Brain activity during distention of the descending colon in humans

Brain-gut interaction is considered to be a major factor in the pathophysiology of irritable bowel syndrome. However, only limited information has been provided on the influence of gastrointestinal tract stimulation on the brain. Our aim in this study was to determine the specific regions of the brain that are responsible for visceral perception and emotion provoked by distention of the descending colon in humans. Fifteen healthy males aged 22 +/- 1 participated in this study. Using a colonoscope, a balloon was inserted into the descending colon of each subject. After sham stimulation, the colon was randomly stimulated with bag pressures of 20 and 40 mmHg, and regional cerebral blood flow was measured by [(15)O] positron emission tomography. The subjects were asked to report visceral perception and emotion using an ordinate scale of 0-10. Colonic distention pressure dependently induced visceral perception and emotion, which significantly correlated with activation of specific regions of the brain including the prefrontal, anterior cingulate, parietal cortices, insula, pons, and the cerebellum. In conclusion, distention of the descending colon induces visceral perception and emotion. These changes significantly correlate with activation of specific regions in the brain including the limbic system and the association cortex, especially the prefrontal cortex.     

Cortical deactivations during gastric fundus distension in health: visceral pain‐specific response or attenuation of ‘default mode’ brain function? A H215O‐PET study

Abstract Gastric distension activates a cerebral network including brainstem, thalamus, insula, perigenual anterior cingulate, cerebellum, ventrolateral prefrontal cortex and potentially somatosensory regions. Cortical deactivations during gastric distension have hardly been reported. To describe brain areas of decreased activity during gastric fundus distension compared to baseline, using data from our previously published study (Gastroenterology, 128, 2005 and 564). H₂¹⁵O‐brain positron emission tomography was performed in 11 healthy volunteers during five conditions (random order): (C₁) no distension (baseline); isobaric distension to individual thresholds for (C₂) first, (C₃) marked, (C₄) unpleasant sensation and (C₅) sham distension. Subtraction analyses were performed (in SPM2) to determine deactivated areas during distension compared to baseline, with a threshold of P_{uncorrected_voxel_level} < 0.001 and P_{corrected_cluster_level} < 0.05. Baseline–maximal distension (C₁–C₄) yielded significant deactivations in: (i) bilateral occipital, lateral parietal and temporal cortex as well as medial parietal lobe (posterior cingulate and precuneus) and medial temporal lobe (hippocampus and amygdala), (ii) right dorsolateral and dorso‐ and ventromedial PFC, (iii) left subgenual ACC and bilateral caudate head. Intragastric pressure and epigastric sensation score correlated negatively with brain activity in similar regions. The right hippocampus/amygdala deactivation was specific to sham. Gastric fundus distension in health is associated with extensive cortical deactivations, besides the activations described before. Whether this represents task‐independent suspension of ‘default mode’ activity (as described in various cognitive tasks) or an visceral pain/interoception‐specific process remains to be elucidated.     

Neural mechanisms of autonomic, affective, and cognitive integration

Influential theoretical models propose a central role for afferent information from the body in the expression of emotional feeling states. Feedback representations of changing states of bodily arousal influence learning and facilitate concurrent and prospective decision-making. Functional neuroimaging studies have increased understanding of brain mechanisms that generate changes in autonomic arousal during behavior and those which respond to internal feedback signals to influence subjective feeling states. In particular, anterior cingulate cortex is implicated in generating autonomic changes, while insula and orbitofrontal cortices may be specialized in mapping visceral responses. Independently, ventromedial prefrontal cortex is recognized to support processes of internal (self-) reference that predominate in states of rest and disengagement and which putatively serve as a benchmark for dynamic interactions with the environment. Lesion data further highlight the integrated role of these cortical regions in autonomic and motivational control. In computational models of control, forward (efference copies) and inverse models are proposed to enable prediction and correction of action and, by extension, the interpretation of the behavior of others. It is hypothesized that the neural substrate for these processes during motivational and affective behavior lies within the interactions of anterior cingulate, insula, and orbitofrontal cortices. Generation of visceral autonomic correlates of control reinforce experiential engagement in simulatory models and underpin concepts such as somatic markers to bridge the dualistic divide.     

Transient cortico-cortical disconnection during psychogenic nonepileptic seizures (PNES)

Psychogenic nonepileptic seizures (PNES) are paroxysmal clinical events that are often misdiagnosed as epileptic seizures, but which are not associated with electrographic discharge. Brain connectivity changes occurring during PNES are not known. We studied functional connectivity (Fc) in two patients with drug-resistant epilepsy, explored by stereotactic electroencephalography (EEG), in whom we recorded both epileptic seizures (ES) and PNES. Functional connectivity using pair-wise nonlinear correlation was computed between signals from seven brain areas: amygdala, hippocampus, lateral temporal cortex, anterior insula, orbitofrontal cortex, prefrontal cortex, and lateral parietal cortex. We assessed changes in global Fc during PNES in comparison with a background period. During PNES, a global decrease of Fc occurred between the different brain regions studied, compared with the interictal period. In both patients, decreased Fc was prominent in connections involving the anterior insula and parietal cortex. In conclusion, some PNES are associated with ictal functional disconnection between brain areas, particularly involving the parietal cortices and the anterior insula.     

Brain responses to social norms: Meta‐analyses of fMRI studies

Social norms have a critical role in everyday decision‐making, as frequent interaction with others regulates our behavior. Neuroimaging studies show that social‐based and fairness‐related decision‐making activates an inconsistent set of areas, which sometimes includes the anterior insula, anterior cingulate cortex, and others lateral prefrontal cortices. Social‐based decision‐making is complex and variability in findings may be driven by socio‐cognitive activities related to social norms. To distinguish among social‐cognitive activities related to social norms, we identified 36 eligible articles in the functional magnetic resonance imaging (fMRI) literature, which we separate into two categories (a) social norm representation and (b) norm violations. The majority of original articles (>60%) used tasks associated with fairness norms and decision‐making, such as ultimatum game, dictator game, or prisoner's dilemma; the rest used tasks associated to violation of moral norms, such as scenarios and sentences of moral depravity ratings. Using quantitative meta‐analyses, we report common and distinct brain areas that show concordance as a function of category. Specifically, concordance in ventromedial prefrontal regions is distinct to social norm representation processing, whereas concordance in right insula, dorsolateral prefrontal, and dorsal cingulate cortices is distinct to norm violation processing. We propose a neurocognitive model of social norms for healthy adults, which could help guide future research in social norm compliance and mechanisms of its enforcement.     

Activation likelihood estimation meta‐analysis of brain correlates of placebo analgesia in human experimental pain

Placebo analgesia (PA) is one of the most studied placebo effects. Brain imaging studies published over the last decade, using either positron emission tomography (PET) or functional magnetic resonance imaging (fMRI), suggest that multiple brain regions may play a pivotal role in this process. However, there continues to be much debate as to which areas consistently contribute to placebo analgesia‐related networks. In the present study, we used activation likelihood estimation (ALE) meta‐analysis, a state‐of‐the‐art approach, to search for the cortical areas involved in PA in human experimental pain models. Nine fMRI studies and two PET studies investigating cerebral hemodynamic changes were included in the analysis. During expectation of analgesia, activated foci were found in the left anterior cingulate, right precentral, and lateral prefrontal cortex and in the left periaqueductal gray (PAG). During noxious stimulation, placebo‐related activations were detected in the anterior cingulate and medial and lateral prefrontal cortices, in the left inferior parietal lobule and postcentral gyrus, anterior insula, thalamus, hypothalamus, PAG, and pons; deactivations were found in the left mid‐ and posterior cingulate cortex, superior temporal and precentral gyri, in the left anterior and right posterior insula, in the claustrum and putamen, and in the right thalamus and caudate body. Our results suggest on one hand that the modulatory cortical networks involved in PA largely overlap those involved in the regulation of emotional processes, on the other that brain nociceptive networks are downregulated in parallel with behavioral analgesia. Hum Brain Mapp, 2013. © 2011 Wiley Periodicals, Inc.     

Two systems of resting state connectivity between the insula and cingulate cortex

The insula and cingulate cortices are implicated in emotional, homeostatic/allostatic, sensorimotor, and cognitive functions. Non‐human primates have specific anatomical connections between sub‐divisions of the insula and cingulate. Specifically, the anterior insula projects to the pregenual anterior cingulate cortex (pACC) and the anterior and posterior mid‐cingulate cortex (aMCC and pMCC); the mid‐posterior insula only projects to the posterior MCC (pMCC). In humans, functional neuroimaging studies implicate the anterior insula and pre/subgenual ACC in emotional processes, the mid‐posterior insula with awareness and interoception, and the MCC with environmental monitoring, response selection, and skeletomotor body orientation. Here, we tested the hypothesis that distinct resting state functional connectivity could be identified between (1) the anterior insula and pACC/aMCC; and (2) the entire insula (anterior, middle, and posterior insula) and the pMCC. Functional connectivity was assessed from resting state fMRI scans in 19 healthy volunteers using seed regions of interest in the anterior, middle, and posterior insula. Highly correlated, low‐frequency oscillations (< 0.05 Hz) were identified between specific insula and cingulate subdivisions. The anterior insula was shown to be functionally connected with the pACC/aMCC and the pMCC, while the mid/posterior insula was only connected with the pMCC. These data provide evidence for a resting state anterior insula–pACC/aMCC cingulate system that may integrate interoceptive information with emotional salience to form a subjective representation of the body; and another system that includes the entire insula and MCC, likely involved in environmental monitoring, response selection, and skeletomotor body orientation. Human Brain Mapp 2009. © 2008 Wiley‐Liss, Inc.     

Dynamic functional network connectivity reveals unique and overlapping profiles of insula subdivisions

The human insular cortex consists of functionally diverse subdivisions that engage during tasks ranging from interoception to cognitive control. The multiplicity of functions subserved by insular subdivisions calls for a nuanced investigation of their functional connectivity profiles. Four insula subdivisions (dorsal anterior, dAI; ventral, VI; posterior, PI; middle, MI) derived using a data‐driven approach were subjected to static‐ and dynamic functional network connectivity (s‐FNC and d‐FNC) analyses. Static‐FNC analyses replicated previous work demonstrating a cognition‐emotion‐interoception division of the insula, where the dAI is functionally connected to frontal areas, the VI to limbic areas, and the PI and MI to sensorimotor areas. Dynamic‐FNC analyses consisted of k‐means clustering of sliding windows to identify variable insula connectivity states. The d‐FNC analysis revealed that the most frequently occurring dynamic state mirrored the cognition‐emotion‐interoception division observed from the s‐FNC analysis, with less frequently occurring states showing overlapping and unique subdivision connectivity profiles. In two of the states, all subdivisions exhibited largely overlapping profiles, consisting of subcortical, sensory, motor, and frontal connections. Two other states showed the dAI exhibited a unique connectivity profile compared with other insula subdivisions. Additionally, the dAI exhibited the most variable functional connections across the s‐FNC and d‐FNC analyses, and was the only subdivision to exhibit dynamic functional connections with regions of the default mode network. These results highlight how a d‐FNC approach can capture functional dynamics masked by s‐FNC approaches, and reveal dynamic functional connections enabling the functional flexibility of the insula across time. Hum Brain Mapp 37:1770–1787, 2016. © 2016 Wiley Periodicals, Inc .     

How task demands shape brain responses to visual food cues

Several previous imaging studies have aimed at identifying the neural basis of visual food cue processing in humans. However, there is little consistency of the functional magnetic resonance imaging (fMRI) results across studies. Here, we tested the hypothesis that this variability across studies might – at least in part – be caused by the different tasks employed. In particular, we assessed directly the influence of task set on brain responses to food stimuli with fMRI using two tasks (colour vs. edibility judgement, between‐subjects design). When participants judged colour, the left insula, the left inferior parietal lobule, occipital areas, the left orbitofrontal cortex and other frontal areas expressed enhanced fMRI responses to food relative to non‐food pictures. However, when judging edibility, enhanced fMRI responses to food pictures were observed in the superior and middle frontal gyrus and in medial frontal areas including the pregenual anterior cingulate cortex and ventromedial prefrontal cortex. This pattern of results indicates that task sets can significantly alter the neural underpinnings of food cue processing. We propose that judging low‐level visual stimulus characteristics – such as colour – triggers stimulus‐related representations in the visual and even in gustatory cortex (insula), whereas discriminating abstract stimulus categories activates higher order representations in both the anterior cingulate and prefrontal cortex. Hum Brain Mapp 38:2897–2912, 2017. © 2017 Wiley Periodicals, Inc.     

Functional neuroimaging of visceral sensation.

The use of functional brain imaging techniques has led to considerable advances in our understanding of brain processing of human visceral sensation. The use of complementary techniques such as functional MRI, positron emission tomography, magnetoencephalography, and EEG has led to the identification of a network of brain areas that process visceral sensation. These studies suggest that unlike somatic sensation, which has an intense homuncular representation in the primary somatosensory cortex (SI), visceral sensation is primarily represented in the secondary somatosensory cortex, whereas representation in SI is vague. This difference could account for the poor localization of visceral sensation in comparison with somatic sensation. However, in a manner similar to that of somatic sensation, visceral sensation is represented in the paralimbic and limbic structures such as the insular, anterior cingulate, and prefrontal cortices. These areas are likely to mediate the affective and cognitive components of visceral sensation. Recent studies suggest that negative emotional factors such as fear, and cognitive factors such as attention can modulate the brain processing of visceral sensation in the insular and anterior cingulate cortices. In addition, alterations in the pattern of cortical processing of visceral sensation have been described in patients with functional gastrointestinal pain. It is likely that future research into the factors that modulate the brain processing of visceral sensation in health and disease are likely to improve further our understanding of the pathophysiology of functional visceral pain disorders.     

State and trait influences on mood regulation in bipolar disorder: blood flow differences with an acute mood challenge.

BACKGROUND: Even in remission, patients with bipolar disorder (BD) remain sensitive to external stressors that can trigger new episodes. Imitating such stressors by the controlled transient exposure to an emotional stimulus may help to identify brain regions modulating this sensitivity. METHODS: Transient sadness was induced in 9 euthymic and in 11 depressed subjects with BD. Regional blood flow (rCBF) changes were measured using (15)O-water positron emission tomography. RESULTS: Common changes in both groups were increased rCBF in anterior insula and cerebellum and decreased rCBF in dorsal-ventral-medial frontal cortex, posterior cingulate, inferior parietal, and temporal cortices. Decreases in dorsal ventral medial frontal cortices occurred in both groups, but subjects in remission showed a greater magnitude of change. Unique to remitted subjects with BD were rCBF increases in dorsal anterior cingulate and in premotor cortex. Lateral prefrontal rCBF decreases were unique to depressed subjects with BD. At baseline, remitted subjects showed a unique increase in dorsal anterior cingulate and orbitofrontal cortex. CONCLUSIONS: Common rCBF changes in remitted and depressed subjects identifies potential sites of disease vulnerability. Unique cingulate and orbitofrontal changes both at baseline and with induced sadness seen in the absence of prefrontal rCBF decreases may identify regional interactions important to the euthymic state in this population.     

Centenary of Christfried Jakob's discovery of the visceral brain: an unheeded precedence in affective neuroscience

The benchmark discovery of the cingulate gyrus as a brain structure receiving stimuli from muscles and viscera (proprioception and interoception) is traced to a 1907/1908 article by neuropathologist Christfried Jakob. Further, the involvement of the mamillary bodies, anterior thalamic nucleus, cingulate cortex and hippocampus in the circuitry of the emotive brain (i.e. all elements of the 1937 'circuit of Papez') was published by Jakob in his 1911 and 1913 monographs on human and comparative neuroanatomy. In those works, Jakob also described the thalamocingulate projection, commonly attributed to a 1933 study by Le Gros Clark and Boggon, and introduced the term 'visceral brain', commonly attributed to a 1949 paper by MacLean. The present article includes the first English translations of Jakob's relevant passages, which incontrovertibly document his chronological priority in discovering the visceral brain and some of its key constituent elements.     

Brain basis of developmental change in visuospatial working memory

Although brain changes associated with the acquisition of cognitive abilities in early childhood involve increasing localized specialization, little is known about the brain changes associated with the refinement of existing cognitive abilities that reach maturity in adolescence. The goal of this study was to investigate developmental changes in functional brain circuitry that support improvements in visuospatial working memory from childhood to adulthood. We tested thirty 8- to 47-year-olds in an oculomotor delayed response task. Developmental transitions in brain circuitry included both quantitative changes in the recruitment of necessary working memory regions and qualitative changes in the specific regions recruited into the functional working memory circuitry. Children recruited limited activation from core working memory regions (dorsal lateral prefrontal cortex [DLPFC] and parietal regions) and relied primarily on ventromedial regions (caudate nucleus and anterior insula). With adolescence emerged a more diffuse network (DLPFC, anterior cingulate, posterior parietal, anterior insula) that included the functional integration of premotor response preparation and execution circuitry. Finally, adults recruited the most specialized network of localized regions together with additional performance-enhancing regions, including left-lateralized DLPFC, ventrolateral prefrontal cortex, and supramarginal gyrus. These results suggest that the maturation of adult-level cognition involves a combination of increasing localization within necessary regions and their integration with performance-enhancing regions.     

Regional cerebral glucose utilization in patients with a range of severities of unipolar depression.

BACKGROUND: Patients with unipolar depression are most often reported to have decreased regional cerebral glucose metabolism (rCMRglu) in dorsal prefrontal and anterior cingulate cortices compared with healthy control subjects, often correlating inversely with severity of depression. METHODS: We measured rCMRglu with fluorine-18 deoxyglucose positron emission tomography (PET) in 38 medication-free patients with unipolar depression and 37 healthy control subjects performing an auditory continuous performance task to further investigate potential prefrontal and anterior paralimbic rCMRglu abnormalities in patients attending to this task. RESULTS: Compared with control subjects, the subgroup of patients with Hamilton depression scores of 22 or greater demonstrated decreased absolute rCMRglu in right prefrontal cortex and paralimbic/amygdala regions as well as bilaterally in the insula and temporoparietal cortex (right > left); they also exhibited increased normalized metabolic activity bilaterally in the cerebellum, lingula/cuneus, and brain stem. Severity of depression negatively correlated with absolute rCMRglu in almost the entire extent of the right cingulate cortex as well as bilaterally in prefrontal cortex, insula, basal ganglia, and temporoparietal cortex (right > left). CONCLUSIONS: Areas of frontal, cingulate, insula, and temporal cortex appear hypometabolic in association with different components of the severity and course of illness in treatment-resistant unipolar depression.     

Functional imaging and the central control of the bladder

The central control of the bladder is a complex, multilevel process. Recent advances in functional brain imaging have allowed research into this control in humans. This article reviews the functional imaging studies published to date and discusses the regions of the brain that have been implicated in the central control of continence. Brain regions that have been implicated include the pons (pontine micturition center, PMC), periaqueductal gray (PAG), thalamus, insula, anterior cingulate gyrus, and prefrontal cortices. The PMC and the PAG are thought to be key in the supraspinal control of continence and micturition. Higher centers such as the insula, anterior cingulate gyrus, and prefrontal regions are probably involved in the modulation of this control and cognition of bladder sensations, and in the case of the insula and anterior cingulate, modulation of autonomic function. Further work should aim to examine how the regions interact to achieve urinary continence.     

Insular cortex and neuropsychiatric disorders: a review of recent literature.

The insular cortex is located in the centre of the cerebral hemisphere, having connections with the primary and secondary somatosensory areas, anterior cingulate cortex, amygdaloid body, prefrontal cortex, superior temporal gyrus, temporal pole, orbitofrontal cortex, frontal and parietal opercula, primary and association auditory cortices, visual association cortex, olfactory bulb, hippocampus, entorhinal cortex, and motor cortex. Accordingly, dense connections exist among insular cortex neurons. The insular cortex is involved in the processing of visceral sensory, visceral motor, vestibular, attention, pain, emotion, verbal, motor information, inputs related to music and eating, in addition to gustatory, olfactory, visual, auditory, and tactile data. In this article, the literature on the relationship between the insular cortex and neuropsychiatric disorders was summarized following a computer search of the Pub-Med database. Recent neuroimaging data, including voxel based morphometry, PET and fMRI, revealed that the insular cortex was involved in various neuropsychiatric diseases such as mood disorders, panic disorders, PTSD, obsessive-compulsive disorders, eating disorders, and schizophrenia. Investigations of functions and connections of the insular cortex suggest that sensory information including gustatory, olfactory, visual, auditory, and tactile inputs converge on the insular cortex, and that these multimodal sensory information may be integrated there.     

Somatic and limbic cortex activation in esophageal distention: A functional imaging study

Little is known about the cerebral representations of visceral sensations in humans. Using functional magnetic resonance imaging (fMRI), we mapped the cortical areas of the human brain that were activated by mechanical stimulation of the esophagus in 5 healthy volunteers. Stimulation probes were placed into the distal part of the esophagus and inflated to produce a local distention. The cerebral activation pattern was related to the strength and quality of the stimulus. The weakest stimulus accompanied by a well-localized albeit weak retrosternal sensation activated only the parietal opercular cortices, probably including the secondary somatosensory cortex (SII). Additional activation of the primary sensorimotor cortex (SI) at the level of the face and mouth representation as well as of the right premotor cortex was found during repetitive distention of the esophagus at 0.5 Hz. Repetitive stimulation at 1 Hz additionally activated the insulabilaterally. The strongest distention stimulus, which caused a painful retrosternal sensation, resulted in an activation of the anterior cingulate cortex. Our findings demonstrate that SII is the primary cortical target of visceral afferents originating in the esophagus. Limbic structures become engaged when the visceral senstion is unpleasant or painful.     

Using fMRI to dissociate sensory encoding from cognitive evaluation of heat pain intensity

Neuroimaging studies of painful stimuli in humans have identified a network of brain regions that is more extensive than identified previously in electrophysiological and anatomical studies of nociceptive pathways. This extensive network has been described as a pain matrix of brain regions that mediate the many interrelated aspects of conscious processing of nociceptive input such as perception, evaluation, affective response, and emotional memory. We used functional magnetic resonance imaging in healthy human subjects to distinguish brain regions required for pain sensory encoding from those required for cognitive evaluation of pain intensity. The results suggest that conscious cognitive evaluation of pain intensity in the absence of any sensory stimulation activates a network that includes bilateral anterior insular cortex/frontal operculum, dorsal lateral prefrontal cortex, bilateral medial prefrontal cortex/anterior cingulate cortex, right superior parietal cortex, inferior parietal lobule, orbital prefrontal cortex, and left occipital cortex. Increased activity common to both encoding and evaluation was observed in bilateral anterior insula/frontal operculum and medial prefrontal cortex/anterior cingulate cortex. We hypothesize that these two regions play a crucial role in bridging the encoding of pain sensation and the cognitive processing of sensory input.     

Common cortical and subcortical targets of the dorsolateral prefrontal and posterior parietal cortices in the rhesus monkey: evidence for a distributed neural network subserving spatially guided behavior

Common efferent projections of the dorsolateral prefrontal cortex and posterior parietal cortex were examined in 3 rhesus monkeys by placing injections of tritiated amino acids and HRP in frontal and parietal cortices, respectively, of the same hemisphere. Terminal labeling originating from both frontal and parietal injection sites was found to be in apposition in 15 ipsilateral cortical areas: the supplementary motor cortex, the dorsal premotor cortex, the ventral premotor cortex, the anterior arcuate cortex (including the frontal eye fields), the orbitofrontal cortex, the anterior and posterior cingulate cortices, the frontoparietal operculum, the insular cortex, the medial parietal cortex, the superior temporal cortex, the parahippocampal gyrus, the presubiculum, the caudomedial lobule, and the medial prestriate cortex. Convergent terminal labeling was observed in the contralateral hemisphere as well, most prominently in the principal sulcal cortex, the superior arcuate cortex, and the superior temporal cortex. In certain common target areas, as for example the cingulate cortices, frontal and parietal efferents terminate in an array of interdigitating columns, an arrangement much like that observed for callosal and associational projections to the principal sulcus (Goldman-Rakic and Schwartz, 1982). In other areas, frontal and parietal terminals exhibit a laminar complementarity: in the depths of the superior temporal sulcus, prefrontal terminals are densely distributed within laminae I, III, and V, whereas parietal terminals occupy mainly laminae IV and VI directly below the prefrontal bands. Subcortical structures also receive apposing or overlapping projections from both prefrontal and parietal cortices. The dorsolateral prefrontal and posterior parietal cortices project to adjacent, longitudinal domains of the neostriatum, as has been described previously (Selemon and Goldman-Rakic, 1985); these projections are also found in close apposition in the claustrum, the amygdala, the caudomedial lobule, and throughout the anterior medial, medial dorsal, lateral dorsal, and medial pulvinar nuclei of the thalamus. In the brain stem, both areas of association cortex project to the intermediate layers of the superior colliculus and to the midline reticular formation of the pons.(ABSTRACT TRUNCATED AT 400 WORDS)     

Resting-state connectivity in the default mode network and insula during experimental low back pain简

Functional magnetic resonance imaging studies have shown that the insular cortex has a significant role in pain identification and information integration, while the default mode network is associated with cognitive and memory-related aspects of pain perception. However, changes in the functional connectivity between the default mode network and insula during pain remain unclear. This study used 3.0 T functional magnetic resonance imaging scans in 12 healthy subjects aged 24.8 ± 3.3 years to compare the differences in the functional activity and connectivity of the insula and default mode network between the baseline and pain condition induced by intramuscular injection of hypertonic saline. Compared with the baseline, the insula was more functionally connected with the medial prefrontal and lateral temporal cortices, whereas there was lower connectivity with the posterior cingulate cortex, precuneus and inferior parietal lobule in the pain condition. In addition, compared with baseline, the anterior cingulate cortex exhibited greater connectivity with the posterior insula, but lower connectivity with the anterior insula, during the pain condition. These data indicate that experimental low back pain led to dysfunction in the connectivity between the insula and default mode network resulting from an impairment of the regions of the brain related to cognition and emotion, suggesting the importance of the interaction between these regions in pain processing.