The cingulate cortex and gastric pathology

Abnormal brain structure implicated in patients with functional dyspepsia

Recent studies suggest dysfunctional brain-gut interactions are involved in the pathophysiology of functional dyspepsia (FD). However, limited studies have investigated brain structural abnormalities in FD patients. This study aimed to identify potential differences in both cortical thickness and subcortical volume in FD patients compared to healthy controls (HCs) and to explore relationships of structural abnormalities with clinical symptoms. Sixty-nine patients and forty-nine HCs underwent 3T structural magnetic resonance imaging scans. Cortical thickness and subcortical volume were compared between the groups across the cortical and subcortical regions, respectively. Regression analysis was then performed to examine relationships between the structure alternations and clinical symptoms in FD patients. Our results showed that FD patients had decreased cortical thickness compared to HCs in the distributed brain regions including the dorsolateral prefrontal cortex (dlPFC), ventrolateral prefrontal cortex (vlPFC), medial prefrontal cortex (mPFC), anterior/posterior cingulate cortex (ACC/PCC), insula, superior parietal cortex (SPC), supramarginal gyrus and lingual gyrus. Significantly negative correlations were observed between the Nepean Dyspepsia Index (NDI) and cortical thickness in the mPFC, second somatosensory cortex (SII), ACC and parahippocampus (paraHIPP). And significantly negative correlations were found between disease duration and the cortical thickness in the vlPFC, first somatosensory cortex (SI) and insula in FD patients. These findings suggest that FD patients have structural abnormalities in brain regions involved in sensory perception, sensorimotor integration, pain modulation, affective and cognitive controls. The relationships between the brain structural changes and clinical symptoms indicate that the alternations may be a consequence of living with FD.

Abnormal activity of default mode network in GERD patients

Background

Abnormal processing of esophageal sensation at the level of the central nervous system has been proven to be involved in gastroesophageal reflux disease (GERD). However, most studies were focused on the possible functions of perceptual processing related network during task status, little attention has been paid to default mode network, which has been manifested to be important in the pathogenesis of many diseases. In our study, we compared the brain activity characteristic in GERD patients with the healthy subjects (HS) at baseline, looking for whether activities of default mode network were abnormal in GERD patients and attempting to identify their possible roles in GERD. In present study, fractional amplitude of low-frequency fluctuation was adopted to detect the brain activities at baseline. Group-level analyses were conducted by one-sample t test within groups (voxel thresholds were p < 0.001 and cluster level >42, corrected P < 0.05) and independent-samples t test between groups (p < 0.01 and cluster level >90, corrected P < 0.05) using SPM5.

Results

The predominant activity area in both groups mainly located in default mode network such as medial superior frontal gyrus, precuneus, posterior cingulate gyrus, etc. However, the activities of precuneus and posterior cingulate gyrus were significantly lower in GERD patients than those in the HS.

Conclusions

The activities of precuneus and posterior cingulate gyrus of default mode network in GERD patients were significantly lower compared to the HS, suggesting abnormal activities of brain regions in default mode network may be involved in pathophysiology of GERD symptom generation.

Inflammatory bowel disease: perspectives from cingulate cortex in the first brain

The article by Agostini et al. (2013) in this issue of Neurogastroenterology and Motility evaluated patients with Crohn's disease (CD) for volumetric changes throughout the brain. They observed decreased gray matter volumes in dorsolateral prefrontal cortex and anterior midcingulate cortex (aMCC) and disease duration was negatively correlated with volumes in subgenual anterior cingulate (sACC), posterior MCC (pMCC), ventral posterior cingulate (vPCC), and parahippocampal cortices. As all patients were in remission and suffered from ongoing abdominal pain, this study provides a critical link between forebrain changes and abdominal pain experience independent of active disease and drug treatment. The aMCC has a role in feedback-mediated decision making and there are specific cognitive tasks that differentiate aMCC and pMCC that can be used to evaluate defects in CD. The sACC is an important area as it has impaired functions in major depression. As depressive symptoms are a feature in a subset of patients with active inflammatory diseases including IBD, treatment targeting this subregion should prove efficacious. Finally, vPCC has a role in ongoing self-monitoring of the personal relevance of sensory stimuli including visceral signals via sACC. This pathway may be interrupted by vPCC atrophy in CD. Cingulate atrophy in CD leads to targeting chronic pain and psychiatric symptoms via cingulate-mediated therapies. These include psychotherapy, guided imagery and relaxation training, analgesic dosages of morphine or antidepressants, and hypnosis. Thus, a new generation of novel treatments may emerge from drug and non-traditional therapies for CD in this formative area of research.

Cingulate cortex: a closer look at its gut-related functional topography

Earlier studies have documented activation of the cingulate cortex during gut related sensory-motor function. However, topography of the cingulate cortex in relationship to various levels of visceromotor sensory stimuli and gender is not completely elucidated. The aim was to characterize and compare the activation topography of the cingulate cortex in response to 1) subliminal, 2) perceived rectal distensions, and 3) external anal sphincter contraction (EASC) in males and females. We studied 18 healthy volunteers (ages 18-35 yr; 10 women, 8 men) using functional MRI blood-oxygenation-level-dependent technique. We obtained 11 axial slices (voxel vol. 2.5-6.0 x 2.5 x 2.5 mm(3)) through the cingulate cortex during barostat-controlled subliminal, liminal, and supraliminal nonpainful rectal distensions as well as EASC. Overall, for viscerosensation, the anterior cingulate cortex exhibited significantly more numbers of activated cortical voxels for all levels of stimulations compared with the posterior cingulate cortex (P < 0.05). In contrast, during EASC, activity in the posterior cingulate was larger than in the anterior cingulate cortex (P < 0.05). Cingulate activation was similar during EASC in males and females (P = 0.58), whereas there was a gender difference in anterior cingulate activation during liminal and supraliminal stimulations (P < 0.05). In females, viscerosensory cortical activity response was stimulus-intensity dependent. Intestinal viscerosensation and EASC induce different patterns of cingulate cortical activation. There may be gender differences in cingulate cortical activation during viscerosensation. In contrast to male subjects, females exhibit increased activity in response to liminal nonpainful stimulation compared with subliminal stimulation suggesting differences in cognition-related recruitment.

Gyrus cinguli transection abolishes delta-opioid receptor-induced gastroprotection and alters alpha 2 adrenoceptor activity in the lower brainstem in rats

Previously, using the acidified ethanol-induced ulcer model in rats, we demonstrated that the mainly vagus-dependent gastroprotective effect of intracerebroventricularly injected clonidine was mediated by beta-endorphin release in the lower brainstem. Presently, retroarcuate transections were used to evaluate the contribution of forebrain beta-endorphinergic projection in this mechanism. Since the transection trajectory affected the cingulate cortex and other forebrain structures, matching lesions were also performed. In control and sham-operated rats intracisternal injection of clonidine and the direct opioid receptor (delta type) stimulant peptide (D-Ala(2), D-Leu(5))-enkephalin caused a potent and fully naloxone-reversible (i.e. opioid receptor-mediated) protection against acidified ethanol-induced mucosal damage. In gyrus cinguli-transected rats (as well as in groups with midline hippocampal, thalamic and hypothalamic lesions) gastric mucosal protection induced centrally by direct delta-opioid receptor stimulation in the lower brainstem was completely abolished. The protective effect of clonidine was significantly reduced but it was still present in these animals. The residual protection by clonidine was naloxone-resistant, i.e. independent of an opioid mediation. Transections of the cingulate gyrus as well as thalamic but not the retroarcuate transections elevated plasma corticosterone levels. The changes seen in the clonidine/opioid-induced gastroprotection did not show any correlation with the changes in plasma corticosterone levels. It was concluded that (i) the transection of the cingulate cortex strongly influences the neural input to the nucleus tractus solitarii-dorsal motor vagal nucleus complex that is required for the activation of gastroprotective vagus outflow by delta-opioid receptor stimulation; (ii) the transection uncovers a direct, clonidine-induced gastroprotective pathway which is probably suppressed in intact animals.

Associational projections of the anterior midline cortex in the rat: intracingulate and retrosplenial connections

Past studies indicate that distinct areas of anterior midline cortex in the rat contribute to diverse functions, such as autonomic nervous system regulation and learning, but the anatomical substrate for these functions has not been fully elucidated. The present study characterizes the associational connections within the midline cortex of the rat by using the anterograde transport of Phaseolus vulgaris leucoagglutinin and Fluororuby. The prelimbic area and the rostral part of the anterior cingulate area (both dorsal and ventral subdivisions) are extensively interconnected with each other. In addition, the caudal half of anterior cingulate cortex has extensive projections to precentral medial cortex and caudally directed projections to retrosplenial cortex. Other cortical areas within anterior midline cortex have relatively limited cortical-cortical projections. The infralimbic, dorsal peduncular, and medial precentral cortices have dense intrinsic projections, but have either very limited or no projections to other areas in the anterior midline cortex. Although it has been suggested that cortical-cortical projections from anterior cingulate cortex and prelimbic cortex to infralimbic cortex may be important for linking learning processes with an autonomic nervous system response, the paucity of direct projections between these areas calls this hypothesis into question. Conversely, the results suggest that the anterior midline cortex contains two regions that are functionally and connectionally distinct.

Pressor and depressor sites are intermingled in the cingulate cortex of the rat

Electrical stimulation of area infraradiata in the rat evokes transient changes in arterial pressure, but the locations that evoke these responses have not been mapped by neurochemical methods. To localize more specifically the regions of area infraradiata that modify cardiovascular activity, the present study measured cardiovascular responses to localized chemical stimulation of neurons in area infraradiata of urethane-anesthetized rats (n = 21). Microinjections (50-200 nl) of the glutamate agonist D,L-homocysteic acid into area infraradiata evoked both increases and decreases in arterial pressure and heart rate. Injections in the ventral subdivisions of rostral area infraradiata (IRa alpha and IRb alpha) produced cardiovascular responses with the highest probability and greatest magnitude. Of 53 injections in this area, 18 decreased arterial pressure and heart rate, whereas 4 increased arterial pressure and heart rate. In contrast to the results from the ventral subdivision of rostral infraradiata cortex, injections of D,L-homocysteic acid in the dorsal subdivision of rostral infraradiata cortex (IRc alpha) or any of the caudal subdivisions of area infraradiata (IR beta) produced less consistent changes in arterial pressure. To demonstrate that the general anesthesia did not significantly alter the evoked responses in this study, similar injections of D,L-homocysteic acid were made into area infraradiata of unrestrained, conscious rats (n = 10) and the responses were similar to the responses evoked in urethane-anesthetized rats. These results indicate that the ventral subdivisions of rostral area infraradiata (IRa alpha and IRb alpha) are more involved in cardiovascular regulation than other areas of infraradiata cortex (IRc alpha and IR beta), and that both pressor and depressor sites are present in both areas.

Organization of cortical and subcortical projections to anterior cingulate cortex in the cat

The aim of the experiments reported here was to identify cortical and subcortical forebrain structures from which anterior cingulate cortex (CGa) receives input in the cat. Deposits of retrograde tracers were placed at nine sites spanning the anterior cingulate area and patterns of retrograde transport were analyzed. Thalamic projections to CGa, in descending order of strength, originate in the anteromedial nucleus, lateroposterior nucleus, ventroanterior nucleus, rostral intralaminar complex, reuniens nucleus, mediodorsal nucleus, and laterodorsal nucleus. Minor and inconsistent ascending pathways arise in the paraventricular, parataenial, parafascicular, and subparafascicular thalamic nuclei. The basolateral nucleus of the amygdala, the hypothalamus, the nucleus of the diagonal band, and the claustrum are additional sources of ascending input. Cortical projections to CGa, in descending order of strength, derive from posterior cingulate cortex, prefrontal cortex, motor cortex (areas 4 and 6), parahippocampal cortex (entorhinal, perirhinal, postsubicular, parasubicular, and subicular areas), insular cortex, somesthetic cortex (areas 5 and SIV), and visual cortex (areas 7p, 20b, AMLS, PS and EPp). In general, the limbic, sensory, and motor afferents of CGa are weak. The dominant sources of input to CGa are other cortical areas with high-order functions. This finding calls into question the traditional characterization of cingulate cortex as a bridge between neocortical association areas and the limbic system.

The rat medial frontal cortex projects directly to autonomic regions of the brainstem

Pressure injections of the anterograde tracer wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) into the infralimbic (IL) and prelimbic (PL) regions of the medial frontal cortex of the rat produced anterograde, terminal-like labeling in the lateral dorsal tegmental nucleus (LDTg) of the dorsal pons and the ventral, ventrolateral, intermediate, medial and commissural subnuclei of the nucleus of the solitary nucleus (NTS) in the dorsomedial medulla. Injections involving IL resulted in heavier labeling than the labeling seen after PL injections only. The LDTg has been described as the pontine micturition center, involved in the micturition reflex. The possible role that the projections to the LDTg may play in fluid homeostasis is discussed. The labeled NTS subnuclei receive visceral afferent inputs from the heart, baroreceptors, lungs and gut. The direct cortical projections to these areas may be involved in mediating the bradycardia, depressor responses, and changes in respiratory and gastric activity which are seen after electrical stimulation of the rat medial frontal cortex. The present data support the concept that the infralimbic and prelimbic cortices function as a "visceral motor" cortex, involved in control of a variety of autonomic functions.

Cardiac and respiratory relationships with neural discharge in the anterior cingulate cortex during sleep-walking states

The discharge properties of single neurons in the anterior cingulate cortex were correlated with timing aspects of the respiratory and cardiac cycle and with arterial pressure in undrugged, freely moving cats during waking, quiet sleep, and rapid eye movement sleep (REM). Two types of analyses were carried out. Discharge timing relationships with the cardiac or respiratory cycle were examined using cross-correlation histograms. Tonic rate correlations were calculated as a linear regression between breath-by-breath mean discharge rate of the cell and breath-by-breath values of respiratory parameters or arterial pressure. Eight of fifty-five cells recorded showed a discharge timing relationship with either the cardiac or the respiratory cycle. Seven of these were state-dependent (six in waking, one in REM). Thirty cells showed a tonic rate correlation with the respiratory period, and 23 cells had tonic correlations with maximum arterial pressure. All tonic correlations for a given cell were state-dependent, but such correlations were observed in all states. Correlation coefficients, while statistically significant, were generally low, and r2 values rarely exceeded 0.2. The relative paucity of discharge timing relationships, the state dependency, and the low r values of the tonic rate correlations suggest that the anterior cingulate cortex has a complex and indirect relationship to central cardiovascular and respiratory control mechanisms.

The anterior midline cortex and adaptation to stress ulcers in rats

Rats with bilateral radio-frequency lesions of the anterior midline cortex were subjected to either single or repeated immobilization stress treatments. As previously demonstrated, the lesions greatly reduced gastric pathology in the acute stress treatment. Conversely, the lesions were found to aggravate gastric pathology in animals stressed repeatedly, thus eliminating the adaptive (i.e., pathology-reducing) effects of repeated stress seen in controls. The role of the anterior midline cortex in stress and stress adaptation is discussed with reference to noradrenergic mechanisms.

The medial frontal cortex and gastric motility: microstimulation results and their possible significance for the overall pattern of organization of rat frontal and parietal cortex

Bilateral intracortical microstimulation (60-90 strains of 0.5 ms pulses at 10 Hz, currents below 50 microA) of medial frontal infralimbic and prelimbic cortical areas in ketamine-anesthetized rats produces clear and consistent decreases in ongoing gastric motility. The majority of responses consists of reductions in gastric tone, reductions in the amplitude of gastric contractions, or combined reductions in tone and amplitude. Bilateral section of the vagus nerves eliminates most of the responses, suggesting that the responses are mediated by this nerve. The effective cortical stimulation zone (the 'visceral motor' cortex) largely overlaps the source of the recently described direct projection from medial frontal cortex to the nucleus of the solitary tract; this pathway may be involved in producing the effect. Connections of this cortex with the limbic system suggest it may be involved in producing physiological responses to stress. The topographical, medial to lateral sequence of cortical functional areas revealed by these and other experiments (visceral motor, frontal eye fields, somatic motor, somatic sensory, visceral sensory) is discussed, as well as the possible implications of this pattern to the question of cortical evolutionary development.

The involvement of the anterior cingulate cortex in blood pressure control

The visceromotor nature of the rat anterior cingulate cortex was investigated by electrically stimulating this area in both anesthetized and awake animals. Initial studies demonstrated that electrical stimulation of any division of the anterior cingulate cortex elicits a significant fall in blood pressure in the sodium pentobarbital-anesthetized rat. Depressor responses were greatest (up to 50% decreases) following stimulation of the ventral third of the anterior cingulate cortex. Heart rate was not altered by cingulate cortex stimulation. In the awake animal, stimulation of previously identified depressor sites in the rostral third of the pregenual cingulate cortex elicited pressor responses. In contrast, stimulation of the caudal third of this cortex elicited depressor responses, and stimulation of the middle third elicited biphasic (pressor followed by depressor) responses. These results indicate that the anterior cingulate cortex is a visceromotor region which may provide a cortical output for the regulation of blood pressure responses associated with learning and or stress.

The topography of the mesencephalic and pontine projections from the cingulate cortex of the rat

A projection from the rat midline cortex to the midbrain and pons has been recognized for several years. The present study is a detailed analysis of this projection using the autoradiographic technique. Small injections of [3H]amino acids were placed within individual segments of the cingulate cortex in 68 rats. The resulting material reaffirmed the existence of the cingulo-brainstem projections and demonstrated that a precise topographical relationship exists between the cingulate cortex cells of origin and their termination fields within the brainstem. The most ventral and anterior segment of the cortex (IRaa) projects to the ventral periaqueductal gray, to the dorso-medial ventral pontine nuclei and to the lateral tegmental region. Conversely, the dorso-anterior cortex (IRca) projects to the superior colliculus, the dorso-lateral periaqueductal gray, and the medio-ventral ventral pontine nuclei. The intermediate anterior cortex projects to both dorsal and ventral periaqueductal gray, lightly to the superior colliculus, and to the medio-intermediate ventral pontine nuclei. The posterior half of the infraradiata (IR) cortex projects to the dorso-lateral periaqueductal gray, to the superior colliculus, and to the region of the ventral pontine nuclei slightly lateral to the terminal zone occupied by the anterior IR cortex. Increasingly dorsal segments of the IR beta cortex project to more increasingly ventral areas of the ventral nuclei. The posterior portion of the midline cortex (retrosplenial cortex, R) does not project to the dorsal midbrain, but it does topographically project to the ventral pontine nuclei, lateral to the terminal zone of the IR axons. Increasingly, posterior regions of the R cortex project to more lateral regions of the ventral nuclei, and increasingly, dorsal cells of the R cortex project to more dorsal regions of the ventral nuclei. These data demonstrate a very precise topography of brainstem projections which may underlie the visceral and somatic motor functions of the cingulate cortex, as well as the ability of the cingulate cortex to modulate sensory information and emotional behavior.

The bed nucleus of the stria terminalis and immobilization-stress: unit activity, escape behaviour, and gastric pathology in rats

Multiple unit-activity in the bed nucleus of the stria terminalis was increased or decreased, relative to baselines, during physical restraint in rats. Changes in unit-activity were also obtained by presenting an auditory stimulus that had been paired with the immobilization treatment. The animals escaped from that stimulus in behavioural tests, and bilateral lesions in the bed nucleus reduced the latencies of escape responses. The lesion also increased the severity of restraint-induced mucosal erosions. The latter effect was most pronounced when the damage was in the lateral portion of the bed nucleus. It was concluded that the bed nucleus of the stria terminalis is part of a coping system which responds when the organism is placed in a stressful situation.

Rat medial frontal cortex: a visceral motor region with a direct projection to the solitary nucleus

Pressure injections of the neuroanatomical tracer wheat germ agglutinin conjugated with HRP (WGA-HRP) were made into either the dorsal medulla or the medial frontal cortex of the rat. Following the brainstem injections, retrogradely labeled neurons were found in the paraventricular nucleus of the hypothalamus, central nucleus of the amygdala, insular cortex and in the infralimbic, prelimbic and anterior cingulate regions of the medial frontal cortex. The infralimbic labeling consisted of a dense band of neurons and was bilateral. Cells in the prelimbic and anterior cingulate regions were less densely packed. Following injections of WGA-HRP into the medial frontal cortex anterograde labeling in the dorsal medulla was confined to the solitary nucleus (NTS). Label was found throughout the rostro-caudal extent of the NTS and was bilateral although heavier contralaterally. The projection from the medial frontal cortex to the solitary nucleus suggests that this area of cortex may function primarily as a visceral 'motor' cortical region that may play a role in regulating autonomic activities.

Mucosal damage following electrical stimulation of the anterior cingulate cortex and pretreatment with atropine and cimetidine

Bipolar electrical stimulation of a restricted area of the anterior cingulate cortex in anesthetized rats produced stomach erosions. Pretreatment with atropine sulfate prevented the pathological effects of stimulation. Cimetidine was not effective in preventing the gastric damage. It was concluded that the pathological effects of electrical stimulation were cholinergically mediated, whereas, histamine-2 receptors were not involved.

The telencephalic limbic system and experimental gastric pathology: a review

The effects of lesions and stimulations of the telencephalic limbic system on experimental gastric ulcers and erosions are reviewed. It is concluded that the centromedial amygdala and the anterior cingulate gyrus are facilitatory structures, whereas the medial prefrontal cortex, posterior cingulate cortex, entorhinal cortex, hippocampus and posterolateral amygdala are inhibitory areas during stressful experiences, e.g., immobilization. Both the centromedial amygdala and the anterior cingulate gyrus may be part of an "ancillary" pain system, mediating the affective components of aversive experiences. The inhibitory structures, on the other hand, are assumed to be part of a "preventive" mechanism which is initiated by the selective nuclear binding of glucocorticoids when under stress.