency (REML) were negatively correlated with age. Significant degenerations of sleep during normal aging were occurred after 50 years of age; however, significant declines of autonomic activity were showed before 50 years of age. Before 50 years of age, vagal function during sleep was negatively correlated with arousal index; however, after 50 years of age, it was positively correlated with S1 and S1%. In addition, sympathetic activity during wake stage was positively related to S2% only after 50 years of age. Our results imply that the age-related changes in autonomic functioning decline promptly as individuals leave the younger part of their adult life span and that age-related changes in sleep slowly develop as individuals enter the older part of their adult life span. Furthermore, while various aspects of sleep architecture are modulated by both the sympathetic and vagal nervous systems during adult life span, the sleep quality is mainly correlated with the sympathetic division after 50 years of age.

Changes in hippocampal theta rhythm and their correlations with speed during different phases of voluntary wheel running in rats.

Hippocampal theta rhythm (4-12 Hz) can be observed during locomotor behavior, but findings on the relationship between locomotion speed and theta frequency are inconsistent if not contradictory. The inconsistency may be because of the difficulties that previous analyses and protocols have had excluding the effects of behavior training. We recorded the first or second voluntary wheel running each day, and assumed that theta frequency and activity are correlated with speed in different running phases. By simultaneously recording electroencephalography, physical activity, and wheel running speed, this experiment explored the theta oscillations during spontaneous running of the 12-h dark period. The recording was completely wireless and allowed the animal to run freely while being recorded in the wheel. Theta frequency and theta power of middle frequency were elevated before running and theta frequency, theta power of middle frequency, physical activity, and running speed maintained persistently high levels during running. The slopes of the theta frequency and theta activity (4-9.5 Hz) during the initial running were different compared to the same values during subsequent running. During the initial running, the running speed was positively correlated with theta frequency and with theta power of middle frequency. Over the 12-h dark period, the running speed did not positively correlate with theta frequency but was significantly correlated with theta power of middle frequency. Thus, theta frequency was associated with running speed only at the initiation of running. Furthermore, theta power of middle frequency was associated with speed and with physical activity during running when chronological order was not taken into consideration.

Changes in hippocampal θ activity during initiation and maintenance of running in the rat.

Hippocampal theta wave can be induced by running and is linked to cognitive functions. The initiation and maintenance of hippocampal theta during a complete course of running, however, is not well understood. Using a treadmill exercise model, this study wirelessly recorded the hippocampal electroencephalogram, nuchal electromyogram, electrocardiogram, and three-dimensional accelerations of 15 male young rats. Although the speed of the treadmill was constant during the entire 30-min running course, the frequency (Frq) and amplitude (Amp) of hippocampal theta changed dynamically. During the first 24 s (phase I), the Frq, Amp, electromyogram amplitude (EMG), heart rate (HR), and physical activity (PA) all increased. The changes in the Frq, EMG, and PA were among the fastest and the change in the HR was the slowest. After 24 s (phase II), the Frq declined to near baseline but the Amp remained persistently high. The slope of the Frq, Amp, and HR over time during phase I was different to that during phase II. During phase II, the Frq and Amp were significantly correlated with the PA and EMG. We conclude that treadmill running can be classified into two phases based on hippocampal functioning, and hippocampal theta varies with exercise effort during the treadmill running.

The influence of autonomic interventions on the sleep-wake-related changes in gastric myoelectrical activity in rats.

BACKGROUND: Significant changes in autonomic activity occur at sleep-wake transitions and constitute an ideal setting for investigating the modulatory role of the autonomic nervous system on gastric myoelectrical activity (GMA). METHODS: Using continuous power spectral analysis of electroencephalogram, electromyogram, and electrogastromyogram (EGMG) data from freely moving rats that had undergone chemical sympathetomy and/or truncal vagotomy, sleep-wake-related fluctuations in GMA were compared among the intervention groups. KEY RESULTS: The pattern and extent of fluctuations in EGMG power across the sleep-wake states was blunted most significantly in rats undergoing both chemical sympathectomy and truncal vagotomy. The effect of these interventions also varied with respect to the transition between different sleep-wake states. The most prominent influences were observed between active waking and quiet sleep and between paradoxical sleep and quiet sleep. CONCLUSIONS & INFERENCES: The sleep-wake-related fluctuations in EGMG power are a result of joint contributions from both sympathetic and vagal innervation. Vagotomy mainly resulted in a reduction in EGMG power, while the role of sympathetic innervation was unveiled by vagotomy and this was reflected most obviously in the extent of the fluctuations in EGMG power.

Heart rate variability during hemodialysis and following renal transplantation.

Previous studies have shown awareness of uremic dysfunction in end-stage renal disease (ESRD) patients. Dysautonomia in ESRD patients may be reversible after renal transplantation. We used a power spectral analysis (PSA) of heart rate variability (HRV) to assess alterations of autonomic activity in 14 controls and 14 nondiabetic hemodialysis ESRD patients who had undergone renal transplantation. Compared with matched control subjects, the power frequency determinations of low frequency (LF; 3.42 ln(ms(2)) vs 6.38 ln(ms(2)); P < .05 high frequency (HF; 2.29 ln(ms(2)) vs 5.27 ln(ms(2)); P < .05)), and total power (TP; 5.39 ln(ms(2)) vs 7.53 ln(ms(2)); P < .05) were significantly suppressed in ESRD patients undergoing hemodialysis. ESRD patients showed significantly improved HRV after renal transplantation. After renal transplantation, there was no significant difference in the TP (6.82 ln(ms(2)) vs 7.53 ln(ms(2)); P = .15) component between measurements in both patient subgroups. We further divided the ESRD patients into 2 groups based on their pretransplantation HRV, observing alterations in HRV after renal transplantation. Patients with significantly improved HRV were those with more suppressed HRV before transplantation (HF <3 In(ms(2)). Autonomic dysfunction in ESRD patients was not irreversible even if severe, and recovery was observed as early as 6 months after transplantation.

Acute effects of ephedra on autonomic nervous modulation in healthy young adults.

The aim of this study was to assess the acute effects of ephedra on autonomic nervous modulation by means of heart rate variability (HRV) analysis, using a randomized, double-blind, placebo-controlled, crossover design. On three separate days, 20 healthy subjects took capsules containing either 1 or 2 g of ephedra dry extract or a placebo, and the sequential percentage changes in HRV measures were compared. After the subjects took ephedra, the normalized low-frequency component (LF) and the ratio of LF to high-frequency component (HF) increased significantly in a dose-dependent manner, whereas the normalized HF (HF%) decreased significantly. We conclude that ingestion of ephedra tilts the sympathovagal balance dose-dependently toward increased sympathetic activity and impairs parasympathetic activity.

Effect of hyperbaric oxygen on cardiac neural regulation in diabetic individuals with foot complications.

AIMS: There are relatively few effective methods to treat autonomic neuropathy in patients with diabetes mellitus. Our aim was to test the hypothesis that hyperbaric oxygen therapy may restore cardiac neural regulation dysfunction in diabetic individuals with foot complications. METHODS: We conducted a prospective randomized controlled study in patients with diabetic foot problems. Daily heart-rate variability analysis from 5-min electrocardiography was used to evaluate the temporal change of cardiac neural regulation. The experimental group consisted of 23 subjects exposed to hyperbaric oxygen therapy of 202.65 kPa for 90 min every Monday to Friday for 4 weeks (20 treatments). The control group consisted of 15 age-, sex- and disease-matched subjects who were not exposed to hyperbaric therapy. Patients with medical complications and failure of wound healing were excluded to eliminate possible confounding effects. RESULTS: There was no significant difference in baseline R-R interval (RR), variance, high-frequency power (HF), low-frequency power (LF), and LF/HF ratio between the two groups. In the hyperbaric oxygen group there were significant increases in changes of RR (82.7 +/- 16.02 ms); variance 0.88 +/- 0.12 ln(ms2); HF 1.06 +/- 0.18 ln(ms2); and LF 0.87 +/- 0.15 ln(ms2) after the treatment. Measurements of tissue oxygen demonstrated significant increases in local tissue oxygenation in the hyperbaric oxygen group (53.0 +/- 2.6 mmHg) compared with the control group (27.5 +/- 3.1 mmHg), P < 0.05. CONCLUSION: Hyperbaric oxygen therapy has a significant vagotonic effect, which is beneficial in improving cardiac neural regulation in patients with diabetic autonomic dysfunction.

Enhanced sympathetic outflow and decreased baroreflex sensitivity are associated with intermittent hypoxia-induced systemic hypertension in conscious rats.

Long-term exposure to intermittent hypoxia (IH), such as that occurring in association with sleep apnea, may result in systemic hypertension; however, the time course changes in arterial pressure, autonomic functions, and baroreflex sensitivity are still unclear. We investigated the changes in cardiovascular neural regulations during the development of chronic IH-induced hypertension in rats. Sprague-Dawley rats were exposed to repetitive 1.25-min cycles (30 s of N2+45 s of 21% O2) of IH or room air (RA) for 6 h/day during light phase (10 AM-4 PM) for 30 days. Arterial pressure was measured daily using the telemetry system during RA breathing. The mean arterial pressure (MAP) and interpulse interval (PPI) signals were then used to assess the autonomic functions and spontaneous baroreflex sensitivity by auto- and cross-spectral analysis, respectively. Stable MAP, low-frequency power of MAP (BLF), and low-frequency power (LF)-to-high frequency power (HF) ratio of PPI (LF/HF) were significantly higher in IH-exposed rats, compared with those of RA-exposed rats. Elevation of the MAP, BLF, LF/HF, and minute ventilation started 5 days after IH exposure and lasted until the end of the 30-day observation period. Additionally, IH-exposed rats had significant lower slope of MAP-PPI linear regression (under a successively descending and ascending) and magnitude of MAP-PPI transfer function (at frequency ranges of 0.06-0.6 Hz or 0.6-2.4 Hz) after IH exposure for 17 days. However, RA-exposed rats did not exhibit these changes. The results of this study indicate that chronic IH-induced hypertension is associated with a facilitation of cardiovascular sympathetic outflow and inhibition of baroreflex sensitivity in conscious rats.

Further Characterization of Nociception-Related and Arterial Pressure-Related Neuronal Responses in the Nucleus Reticularis Gigantocellularis of the Rat.

The present study was undertaken to further characterize the nucleus reticularis gigantocellularis (NRGC) of the medulla oblongata in the central processing of nociceptive and cardiovascular signals, and its modulation by met-enkephalin. In Sprague-Dawley rats anesthetized with pentobarbital sodium, we found that all 125 spontaneously active NRGC neurons that responded to noxious stimuli (tail clamp) also exhibited arterial pressure-relatedness. Forty neurons additionally manifested cardiac periodicity that persisted even during nociceptive responses. While maintaining their cardiovascular responsive characteristics, the nociception-related NRGC neuronal activity was blocked, naloxone-reversibly (0.5 mg/kg, i.v.), by morphine (5 mg/kg, i.v.). Microiontophoretically applied met-enkephalin suppressed the responsiveness of NRGC neurons to individually delivered tail clamp or transient hypertension induced by phenylephrine (5 &mgr;g/kg, i.v.). Interestingly, in NRGC neurons that manifested both nociception and arterial pressure relatedness, the preferential reduction in the response to noxious stimuli upon simultaneous elevation in systemic arterial pressure was reversed to one that favored nociception in the presence of met-enkephalin. All actions of met-enkephalin were discernibly blocked by the opioid receptor antagonist, naloxone. Our results suggest that individual NRGC neurons may participate in the processing of both nociceptive and cardiovascular information, or in the coordination of the necessary circulatory supports during nociception. In addition, neuropeptides such as met-enkephalin may exert differential modulation on neuronal responsiveness according to the prevailing physiologic status of the animal. They also showed that NRGC may be a central integrator for pain and cardiovascular-related functions. Copyright 1996 S. Karger AG, Basel

Physiological Role of Brain Angiotensin III in Drinking Behavior in the Rat.

We examined the physiologic role of endogenous brain angiotensin III (AIII), an active degradative product of angiotensin II, in drinking behavior. Adult, male spontaneously hypertensive (SH) and Wistar-Kyoto normotensive (WKY) rats that were instrumented with an intracerebroventricular (i.c.v.) cannula connected to an osmotic minipump for chronic infusion were used. 7-day i.c.v. infusion of the specific AIII antagonist, Ile(7)-AIII (10 or 100 pmol/min), resulted in no significant alteration in daily (24 h), diurnal (8:00 a.m.-8.00 p.m.) or nocturnal (8:00 p.m.-8:00 a.m.) basal water intake in both SH and WKY rats. Similar results were obtained with i.c.v. infusion of the aminopeptidase inhibitor, bestatin (150 or 300 pmol/min), given alone or simultaneously with Ile(7)-AIII (10 pmol/min). Rats that were water-deprived for the first 3 days of 7-day infusion of Ile(7)-AIII consumed significantly less water during the first 2 h after water became available. Furthermore, the accumulated water intake during the first 24 h was appreciably greater in SH than WKY rats. We interpret these results to suggest that the endogenous brain AIII may not be tonically involved in fluid homeostasis. Instead, it must be activated under conditions of dehydration, such as water deprivation, particularly in the SHRs, to initiate drinking behavior. Copyright 1996 S. Karger AG, Basel