Posterior Medial Prefrontal Cortex Research Articles

Brain structural indicators of β-amyloid neuropathology

Recent efforts demonstrated the efficacy of identifying early-stage neuropathology of Alzheimer’s disease (AD) through lumbar puncture cerebrospinal fluid assessment and positron emission tomography (PET) radiotracer imaging. These methods are effective yet are invasive, expensive, and not widely accessible. We extend and improve the multiscale structural mapping (MSSM) procedure to develop structural indicators of β-amyloid neuropathology in preclinical AD, by capturing both macrostructural and microstructural properties throughout the cerebral cortex using a structural MRI. We find that the MSSM signal is regionally altered in clear positive and negative cases of preclinical amyloid pathology (N = 220) when cortical thickness alone or hippocampal volume is not. It exhibits widespread effects of amyloid positivity across the posterior temporal, parietal, and medial prefrontal cortex, surprisingly consistent with the typical pattern of amyloid deposition. The MSSM signal is significantly correlated with amyloid PET in almost half of the cortex, much of which overlaps with regions where beta-amyloid accumulates, suggesting it could provide a regional brain ‘map’ that is not available from systemic markers such as plasma markers.

Memory reactivation and suppression modulate integration of the semantic features of related memories in hippocampus.

Encoding an event that overlaps with a previous experience may involve reactivating an existing memory and integrating it with new information or suppressing the existing memory to promote formation of a distinct, new representation. We used fMRI during overlapping event encoding to track reactivation and suppression of individual, related memories. We further used a model of semantic knowledge based on Wikipedia to quantify both reactivation of semantic knowledge related to a previous event and formation of integrated memories containing semantic features of both events. Representational similarity analysis revealed that reactivation of semantic knowledge related to a prior event in posterior medial prefrontal cortex (pmPFC) supported memory integration during new learning. Moreover, anterior hippocampus (aHPC) formed integrated representations combining the semantic features of overlapping events. We further found evidence that aHPC integration may be modulated on a trial-by-trial basis by interactions between ventrolateral PFC and anterior mPFC, with suppression of item-specific memory representations in anterior mPFC inhibiting hippocampal integration. These results suggest that PFC-mediated control processes determine the availability of specific relevant memories during new learning, thus impacting hippocampal memory integration.

Non-overlapping sets of neurons encode behavioral response determinants across different tasks in the posterior medial prefrontal cortex.

Higher mammals are able to simultaneously learn and perform a wide array of complex behaviors, which raises questions about how the neural representations of multiple tasks coexist within the same neural network. Do neurons play invariant roles across different tasks? Alternatively, do the same neurons play different roles in different tasks? To address these questions, we examined neuronal activity in the posterior medial prefrontal cortex of primates while they were performing two versions of arm-reaching tasks that required the selection of multiple behavioral tactics (i.e., the internal protocol of action selection), a critical requirement for the activation of this area. During the performance of these tasks, neurons in the pmPFC exhibited selective activity for the tactics, visuospatial information, action, or their combination. Surprisingly, in 82% of the tactics-selective neurons, the selective activity appeared in a particular task but not in both. Such task-specific neuronal representation appeared in 72% of the action-selective neurons. In addition, 95% of the neurons representing visuospatial information showed such activity exclusively in one task but not in both. Our findings indicate that the same neurons can play different roles across different tasks even though the tasks require common information, supporting the latter hypothesis.

Characteristic cortico-cortical connection profile of human precuneus revealed by probabilistic tractography

It is generally hypothesized that functional connectivity (FC) reflects the underlying structural connectivity (SC). The precuneus is associated with highly integrated cognitive functions. However, our understanding of the structural connections that could underlie them is limited. This study aimed to characterize the cortico-cortical connections by probabilistic tractography. The precuneus corresponds to the five cortical areas (7Am, PCV, 7Pm, 7m, POS2) on the HCP MMP atlas. We first conducted the atlas-based probabilistic tractography. The anterior part (7Am) was strongly connected to the sensorimotor region. The dorsal part (7Am, 7Pm) was highly connected with the adjacent parietal and temporal cortex, while the ventral part (PCV, 7m) showed strong connections with the adjacent posterior cingulate and medial prefrontal cortex. The most posterior part (POS2) was explicitly connected to the visual cortex. In addition, there was a correlation between SC and resting-state fMRI connectivity (Spearman’s rank correlation coefficient = 0.322 ± 0.019, p < 0.05 corrected at subject level). Collectively, the current study revealed the characteristic connectional profile of precuneus, which could shed light on the structural heterogeneity for the future functional analyses.

Differential patterns of default mode network activity associated with negative and positive rumination in bipolar disorder

BackgroundPatients with bipolar disorder (BD) engage in both negative and positive rumination, defined as maladaptive self-focused thinking, and this tendency predicts depressive and manic episodes, respectively. Prior research in patients with major depression implicates regions of the default mode network (DMN) consistent with the self-focused nature of rumination. Little is known about the neural correlates of rumination in bipolar disorder. MethodsFifteen euthymic patients with BD (twelve with Type I) and 17 healthy controls (HC) performed negative and positive rumination induction tasks, as well as a distraction task, followed by a self-related trait judgment task while undergoing functional magnetic resonance imaging (fMRI). Participants also underwent resting state scans. We examined functional connectivity at rest and during the induction tasks, as well as task-based activation during the trait judgment task, in core regions of the DMN. ResultsCompared to HC, patients with BD showed greater functional connectivity between the posterior cingulate cortex (PCC) and medial prefrontal cortex (MPFC) at rest and during positive rumination, compared to distraction. They also showed greater activity in the PCC and MPFC during processing of positive traits, following positive rumination. At rest and during negative rumination compared to distraction, patients with BD showed greater functional connectivity between the PCC and inferior parietal lobule than HC. ConclusionsThese findings demonstrate that negative and positive rumination are subserved by different patterns of connectivity within the DMN in BD. Additionally, the PCC and MPFC are key regions involved in the processing of positive self-relevant traits following positive rumination.

Brain TSPO expression is associated with plasma pTau181 &amp; pTau231 across the AD spectrum

AbstractBackgroundMicroglial activation is an important component of the immune response in the brain of AD patients and has been shown to follow a similar propagation pattern to tau tangle accumulation. However, it is unclear to what extent cerebral microglial activation is associated with biofluid concentrations of phosphorylated tau (pTau). The objective was to investigate whether concentrations of pTau181 and pTau231 are correlated with microglial activation indexed by [11C]PBR28 PET across the AD spectrum.MethodThe present study was conducted in a population of 130 individuals from the Translational Biomarkers of Aging and Dementia (TRIAD) cohort: 20 young cognitively unimpaired, 65 cognitively unimpaired elderlies, 31 with mild cognitive impairment and 14 with AD dementia. Participants were evaluated with blood biomarkers and [11C]PBR28 PET. Plasma pTau181 and pTau231 concentrations were quantified using a Simoa assay. Microglial activation was assessed via [11C]PBR28 PET, standardized uptake value ratios (SUVRs) were calculated between 0 and 90 minutes post‐injection, using cerebellum grey matter as the reference region. Voxel‐based regression models evaluated the relationship between plasma pTau181 and pTau231 with neuroinflammation as assessed by PET, correcting for age and sex.ResultIn the present study, positive correlations were found between concentrations of both pTau181 and pTau231 and neuroinflammation indexed by PET‐imaging. Voxel‐level analyses indicated that these associations prenominated in regions of the default mode network including the precuneus, posterior cingulate cortex and medial prefrontal cortex. These regional associations survived corrections for multiple comparisons.ConclusionPeripheral phosphorylated tau is associated with neuroinflammation in brain regions associated with AD. Our findings highlight the importance of neuroinflammation in the pathogenesis of AD.

Brain TSPO expression is associated with plasma pTau181 &amp; pTau231 across the AD spectrum

AbstractBackgroundMicroglial activation is an important component of the immune response in the brain of AD patients and has been shown to follow a similar propagation pattern to tau tangle accumulation. However, it is unclear to what extent cerebral microglial activation is associated with biofluid concentrations of phosphorylated tau (pTau). The objective was to investigate whether concentrations of pTau181 and pTau231 are correlated with microglial activation indexed by [11C]PBR28 PET across the AD spectrum.MethodThe present study was conducted in a population of 130 individuals from the Translational Biomarkers of Aging and Dementia (TRIAD) cohort: 20 young cognitively unimpaired, 65 cognitively unimpaired elderlies, 31 with mild cognitive impairment and 14 with AD dementia. Participants were evaluated with blood biomarkers and [11C]PBR28 PET. Plasma pTau181 and pTau231 concentrations were quantified using a Simoa assay. Microglial activation was assessed via [11C]PBR28 PET, standardized uptake value ratios (SUVRs) were calculated between 0 and 90 minutes post‐injection, using cerebellum grey matter as the reference region. Voxel‐based regression models evaluated the relationship between plasma pTau181 and pTau231 with neuroinflammation as assessed by PET, correcting for age and sex.ResultIn the present study, positive correlations were found between concentrations of both pTau181 and pTau231 and neuroinflammation indexed by PET‐imaging. Voxel‐level analyses indicated that these associations prenominated in regions of the default mode network including the precuneus, posterior cingulate cortex and medial prefrontal cortex. These regional associations survived corrections for multiple comparisons.ConclusionPeripheral phosphorylated tau is associated with neuroinflammation in brain regions associated with AD. Our findings highlight the importance of neuroinflammation in the pathogenesis of AD.

P560. Impaired Obesity Awareness May Be Related to Interhemispheric Imbalance in the Posterior Parietal Areas

The prevalence of obesity is higher in individuals with schizophrenia (40-60%) than the general population. Approximately 80% of overweight individuals fail to achieve sustained weight loss. Several factors may affect adherence to interventions, including impaired obesity awareness. Individuals with poor awareness may underestimate their weight, minimize the risks of obesity and decline or discontinue treatment. This novel study aims to evaluate the neuroanatomical model of impaired illness awareness (IA) in individuals with obesity using fMRI. Based on brain regions identified in other conditions, including schizophrenia, that feature impaired IA, it is proposed that impaired IA may be related to interhemispheric imbalance, specifically left hemisphere dominance in the posterior parietal area (PPA) and medial prefrontal cortex (mPFC).

Functional connectivity modulations during offset analgesia in chronic pain patients: an fMRI study

Patients with neuropathic pain and fibromyalgia showed reduced or absent offset analgesia (OA) response and attenuated cerebral activity in descending pain modulatory and reward systems in patients. However, neural network modifications of OA in chronic pain have not been determined. We enrolled 23 patients with various chronic pain and 17 age- and gender- matched healthy controls. All participants were given OA-related noxious thermal stimuli, including 3 repeats of offset analgesia paradigm at 46-47-46°C and constant paradigm at 46°C on the left volar forearm under whole-brain functional magnitude resonance imaging (fMRI). We evaluated magnitude of OA, examined OA modulated functional connectivity using psychophysiological interaction analysis and resting-state functional connectivity analysis and explored their behavioral correlations in patients compared with controls.Compared to controls, chronic pain patients showed smaller magnitude of OA (P = 0.047). OA modulated connectivity decreased between posterior cingulate cortex (PCC) and right medial prefrontal cortex (MPFC) in proportion to current chronic pain (P = 0.018); decreased between right pallidum and right thalamus, and increased between right caudate nucleus and left primary somatosensory cortex (P FDR < 0.05).The impaired PCC-MPFC connectivity might play an important role in dysfunction of OA and contribute to pain chronification.

Neural representation of others during action observation in posterior medial prefrontal cortex.

Making decisions based on the actions of others is critical to daily interpersonal interactions. We investigated the representations of other's actions at single neural level in posterior medial prefrontal cortex (pmPFC) in two monkeys during the observation of actions of another agent, in a social interaction task. Each monkey separately interacted with a human partner. The monkey and the human alternated turns as actor and observer. The actor was required to reach one of two visual targets, avoiding the previously chosen target, while the observer monitored that action. pmPFC neurons decoupled in most cases self from others during both the execution and the observation of explicit actions. pmPFC neurons showed selective directional tuning specific for the agent who was executing the task. Moreover, we assessed the relationship of the response coding between the periods immediately before and after the action, by using a cross-modal decoding analysis. We found neural network stability from the action anticipation period to the observation of other's actions, suggesting a strong relationship between the anticipation and the execution of an action. When the monkey was the actor, the population coding appeared dynamic, possibly reflecting a goal-action transformation unique to the monkey's own action execution.

A Distributed Model of Face and Body Integration.

Separated face- and body-responsive brain networks have been identified that show strong responses when observers view faces and bodies. It has been proposed that face and body processing may be initially separated in the lateral occipitotemporal cortex and then combined into a whole person representation in the anterior temporal cortex, or elsewhere in the brain. However, in contrast to this proposal, our recent study identified a common coding of face and body orientation (ie, facing direction) in the lateral occipitotemporal cortex, demonstrating an integration of face and body information at an early stage of face and body processing. These results, in combination with findings that show integration of face and body identity in the lateral occipitotemporal, parahippocampal and superior parietal cortex, and face and body emotional expression in the posterior superior temporal sulcus and medial prefrontal cortex, suggest that face and body integration may be more distributed than previously considered. I propose a new model of face and body integration, where areas at the intersection of face- and body-responsive regions play a role in integrating specific properties of faces and bodies, and distributed regions across the brain contribute to high-level, abstract integration of shared face and body properties.

Alterations in Effective Connectivity of the Hippocampus in Migraine without Aura.

PurposeNeuroimaging studies on migraine have revealed structural and functional alterations in the hippocampus, a region involved in pain processing and stress response. This study was designed to investigate whether effective connectivity of this region is disrupted in migraine and relates to chronicity of this disease.Patients and MethodsIn 39 episodic migraine (EM) patients, 17 chronic migraine (CM) patients, and 35 healthy controls, we investigated differences in the directional influences between the hippocampus and the rest of the brain by combining resting-state functional magnetic resonance imaging and Granger causality analysis (GCA), with bilateral hippocampus as seed regions. The associations between directional influences and the clinical variables were also examined.ResultsComparing each patient group to the control group, we found increased and decreased negative influence on the hippocampus exerted by the bilateral visual areas and right dorsolateral prefrontal cortex (dlPFC), respectively. The hippocampus showed increased positive influence on the right posterior insula and medial prefrontal cortex (mPFC), as well as increased negative influence on the left cerebellum in CM patients relative to EM patients and healthy controls. Furthermore, across all patients, the migraine frequency exhibited a positive and negative association with causal influence from the hippocampus to mPFC and left cerebellum, respectively.ConclusionMigraine patients have abnormal effective connectivity between the hippocampus and multiple brain regions involved in the sensory and cognitive processing of pain. Disrupted directional influences to the hippocampus exerted by dlPFC and bilateral visual areas were common features of EM and CM patients. Directional influences from the hippocampus to mPFC and left cerebellum may be useful imaging biomarkers for assessing migraine frequency.

Peripheral inflammation is associated with micro-structural and functional connectivity changes in depression-related brain networks

Inflammation is associated with depressive symptoms and innate immune mechanisms are likely causal in some cases of major depression. Systemic inflammation also perturbs brain function and microstructure, though how these are related remains unclear. We recruited N = 46 healthy controls, and N = 83 depressed cases stratified by CRP (> 3 mg/L: N = 33; < 3 mg/L: N = 50). All completed clinical assessment, venous blood sampling for C-reactive protein (CRP) assay, and brain magnetic resonance imaging (MRI). Micro-structural MRI parameters including proton density (PD), a measure of tissue water content, were measured at 360 cortical and 16 subcortical regions. Resting-state fMRI time series were correlated to estimate functional connectivity between individual regions, as well as the sum of connectivity (weighted degree) of each region. Multiple tests for regional analysis were controlled by the false discovery rate (FDR = 5%). We found that CRP was significantly associated with PD in precuneus, posterior cingulate cortex (pC/pCC) and medial prefrontal cortex (mPFC); and with functional connectivity between pC/pCC, mPFC and hippocampus. Depression was associated with reduced weighted degree of pC/pCC, mPFC, and other nodes of the default mode network (DMN). Thus CRP-related increases in proton density—a plausible marker of extracellular oedema—and changes in functional connectivity were anatomically co-localised with DMN nodes that also demonstrated significantly reduced hubness in depression. We suggest that effects of peripheral inflammation on DMN node micro-structure and connectivity may mediate inflammatory effects on depression.

Modulation of Sustained Attention by Theta-tACS over the Lateral and Medial Frontal Cortices.

Theta oscillations over the posterior medial frontal cortex (pMFC) and lateral prefrontal cortex (LPFC) play vital roles in sustained attention. Specifically, pMFC power and pMFC-LPFC synchronization correlate with cognitive control in sustained-attention-related tasks, but the causal relationships remain unknown. In the present study, we first analyzed the correlation between EEG theta oscillations (characterized by time-frequency power and phase-based connectivity) and the level of sustained attention (Experiment 1) and then utilized transcranial alternating current stimulation (tACS) to modulate theta oscillations and in turn observed its effects on sustained attention (Experiment 2). In Experiment 1, two time-frequency regions of interest (ROIs) were determined, in which high/low time-frequency power and high/low phase-based connectivity corresponded to high/low-level sustained attention. In Experiment 2, time-frequency power and phase-based connectivity of theta oscillations were compared between the sham and tACS groups within the time-frequency ROIs determined in Experiment 1. Results showed that phase-based connectivity between pMFC and LPFC significantly decreased in the tACS group compared with the sham group during the first five minutes of the poststimulation period. Moreover, a marginal trend existed that sustained attention was downregulated by tACS in the same time interval, suggesting that theta phase synchronization between pMFC and LPFC may play a causal role in sustained attention.

Reinstatement of item-specific contextual details during retrieval supports recombination-related false memories

Flexible retrieval mechanisms that allow us to infer relationships across events may also lead to memory errors or distortion when details of one event are misattributed to the related event. Here, we tested how making successful inferences alters representation of overlapping events, leading to false memories. Participants encoded overlapping associations (‘AB’ and ‘BC’), each of which was superimposed on different indoor and outdoor scenes that were pre-exposed prior to associative learning. Participants were subsequently tested on both the directly learned pairs (‘AB’ and ‘BC’) and inferred relationships across pairs (‘AC’). We predicted that when people make a correct inference, features associated with overlapping events may become integrated in memory. To test this hypothesis, participants completed a final detailed retrieval test, in which they had to recall the scene associated with initially learned ‘AB’ pairs (or ‘BC’ pairs). We found that the outcome of inference decisions impacted the degree to which neural patterns elicited during detailed ‘AB’ retrieval reflected reinstatement of the scene associated with the overlapping ‘BC’ event. After successful inference, neural patterns in the anterior hippocampus, posterior medial prefrontal cortex, and our content-reinstatement region (left inferior temporal gyrus) were more similar to the overlapping, yet incorrect ‘BC’ context relative to after unsuccessful inference. Further, greater hippocampal activity during inference was associated with greater reinstatement of the incorrect, overlapping context in our content-reinstatement region, which in turn tracked contextual misattributions during detailed retrieval. These results suggest recombining memories during successful inference can lead to misattribution of contextual details across related events, resulting in false memories.

Reduced structural covariance connectivity of defaut mode network and salience network in MRI-normal focal epilepsy.

Neuroimaging studies have found altered functional connectivity of default mode network (DMN) and salience network (SN) in patients with focal epilepsy (FE). However, the structural basis underlying the functional connectivity disturbance in the patients is still unclear. Sixteen MRI-normal FE and 22 healthy controls were included in the current study. The T1 structural image of each participant was obtained. Seed-based structural covariance connectivity was employed to investigate changes of structural covariance connectivity of DMN and SN in FE patients. We further evaluated gray matter volume changes of brain areas showing altered structural connectivity in the patients. We found that patients with FE showed reduced connectivity of posterior cingulate cortex and left medial prefrontal cortex, hippocampus and orbitofrontal cortex, and reduced connectivity of right fronto-insula cortex with left insula, orbitofrontal cortex, opercum part of inferior frontal cortex and right medial prefrontal cortex compared with healthy controls. Moreover, those brain areas showing significant reduced structural covariance connectivity in patients with FE also had a loss of gray matter volume, indicating that reduced structural connectivity of DMN and SN might be associated with gray matter atrophy in the patients. Those results highlight the crucial role of DMN and SN in the pathology of patients with FE, and provided structural basis for the functional disturbance of the two networks in this disease.

Neuronal Representations of Tactic-Based Sensorimotor Transformations in the Primate Medial Prefrontal, Presupplementary, and Supplementary Motor Areas: A Comparative Study.

Adaptive context-dependent behaviors necessitate the flexible selection of multiple behavioral tactics, i.e., internal protocols for selecting an action. Previous primate studies have shown that the posterior medial prefrontal cortex (pmPFC) contributes to the selection, retention, and use of tactics, but the manner in which this area employs selected tactics to convert sensory information into action and how that manner differs from downstream cortical motor areas have yet to be fully elucidated. To address this issue, the present study recorded neuronal activity in two monkeys as they performed a two-choice arm reaching task that required the selection of multiple tactics when converting spatial cue information into the direction of arm reaching. Neuronal populations in both pmPFC and presupplementary motor area (pre-SMA) represented tactics during their selection, maintenance in memory, and their use in determining an action. Additionally, they represented the monkeys’ action in the behavioral epoch in which the direction of reaching was determined. A striking contrast between the pmPFC and the pre-SMA was the representation of the spatial cue location in the former and its absence in the latter area. In individual neurons, neurons in pmPFC and pre-SMA had either single or mixed representation of tactics and action. Some of the pmPFC neurons additionally encoded cue location. Finally, neurons in the supplementary motor area mainly represented the action. Taken together, the present results indicate that, of these three areas, the pmPFC plays a cardinal role during the integration of behavioral tactics and visuospatial information when selecting an action.

Cognitive control increases honesty in cheaters but cheating in those who are honest

Every day, we are faced with the conflict between the temptation to cheat for financial gains and maintaining a positive image of ourselves as being a "good person." While it has been proposed that cognitive control is needed to mediate this conflict between reward and our moral self-image, the exact role of cognitive control in (dis)honesty remains elusive. Here we identify this role, by investigating the neural mechanism underlying cheating. We developed a task which allows for inconspicuously measuring spontaneous cheating on a trial-by-trial basis in the MRI scanner. We found that activity in the nucleus accumbens promotes cheating, particularly for individuals who cheat a lot, while a network consisting of posterior cingulate cortex, temporoparietal junction, and medial prefrontal cortex promotes honesty, particularly in individuals who are generally honest. Finally, activity in areas associated with cognitive control (anterior cingulate cortex and inferior frontal gyrus) helped dishonest participants to be honest, whereas it enabled cheating for honest participants. Thus, our results suggest that cognitive control is not needed to be honest or dishonest per se but that it depends on an individual's moral default.

Functional Alterations Associated with Structural Abnormalities in Adults with High-Functioning Autism Spectrum Disorder.

Background: The combination of structural and functional analyses is a biologically valid approach that offers methodological advantages in autism spectrum disorder (ASD) neuroimaging science. The paucity of studies combining these methods constitutes an important knowledge gap. In this study, we investigate structural abnormalities and their associated functional differences in a developmentally homogeneous ASD cohort. Methods: Whole-brain voxel-based morphometry (VBM) analyses were performed on 28 ASD participants and 38 age-matched typically developing healthy controls (HC) to derive gray matter (GM) volume differences. The anatomically relevant clusters identified by VBM served as seed regions of interest (ROI) for resting-state functional-connectivity (RsFc) analysis. Results: Whole-brain VBM analyses revealed significant right lateralized GM volume abnormality in the ASD group, with lower GM volumes in cerebellar lobules VIIb/VIIIa (cluster 1) and significantly higher GM volumes in posterior middle/superior temporal gyri (Brodmann area [BA] 21/22, cluster 2) compared with HC. Whole-brain RsFc analysis in high-functioning ASD (HF-ASD) revealed significant hypoconnectivity of the cerebellar VBM cluster with the right cerebral cortical regions of superior parietal lobule (BA 7) and occipital pole (BA 19) (overlapping with dorsal attention and visual networks, respectively). Cerebral cortical VBM cluster (cluster 2) revealed significant hypoconnectivity in HF-ASD with other task-positive cerebral cortical including the left lateral prefrontal cortex (frontoparietal network) and some aspects of the insula (ventral attention network) and ectopic positive connectivity (lack of anticorrelations) with posterior cingulate cortex and medial prefrontal cortex (default mode network). Conclusions: The cerebro-cerebellar intrinsic functional dysconnectivity based on the whole-brain VBM-derived ROIs may advance our understanding of the compensatory mechanisms associated with ASD and offer cerebellum as a potential target for diagnostic, predictive, prognostic, and therapeutic interventions in ASD. Our findings also provide additional support indicating that functional abnormalities as indexed by RsFc exist in ASD, and highlight that there is likely a relationship between structural and functional abnormalities in this disorder. Impact statement Our findings indicate that functional differences as indexed by resting-state functional connectivity exist in autism spectrum disorder (ASD), and highlight that there is likely a relationship between structural and functional abnormalities in this disorder. Future developments in neuroimaging research should continue investigating structural and associated functional differences in ASD, and in this way complement the behavioral characterization of this disorder, potentially improving diagnosis, prognosis, and prediction.

Posttraumatic Stress Disorder Is Associated with α Dysrhythmia across the Visual Cortex and the Default Mode Network.

Anomalies in default mode network (DMN) activity and α (8–12 Hz) oscillations have been independently observed in posttraumatic stress disorder (PTSD). Recent spatiotemporal analyses suggest that α oscillations support DMN functioning via interregional synchronization and sensory cortical inhibition. Therefore, we examined a unifying pathology of α deficits in the visual-cortex-DMN system in PTSD. Human patients with PTSD (N = 25) and two control groups, patients with generalized anxiety disorder (GAD; N = 24) and healthy controls (HCs; N = 20), underwent a standard eyes-open resting state (S-RS) and a modified resting state (M-RS) of passively viewing salient images (known to deactivate the DMN). High-density electroencephalogram (hdEEG) were recorded, from which intracortical α activity (power and connectivity/Granger causality) was extracted using the exact low-resolution electromagnetic tomography (eLORETA). Patients with PTSD (vs GAD/HC) demonstrated attenuated α power in the visual cortex (VC) and key hubs of the DMN [posterior cingulate cortex (PCC) and medial prefrontal cortex (mPFC)] at both states, the severity of which further correlated with hypervigilance symptoms. With increased visual input (at M-RS vs S-RS), patients with PTSD further demonstrated reduced α-frequency directed connectivity within the DMN (PCC→mPFC) and, importantly, from the VC to both DMN hubs (VC→PCC and VC→mPFC), linking α deficits in the two systems. These interrelated α deficits align with DMN hypoactivity/hypoconnectivity, sensory disinhibition, and hypervigilance in PTSD, representing a unifying neural underpinning of these anomalies. The identification of visual-cortex-DMN α dysrhythmia in PTSD further presents a novel therapeutic target, promoting network-based intervention of neural oscillations.