Interoceptive training impacts the neural circuit of the anterior insula cortex.

Interoception is the perception of afferent information that arises from anywhere and everywhere within the body. Recently, interoceptive accuracy could be enhanced by cognitive training. Given that the anterior insula cortex (AIC) is a key node of interoception, we hypothesized that resting functional connectivity (RSFC) from AIC was involved in an effect of interoceptive training. To address this issue, we conducted a longitudinal intervention study using interoceptive training and obtained RSFC using fMRI before and after the intervention. A heartbeat perception task evaluated interoceptive accuracy. Twenty-two healthy volunteers (15 females, age 19.9 ± 2.0 years) participated. After the intervention, interoceptive accuracy was enhanced, and anxiety levels and somatic symptoms were reduced. Also, RSFC from AIC to the dorsolateral prefrontal cortex (DLPFC), superior marginal gyrus (SMG), anterior cingulate cortex (ACC), and brain stem, including nucleus tractus solitarius (NTS) were enhanced, and those from AIC to the visual cortex (VC) were decreased according to enhanced interoceptive accuracy. The neural circuit of AIC, ACC, and NTS is involved in the bottom-up process of interoception. The neural circuit of AIC, DLPFC, and SMG is involved in the top-down process of interoception, which was thought to represent the cognitive control of emotion. The findings provided a better understanding of neural underpinnings of the effect of interoceptive training on somatic symptoms and anxiety levels by enhancing both bottom-up and top-down processes of interoception, which has a potential contribution to the structure of psychotherapies based on the neural mechanism of psychosomatics.

[Perspective on Emotion from Allostasis Mediated by Interoception].

Feeling emotional responses, such as heartbeat and respiration, influence subjective feeling of emotion. The role of interoception as a link in this relationship has been the focus of much attention. The predictive coding model is suggested for understanding the mechanism of interoception, and the model is also closely related to allostasis. This paper introduces a perspective on emotion from the allostasis mediated by interoception.

[Mental Disorders from the Perspective of Interoception and Allostasis].

The classical concept of allostasis is proposed as a dynamic adaptive capacity to stressors. The overload of allostasis results in adaptive disorders, and then lead to various psychiatric disorders. The recent concept of allostasis explains not only physiological adaptation but also behavioural changes. Furthermore, the relationship between interoception and the sense of self as well as emotion has attracted attention in recent years. These conceptual extensions and their abnormalities could help in understanding the symptoms of schizophrenia.

Effect of subconscious changes in bodily response on thought shifting in people with accurate interoception.

Our thought states shift from one state to another from moment to moment. The relationship between the thought shifting and bodily responses is yet to be directly examined. This exploratory study examined the influence of cardiovascular reactivity and interoception-sensing an internal bodily state-on the shifting of thought states. Participants (N = 100, 70 women) completed two tasks: the heartbeat counting task (HCT) and the vigilance task (VT). We assessed their interoceptive accuracy through their performance on the HCT. The VT was a simple sustained attention task in which participants pressed a key when the target stimulus appeared and were asked to report their thoughts. We presented subliminal vibration stimuli to induce alterations in heart rate (i.e., vibration block). Results showed that participants with higher interoceptive accuracy reported more continuation of self-referential thought (about past episodes and future plans regarding themselves) during the vibration block than did those with lower interoceptive accuracy. These results suggest that individuals with higher interoceptive accuracy are more likely to be influenced by their subliminal bodily response, resulting in divergent attention from the task and intermittent self-referential thought.

Modulation of heartbeat-evoked potential and cardiac cycle effect by auditory stimuli.

Interoception has been proposed as a factor that influences various psychological processes (Khalsa et al., 2018). Afferent signals from the cardiovascular system vary across cardiac cycle phases. Heartbeat-evoked potentials (HEP) and event-related potentials (ERP) were measured to examine whether interoceptive signals differed between cardiac cycle phases. Simultaneously, participants performed an auditory oddball task in which the timing of the presenting stimulus was synchronized with the heartbeat. Pure tones were presented at 10 ms (late diastole condition), 200 ms (systole condition), or 500 ms after the R wave (diastole condition). Greater HEP amplitudes were observed when the tone was presented during diastole than during systole or late diastole. ERP showed the same tendency: a greater amplitude was observed during diastole than systole or late diastole. These results suggest that the processing of interoception reflected by HEP and exteroception reflected by ERP share attentional resources when both stimuli coincide. When the tone was presented during systole, attention to the internal state decreased compared with when the tone was presented during diastole, and attention was distributed to both exteroception and interoception. Our study suggests that HEP may be considered an indication of a relative amount of resources to process the interoception.

Functional connectivity changes between frontopolar cortex and nucleus accumbens following cognitive behavioral therapy in major depression: A randomized clinical trial.

Cognitive behavioral therapy (CBT) is a psychotherapy that challenges distorted cognitions; however, the neural mechanisms that underpin CBT remain unclear. Hence, we aimed to assess the treatment-related resting-state functional connectivity (rsFC) changes in the brain regions associated with future thinking and the associations between rsFC changes and clinical improvements. Thirty-eight adult patients with MDD were randomly assigned with equal likelihood to receive 16-week individual CBT or talking control with a 12-month follow-up period. We evaluated the rsFC changes in the frontal regions, nucleus accumbens, amygdala, and limbic structures key to the depression pathophysiology and future thinking with 2 ×  2 mixed ANOVA interaction analysis. Pearson's correlation analysis with Bonferroni's correction was also performed to examine the associations with clinical symptoms, such as depression severity and automatic thoughts in follow-up evaluations. Treatment-specific changes include enhancement in frontopolar connectivity with the nucleus accumbens. An increased rsFC was associated with lower negative automatic thoughts postoperatively, together with lower depressive symptoms and higher positive automatic thoughts at follow-up. Conclusively, rsFC changes in the fronto-limbic neural control circuit after CBT, particularly between the frontal pole and nucleus accumbens, may be clinically meaningful functional changes related to the depression recovery process.

The effect of cognitive behavioral therapy on future thinking in patients with major depressive disorder: A randomized controlled trial.

Background: Pessimistic thinking about the future is one of the cardinal symptoms of major depression. Few studies have assessed changes in pessimistic thinking after undergoing cognitive behavioral therapy (CBT). A randomized clinical trial (RCT) was conducted with patients diagnosed with major depressive disorder (MDD) to determine whether receiving a course of CBT affects pessimistic future thinking using a future thinking task. Methods: Thirty-one patients with MDD were randomly assigned to either CBT (n = 16) or a talking control (TC) (n = 15) for a 16-week intervention. The main outcomes were the change in response time (RT) and the ratio of the responses for positive valence, measured by the future thinking task. Secondary outcomes included the GRID-Hamilton Depression Rating Scale, the Beck Depression Inventory-Second Edition (BDI-II), the Dysfunctional Attitude Scale (DAS), and the word fluency test (WFT). Results: Regarding the main outcomes, the CBT group showed reduced RT for the positive valence (within-group Cohen's d = 0.7, p = 0.012) and negative valence (within-group Cohen's d = 0.6, p = 0.03) in the distant future condition. The ratio of positive valence responses in both groups for all temporal conditions except for the distant past condition increased within group (distant future: CBT: Cohen's d = 0.5, p = 0.04; TC: Cohen's d = 0.8, p = 0.008; near future: CBT: Cohen's d = 1.0, p < 0.001; TC: Cohen's d = 1.1, p = 0.001; near past: CBT: Cohen's d = 0.8, p = 0.005; TC: Cohen's d = 1.0, p = 0.002). As for secondary outcomes, the CBT group showed greater improvement than the TC group regarding the need for social approval as measured by the DAS (p = 0.012). Conclusion: Patients with MDD who received CBT showed a reduced RT for the positive and negative valence in the distant future condition. RT in the future thinking task for depressed patients may be a potential objective measure for the CBT treatment process. Because the present RCT is positioned as a pilot RCT, a confirmatory trial with a larger number of patients is warranted to elucidate the CBT treatment process that influences future thinking. Clinical trial registration: https://center6.umin.ac.jp/cgi-open-bin/icdr_e/ctr_view.cgi?recptno=R000021028, identifier UMIN000018155.

Word recall process and physiological activation in the tip-of-the-tongue state: Comparison of young and middle-aged groups.

To clarify the feeling of knowing a name but not being able to recall it, known as having a "tip-of-the-tongue" (TOT) experience, we proposed a TOT model consisting of three stages combining a face recognition model and autonomic sympathetic nerve activity. Since TOT increases with age, we compared two age groups: young (N = 27, M = 20.4 ± 1.5 years) and middle-aged (N = 29, M = 58.5 ± 8.0 years). Experiment 1 showed that successfully naming low-frequency common names increased the skin conductance response (SCR) value, and the time to reach the maximum SCR value was longer. Experiment 2 was a naming task for face photographs. The younger group showed higher SCR values during successfully naming, while the middle-aged group showed similar SCR values for successfully naming and experiencing TOT. Both groups had the longest time to reach maximum SCR in TOT. In this study, physiological arousal of TOT was not affected by aging.

Passive Way of Measuring QOL/Well-Being Levels Using Smartphone Log.

Research on mental health states involves paying increasing attention to changes in daily life. Researchers have attempted to understand such daily changes by relying on self-reporting through frequent assessment using devices (smartphones); however, they are mostly focused on a single aspect of mental health. Assessing the mental health of a person from various perspectives may help in the primary prevention of mental illness and the comprehensive measurement of mental health. In this study, we used users' smartphone logs to build a model to estimate whether the scores on three types of questionnaires related to quality of life and well-being would increase compared to the previous week (fluctuation model) and whether they would be higher compared to the average for that user (interval model). Sixteen participants completed three questionnaires once per week, and their smartphone logs were recorded over the same period. Based on the results, estimation models were built, and the F-score ranged from 0.739 to 0.818. We also analyzed the features that the estimation model emphasized. Information related to "physical activity," such as acceleration and tilt of the smartphone, and "environment," such as atmospheric pressure and illumination, were given more weight in the estimation than information related to "cyber activity," such as usage of smartphone applications. In particular, in the Positive and Negative Affect Schedule (PANAS), 9 out of 10 top features in the fluctuation model and 7 out of 10 top features in the interval model were related to activities in the physical world, suggesting that short-term mood may be particularly heavily influenced by subjective activities in the human physical world.

Cognitive behavioral therapy effects on frontopolar cortex function during future thinking in major depressive disorder: A randomized clinical trial.

BACKGROUND: Despite the importance of Beck's theoretical cognitive model of psychopathology, the neural mechanisms underlying future thinking in cognitive behavioral therapy (CBT) remain elusive. Recent neuroimaging studies have shown that the function of the frontopolar cortex (Brodmann area 10 [BA10]) is associated with future thinking. We hypothesized that, compared with unstructured psychotherapy (talking control: TC), CBT may involve different neural responses in BA10 associated with future thinking. METHODS: This randomized clinical trial included 38 adult patients with moderate-to-severe major depressive disorder who underwent up to 16 weeks of CBT or TC with a 6-month follow-up period. We evaluated changes in BA10 activation during distant future thinking using functional magnetic resonance imaging with a future-thinking task. We assessed frontal neurocognitive function and clinical symptoms at baseline and post-treatment. Depression severity and automatic thoughts were assessed at the 6-month follow-up. RESULTS: We found decreased activation in the frontopolar cortex during distant future thinking after CBT (t = 3.00, df=15, p = 0.009) and no changes after TC. Further, the reduction in BA10 activity significantly correlated with changes in frontal cognitive function after the treatment (r = 0.48, p = 0.007), and in positive automatic thought after 6 months of treatments (r = 0.39; p = 0.03). LIMITATIONS: Relatively small sample size and homogenous clinical profile could limit the generalizability. Patients received pharmacotherapy including antidepressant. CONCLUSIONS: CBT appears to improve frontopolar cortex function during future thinking in a manner distinct from TC. Larger clinical trials are necessary to provide firm evidence whether BA10 activity may serve as a neuro-marker for monitoring successful depression treatment with CBT.

[Dynamic Functional Connectivity in Resting-State fMRI and Its Clinical Applications].

The conventional analysis assumes a constant mental state during scanning and assesses the strength of functional connectivity as the average of the entire fMRI data. However, it is suggested that even at rest, functional connectivity may change with time, and the conventional analysis has not been able to fully evaluate its properties. To overcome this limitation, many studies propose an index called dynamic functional connectivity (dFC) or time-varying functional connectivity (TVFC) or the chronnectome. This article reviews the significance and methods of dFC, examples of its application in clinical studies, and its limitations. Finally, we discuss its potential for clinical application.

Paradoxical somatic information processing for interoception and anxiety in alexithymia.

The concept of alexithymia has garnered much attention in an attempt to understand the psychological mechanisms underlying the experience of feeling an emotion. In this study, we aimed to understand how the interoceptive processing in an emotional context relates to problems of alexithymia in recognizing self-emotions. Therefore, we prepared experimental conditions to induce emotional awareness based on interoceptive information. As such, we asked participants to be aware of interoception under an anxiety-generating situation anticipating pain, having them evaluate their subjective anxiety levels in this context. High alexithymia participants showed attenuated functional connectivity within their 'interoception network', particularly between the insula and the somatosensory areas when they focused on interoception. In contrast, they had enhanced functional connectivity between these regions when they focused on their anxiety about pain. Although access to somatic information is supposed to be more strongly activated while attending to interoception in the context of primary sensory processing, high alexithymia individuals were biased as this process was activated when they felt emotions, suggesting they recognize primitive and unprocessed bodily sensations as emotions. The paradoxical somatic information processing may reflect their brain function pathology for feeling emotions and their difficulty with context-dependent emotional control.

Products With High Purchase Frequency Require Greater Inhibitory Control: An Event-Related Potential Study.

One's past behavior influences their present behavior. The effects of such response history have often been tested using response inhibition tasks. Since previous studies have highlighted the effect of immediate action history formed directly before the subsequent response in a laboratory environment, we aimed to elucidate the longer-term effects of response history, using repetitive and habitual consumer behavior in daily life as the response history. We used event-related potentials recorded in a Go/No-go task to investigate brain activity related to inhibitory control, hypothesizing that stimuli with a high frequency of choice in everyday life would elicit stronger inhibition-related activity, that is, the No-go-N2 component. Participants were asked to evaluate the frequency of purchase and use of some products, such as food and drink or social networking services (SNS) in everyday situations. Images of each product were assigned as stimuli in the Go and No-go trials according to the frequency of choice. The results showed that frequently purchased No-go stimuli yielded a larger amplitude of the No-go-N2 component and a negative shift between 200 and 300ms after the presentation of No-go stimuli. The results suggest that frequently chosen products evoke stronger inhibition conflicts and require greater cognitive control to withhold a response. Our findings showed that repeated purchase behavior in daily life forms a response history and has a long-term influence on the inhibition of even simple approaching behaviors, such as button pressing.

The effect of haptic stimulation simulating heartbeats on the regulation of physiological responses and prosocial behavior under stress: The influence of interoceptive accuracy.

Research has discovered the modulatory effect of peripheral stimulation simulating altered bodily signals on emotion. Whether such an effect varies depending on one's interoceptive accuracy (IAc) remains unclear. Therefore, we provided haptic stimulation simulating participants' slowed-down heartbeats or no stimulation while they engaged in socially stressful tasks to examine whether participants reacted differently depending on their IAc. Results showed that haptic stimulation exhibited the opposite effect on participants with different levels of IAc for both heart rate and heart rate variability (HRV). When receiving the stimulation, participants with higher IAc showed less increased heart rate and more elevated HF than participants with lower IAc. In contrast, in the absence of stimulation, an opposite pattern of response depending on participants' IAc was observed. The modulatory effect of stimuli and IAc on prosocial behavior was not significant. Individual differences in IAc were shown to affect how one perceives/responds to altered bodily signals.

Effects of interoceptive accuracy in autonomic responses to external stimuli based on cardiac rhythm.

Interoceptive accuracy is an index of the ability to perceive an individual's internal bodily state, including heartbeat and respiration. Individual differences in interoceptive accuracy influence emotional recognition through autonomic nervous activity. However, the precise mechanism by which interoceptive accuracy affects autonomic reactivity remains unclear. Here, we investigated how cardiac reactivity induced by a non-affective external rhythm differed among individuals, using a heartbeat counting task. Because individuals with poor interoceptive accuracy cannot distinguish an external rhythm from their cardiac cycles, it has been hypothesized that the interoceptive effect on heart rate works differently in individuals with good interoceptive accuracy and those with poor interoceptive accuracy. Study participants observed a visual or auditory stimulus presented at a rhythm similar to the participants' resting heart rates. The stimulus rhythm was gradually changed from that of their resting heart rate, and we recorded electrocardiographs while participants were exposed to the stimuli. Individuals with good interoceptive accuracy exhibited a deceleration in heart rate when the rhythm of the auditory stimulus changed. In contrast, in the group with poor interoceptive accuracy, the heart rate decreased only when the stimulus became faster. They were unable to distinguish the rhythm of their own heartbeat from that of the external rhythm; therefore, we propose that such individuals recognize the stimuli at the pace of their heart rate. Individuals with good interoceptive accuracy were able to distinguish their heart rates from the external rhythm. A modality difference was not observed in this study, which suggests that both visual and auditory stimuli help mimic heart rate. These results may provide physiological evidence that autonomic reactivity influences the perception of the internal bodily state, and that interoception and the autonomic state interact to some degree.

The Role of the Thalamus in the Neurological Mechanism of Subjective Sleepiness: An fMRI Study.

PURPOSE: The thalamus, the region that forms the attentional network and transmits external sensory signals to the entire brain, is important for sleepiness. Herein, we examined the relationship between activity in the thalamus-seed brain network and subjective sleepiness. MATERIALS AND METHODS: Fifteen healthy male participants underwent an experiment comprising a baseline evaluation and two successive interventions, a 9-day sleep extension followed by 1-night total sleep deprivation. Pre- and post-intervention tests included the Karolinska sleepiness scale and neuroimaging for arterial spin labeling and functional connectivity. We examined the association between subjective sleepiness and the functional magnetic resonance imaging indices. RESULTS: The functional connectivity between the left or right thalamus and various brain regions displayed a significant negative association with subjective sleepiness, and the functional connectivity between the left and right thalamus displayed a significant positive association with subjective sleepiness. The graph theory analysis indicated that the number of positive functional connectivity related to the thalamus showed a strong negative association with subjective sleepiness, and conversely, the number of negative functional connectivity showed a positive association with subjective sleepiness. Arterial spin labeling analysis indicated that the blood flow in both the left and right thalami was significantly negatively associated with subjective sleepiness. Functional connectivity between the anterior cingulate cortex and salience network areas of the left insular cortex, and that between the anterior and posterior cingulate cortices showed a strong positive and negative association with subjective sleepiness, respectively. CONCLUSION: Subjective sleepiness and the thalamic-cortical network dynamics are strongly related, indicating the application of graph theory to study sleepiness and consciousness. These results also demonstrate that resting functional connectivity largely reflects the "state" of the subject, suggesting that the control of sleep and conscious states is essential when using functional magnetic resonance imaging indices as biomarkers.

Effects of insular resection on interactions between cardiac interoception and emotion recognition.

The insular cortex is considered an important region for feeling emotions through interoception. Most studies that report the role of the insula in integrating interoception and emotion have used neuroimaging techniques such as functional magnetic resonance imaging (fMRI); however, there are limited neuropsychological studies. The effects of insular lesions on emotion and interoception have not been suitably investigated. In this study, we examined the role of the insular cortex in cardiac interoception and recognizing emotions from facial expressions by comparing them pre- and post-operatively in patients with glial tumors or brain metastases associated with the insular lobe. Although no significant difference in interoceptive accuracy was observed between the two phases, there were significant associations between the changes in interoceptive accuracy and sensitivity to expressions of anger and happiness. An increased error rate in the heartbeat counting task in the post-operation phase was associated with a decreased accuracy in recognizing anger and happiness. Since most patients had left insula lesions, generalizability of the findings to patients with right lesions is a future subject. To the best of our knowledge, this is the first study to examine the change in interoception and emotion after insular resection in humans. The study results indicate that removal of the insula affects the recognition of emotions such as anger and happiness through interoceptive processing.

Decreased activity in the reward network of chronic insomnia patients.

In modern society, many people have insomnia. Chronic insomnia has been noted as a risk factor for depression. However, there are few functional imaging studies of the brain on affective functions in chronic insomnia. This study aimed to investigate brain activities induced by emotional stimuli in chronic insomnia patients. Fifteen patients with primary insomnia and 30 age and gender matched healthy controls participated in this study. Both groups were presented images of fearful, happy, and neutral expressions consciously and non-consciously while undergoing MRI to compare the activity in regions of the brain responsible for emotions. Conscious presentation of the Happy-Neutral contrast showed significantly lower activation in the right orbitofrontal cortex of patients compared to healthy controls. The Happy-Neutral contrast presented in a non-conscious manner resulted in significantly lower activation of the ventral striatum, right insula, putamen, orbitofrontal cortex and ventral tegmental area in patients compared to healthy controls. Our findings revealed that responsiveness to positive emotional stimuli were decreased in insomniac patients. Specifically, brain networks associated with rewards and processing positive emotions showed decreased responsiveness to happy emotions especially for non-conscious image. The magnitude of activity in these areas also correlated with severity of insomnia, even after controlling for depression scale scores. These findings suggest that insomnia induces an affective functional disorder through an underlying mechanism of decreased sensitivity in the regions of the brain responsible for emotions and rewards to positive emotional stimuli.

Effects of interoceptive training on decision making, anxiety, and somatic symptoms.

BACKGROUND: Interoception is the perception of afferent information that arises from any point within the body. Individual differences in interoception have been associated with affective processing and decision-making processing. The somatic marker hypothesis summarizes the potential effects of interoception on decision-making processes. According to this theory, individuals with interoceptive dysfunction exhibit disadvantageous decision making. Recently, enhancement of interoceptive accuracy, an element of interoception assessed by objective decision-making tasks, has been demonstrated using biofeedback. Garfinkle et al. developed an interoceptive training task, modified from the heartbeat perception task, which enhanced interoceptive accuracy and reduced anxiety symptoms. The purpose of this study was to determine the effects of interoceptive training on decision-making processes. Based on improvements in interoceptive accuracy, we hypothesized that decision-making scores would change in a manner indicative of increased rationality. METHODS: This longitudinal interventional study was performed with interoceptive training. Before and after the intervention, interoceptive accuracy and rationality of decision-making processes were assessed using a heartbeat perception task and rational decision-making tasks, respectively. Fourteen healthy volunteers (nine women; mean age, 21.9 ± 4.5 years) participated. The analysis included data from 12 participants. To detect individual differences in the effects of interoceptive accuracy on rationality of decision making, correlation analysis was conducted on change ratios of the indices of interoceptive accuracy and rationality of decision making. RESULTS: Interoceptive training resulted in significant enhancement of interoceptive accuracy scores and significant reductions in somatic symptom and state anxiety scores. In contrast, interoceptive training did not cause significant changes in decision-making indices. There was a significant positive correlation between change ratios of indices of interoceptive accuracy and rationality of decision making. CONCLUSIONS: The results suggested a causal relation between interoception and rationality of decision making. These findings will enhance the understanding of mechanisms underlying alterations of decision-making related to psychotherapy by focusing on interoception. TRIAL REGISTRATION: Trial registration number: UMIN000037548.

Neural and clinical changes of cognitive behavioural therapy versus talking control in patients with major depression: a study protocol for a randomised clinical trial.

INTRODUCTION: While major depression causes substantial distress and impairment for affected individuals and society, the effectiveness of cognitive behavioural therapy (CBT) in treating the condition has been established. However, the therapeutic mechanism underlying the efficacy of CBT remains unknown. This study aimed to describe a protocol for a randomised controlled trial that will measure the CBT-induced clinical and neural changes in patients with non-psychotic major depression. METHODS AND ANALYSIS: The current study is a 16-week assessor-blinded, randomised, parallel-group trial with a 12-month follow-up as part of usual depression care at an outpatient clinic. Patients aged 20-69 years with major depressive disorder will be randomly assigned to receive either CBT in addition to their usual treatment or talking control in addition to their usual treatment for 16 weeks. The primary outcome is the functional changes in the brain areas that have been associated with future-oriented thinking at 16 weeks; secondary outcomes include changes in functional brain connectivity, severity and changes in the scores of objective and subjective clinical depression symptoms, proportion of responders and remitters and quality of life. The intention-to-treat analysis will be used. ETHICS AND DISSEMINATION: All protocols and the informed consent form are compliant with the Ethics Guideline for Clinical Research (Japanese Ministry of Health, Labour and Welfare). Ethical Review Committees at the Keio University School of Medicine have approved the study protocol (version 3, 11 September 2017). We will disseminate research findings to scientific and general audiences through national and international conference presentations as well as lay summaries to the general public, including mental health consumer and publications in international peer-reviewed psychiatry and brain imaging journals. TRIAL REGISTRATION NUMBER: UMIN Clinical Trials Registry (UMIN000018155); Pre-results.