A study of the cortical processing of ano-rectal sensation using functional MRI

Primary somatosensory cortex organization for engineering artificial somatosensation

Somatosensory deficits from stroke, spinal cord injury, or other neurologic damage can lead to a significant degree of functional impairment. The primary (SI) and secondary (SII) somatosensory cortices encode information in a medial to lateral organization. SI is generally organized topographically, with more discrete cortical representations of specific body regions. SII regions corresponding to anatomical areas are less discrete and may represent a more functional rather than topographic organization. Human somatosensory research continues to map cortical areas of sensory processing with efforts primarily focused on hand and upper extremity information in SI. However, research into SII and other body regions is lacking. In this review, we synthesize the current state of knowledge regarding the cortical organization of human somatosensation and discuss potential applications for brain computer interface. In addition to accurate individualized mapping of cortical somatosensation, further research is required to uncover the neurophysiological mechanisms of how somatosensory information is encoded in the cortex.

Bowel dysfunctions after acquired brain injury: a scoping review

Bowel dysfunction is a common consequence of neurological diseases and has a major impact on the dignity and quality of life of patients. Evidence on neurogenic bowel is focused on spinal cord injury and multiple sclerosis; few studies have focused on patients with acquired brain injury (ABI). Neurogenic bowel dysfunction is related to a lifelong condition derived from central neurological disease, which further increases disability and social deprivation. The manifestations of neurogenic bowel dysfunction include fecal incontinence and constipation. Almost two out of three patients with central nervous system disorder have bowel impairment. This scoping review aims to comprehend the extent and type of evidence on bowel dysfunction after ABI and present conservative treatment. For this scoping review, the PCC (population, concept, and context) framework was used: patients with ABI and bowel dysfunction; evaluation and treatment; and intensive/extensive rehabilitation path. Ten full-text articles were included in the review. Oral laxatives are the most common treatment. The Functional Independence Measure (FIM) subscale is the most common scale used to assess neurogenic bowel disease (60%), followed by the Rome II and III criteria, and the colon transit time is used to test for constipation; however, no instrumental methods have been used for incontinence. An overlapping between incontinence and constipation, SCI and ABI increase difficulties to manage NBD. The need for a consensus between the rehabilitative and gastroenterological societies on the diagnosis and medical care of NBD.

Systematic review registration

Open Science Framework on August 16, 2022 https://doi.org/10.17605/OSF.IO/NEQMA.

Imaging and clinical predictors of acute constipation in patients with acute ischemic stroke

Background

Constipation symptoms are highly prevalent in acute ischemic stroke, but the clinical and neuroimaging predictors are unknown. This study aimed to identify lesions and clinical features associated with acute constipation.

Methods

Data from patients with acute ischemic stroke registered in a hospital-based stroke registry between January 2018 and December 2019 were analyzed. Clinical, laboratory, and imaging features were examined for associations with acute constipation. Using the topographic lesion on diffusion-weighted images, multivariate support vector regression-based lesion-symptom mapping (SVR-LSM) was conducted and compared between the non-constipation and acute constipation groups.

Results

A total of 256 patients (mean age 67 years, men: 64%) were included. Acute constipation was noted in 81 patients (32%). Initial stroke severity, represented by initial National Institutes of Health and Stroke Scale (NIHSS) scores, was associated with acute constipation. Laboratory parameters, including fibrin degradation products (FDP), fibrinogen, D-dimer, lipoprotein (a), and free fatty acid levels, also showed statistically significant differences between the non-constipation and constipation groups. FDP, D-dimer, and free fatty acid levels were independently associated with acute constipation in the logistic regression model after adjusting for initial NIHSS scores and potassium levels. SVR-LSM revealed that bilateral lesions in the precentral gyrus, insula, opercular part of the inferior frontal gyrus, the inferior parietal lobule, and lesions in the right middle frontal gyrus were significantly associated with acute constipation. The results were consistent after controlling for the initial NIHSS scores and poststroke potassium levels. When cardioembolic stroke subjects were excluded, the right insular and prefrontal cortex lesions lost their association with acute constipation.

Conclusion

Acute constipation symptoms after acute ischemic stroke are mainly related to bilateral lesions in the insula, precentral gyrus, postcentral gyrus, and inferior parietal lobule. Clinically important predictors of acute constipation include initial neurological severity and thromboembolic markers of stroke.

Sensory brain activation during rectal balloon distention: a pilot study in healthy volunteers to assess safety and feasibility at 1.5T

OBJECTIVE

Although increasing evidence suggests a central mechanism of action for sacral neuromodulation, the exact mechanism remains unclear. We set up a scanning paradigm to measure brain activation related to various stages of rectal filling using rectal balloon distention.

MATERIALS AND METHODS

Six healthy volunteers underwent rectal balloon distention during MRI scanning at a 1.5T scanner with a Tx/Rx head coil. MR images were collected at four levels of distention: empty balloon (EB), first sensation volume (FSV), desire to defecate volume (DDV), maximum tolerable volume (MTV). Data were analyzed using BrainVoyager 20.4. Whole brain and ROI-based fixed-effects general linear model analyses were performed on the fMRI time-course data from all participants.

RESULTS

Rectal filling until FSV evoked the most blood-oxygen-level-dependent responses in several clusters throughout the cortex, followed by the responses evoked by rectal filling until DDV. Interestingly, rectal filling until MTV evoked negative responses compared to baseline throughout the cortex. No negative side effects were found.

DISCUSSION

This study shows that a standardized paradigm for functional MRI combined with rectal filling is feasible and safe in healthy volunteers and is ready to be used in fecal incontinent patients to assess whether their brain activity differs from healthy controls.

Neuroimaging Study Investigating the Supraspinal Control of Lower Urinary Tract Function in Man With Orthotopic Ileal Neobladder

Introduction: Recent studies employing functional imaging methodology have revealed reference brain regions of urinary tract function, namely, the midbrain periaqueductal gray matter, thalamus, and cingulate and prefrontal cortices. The orthotopic ileal neobladder is a desirable method for urinary diversion after radical cystectomy, but its supraspinal control remains unknown. We aimed to evaluate brain activity while maintaining urinary urgency and voluntary urinary control in male subjects with ileal orthotopic neobladders by performing functional MRI (fMRI) during a block design experiment. Materials and Methods: Patients were recruited at the Sun Yat-sen Memorial Hospital of the Sun Yat-sen University from October 2017 to May 2019. Two tasks were performed during fMRI scanning: (1) repeated infusion and withdrawal of sterile saline solution into and out of the neobladder to simulate urgency; and (2) repeated contraction of the pelvic floor muscle with a full neobladder to induce inhibition of micturition since the subjects were asked not to urinate. The obtained data were visualized and statistically analyzed. Results: Sixteen subjects were recruited in the study, and data were obtained from 10 subjects: mean age 60.1 years, average postoperative time 20.2 months, and daytime continence rate 100%. The parahippocampus, frontal lobe, vermis, and anterior cingulate cortex were activated with large bladder volumes, and the thalamus and caudate nucleus were deactivated during voluntary urinary control. Conclusion: A complex supraspinal program is involved during ileal orthotopic neobladder control, which is significantly different from that with normal bladders, in which the original intestine visceral volume sensation is preserved.

Insular cortex neurons encode and retrieve specific immune responses

Increasing evidence indicates that the brain regulates peripheral immunity, yet whether and how the brain represents the state of the immune system remains unclear. Here, we show that the brain's insular cortex (InsCtx) stores immune-related information. Using activity-dependent cell labeling in mice (Fos^TRAP), we captured neuronal ensembles in the InsCtx that were active under two different inflammatory conditions (dextran sulfate sodium [DSS]-induced colitis and zymosan-induced peritonitis). Chemogenetic reactivation of these neuronal ensembles was sufficient to broadly retrieve the inflammatory state under which these neurons were captured. Thus, we show that the brain can store and retrieve specific immune responses, extending the classical concept of immunological memory to neuronal representations of inflammatory information.

Atypical interoception as a common risk factor for psychopathology: A review

The inadequacy of a categorial approach to mental health diagnosis is now well-recognised, with many authors, diagnostic manuals and funding bodies advocating a dimensional, trans-diagnostic approach to mental health research. Variance in interoception, the ability to perceive one's internal bodily state, is reported across diagnostic boundaries, and is associated with atypical functioning across symptom categories. Drawing on behavioural and neuroscientific evidence, we outline current research on the contribution of interoception to numerous cognitive and affective abilities (in both typical and clinical populations), and describe the interoceptive atypicalities seen in a range of psychiatric conditions. We discuss the role that interoception may play in the development and maintenance of psychopathology, as well as the ways in which interoception may differ across clinical presentations. A number of important areas for further research on the role of interoception in psychopathology are highlighted.

Interoception and Emotion: A Potential Mechanism for Intervention With Manual Treatment

Interoception is considered a perception pathway as important as the exteroceptive pathways for determining responses to maintain homeostasis. There is evidence about the influence of the interoception on emotional responses as these expressions are considered to be a combination of physical, environmental and individual beliefs. A large percentage of afferent fibers in the body are related to free nerve endings which, when stimulated, reach the insular cortex that participates in the process of emotions. The viscera afferent fibers represent 5% to 15% of all these inputs. Evidence emerges that demonstrates the importance of visceral health as part of the treatment of patients with emotional imbalances. It can be postulated that manual treatment applied to visceral fasciae can assist in interoceptive balance and have a positive impact on emotions. Therefore, the objective of the present study is to discuss the concepts of interoception, central sensitization, emotional health and visceral manual treatment.

Pain matrix shift in the rat brain following persistent colonic inflammation revealed by voxel-based statistical analysis

Inflammatory bowel disease (IBD), mainly comprising Crohn’s disease and ulcerative colitis, is characterized by chronic inflammation in the digestive tract. Approximately 60% of the patients experience abdominal pain during acute IBD episodes, which severely impairs their quality of life. Both peripheral and central mechanisms are thought to be involved in such abdominal pain in IBD. Although much attention has been paid to peripheral mechanisms of abdominal pain in IBD pathophysiology, the involvement of supraspinal mechanisms remains poorly understood. To address this issue, we investigated regional brain activity in response to colorectal distension in normal and IBD model rats using voxel-based statistical analysis of 2-deoxy-2-[18F]fluoro-_D-glucose positron emission tomography imaging. The rat IBD model was generated by colorectal administration of 2,4,6-trinitrobenzene sulfonic acid, a chemical compound widely used to generate colitis. Tissue damage and inflammation were induced and dynamically changed with time after 2,4,6-trinitrobenzene sulfonic acid injection, while colorectal distension-induced visceromotor response showed corresponding temporal changes. We found that characteristic brain activations were observed in response to visceral innocuous and noxious colorectal distension and supraspinal nociception shared some physiological sensory pathway. Moreover, widespread brain regions were activated, and the functional coupling between the central medial thalamic nucleus and anterior cingulate cortex was enhanced after noxious colorectal distension in IBD model of rats. Increased brain activity in the anterior insular cortex and anterior cingulate cortex was positively correlated with noxious colorectal distension-induced pain severity in normal and IBD rats, respectively. These findings suggest that the pain matrix was shifted following persistent colonic inflammation, and thalamocortical sensitization in the pathway from the central medial thalamic nucleus to anterior cingulate cortex might be a central mechanism of the visceral hyperalgesia in IBD pathophysiology.

Single subject and group whole-brain fMRI mapping of male genital sensation at 7 Tesla

Processing of genital sensations in the central nervous system of humans is still poorly understood. Current knowledge is mainly based on neuroimaging studies using electroencephalography (EEG), magneto-encephalography (MEG), and 1.5- or 3- Tesla (T) functional magnetic resonance imaging (fMRI), all of which suffer from limited spatial resolution and sensitivity, thereby relying on group analyses to reveal significant data. Here, we studied the impact of passive, yet non-arousing, tactile stimulation of the penile shaft using ultra-high field 7T fMRI. With this approach, penile stimulation evoked significant activations in distinct areas of the primary and secondary somatosensory cortices (S1 & S2), premotor cortex, insula, midcingulate gyrus, prefrontal cortex, thalamus and cerebellum, both at single subject and group level. Passive tactile stimulation of the feet, studied for control, also evoked significant activation in S1, S2, insula, thalamus and cerebellum, but predominantly, yet not exclusively, in areas that could be segregated from those associated with penile stimulation. Evaluation of the whole-brain activation patterns and connectivity analyses indicate that genital sensations following passive stimulation are, unlike those following feet stimulation, processed in both sensorimotor and affective regions.

Regions of the brain activated in bladder filling vs rectal distention in healthy adults: A meta-analysis of neuroimaging studies

AIMS

Adults with pelvic floor disorders commonly present with overlapping bladder and bowel symptoms; however, the relationship between urinary and defecatory dysfunction is not well understood. Our aim was to compare and determine if overlapping brain regions are activated during bladder filling and rectal distention in healthy adults.

METHODS

We conducted separate Pubmed searches for neuroimaging studies investigating the effects of rectal distention and bladder filling on brain activation in healthy subjects. Coordinates of activated regions were extracted with cluster-level threshold P < .05 and compared using the activation likelihood estimate approach. Results from the various studies were pooled and a contrast analysis was performed to identify any common areas of activation between bladder filling and rectal distension.

RESULTS

We identified 96 foci of activation from 14 neuroimaging studies on bladder filling and 182 foci from 17 studies on rectal distension in healthy adults. Regions activated during bladder filling included right insula, right and left thalamus, and right periaqueductal grey. Regions activated during rectal distention included right and left insula, right and left thalamus, left postcentral gyrus, and right inferior parietal lobule. Contrast analysis revealed common activation of the right insula with both rectal distention and bladder filling.

CONCLUSION

Bladder filling and rectal distention activate several separate areas of the brain involved in sensory processing in healthy adults. The common activation of the insula, the region responsible for interoception, in these two conditions may offer an explanation for the coexistence of bladder and defecatory symptoms in pelvic floor disorders.

Reward

Neurons throughout frontal cortex show robust responses to rewards, but a challenge is determining the specific function served by these different reward signals. Most neuropsychiatric disorders involve dysfunction of circuits between frontal cortex and subcortical structures, such as the striatum. There are multiple frontostriatal loops, and different neuropsychiatric disorders involve different loops to greater or lesser extents. Understanding the role of reward in each of these different circuits is a necessary step in developing novel treatments for these disorders. This chapter summarizes the recent literature that has identified the role of reward in different subregions of the frontal cortex. Orbitofrontal cortex integrates information about multiple aspects of expected rewards in order to derive their value, which can then be used to decide between alternative potential rewards. Neurons in anterior cingulate cortex encode the difference between the expected reward and the actual outcome. This information is useful for learning, since it can ensure that behavior changes when the outcome was not anticipated. Reward also affects signals in lateral prefrontal cortex related to attention and response selection, ensuring that behaviors are optimally prioritized. Finally, the chapter discusses how reward signals contribute to social processing and autonomic control.

No Relationships Between the Within-Subjects' Variability of Pain Intensity Reports and Variability of Other Bodily Sensations Reports

Purpose

The subjective nature of pain assessment and its large variance negatively affect patient–health care provider communication and reduce the assay sensitivity of pain clinical trials. Given the lack of an objective gold standard measure, identifying the source (true or error) of the within-subject variability of pain reports is a challenge. By assessing the within-subjects variability of pain and taste reports, alongside with interoceptive measures, the current study is aimed to investigate if the ability to reliably report bodily sensations is a cross-modal characteristic.

Patients and Methods

This prospective study enrolled healthy volunteers from local universities. After consenting, subjects underwent the Focus Analgesia Selection Task (FAST), to assess within-subjects variability of pain reports in response to experimental noxious stimuli; a taste task, which similarly assesses within-subjects variability of tastes (salty and sweet) intensity reports; and the heartbeat perception task, an interoceptive task aimed to assess how accurate subjects are in monitoring and reporting their own heartbeat. In addition, all subjects completed the Multidimensional Assessment of Interoceptive Awareness (MAIA), the Perceived Stress Scale (PSS), and Hospital Anxiety and Depression Scale (HADS). Spearman’s correlations were used to assess relations between all measures.

Results

Sixty healthy volunteers were recruited. Variability of intensity reports of different modalities were independent of each other (P > 0.05 for all correlations). The only correlation found was within modality, between variability of intensity reports of salt and sweet tastes (Spearman’s r = 0.477, P < 0.001). No correlations were found between any of the task results and questionnaire results.

Conclusion

Within-subjects variability of pain reports do not relate to variability of reports of other modalities or to interoceptive awareness. Further research is ongoing to investigate the clinical relevance of within-subjects’ variability of pain reports.

Defective Conduction of Anorectal Afferents Is a Very Prevalent Pathophysiological Factor Associated to Fecal Incontinence in Women

Background/Aims

Fecal incontinence (FI) is a prevalent condition among women. While biomechanical motor components have been thoroughly researched, anorectal sensory aspects are less known. We studied the pathophysiology of FI in community-dwelling women, specifically, the conduction through efferent/afferent neural pathways.

Methods

A cross-sectional study was conducted on 175 women with FI and 19 healthy volunteers. The functional/structural study included anorectal manometry/endoanal ultrasound. Neurophysiological studies including pudendal nerve terminal motor latency (PNTML) and sensory-evoked-potentials to anal/rectal stimulation (ASEP/RSEP) were conducted on all healthy volunteers and on 2 subgroups of 42 and 38 patients, respectively.

Results

The main conditions associated with FI were childbirth (79.00%) and coloproctological surgery (37.10%). Cleveland score was 11.39 ± 4.09. Anorectal manometry showed external anal sphincter and internal anal sphincter insufficiency in 82.85% and 44.00%, respectively. Sensitivity to rectal distension was impaired in 27.42%. Endoanal ultrasound showed tears in external anal sphincter (60.57%) and internal anal sphincter disruptions (34.80%). Abnormal anorectal sensory conduction was evidenced through ASEP and RSEP in 63.16% and 50.00% of patients, respectively, alongside reduced activation of brain cortex to anorectal stimulation. In contrast, PNTML was delayed in only 33.30%. Stools were loose/very loose in 56.70% of patients.

Conclusions

Pathophysiology of FI in women is mainly associated with mechanical sphincter dysfunctions related to either muscle damage or, to a lesser extent, impaired efferent conduction at pudendal nerves. Impaired conduction through afferent anorectal pathways is also very prevalent in women with FI and may play an important role as a pathophysiological factor and as a potential therapeutic target.

Brain MRI Lesions are Related to Bowel Incontinence in Multiple Sclerosis

BACKGROUND AND PURPOSE

Bowel incontinence in multiple sclerosis might be associated with specific lesion sites. This study intended to determine associations between bowel incontinence and cerebral multiple sclerosis lesions using a voxel-wise lesion symptom mapping analysis.

METHODS

We conducted a retrospective study of multiple sclerosis patients with self-reported bowel incontinence and matched controls. Lesions were manually outlined on T2-weighted MRI scans and transformed into stereotaxic space. We performed a voxel-wise subtraction analysis subtracting the lesion overlap of patients without from patients with bowel incontinence. Finally, we compared the absence or presence of bowel incontinence between patients with and without lesions in a given voxel using the Liebermeister test.

RESULTS

A total of 51 patients were included in the study. The analysis yielded associations between bowel incontinence and lesions in the supramarginal gyrus of the left secondary somatosensory cortex and another lesion cluster in the right parahippocampal gyrus and amygdala.

CONCLUSIONS

Our analysis indicates associations between bowel incontinence and lesions in the left supramarginal gyral area contributing to integrating anorectal-visceral sensation and in the right parahippocampal gyrus and amygdala contributing to generating visceral autonomic arousal states. Moreover, our results suggest left hemispheric dominance of sensory visceral integration, while limbic areas of the right hemisphere seem to contribute to the autonomic component of the defecation process. A limitation of our study is the retrospective evaluation of the bowel incontinence status based on medical records. Further research should evaluate the bowel incontinence status in multiple sclerosis patients prospectively to overcome the limitations of the current study.

Brain responses to mechanical rectal stimulation in patients with faecal incontinence: an fMRI study

AIM

Continence is dependent on anorectal-brain interactions. Consequently, aberrations of the brain-gut axis may be important in the pathophysiology of faecal incontinence (FI) in certain patients. The aim of this study was to assess the feasibility of recording brain responses to rectal mechanical stimulation in patients with FI using functional magnetic resonance imaging (fMRI).

METHOD

A prospective, cohort pilot study was performed to assess brain responses during rectal stimulation in 14 patients [four men, mean (SD) age 62 (15) years]. Blood oxygen level dependent (BOLD) signals were measured by fMRI during rest and mechanical distension, involving random repetitions of isobaric phasic rectal distensions at fixed (15 and 45 mmHg) and variable (10% above sensory perception threshold) pressures.

RESULTS

Increases in BOLD signals in response to high pressure rectal distension (45 mmHg) and maximum toleration were observed in the cingulate gyrus, thalamus, insular cortex, inferior frontal gyrus, cerebellum, caudate nucleus, supramarginal gyrus, putamen and amygdala. Additionally, activation of the supplementary motor cortex and caudate nucleus with inconsistent activity in the frontal lobe was observed.

CONCLUSIONS

This study has demonstrated the feasibility of recording brain responses to rectal mechanical stimulation using fMRI in patients with FI, revealing activity in widespread areas of the brain involved in visceral sensory processing. The observed activity in the supplementary motor cortex and caudate nucleus, with relative paucity of activity in the frontal lobes, warrants investigation in future studies to determine whether aberrations in cerebral processing of rectal stimuli play a role in the pathogenesis of FI.

Neural correlates of interoception: Effects of interoceptive focus and relationship to dimensional measures of body awareness

Interoception has been defined as the sensing of the physiological condition of the body, with interoceptive sensibility (IS) characterizing an individual's self-reported awareness of internal sensation. IS is a multidimensional construct including not only the tendency to be aware of sensation but also how sensations are interpreted, regulated, and used to inform behavior, with different dimensions relating to different aspects of health and disease. Here we investigated neural mechanisms of interoception when healthy individuals attended to their heartbeat and skin temperature, and examined the relationship between neural activity during interoception and individual differences in self-reported IS using the Multidimensional Scale of Interoceptive Awareness (MAIA). Consistent with prior work, interoception activated a network involving insula and sensorimotor regions but also including occipital, temporal, and prefrontal cortex. Differences based on interoceptive focus (heartbeat vs skin temperature) were found in insula, sensorimotor regions, occipital cortex, and limbic areas. Factor analysis of MAIA dimensions revealed 3 dissociable components of IS in our dataset, only one of which was related to neural activity during interoception. Reduced scores on the third factor, which reflected reduced ability to control attention to body sensation and increased tendency to distract from and worry about aversive sensations, was associated with greater activation in many of the same regions as those involved in interoception, including insula, sensorimotor, anterior cingulate, and temporal cortex. These data suggest that self-rated interoceptive sensibility is related to altered activation in regions involved in monitoring body state, which has implications for disorders associated with abnormality of interoception. Hum Brain Mapp 38:6068-6082, 2017. © 2017 Wiley Periodicals, Inc.

Mapping of Brain Activations to Rectal Balloon Distension Stimuli in Male Patients with Irritable Bowel Syndrome Using Functional Magnetic Resonance Imaging

Background/Aims

Irritable bowel syndrome (IBS) is associated with exaggerated cerebral response including emotional processing following visceral stimulation; though data on this issue is available in female IBS patients, it is scanty among males. Hence, we aimed to study brain response of male IBS patients following rectal balloon distension as compared to healthy controls using functional magnetic resonance imaging (fMRI). Data between diarrhea and constipation predominant IBS (IBS-D and IBS-C) were also compared.

Methods

Rectal balloon distension threshold was assessed in 20 male IBS patients (10 IBS-C and 10 IBS-D) and 10 age-matched male healthy controls. Subsequently, fMRI on all the participants was performed at their respective rectal pain threshold. The fMRI data were analysed using the Statistical Parametric Mapping software.

Results

IBS patients showed greater cerebral activations in insula, middle temporal gyrus, and cerebellum in the left hemisphere compared to healthy controls. Neural activation was found in bilateral precuneus/superior parietal lobules in controls but not in patients with IBS. The brain activation differed among IBS-C and IBS-D patients; while the right mid-cingulate cortex was activated in IBS-C, the left inferior orbito-frontal cortex, left calcarine, and bilateral fusiform gyri were activated among patients with IBS-D following rectal balloon distension.

Conclusions

Brain response to rectal balloon distension differed among male patients with IBS and controls and among patients with IBS-C and IBS-D. Differential activation among patients with IBS-C and IBS-D was seen in the brain regions controlling affective motivation, homeostatic emotions, and autonomic responses to pain.

Interoceptive dimensions across cardiac and respiratory axes

Interoception refers to the sensing of signals concerning the internal state of the body. Individual differences in interoceptive sensitivity are proposed to account for differences in affective processing, including the expression of anxiety. The majority of investigations of interoceptive accuracy focus on cardiac signals, typically using heartbeat detection tests and self-report measures. Consequently, little is known about how different organ-specific axes of interoception relate to each other or to symptoms of anxiety. Here, we compare interoception for cardiac and respiratory signals. We demonstrate a dissociation between cardiac and respiratory measures of interoceptive accuracy (i.e. task performance), yet a positive relationship between cardiac and respiratory measures of interoceptive awareness (i.e. metacognitive insight into own interoceptive ability). Neither interoceptive accuracy nor metacognitive awareness for cardiac and respiratory measures was related to touch acuity, an exteroceptive sense. Specific measures of interoception were found to be predictive of anxiety symptoms. Poor respiratory accuracy was associated with heightened anxiety score, while good metacognitive awareness for cardiac interoception was associated with reduced anxiety. These findings highlight that detection accuracies across different sensory modalities are dissociable and future work can better delineate their relationship to affective and cognitive constructs.This article is part of the themed issue 'Interoception beyond homeostasis: affect, cognition and mental health'.

Influence of Rectal Decompression on Abdominal Symptoms and Anorectal Physiology following Colonoscopy in Healthy Adults

Background. Postcolonoscopy abdominal discomfort and bloating are common. The aim of this study was to evaluate whether rectal decompression improved distension-induced abdominal symptoms and influenced anorectal physiology. Methods. In 15 healthy subjects, rectal distension was achieved by direct air inflation into the rectum by colonoscopy. Placement of rectal and sham tube was then performed in each subject on a separate occasion. The anorectal parameters and distension-induced abdominal symptoms were recorded. Results. Anorectal parameters were similar between placements of rectal tube and sham tube except for greater rectal compliance with rectal tube than with sham tube (P < 0.05). Abdominal pain and bloating were significantly reduced by rectal tube and sham tube at 1 minute (both P < 0.05) and 3 minutes (both P < 0.05). After placement of rectal tube, abdominal pain at 3 minutes correlated positively with first sensation (r = 0.53, P = 0.04), and bloating at 3 minutes also correlated positively with urge sensation (r = 0.55, P = 0.03). Conclusions. Rectal decompression with either rectal or sham tube improved distension-induced abdominal symptoms. Our study indicates that the mechanisms that improved abdominal symptoms by rectal decompression might be mediated by a central pathway instead of a peripheral mechanism.

Abdominal Pain, the Adolescent and Altered Brain Structure and Function

Irritable bowel syndrome (IBS) is a functional gastrointestinal (GI) disorder of unknown etiology. Although relatively common in children, how this condition affects brain structure and function in a pediatric population remains unclear. Here, we investigate brain changes in adolescents with IBS and healthy controls. Imaging was performed with a Siemens 3 Tesla Trio Tim MRI scanner equipped with a 32-channel head coil. A high-resolution T1-weighted anatomical scan was acquired followed by a T2-weighted functional scan. We used a surface-based morphometric approach along with a seed-based resting-state functional connectivity (RS-FC) analysis to determine if groups differed in cortical thickness and whether areas showing structural differences also showed abnormal RS-FC patterns. Patients completed the Abdominal Pain Index and the GI Module of the Pediatric Quality of Life Inventory to assess abdominal pain severity and impact of GI symptoms on health-related quality of life (HRQOL). Disease duration and pain intensity were also assessed. Pediatric IBS patients, relative to controls, showed cortical thickening in the posterior cingulate (PCC), whereas cortical thinning in posterior parietal and prefrontal areas were found, including the dorsolateral prefrontal cortex (DLPFC). In patients, abdominal pain severity was related to cortical thickening in the intra-abdominal area of the primary somatosensory cortex (SI), whereas HRQOL was associated with insular cortical thinning. Disease severity measures correlated with cortical thickness in bilateral DLPFC and orbitofrontal cortex. Patients also showed reduced anti-correlations between PCC and DLPFC compared to controls, a finding that may reflect aberrant connectivity between default mode and cognitive control networks. We are the first to demonstrate concomitant structural and functional brain changes associated with abdominal pain severity, HRQOL related to GI-specific symptoms, and disease-specific measures in adolescents with IBS. It is possible such changes will be responsive to therapeutic intervention and may be useful as potential markers of disease progression or reversal.

Frequency of Irritable Bowel Syndrome Among Healthcare Personnel

This study aims to investigate the frequency of irritable bowel syndrome (IBS) among healthcare professionals. A total of 394 healthcare professionals and 207 individuals who were selected as a control group were included in the study. A questionnaire form containing Rome III diagnostic criteria was administered to health workers and the control group. The study groups were evaluated according to age, gender, occupation, profession, presence of chronic disease, drug usage, smoking, awareness of IBS, alarm symptoms, and the type of IBS they have. Irritable bowel syndrome was diagnosed in 44 healthcare workers and 10 control group participants. Of the 44 healthcare professionals with IBS, 6 had alternate, 13 had constipated-dominant, and 25 had diarrhea-dominant IBS. Of the 10 persons in the control group who were diagnosed as having IBS, 5 were diarrhea-dominant and 5 were constipated-dominant type. Irritable bowel syndrome was more frequent in healthcare professionals than in the control group. Healthcare workers are more prone to IBS due to their stressful working environment.

Bilateral transcutaneous tibial nerve stimulation for chronic constipation

AIM

Chronic constipation is difficult to treat when symptoms are intractable. Colonic propulsion may be altered by distal neuromodulation but this is conventionally delivered percutaneously. Transcutaneous tibial nerve stimulation is noninvasive and cheap: this study aimed to assess its efficacy in chronic constipation.

METHOD

Eighteen patients (median age 46 years, 12 female) with chronic constipation were recruited consecutively. Conservative and behavioural therapy had failed to improve symptoms in all 18. Thirty minutes of daily bilateral transcutaneous tibial nerve stimulation was administered by each patient at home for 6 weeks. The primary outcome measure was a change in the Patient Assessment of Constipation Quality of Life (PAC-QoL) score. Change in Patient Assessment of Constipation Symptoms (PAC-SYM), weekly bowel frequency and visual analogue scale (VAS) score were also measured.

RESULTS

Fifteen patients (12 female) completed the trial. The PAC-QoL score improved significantly with treatment [pretreatment, median 2.95, interquartile range (IQR) 1.18; posttreatment, median 2.50, IQR 0.70; P = 0.047]. There was no change in PAC-SYM score (pretreatment, median 2.36, IQR 1.59; posttreatment, median 2.08, IQR 0.92; P = 0.53). Weekly stool frequency improved as did VAS score, but these did not reach statistical significance (P = 0.229 and 0.161). The PAC-QoL and PAC-SYM scores both improved in four (26%) patients. Two patients reported complete cure. There were no adverse events reported.

CONCLUSION

Bilateral transcutaneous tibial nerve stimulation appears to be effective in a quarter of patients with chronic constipation. Carefully selected patients with less severe disease may benefit more. This requires further study.

Brain and gut interactions in irritable bowel syndrome: new paradigms and new understandings

Irritable bowel syndrome (IBS) is characterized by abdominal pain and altered bowel habits. Visceral hypersensitivity is believed to be a key underlying mechanism that causes pain. There is evidence that interactions within the brain and gut axis (BGA), that involves both the afferent-ascending and the efferent-descending pathways, as well as the somatosensory cortex, insula, amygdala, anterior cingulate cortex, and hippocampus, are deranged in IBS showing both the activation and inactivation. Clinical manifestations of IBS such as pain, altered gut motility, and psychological dysfunction may each be explained, in part, through the changes in the BGA, but there is conflicting information, and its precise role is not fully understood. A better understanding of the BGA may shed more knowledge regarding the pathophysiology of IBS that in turn may lead to the discovery of novel therapies for this common disorder.

Functional brain imaging in gastroenterology: to new beginnings

With more than 100 studies published over the past two decades, functional brain imaging research in gastroenterology has become an established field; one that has enabled improved insight into the supraspinal responses evoked by gastrointestinal stimulation both in health and disease. However, there remains considerable inter-study variation in the published results, largely owing to methodological differences in stimulation and recording techniques, heterogeneous patient selection, lack of control for psychological factors and so on. These issues with reproducibility, although not unique to studies of the gastrointestinal tract, can lead to unjustified inferences. To obtain consistent and more clinically relevant results, there is a need to optimize and standardize brain imaging studies across different centres. In addition, the use of complementary and more novel brain imaging modalities and analyses, which are now being used in other fields of research, might help unravel the factors at play in functional gastrointestinal disorders. This Review highlights the areas in which functional brain imaging has been useful and what it has revealed, the areas that are in need of improvement, and finally suggestions for future directions.

Elimination communication as colic therapy

Colic is generally defined as excessive crying in early infancy and can have negative consequences on the infant as well as on the infant's family life. Excessive crying can result in escalating parental stress levels, abusive caregiver response, increased risk of shaken baby syndrome and parental postpartum depression. In addition to excessive crying, symptoms and descriptors of infant colic include inconsolable crying, screaming, legs drawn up against the abdomen, furrowing of eyebrows, distended abdomen, arched back, passing gas, post-feeding crying and difficulty defecating. There are few well-designed, reproducible, randomized, large-scale studies which demonstrate efficacy of any therapeutic method for colic. An unexplored etiology is that colic is functionally related to a decrease in stooling frequency. Gut distention may periodically result in intensifying discomfort for the infant and in concomitant inconsolable crying. Elimination communication (EC; also known as Natural Infant Hygiene and sometimes referred to as infant potty training, baby-led potty training or assisted infant toilet training) involves the use of cues by which the infant signals to the caregiver that the infant needs to micturate or defecate. Such cues can include types of crying, squirming, straining, wriggling, grimacing, fussing, vocalizing, intent look at caregiver, red face, passing gas and grunting, many of which are the same initial symptoms related to the onset of colicky infant states. A caregiver's attentive and nurturant response to an infant's cues involve uncovering the infant's intergluteal cleft and cradling the infant gently and non-coercively in a supported, secure squatting position. This position will increase the infant's anorectal angle thus facilitating complete defecation. It is hypothesized that effective and timely elimination will cause increased physical comfort for the infant; colic symptoms will concomitantly decrease.

Examining mechanisms of brain control of bladder function with resting state functional connectivity MRI

AIMS

This aim of this study is to identify the brain mechanisms involved in bladder control.

METHODS

We used fMRI to identify brain regions that are activated during bladder filling. We then used resting state connectivity fMRI (rs-fcMRI) to assess functional connectivity of regions identified by fMRI with the rest of the brain as the bladder is filled to capacity.

RESULTS

Female participants (n = 20) were between ages 40 and 64 with no significant history of symptomatic urinary incontinence. Main effect of time (MET) fMRI analysis resulted in 20 regions of interest (ROIs) that have significant change in BOLD signal (z = 3.25, P <0.05) over the course of subtle bladder filling and emptying regardless of full versus empty bladder state. Bladder-state by time (BST) fMRI analysis resulted in three ROIs that have significant change in BOLD signal (z = 3.25, P <0.05) over the course of bladder runs comparing full versus empty bladder state. Rs-fcMRI fixed effects analysis identified significant changes in connectivity between full and empty bladder states in seven brain regions (z = 4.0) using the three BST ROIs and sixteen brain regions (z = 7) using the twenty MET ROIs. Regions identified include medial frontal gyrus, posterior cingulate (PCC), inferiolateral temporal and post-central gyrus, amygdale, the caudate, inferior parietal lobe as well as anterior and middle cingulate gyrus.

CONCLUSIONS

There is significant and vast changes in the brain's functional connectivity when bladder is filled suggesting that the central process responsible for the increased control during the full bladder state appears to largely rely on the how distributed brain systems are functionally integrated.

Effects of preceding stimulation on brain activation in response to colonic distention in humans

OBJECTIVE

It has been suggested that the pattern of distension (moderate following mild and vice versa) might influence brain activation and the experience of hypersensitivity, offset analgesia, and anticipation. Nevertheless, how the pattern of stimulation affects sensitization and/or desensitization to visceral stimulation remains unknown.

METHODS

In 45 nonclinical healthy participants (12 women, 33 men; 20-26 years old), brain processing of visceral sensation induced by colonic distension was examined using H2(15)O positron emission tomography. Subjective feelings regarding the stimuli were also measured. The descending colon was stimulated using six patterns of three bag pressures (0, 20, and 40 mm Hg). To evaluate the neural sensitization to visceral stimulation arising from the precedence effect, the effects of a 20- or 40-mm Hg distention after a sham or 20- or 40-mm Hg distension were analyzed using statistical parametric mapping. The level of significance was set at a voxelwise level of p < .0001, with cluster extent sizes of k > 50.

RESULTS

The midbrain, insula, and cerebellum, were more strongly activated by a 20-mm Hg distension with a preceding 40-mm Hg distention than by a 20-mm Hg distention without a preceding stimulation (p < .0001). Conversely, a sham stimulation after the experience of an intense stimulation activated the midcingulate cortex, compared with a sham stimulation without the experience of actual visceral stimulation (p < .0001).

CONCLUSIONS

By directly comparing different patterns of visceral stimuli, preceding visceral stimuli may affect neural sensitization and/or desensitization in humans, including elevated midbrain, insula, and midcingulate cortex.

Visceral influences on brain and behavior

Mental processes and their neural substrates are intimately linked to the homeostatic control of internal bodily state. There are a set of distinct interoceptive pathways that directly and indirectly influence brain functions. The anatomical organization of these pathways and the psychological/behavioral expressions of their influence appear along discrete, evolutionarily conserved dimensions that are tractable to a mechanistic understanding. Here, we review the role of these pathways as sources of biases to perception, cognition, emotion, and behavior and arguably the dynamic basis to the concept of self.

Interaction between cognition, emotion, and the autonomic nervous system

The mind and body are intrinsically and dynamically coupled. Perceptions, thoughts and feelings change, and respond to, the state of the body. This chapter describes the integration of cognitive and affective processes with the autonomic control of bodily arousal, focusing on reciprocal effects of autonomic responses on decision making, error detection, memory and emotions. Neuroimaging techniques are beginning to detail the neuronal substrates mediating these interactions between mental and physiological states, implicating cortical regions (specifically insular and cingulate cortices) alongside subcortical (amygdala) and brainstem (notably dorsal pons) in these mechanisms. The extent to which bodily states influence mental processes is determined in part by "interoceptive sensitivity," an index of individual differences in the ability to detect one's own bodily sensations. Moreover, the misidentification or misattribution of interoceptive responses is implicated in a number of pathologies such as depersonalization, schizophrenia, and anxiety. Increasing knowledge of the mechanisms of body-mind interactions has wide ranging implications, from decision making to empathy, and may serve elucidate potential avenues of intervention for stress-sensitive conditions in which psychological, cognitive, and emotional factors impact on the expression of physical symptoms.

Motor cortex stimulation in refractory pelvic and perineal pain: report of two successful cases

AIMS

In some patients, with refractory chronic pelvic and perineal pain, pain and quality of life are barely alleviated despite optimal medical treatment, infiltrations and surgical release of the pudendal nerve. The management of these patients is complex, especially after failure of neuromodulation techniques (spinal cord stimulation. S3 nerve root stimulation and direct stimulation of the pudendal nerve). We report the first two cases illustrating the value of motor cortex stimulation (MCS), in this new indication.

METHODS

The history, decision-making process, intraoperative findings and results of this technique are presented. The perineal cortical area was identified by intraoperative motor evoked potentials in the external anal sphincter, confirming its location in the primary motor cortex between the inferior and superior limb positions. As predictive value of repetitive transcranial magnetic stimulation (rTMS) in the identification of responders to MCS for pain is now established, we performed pre-operative rTMS sessions for both patients.

RESULTS

The first patient was a 74-years-old woman who reported an 11-year history of left lateral perineal pain. The second patient was a 45-year-old woman who reported a 4-year history of perineal pain following hysterectomy with ovariectomy. After respectively 40 months and 19 months of follow up, both patients reported an improvement of pain ranging from 40 to 50%. Time to onset of pain on sitting was markedly improved from a few minutes to 90 minutes, and largely contributing to improvement of activities of daily living and of quality of life.

CONCLUSION

These two first cases suggest that motor cortex stimulation constitutes a new treatment for refractory pelvic and perineal pain, and should be considered after failure of conventional neuromodulation techniques, especially spinal cord stimulation.

Topographic and manometric characterization of the recto-anal inhibitory reflex

BACKGROUND

Recto-anal inhibitory reflex (RAIR) is an integral part of normal defecation. The physiologic characteristics of RAIR along anal length and anterior-posterior axis are unknown. The aim of this study was to perform topographic and vector-graphic evaluation of RAIR along anal canal using high definition manometry (HDM), and examine the role of various muscle components.

METHODS

Anorectal topography was assessed in 10 healthy volunteers using HDM probe with 256 sensors. Recto-anal inhibitory reflex data were analyzed every mm along the length of anal canal for topographic, baseline, residual, and plateau pressures during five mean volumes of balloon inflation (15 cc, 40 cc, 71 cc, 101 cc, 177 cc), and in 3D by dividing anal canal into 4 × 2.1 mm grids.

KEY RESULTS

Relaxation pressure progressively increases along anal canal with increasing balloon volume up to 71 cc and thereafter plateaus. In 3D, RAIR is maximally seen at the middle and upper portions of anal canal (levels 1.2-3.2 cm) and posteriorly. Peak residual pressure was seen at proximal anal canal.

CONCLUSIONS & INFERENCES

Recto-anal inhibitory reflex is characterized by differential anal relaxation along anterior-posterior axis, longitudinally along the length of anal canal, and it depends on the rectal distention volume. It is maximally seen at internal anal sphincter pressure zone. Multidimensional analyses indicate that external anal sphincter provides bulk of anal residual pressure. Our findings emphasize importance of sensor location and orientation; as anterior and more distal location may miss RAIR.

Visceral hyperalgesia induced by forebrain-specific suppression of native Kv7/KCNQ/M-current in mice

BACKGROUND

Dysfunction of brain-gut interaction is thought to underlie visceral hypersensitivity which causes unexplained abdominal pain syndromes. However, the mechanism by which alteration of brain function in the brain-gut axis influences the perception of visceral pain remains largely elusive. In this study we investigated whether altered brain activity can generate visceral hyperalgesia.

RESULTS

Using a forebrain specific αCaMKII promoter, we established a line of transgenic (Tg) mice expressing a dominant-negative pore mutant of the Kv7.2/KCNQ2 channel which suppresses native KCNQ/M-current and enhances forebrain neuronal excitability. Brain slice recording of hippocampal pyramidal neurons from these Tg mice confirmed the presence of hyperexcitable properties with increased firing. Behavioral evaluation of Tg mice exhibited increased sensitivity to visceral pain induced by intraperitoneal (i.p.) injection of either acetic acid or magnesium sulfate, and intracolon capsaicin stimulation, but not cutaneous sensation for thermal or inflammatory pain. Immunohistological staining showed increased c-Fos expression in the somatosensory SII cortex and insular cortex of Tg mice that were injected intraperitoneally with acetic acid. To mimic the effect of cortical hyperexcitability on visceral hyperalgesia, we injected KCNQ/M channel blocker XE991 into the lateral ventricle of wild type (WT) mice. Intracerebroventricular injection of XE991 resulted in increased writhes of WT mice induced by acetic acid, and this effect was reversed by co-injection of the channel opener retigabine.

CONCLUSIONS

Our findings provide evidence that forebrain hyperexcitability confers visceral hyperalgesia, and suppression of central hyperexcitability by activation of KCNQ/M-channel function may provide a therapeutic potential for treatment of abdominal pain syndromes.

A bi-directional assessment of the human brain-anorectal axis

BACKGROUND

Brain-gut dysfunction has been implicated in gastrointestinal disorders but a comprehensive test of brain-gut axis is lacking. We developed and tested a novel method for assessing both afferent anorectal-brain function using cortical evoked potentials (CEP), and efferent brain-anorectal function using motor evoked potentials (MEP).

METHODS

Cortical evoked potentials was assessed following electrical stimulations of anus and rectum with bipolar electrodes in 26 healthy subjects. Anorectal MEPs were recorded following transcranial magnetic stimulation (TMS) over paramedian motor cortices bilaterally. Anal and rectal latencies/amplitudes for CEP and MEP responses and thresholds for first sensation and pain (mA) were analyzed and compared. Reproducibility and interobserver agreement of responses were examined.

KEY RESULTS

Reproducible polyphasic rectal and anal CEPs were recorded in all subjects, without gender differences, and with negative correlation between BMI and CEP amplitude (r -0.66, P=0.001). Transcranial magnetic stimulation evoked triphasic rectal and anal MEPs, without gender differences. Reproducibility for CEP and MEP was excellent (CV <10%). The inter-rater CV for anal and rectal MEPs was excellent (ICC 97-99), although there was inter-subject variation.

CONCLUSIONS & INFERENCES

Combined CEP and MEP studies offer a simple, inexpensive and valid method of examining bidirectional brain-anorectal axes. This comprehensive method could provide mechanistic insights into lower gut disorders.

Quantitative meta-analysis identifies brain regions activated during rectal distension in irritable bowel syndrome

BACKGROUND AND AIMS

The responsiveness of the central nervous system is altered in patients with irritable bowel syndrome (IBS). However, because of variations in experimental paradigms, analytic techniques, and reporting practices, little consensus exists on brain responses to visceral stimulation. We aimed to identify brain regions consistently activated by supraliminal rectal stimulation in IBS patients and healthy subjects (controls) by performing a quantitative meta-analysis of published studies.

METHODS

Significant foci from within-group statistical parametric maps were extracted from published neuroimaging studies that employed rectal distension. Voxel-based activation likelihood estimation was applied, pooling the results and comparing them across groups.

RESULTS

Across studies, there was consistent activation in regions associated with visceral afferent processing (ie, thalamus, insula, anterior midcingulate) among IBS patients and controls, but considerable differences in the extent and specific location of foci. IBS patients differed from controls in that there were more consistent activations in regions associated with emotional arousal (pregenual anterior cingulate cortex, amygdala) and activation of a midbrain cluster, a region playing a role in endogenous pain modulation. Controls showed more consistent activation of the medial and lateral prefrontal cortex.

CONCLUSIONS

Patients with IBS have greater engagement of regions associated with emotional arousal and endogenous pain modulation, but similar activation of regions involved in processing of visceral afferent information. Controls have greater engagement of cognitive modulatory regions. These results support a role for central nervous system dysregulation in IBS. These findings provide specific targets for guiding development of future neuroimaging protocols to more clearly define altered brain-gut interactions in IBS.

Brain activity following esophageal acid infusion using positron emission tomography

AIM: To investigate symptoms and brain activity following esophageal acid infusion.

METHODS: Fifteen healthy volunteers were recruited for the study. Hydrochloric acid (pH 1 and 2) and distilled water (pH 7) were randomly and repeatedly infused into the esophagus. The brain activity was evaluated by positron emission tomography. The severity of heartburn elicited by the infusion was rated on an auditory analog scale of 0-10.

RESULTS: The severity of heartburn following each infusion showed a step-wise increase with increasing acidity of the perfusate. The heartburn scores were significantly higher in the second pH 1 infusion compared with the first infusion. Acid and distilled water infusion induced activation of various brain areas such as the anterior insula, temporal gyrus, and anterior/posterior cingulate cortex. At pH 1 or 2, in particular, activation was observed in some emotion-related brain areas such as the more anterior part of the anterior cingulate cortex, parahippocampal gyrus, or the temporal pole. Strong activation of the orbitofrontal cortex was found by subtraction analysis of the two second pH 1 infusions, with a significant increase of heartburn symptoms.

CONCLUSION: Emotion-related brain areas were activated by esophageal acid stimulation. The orbitofrontal area might be involved in symptom processing, with esophageal sensitization induced by repeated acid stimulation.

Somatosensory processing of the tongue in humans

We review research on somatosensory (tactile) processing of the tongue based on data obtained using non-invasive neurophysiological and neuroimaging methods. Technical difficulties in stimulating the tongue, due to the noise elicited by the stimulator, the fixation of the stimulator, and the vomiting reflex, have necessitated the development of specialized devices. In this article, we show the brain activity relating to somatosensory processing of the tongue evoked by such devices. More recently, the postero-lateral part of the tongue has been stimulated, and the brain response compared with that on stimulation of the antero-lateral part of the tongue. It is likely that a difference existed in somatosensory processing of the tongue, particularly around primary somatosensory cortex, Brodmann area 40, and the anterior cingulate cortex.

Sacral nerve stimulation induces changes in the pelvic floor and rectum that improve continence and quality of life

PURPOSE

Sacral nerve stimulation (SNS) can improve fecal incontinence, though the exact mechanism is not known. This study examines the following hypotheses: SNS leads to contraction of the pelvic floor, influences rectal perception, and improves continence and quality of life.

METHODS

Fourteen patients with sacral nerve stimulators implanted for fecal incontinence were examined prospectively. Morphological and functional assessment was done by endosonography, manometry, and volumetry with the stimulator turned on and off in direct succession. Questionnaires were used to determine incontinence and quality of life.

RESULTS

With the stimulator turned on, rectal filling conditions were perceived only at higher volumes; in particular, the defecation urge was sensed only at higher volumes. There was also a reduction in the diameters of the external and internal anal sphincters and a decrease in the distance between the anal mucosa and the symphysis as a sign of pelvic floor elevation. Six months after surgery, continence and quality of life were markedly better than before the operation.

CONCLUSIONS

We were able to confirm the hypotheses given above. The improvements of pelvic floor contraction and rectal perception are rapid adjustment processes in response to stimulation of sacral nerves S3/S4 when turning on the stimulator.

Site-specific differences in central processing of visceral stimuli from the rectum and the descending colon in men

BACKGROUND

It has been reported that different brain activation areas are demonstrated during somatosensory and visceral stimulation. However, no study thus far has investigated how activated patterns in the human brain differ during visceral stimulation of different sites of the digestive tracts. The aim of this study was to determine possible site-specific differences in brain responses and perceptions during visceral stimulation of two different sites, the intraluminal distentions of the rectum and descending colon.

METHODS

Regional cerebral blood flow was assessed in 32 healthy right-handed male subjects using H(2)(15)O positron emission tomography during distention of the rectum (R group, n = 16) or descending colon (DC group, n = 16) at 40 or 20 mmHg.

KEY RESULTS

R group reported significantly higher scores of abdominal pain (P < 0.05) and urge to defecate (P < 0.001) during the application of stimulus at 40 mmHg compared with DC group but not of abdominal bloating or anxiety. In comparisons of response to the 40-mmHg stimulus, R group showed significantly greater activation in posterior midcingulate cortex (MCC) and right anterior and posterior insula, whereas DC group showed greater activation in subgenual anterior cingulate cortex (ACC), perigenual ACC and left orbitofrontal and superior temporal cortices.

CONCLUSIONS & INFERENCES

These findings suggest that central projections of painful visceral stimulation from the rectum and descending colon differ in affective, cognitive and nociceptive processing in the brain, which may result in different perceptions of visceral stimulation from different sites.