Functional resting-state networks are differentially affected in schizophrenia

Neurobiological theories posit that schizophrenia relates to disturbances in connectivity between brain regions. Resting-state functional magnetic resonance imaging is a powerful tool for examining functional connectivity and has revealed several canonical brain networks, including the default mode, dorsal attention, executive control, and salience networks. The purpose of this study was to examine changes in these networks in schizophrenia. 42 patients with schizophrenia and 61 healthy subjects completed a RS-fMRI scanning session. Seed-based region-of-interest correlation analysis was used to identify the default mode, dorsal attention, executive control, and salience networks. Compared to healthy subjects, individuals with schizophrenia demonstrated greater connectivity between the posterior cingulate cortex, a key hub of the default mode, and the left inferior gyrus, left middle frontal gyrus, and left middle temporal gyrus. Interestingly, these regions were more strongly connected to the executive control network in healthy control subjects. In contrast to the default mode, patients demonstrated less connectivity in the executive control and dorsal attention networks. No differences were observed in the salience network. The results indicate that resting-state networks are differentially affected in schizophrenia. The alterations are characterized by reduced segregation between the default mode and executive control networks in the prefrontal cortex and temporal lobe, and reduced connectivity in the dorsal attention and executive control networks. The changes suggest that the process of functional specialization is altered in schizophrenia. Further work is needed to determine if the alterations are related to disturbances in white matter connectivity, neurodevelopmental abnormalities, and genetic risk for schizophrenia.     

Switching between executive and default mode networks in posttraumatic stress disorder: alterations in functional connectivity

Background

Working memory processing and resting-state connectivity in the default mode network are altered in patients with post-traumatic stress disorder (PTSD). Because the ability to effortlessly switch between concentration on a task and an idling state during rest is implicated in both these alterations, we undertook a functional magnetic resonance imaging study with a block design to analyze task-induced modulations in connectivity.

Methods

We performed a working memory task and psychophysiologic interaction analyses with the posterior cingulate cortex and the medial prefrontal cortex as seed regions during fixation in 12 patients with severe, chronic PTSD and 12 healthy controls.

Results

During the working memory task, the control group showed significantly stronger connectivity with areas implicated in the salience and executive networks, including the right inferior frontal gyrus and the right inferior parietal lobule. The PTSD group showed stronger connectivity with areas implicated in the default mode network, namely enhanced connectivity between the posterior cingulate cortex and the right superior frontal gyrus and between the medial prefrontal cortex and the left parahip-pocampal gyrus.

Limitations

Because we were studying alterations in patients with severe, chronic PTSD, we could not exclude patients taking medication. The small sample size may have limited the power of our analyses. To avoid multiple testing in a small sample, we only used 2 seed regions for our analyses.

Conclusion

The different patterns of connectivity imply significant group differences with task-induced switches (i.e., engaging and disengaging the default mode network and the central-executive network).     

Sustained activity within the default mode network during an implicit memory task

Recent neuroimaging studies have shown that several brain regions - namely, the posterior cingulate cortex (PCC), ventral medial prefrontal cortex (vmPFC), and the bilateral angular gyrus - are more active during resting states than during cognitive tasks (i.e., default mode network). Although there is evidence showing that the default mode network is associated with unconscious state, it is unclear whether this network is associated with unconscious processing when normal human subjects perform tasks without awareness. We manipulated the level of conscious processing in normal subjects by asking them to perform an implicit and an explicit memory task, and analyzed signal changes in the default mode network for the stimuli versus baseline in both tasks. The functional magnetic resonance imaging (fMRI) analysis showed that the level of activation in regions within this network during the implicit task was not significantly different from that during the baseline, except in the left angular gyrus and the insula. There was strong deactivation for the explicit task when compared with the implicit task in the default mode regions, except in the left angular gyrus and the left middle temporal gyrus. These data suggest that the activity in the default network is sustained and less disrupted when an implicit memory task is performed, but is suspended when explicit retrieval is required. These results provide evidence that the default mode network is associated with unconscious processing when human subjects perform an implicit memory task.     

Proactive response inhibition abnormalities in the sensorimotor cortex of patients with schizophrenia

BackgroundPrevious studies of response inhibition in patients with schizophrenia have focused on reactive inhibition tasks (e.g., stop-signal, go/no-go), primarily observing lateral prefrontal cortex abnormalities. However, recent studies suggest that purposeful and sustained (i.e., proactive) inhibition may also be affected in these patients.MethodsPatients with chronic schizophrenia and healthy controls underwent fMRI while inhibiting motor responses during multisensory (audiovisual) stimulation. Resting state data were also collected.ResultsWe included 37 patients with schizophrenia and 37 healthy controls in our study. Both controls and patients with schizophrenia successfully inhibited the majority of overt motor responses. Functional results indicated basic inhibitory failure in the lateral premotor and sensorimotor cortex, with opposing patterns of positive (schizophrenia) versus negative (control) activation. Abnormal activity was associated with independently assessed signs of psychomotor retardation. Patients with schizophrenia also exhibited unique activation of the pre–supplementary motor area (pre-SMA)/SMA and precuneus relative to baseline as well as a failure to deactivate anterior nodes of the default mode network. Independent resting-state connectivity analysis indicated reduced connectivity between anterior (task results) and posterior regions of the sensorimotor cortex for patients as well as abnormal connectivity between other regions (cerebellum, thalamus, posterior cingulate gyrus and visual cortex).LimitationsAside from rates of false-positive responses, true proactive response inhibition tasks do not provide behavioural metrics that can be independently used to quantify task performance.ConclusionOur results suggest that basic cortico-cortico and intracortical connections between the sensorimotor cortex and adjoining regions are impaired in patients with schizophrenia and that these impaired connections contribute to inhibitory failures (i.e., a positive rather than negative hemodynamic response).     

Schizophrenic Patients and Their Unaffected Siblings Share Increased Resting-State Connectivity in the Task-Negative Network but Not Its Anticorrelated Task-Positive Network

Background:

Abnormal connectivity of the anticorrelated intrinsic networks, the task-negative network (TNN), and the task-positive network (TPN) is implicated in schizophrenia. Comparisons between schizophrenic patients and their unaffected siblings enable further understanding of illness susceptibility and pathophysiology. We examined the resting-state connectivity differences in the intrinsic networks between schizophrenic patients, their unaffected siblings, and healthy controls.

Methods:

Resting-state functional magnetic resonance images were obtained from 25 individuals in each subject group. The posterior cingulate cortex/precuneus and right dorsolateral prefrontal cortex were used as seed regions to identify the TNN and TPN through functional connectivity analysis. Interregional connectivity strengths were analyzed using overlapped intrinsic networks composed of regions common to all subject groups.

Results:

Schizophrenic patients and their unaffected siblings showed increased connectivity in the TNN between the bilateral inferior temporal gyri. By contrast, schizophrenic patients alone demonstrated increased connectivity between the posterior cingulate cortex/precuneus and left inferior temporal gyrus and between the ventral medial prefrontal cortex and right lateral parietal cortex in the TNN. Schizophrenic patients exhibited increased connectivity between the left dorsolateral prefrontal cortex and right inferior frontal gyrus in the TPN relative to their unaffected siblings, though this trend only approached statistical significance in comparison to healthy controls.

Conclusion:

Resting-state hyperconnectivity of the intrinsic networks may disrupt network coordination and thereby contribute to the pathophysiology of schizophrenia. Similar, though milder, hyperconnectivity of the TNN in unaffected siblings of schizophrenic patients may contribute to the identification of schizophrenia endophenotypes and ultimately to the determination of schizophrenia risk genes.     

Frequency‐specific changes in the default mode network in patients with cingulate gyrus epilepsy

To identify abnormal functional connectivity of the default mode network in cingulate gyrus epilepsy, which may yield new information about the default mode network and suggest a new cingulate gyrus epilepsy biomarker. Fifteen patients with cingulate gyrus epilepsy (mean age = 21 years) and 15 healthy controls (mean age = 24 years) were studied in the resting state using magnetoencephalography. Twelve brain areas of interest in the default mode network were extracted and investigated with multifrequency signals that included alpha (α, 8–13 Hz), beta (β, 14–30 Hz), and gamma (γ, 31–80 Hz) band oscillations. Patients with cingulate gyrus epilepsy had significantly greater connectivity in all three frequency bands (α, β, γ). A frequency‐specific elevation of functional connectivity was found in patients compared to controls. The greater functional connectivity in the γ band was significantly more prominent than that of the α and β bands. Patients with cingulate gyrus epilepsy and controls differed significantly in functional connectivity between the left angular gyrus and left posterior cingulate cortex in the α, β, and γ bands. The results of the node degree analysis were similar to those of the functional connectivity analysis. Our findings reveal for the first time that brain activity in the γ band may play a key role in the default mode network in cingulate gyrus epilepsy. Altered functional connectivity of the left angular gyrus and left posterior cingulate cortex may be a new biomarker for cingulate gyrus epilepsy.     

Functional disintegration in paranoid schizophrenia using resting-state fMRI

Functional disintegration has been observed in schizophrenia during task performance. We sought to investigate functional disintegration during rest because an intrinsic functional brain organization, including both "task-negative" (i.e., "default mode") and "task-positive" networks, has been suggested to play an important role in integrating ongoing information processing. Additionally, the brain regions that are involved in the intrinsic organization are believed to be abnormal in schizophrenia. Patients with paranoid schizophrenia (N=18) and healthy volunteers (N=18) underwent a resting-state fMRI scan. Functional connectivity analysis was used to identify the connectivity between each pair of brain regions within this intrinsic organization, and differences were examined in patients versus healthy volunteers. Compared to healthy volunteers, patients showed significant differences in connectivity within networks and between networks, most notably in the connectivities associated with the bilateral dorsal medial prefrontal cortex, the lateral parietal region, the inferior temporal gyrus of the "task-negative" network and with the right dorsolateral prefrontal cortex and the right dorsal premotor cortex of the "task-positive" network. These results suggested that the interregional functional connectivities in the intrinsic organization are altered in patients with paranoid schizophrenia. These abnormalities could be the source of abnormalities in the coordination of and competition between information processing activities in the resting brain of paranoid patients.     

Default mode network activity in schizophrenia studied at resting state using probabilistic ICA

Alterations in brain function in schizophrenia and other neuropsychiatric disorders are evident not only during specific cognitive challenges, but also from functional MRI data obtained during a resting state. Here we apply probabilistic independent component analysis (pICA) to resting state fMRI series in 25 schizophrenia patients and 25 matched healthy controls. We use an automated algorithm to extract the ICA component representing the default mode network (DMN) as defined by a DMN-specific set of 14 brain regions, resulting in z-scores for each voxel of the (whole-brain) statistical map. While goodness of fit was found to be similar between the groups, the region of interest (ROI) as well as voxel-wise analysis of the DMN showed significant differences between groups. Healthy controls revealed stronger effects of pICA-derived connectivity measures in right and left dorsolateral prefrontal cortices, bilateral medial frontal cortex, left precuneus and left posterior lateral parietal cortex, while stronger effects in schizophrenia patients were found in the right amygdala, left orbitofrontal cortex, right anterior cingulate and bilateral inferior temporal cortices. In patients, we also found an inverse correlation of negative symptoms with right anterior prefrontal cortex activity at rest and negative symptoms. These findings suggest that aberrant default mode network connectivity contributes to regional functional pathology in schizophrenia and bears significance for core symptoms.     

Some observations on the course and composition of the cingulum bundle in the rhesus monkey

The course and composition of the cingulum bundle was examined by using the autoradiographic tracer technique in the rhesus monkey. The cingulum bundle is observed to consist of three major fiber components originating from thalamus, cingulate gyrus, and cortical association areas. Following isotope injections in the anterior and lateral dorsal thalamic nuclei, labelled fibers form an arch in the white matter behind the cingulate sulcus and occupy the ventral sector of the cingulum bundle. The fibers from the anterior thalamic nucleus coursing in the cingulum bundle extended rostrally to the frontal cortex and caudally to area 23 and the retrosplenial cortex. In contrast, the fibers from lateral dorsal nucleus reached the retrosplenial cortex as well as the parahippocampal gyrus and presubiculum. Efferent fibers from the cingulate gyrus occupy a dorsolateral sector of the cingulum bundle. Those fibers from area 24 of the cingulate gyrus are directed to the premotor and prefrontal regions as well as area 23 and retrosplenial cortex. The fibers from area 23 extend rostrally to the prefrontal cortex and caudoventrally to the presubiculum and parahippocampal gyrus. Finally, an association component originates mainly from prefrontal cortex and posterior parietal region. These fibers occupy a more dorsal and lateral periphery in the cingulate white matter. Cingulum bundle fibers from the prefrontal cortex extend up to the retrosplenial cortex while those from the posterior parietal cortex extend caudally to the parahippocampal gyrus and presubiculum, and rostrally up to the prefrontal cortex.     

Altered insula-prefrontal functional connectivity correlates to decreased vigilant attention after total sleep deprivation

BackgroundSleep deprivation can robustly affect vigilant attention. The insula is a key hub of the salience network that mediates shifting attention between endogenous and exogenous states. However, little is known regarding the involvement of insular functional connectivity in impaired vigilant attention after total sleep deprivation (TSD). The purpose of this study is to explore the alterations in insular functional connectivity and its association with vigilant attention performance following TSD.MethodsTwenty-six adult men were enrolled in the study. Participants underwent two counterbalanced resting-state functional magnetic resonance imaging (rs-fMRI) scans, once in rested wakefulness (RW) and once after 36 h of TSD. Seed-based functional connectivity analysis was performed using rs-fMRI data for the left and right insula. The vigilant attention was measured using a psychomotor vigilance test (PVT). Furthermore, Pearson correlation analysis was conducted to investigate the relationship between altered insular functional connectivity and PVT performance.ResultsCompared to RW, enhanced functional connectivity was observed between the insula and prefrontal cortex and anterior cingulate cortex, while reduced functional connectivity was observed between the insula and temporal, parietal, and occipital regions following TSD. Moreover, altered insular functional connectivity with the prefrontal cortex, ie superior frontal gyrus and middle frontal gyrus, and inferior temporal gyrus was correlated with PVT performance after TSD.ConclusionOur results suggest that insular coupling with the prefrontal cortex and inferior temporal gyrus may act as neural indicators for vigilant attention impairment, which further reveals the critical role of the salience network in cognitive decline following TSD.     

长期海洛因依赖者前额叶功能连接的变化

以前额叶为种子点,利用静息态fMRI进行全脑时域相关的功能连接分析,观察长期海洛因成瘾者前额叶功能连接的变化。结果发现相比于正常对照,以左侧前额叶为种子点进行功能连接分析,海洛因成瘾者左侧前额叶与左侧海马、右侧前扣带回、左侧额中回、右侧额中回、右侧楔前叶功能连接明显降低;以右侧前额叶为种子点进行功能连接分析,海洛因成瘾者右侧前额叶与左侧眶额叶、左侧额中回功能连接明显降低。提示长期海洛因成瘾者前额叶与相关脑区的功能连接减弱,可能与海洛因成瘾的维持与戒断后复吸相关。     

Aberrant "default mode" functional connectivity in schizophrenia

OBJECTIVE: The "default mode" has been defined as a baseline condition of brain function and is of interest because its component brain regions are believed to be abnormal in schizophrenia. It was hypothesized that the default mode network would show abnormal activation and connectivity in patients with schizophrenia. METHOD: Patients with schizophrenia (N=21) and healthy comparison subjects (N=22) performed an auditory oddball task during functional magnetic resonance imaging (fMRI). Independent component analysis was used to identify the default mode component. Differences in the spatial and temporal aspects of the default mode network were examined in patients versus comparison subjects. RESULTS: Healthy comparison subjects and patients had significant spatial differences in the default mode network, most notably in the frontal, anterior cingulate, and parahippocampal gyri. In addition, activity in patients in the medial frontal, temporal, and cingulate gyri correlated with severity of positive symptoms. The patients also showed significantly higher frequency fluctuations in the temporal evolution of the default mode. CONCLUSIONS: Schizophrenia is associated with altered temporal frequency and spatial location of the default mode network. The authors hypothesized that this network may be under- or overmodulated by key regions, including the anterior and posterior cingulate cortex. In addition, the altered temporal fluctuations in patients may result from a change in the connectivity of these regions with other brain networks.     

Remote effects of hippocampal damage on default network connectivity in the human brain

In the healthy human brain the hippocampus is known to work in concert with a variety of cortical brain regions. It has recently been linked to the default network of the brain, with the precuneus being its core hub. Here we studied the remote effects of damage to the hippocampus on functional connectivity patterns of the precuneus. From 14 epilepsy patients with selective, unilateral hippocampal sclerosis and 8 healthy control subjects, we acquired functional MRI data during performance of an object-location memory task. We assessed functional connectivity of a functionally defined region in the precuneus, which showed the typical properties of the default network: significant task-related deactivation, which was reduced in patients compared to control subjects. In control subjects, a largely symmetrical pattern of functional coherence to the precuneus emerged, including canonical default network areas such as ventral medial prefrontal cortex, inferior parietal cortex, and the hippocampi. Assessment of group differences within the default network areas revealed reduced connectivity to the precuneus in ipsilesional middle temporal gyrus and hippocampus in left hippocampal sclerosis patients compared to controls. Furthermore, left hippocampal sclerosis patients showed lower connectivity than right hippocampal sclerosis patients in left middle temporal gyrus, ventral medial prefrontal cortex, and left amygdala. We report remote effects of unilateral hippocampal damage on functional connectivity between distant brain regions associated with the default network of the human brain. These preliminary results underline the impact of circumscribed pathology on functionally connected brain regions.     

Changes of resting state brain networks in amyotrophic lateral sclerosis

The defining feature of amyotrophic lateral sclerosis is degeneration of upper and lower motor neurons but extramotor involvement, evidenced for example by executive dysfunction, has also been demonstrated. Here we employed a novel functional imaging approach, the analysis of resting state activity, followed by the definition of functionally connected brain networks by independent component analysis (ICA) to assess differences between ALS patients (n = 20) and healthy controls (n = 20). ICA analysis revealed 5 typical brain networks among which the so-called default mode network and the sensori-motor network showed distinct differences between patients and controls. The default mode network showed less activation in patients in several regions including the ventral anterior cingulate cortex, posterior cingulate cortex and the left and right inferior parietal cortex, regions that have been linked previously to executive functions. The sensori-motor network showed group differences in the premotor cortex. We propose that resting state analysis affords a new and simple means to assess disease-related neurofunctional alterations in widespread brain networks. A decisive advantage is that no task is demanded from the subjects and, thus, the problem of differential task difficulty and effort between groups is circumvented.     

Neuropsychiatric symptoms in Alzheimer's disease are related to functional connectivity alterations in the salience network

Neuropsychiatric syndromes are highly prevalent in Alzheimer's disease (AD), but their neurobiology is not completely understood. New methods in functional magnetic resonance imaging, such as intrinsic functional connectivity or “resting‐state” analysis, may help to clarify this issue. Using such approaches, alterations in the default‐mode and salience networks (SNs) have been described in Alzheimer's, although their relationship with specific symptoms remains unclear. We therefore carried out resting‐state functional connectivity analysis with 20 patients with mild to moderate AD, and correlated their scores on neuropsychiatric inventory syndromes (apathy, hyperactivity, affective syndrome, and psychosis) with maps of connectivity in the default mode network and SN. In addition, we compared network connectivity in these patients with that in 17 healthy elderly control subjects. All analyses were controlled for gray matter density and other potential confounds. Alzheimer's patients showed increased functional connectivity within the SN compared with controls (right anterior cingulate cortex and left medial frontal gyrus), along with reduced functional connectivity in the default‐mode network (bilateral precuneus). A correlation between increased connectivity in anterior cingulate cortex and right insula areas of the SN and hyperactivity syndrome (agitation, irritability, aberrant motor behavior, euphoria, and disinhibition) was found. These findings demonstrate an association between specific network changes in AD and particular neuropsychiatric symptom types. This underlines the potential clinical significance of resting state alterations in future diagnosis and therapy. Hum Brain Mapp 35:1237–1246, 2014. © 2013 Wiley Periodicals, Inc.     

Default network connectivity during a working memory task

The default network exhibits correlated activity at rest and has shown decreased activation during performance of cognitive tasks. There has been little investigation of changes in connectivity of this network during task performance. In this study, we examined task‐related modulation of connectivity between two seed regions from the default network posterior cingulated cortex (PCC) and medial prefrontal cortex (mPFC) and the rest of the brain in 12 healthy adults. The purpose was to determine (1) whether connectivity within the default network differs between a resting state and performance of a cognitive (working memory) task and (2) whether connectivity differs between these nodes of the default network and other brain regions, particularly those implicated in cognitive tasks. There was little change in connectivity with the other main areas of the default network for either seed region, but moderate task‐related changes in connectivity occurred between seed regions and regions outside the default network. For example, connectivity of the mPFC with the right insula and the right superior frontal gyrus decreased during task performance. Increased connectivity during the working memory task occurred between the PCC and bilateral inferior frontal gyri, and between the mPFC and the left inferior frontal gyrus, cuneus, superior parietal lobule, middle temporal gyrus and cerebellum. Overall, the areas showing greater correlation with the default network seed regions during task than at rest have been previously implicated in working memory tasks. These changes may reflect a decrease in the negative correlations occurring between the default and task‐positive networks at rest. Hum Brain Mapp, 2011. © 2010 Wiley‐Liss, Inc.     

Alterations of fronto-temporal connectivity during word encoding in schizophrenia

Cognitive deficits, including impaired verbal memory, are prominent in schizophrenia and lead to increased disability. Functional neuroimaging of patients with schizophrenia performing memory tasks has revealed abnormal activation patterns in prefrontal cortex and temporo-limbic regions. Aberrant fronto-temporal interactions thus represent a potential pathophysiological mechanism underlying verbal memory deficits, yet this hypothesis of disturbed connectivity is not tested directly with standard activation studies. We performed within-subject correlations of frontal and temporal timeseries to measure functional connectivity during verbal encoding. Our results confirm earlier findings of aberrant fronto-temporal connectivity in schizophrenia, and extend them by identifying distinct alterations within dorsal and ventral prefrontal cortex. Relative to healthy controls, patients with schizophrenia had reduced connectivity between the dorsolateral prefrontal cortex (DLPFC) and temporal lobe areas including parahippocampus and superior temporal gyrus. In contrast, patients showed increased connectivity between a region of ventrolateral prefrontal cortex (VLPFC) and these same temporal lobe regions. Higher temporal-DLPFC connectivity during encoding was associated with better subsequent recognition accuracy in controls, but not patients. Temporal-VLPFC connectivity was uncorrelated with recognition accuracy in either group. The results suggest that reduced temporal-DLPFC connectivity in schizophrenia could underlie encoding deficits, and increased temporal-VLPFC connectivity may represent an ineffective compensatory effort.     

Significance of longitudinal changes in the default‐mode network for cognitive recovery after stroke

Although a considerable number of patients suffer from cognitive impairments after stroke, the neural mechanism of cognitive recovery has not yet been clarified. Repeated resting‐state functional magnetic resonance imaging (fMRI) was used in this study to examine longitudinal changes in the default‐mode network (DMN) during the 6 months after stroke, and to investigate the relationship between DMN changes and cognitive recovery. Out of 24 initially recruited right‐hemispheric stroke patients, 11 (eight males, mean age 55.7 years) successfully completed the repeated fMRI protocol. Patients underwent three fMRI sessions at 1, 3 and 6 months after stroke. Their DMNs were analysed and compared with those of 11 age‐matched healthy subjects (nine males, mean age 56.2 years). Correlations between DMN connectivity and improvement of the cognitive performance scores were also assessed. The stroke patients were found to demonstrate markedly decreased DMN connectivity of the posterior cingulate cortex, precuneus, medial frontal gyrus and inferior parietal lobes at 1 month after stroke. At 3 months after stroke, the DMN connectivity of these brain areas was almost restored, suggesting that the period is critical for neural reorganization. The DMN connectivity of the dorsolateral prefrontal cortex in the contralesional hemisphere showed a significant correlation with cognitive function recovery in stroke patients, and should be considered a compensatory process for overcoming cognitive impairment due to brain lesion. This is the first longitudinal study to demonstrate the changes in DMN during recovery after stroke and the key regions influencing cognitive recovery.     

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.     

Altered resting-state functional connectivity and anatomical connectivity of hippocampus in schizophrenia

Hippocampus has been implicated in participating in the pathophysiology of schizophrenia. However, the functional and anatomical connectivities between hippocampus and other regions are rarely concurrently investigated in schizophrenia. In the present study, both functional magnetic resonance imaging (fMRI) during rest and diffusion tensor imaging (DTI) were performed on 17 patients with paranoid schizophrenia and 14 healthy subjects. Resting-state functional connectivities of the bilateral hippocampi were separately analyzed by selecting the anterior hippocampus as region of interest. The fornix body was reconstructed by diffusion tensor tractography, and the integrity of this tract was evaluated using fractional anisotropy (FA). In patients with schizophrenia, the bilateral hippocampi showed reduced functional connectivities to some regions which have been reported to be involved in episodic memory, such as posterior cingulate cortex, extrastriate cortex, medial prefrontal cortex, and parahippocampus gyrus. We speculated that these reduced connectivity may reflect the disconnectivity within a neural network related to the anterior hippocampus in schizophrenia. Meanwhile the mean FA of the fornix body was significantly reduced in patients, indicating the damage in the hippocampal anatomical connectivity in schizophrenia. The concurrence of the functional disconnectivity and damaged anatomical connectivity between the hippocampus and other regions in schizophrenia suggest that the functional–anatomical relationship need to be further investigated.