Structural and functional connectivity associations with anterior cingulate sulcal variability.

Sulcation of the anterior cingulate may be defined by presence of a paracingulate sulcus, a tertiary sulcus developing during the third gestational trimester with implications on cognitive function and disease. In this cross-sectional study we examine task-free resting state functional connectivity and diffusion-weighted tract segmentation data from a cohort of healthy adults (< 60-year-old, n = 129), exploring the impact of ipsilateral paracingulate sulcal presence on structural and functional connectivity. Presence of a left paracingulate sulcus was associated with reduced fractional anisotropy in the left cingulum bundle and the left peri-genual and dorsal bundle segments, suggesting reduced structural organisational coherence in these tracts. This association was not observed in the offsite temporal cingulum bundle segment. Left paracingulate sulcal presence was associated with increased left peri-genual radial diffusivity and tract volume possibly suggesting increased U-fibre density in this region. Greater network dispersity was identified in individuals with an absent left paracingulate sulcus by presence of a significant, predominantly intraregional, frontal component of resting state functional connectivity which was not present in individuals with a present left paracingulate sulcus. Seed-based functional connectivity in pre-defined networks was not associated with paracingulate sulcal presence. These results identify a novel association between sulcation and structural connectivity in a healthy adult population with implications for conditions where this variation is of interest. Presence of a left paracingulate sulcus appears to alter local structural and functional connectivity, possibly as a result of the presence of a local network reliant on short association fibres.

Microstructural differences in the cingulum and the inferior longitudinal fasciculus are associated with (extinction) learning.

Cognitive functions, such as learning and memory processes, depend on effective communication between brain regions which is facilitated by white matter tracts (WMT). We investigated the microstructural properties and the contribution of WMT to extinction learning and memory in a predictive learning task. Forty-two healthy participants completed an extinction learning paradigm without a fear component. We examined differences in microstructural properties using diffusion tensor imaging to identify underlying neural connectivity and structural correlates of extinction learning and their potential implications for the renewal effect. Participants with good acquisition performance exhibited higher fractional anisotropy (FA) in WMT including the bilateral inferior longitudinal fasciculus (ILF) and the right temporal part of the cingulum (CNG). This indicates enhanced connectivity and communication between brain regions relevant to learning and memory resulting in better learning performance. Our results suggest that successful acquisition and extinction performance were linked to enhanced structural connectivity. Lower radial diffusivity (RD) in the right ILF and right temporal part of the CNG was observed for participants with good acquisition learning performance. This observation suggests that learning difficulties associated with increased RD may potentially be due to less myelinated axons in relevant WMT. Also, participants with good acquisition performance were more likely to show a renewal effect. The results point towards a potential role of structural integrity in extinction-relevant WMT for acquisition and extinction.

Unveiling the axonal connectivity between the precuneus and temporal pole: Structural evidence from the cingulum pathways.

Neuroimaging studies have consistently demonstrated concurrent activation of the human precuneus and temporal pole (TP), both during resting-state conditions and various higher-order cognitive functions. However, the precise underlying structural connectivity between these brain regions remains uncertain despite significant advancements in neuroscience research. In this study, we investigated the connectivity of the precuneus and TP by employing parcellation-based fiber micro-dissections in human brains and fiber tractography techniques in a sample of 1065 human subjects and a sample of 41 rhesus macaques. Our results demonstrate the connectivity between the posterior precuneus area POS2 and the areas 35, 36, and TG of the TP via the fifth subcomponent of the cingulum (CB-V) also known as parahippocampal cingulum. This finding contributes to our understanding of the connections within the posteromedial cortices, facilitating a more comprehensive integration of anatomy and function in both normal and pathological brain processes. PRACTITIONER POINTS: Our investigation delves into the intricate architecture and connectivity patterns of subregions within the precuneus and temporal pole, filling a crucial gap in our knowledge. We revealed a direct axonal connection between the posterior precuneus (POS2) and specific areas (35, 35, and TG) of the temporal pole. The direct connections are part of the CB-V pathway and exhibit a significant association with the cingulum, SRF, forceps major, and ILF. Population-based human tractography and rhesus macaque fiber tractography showed consistent results that support micro-dissection outcomes.

Aging, cingulate cortex, and cognition: insights from structural MRI, emotional recognition, and theory of mind.

The cingulate cortex is a limbic structure involved in multiple functions, including emotional processing, pain, cognition, memory, and spatial orientation. The main goal of this structural Magnetic Resonance Imaging (MRI) study was to investigate whether age affects the cingulate cortex uniformly across its anteroposterior dimensions and determine if the effects of age differ based on sex, hemisphere, and regional cingulate anatomy, in a large cohort of healthy individuals across the adult lifespan. The second objective aimed to explore whether the decline in emotional recognition accuracy and Theory of Mind (ToM) is linked to the potential age-related reductions in the pregenual anterior cingulate (ACC) and anterior midcingulate (MCC) cortices. We recruited 126 healthy participants (18-85 years) for this study. MRI datasets were acquired on a 4.7 T system. The cingulate cortex was manually segmented into the pregenual ACC, anterior MCC, posterior MCC, and posterior cingulate cortex (PCC). We observed negative relationships between the presence and length of the superior cingulate gyrus and bilateral volumes of pregenual ACC and anterior MCC. Age showed negative effects on the volume of all cingulate cortical subregions bilaterally except for the right anterior MCC. Most of the associations between age and the cingulate subregional volumes were linear. We did not find a significant effect of sex on cingulate cortical volumes. However, stronger effects of age were observed in men compared to women. This study also demonstrated that performance on an emotional recognition task was linked to pregenual ACC volume, whist the ToM capabilities were related to the size of pregenual ACC and anterior MCC. These results suggest that the cingulate cortex contributes to emotional recognition ability and ToM across the adult lifespan.

Cingulate Cortex: Anatomy, Structural and Functional Connectivity.

SUMMARY: The cingulate cortex is a paired brain region located on the medial wall of each hemisphere. This review explores the anatomy as well as the structural and functional connectivity of the cingulate cortex underlying essential roles this region plays in emotion, autonomic, cognitive, motor control, visual-spatial processing, and memory.

Cingulate sulcus morphology and paracingulate sulcus variations: Anatomical and radiological studies.

The sulci and gyri found across the cerebrum differ in morphology between individuals. The cingulate sulcus is an important landmark for deciding the surgical approach for neighboring pathological lesions. Identifying the anatomical variations of anterior cingulate cortex morphology would help to determine the safe-entry route through neighboring lesions. In this study, magnetic resonance imaging data acquired from 149 healthy volunteers were investigated retrospectively for anatomical variations of the paracingulate sulcus. Also, human cadaveric brain hemispheres were investigated for cingulate and paracingulate sulcus anatomy. All participants had cingulate sulci in both hemispheres (n = 149, 100%). Three types of paracingulate sulcus patterns were identified: "prominent," "present," and "absent." Hemispheric comparisons indicated that the paracingulate sulcus is commonly "prominent" in the left hemisphere (n = 48, 32.21%) and more commonly "absent" in the right hemisphere (n = 73, 48.99%). Ten (6.71%) people had a prominent paracingulate sulcus in both the right and left hemispheres. Seven (4.70%) of them were male, and 3 (2.01%) of them were female. Paracingulate sulci were present in both hemispheres in 19 people (12.75%), of which 9 (6.04%) were male and 10 (6.71%) were female. There were 35 (23.49%) participants without paracingulate sulci in both hemispheres. Eleven (7.38%) were male and 24 (16.11%) were female. There were 73 (48.99%) participants without right paracingulate sulcus and 57 (38.26%) participants without left paracingulate sulcus (p = 0.019). In the examinations of the cadaver hemispheres, the paracingulate sulcus was present and prominent in 25%, and the intralimbic sulcus was present in 15%. It has been observed that the paracingulate sulcus is more prominent in the normal male brain compared to females. In females, there were more participants without paracingulate sulcus. This study shows that there are both hemispheric and sex differences in the anatomy of the paracingulate sulcus. Understanding the cingulate sulcus anatomy and considering the variations in the anterior cingulate cortex morphology during surgery will help surgeons to orient this elegant and complex area.

Retrosplenial cortex inactivation during retrieval, but not encoding, impairs remotely acquired auditory fear conditioning in male rats.

Prior studies with permanent lesion methods have demonstrated a role for the retrosplenial cortex (RSC) in the retrieval of remotely, but not recently, acquired delay fear conditioning. To extend the generalizability of these prior findings, the present experiments used chemogenetics to temporarily inactivate the RSC during either retrieval or encoding of delay auditory fear conditioning. Inactivation of the RSC at the time of test impaired retrieval of a remotely conditioned auditory cue, but not a recently conditioned one. In addition, inactivation of the RSC during encoding had no impact on freezing during later retrieval testing for both a remotely and recently conditioned auditory cue. These findings indicate that the RSC contributes to the retrieval, but not encoding, of remotely acquired auditory fear conditioning, and suggest it has less of a role in both retrieval and encoding of recently acquired auditory fear conditioning.

The separate and combined properties of the granular (area 29) and dysgranular (area 30) retrosplenial cortex.

Retrosplenial cortex contains two principal subdivisions, area 29 (granular) and area 30 (dysgranular). Their respective anatomical connections in the rat brain reveal that area 29 is the primary recipient of hippocampal and parahippocampal spatial and contextual information while area 30 is the primary interactor with current visual information. Lesion studies and measures of neuronal activity in rodents indicate that retrosplenial cortex helps to integrate space from different perspectives, e.g., egocentric and allocentric, providing landmark and heading cues for navigation and spatial learning. It provides a repository of scene information that, over time, becomes increasingly independent of the hippocampus. These processes, reflect the interactive actions between areas 29 and 30, along with their convergent influences on cortical and thalamic targets. Consequently, despite their differences, both areas 29 and 30 are necessary for an array of spatial and learning problems.

Evidence for two distinct thalamocortical circuits in retrosplenial cortex.

Retrosplenial cortex (RSC) lies at the interface between sensory and cognitive networks in the brain and mediates between these, although it is not yet known how. It has two distinct subregions, granular (gRSC) and dysgranular (dRSC). The present study investigated how these subregions differ with respect to their electrophysiology and thalamic connectivity, as a step towards understanding their functions. The gRSC is more closely connected to the hippocampal formation, in which theta-band local field potential oscillations are prominent. We, therefore, compared theta-rhythmic single-unit activity between the two RSC subregions and found, mostly in gRSC, a subpopulation of non-directional cells with spiking activity strongly entrained by theta oscillations, suggesting a stronger coupling of gRSC to the hippocampal system. We then used retrograde tracers to test for differential inputs to RSC from the anteroventral thalamus (AV). We found that gRSC and dRSC differ in their afferents from two AV subfields: dorsomedial (AVDM) and ventrolateral (AVVL). Specifically: (1) as a whole AV projects more strongly to gRSC; (2) AVVL targets both gRSC and dRSC, while AVDM provides a selective projection to gRSC, (3) the gRSC projection is layer-specific: AVDM targets specifically gRSC superficial layers. These same AV projections are topographically organized with ventral AV neurons innervating rostral RSC and dorsal AV neurons innervating caudal RSC. These combined results suggest the existence of two distinct but interacting RSC subcircuits: one connecting AVDM to gRSC that may comprise part of the cognitive hippocampal system, and the other connecting AVVL to both RSC regions that may link hippocampal and perceptual regions. We suggest that these subcircuits are distinct to allow for differential weighting during integration of converging sensory and cognitive computations: an integration that may take place in thalamus, RSC, or both.

Optogenetic inhibition of either the anterior or posterior retrosplenial cortex disrupts retrieval of a trace, but not delay, fear memory.

Previous work investigating the role of the retrosplenial cortex (RSC) in memory formation has demonstrated that its contributions are not uniform throughout the rostro-caudal axis. While the anterior region was necessary for encoding CS information in a trace conditioning procedure, the posterior retrosplenial cortex was needed to encode contextual information. Using the same behavioral procedure, we tested if there was a similar dissociation during memory retrieval. First, we found that memory retrieval following trace conditioning results in increased neural activity in both the anterior and posterior retrosplenial cortex, measured using the immediate early gene zif268. Similar increases were not found in either RSC subregion using a delay conditioning task. We then found that optogenetic inhibition of neural activity in either subregion impairs retrieval of a trace, but not delay, memory. Together these results add to a growing literature showing a role for the retrosplenial cortex in memory formation and retention. Further, they suggest that following formation, memory storage becomes distributed to a wider network than is needed for its initial consolidation.

Regional gray matter volume associated with exercise dependence: A voxel-based morphometry study.

Although regular physical exercise has multiple positive benefits for the general population, excessive exercise may lead to exercise dependence (EXD), which is harmful to one's physical and mental health. Increasing evidence suggests that stress is a potential risk factor for the onset and development of EXD. However, little is known about the neural substrates of EXD and the underlying neuropsychological mechanism by which stress affects EXD. Herein, we investigate these issues in 86 individuals who exercise regularly by estimating their cortical gray matter volume (GMV) utilizing a voxel-based morphometry method based on structural magnetic resonance imaging. Whole-brain correlation analyses and prediction analyses showed negative relationships between EXD and GMV of the right orbitofrontal cortex (OFC), left subgenual cingulate gyrus (sgCG), and left inferior parietal lobe (IPL). Furthermore, mediation analyses found that the GMV of the right OFC was an important mediator between stress and EXD. Importantly, these results remained significant even when adjusting for sex, age, body mass index, family socioeconomic status, general intelligence and total intracranial volume, as well as depression and anxiety. Collectively, the results of the present study provide crucial evidence of the neuroanatomical basis of EXD and reveal a potential neuropsychological pathway in predicting EXD in which GMV mediates the relationship between stress and EXD.

Gray matter structures associated with neuroticism: A meta-analysis of whole-brain voxel-based morphometry studies.

Neuroticism is major higher-order personality trait and has been robustly associated with mental and physical health outcomes. Although a growing body of studies have identified neurostructural markers of neuroticism, the results remained highly inconsistent. To characterize robust associations between neuroticism and variations in gray matter (GM) structures, the present meta-analysis investigated the concurrence across voxel-based morphometry (VBM) studies using the anisotropic effect size signed differential mapping (AES-SDM). A total of 13 studies comprising 2,278 healthy subjects (1,275 females, 29.20 ± 14.17 years old) were included. Our analysis revealed that neuroticism was consistently associated with the GM structure of a cluster spanning the bilateral dorsal anterior cingulate cortex and extending to the adjacent medial prefrontal cortex (dACC/mPFC). Meta-regression analyses indicated that the neuroticism-GM associations were not confounded by age and gender. Overall, our study is the first whole-brain meta-analysis exploring the brain structural correlates of neuroticism, and the findings may have implications for the intervention of high-neuroticism individuals, who are at risk of mental disorders, by targeting the dACC/mPFC.

Variability of white matter anatomy in the subcallosal cingulate area.

The subcallosal cingulate (SCC) area is a putative hub in the brain network underlying depression. Deep brain stimulation (DBS) targeting a particular subregion of SCC, identified as the intersection of forceps minor (FM), uncinate fasciculus (UCF), cingulum and fronto-striatal fiber bundles, may be critical to a therapeutic response in patients with severe, treatment-resistant forms of major depressive disorder (MDD). The pattern and variability of the white matter anatomy and organization within SCC has not been extensively characterized across individuals. The goal of this study is to investigate the variability of white matter bundles within the SCC that structurally connect this region with critical nodes in the depression network. Structural and diffusion data from 100 healthy subjects from the Human Connectome Project database were analyzed. Anatomically defined SCC regions were used as seeds to perform probabilistic tractography and to estimate the connectivity from the SCC to subject-specific target areas believed to be involved in the pathology of MDD including ventral striatum (VS), UCF, anterior cingulate cortex (ACC), and medial prefrontal cortex (mPFC). Four distinct areas of connectivity were identified within SCC across subjects: (a) postero-lateral SCC connectivity to medial temporal regions via UCF, (b) postero-medial connectivity to VS, (c) superior-medial connectivity to ACC via cingulum bundle, and (d) antero-lateral connectivity to mPFC regions via forceps minor. Assuming white matter connectivity is critical to therapeutic response, the improved anatomic understanding of SCC as well as an appreciation of the intersubject variability are critical to developing optimized therapeutic targeting for SCC DBS.

Distribution and overlap of entorhinal, premotor, and amygdalar connections in the monkey anterior cingulate cortex.

The anterior cingulate cortex (ACC) is important for decision-making as it integrates motor plans with affective and contextual limbic information. Disruptions in these networks have been observed in depression, bipolar disorder, and post-traumatic stress disorder. Yet, overlap of limbic and motor connections within subdivisions of the ACC is not well understood. Hence, we administered a combination of retrograde and anterograde tracers into structures important for contextual memories (entorhinal cortex), affective processing (amygdala), and motor planning (dorsal premotor cortex) to assess overlap of labeled projection neurons from (outputs) and axon terminals to (inputs) the ACC of adult rhesus monkeys (Macaca mulatta). Our data show that entorhinal and dorsal premotor cortical (dPMC) connections are segregated across ventral (A25, A24a) and dorsal (A24b,c) subregions of the ACC, while amygdalar connections are more evenly distributed across subregions. Among all areas, the rostral ACC (A32) had the lowest relative density of connections with all three regions. In the ventral ACC, entorhinal and amygdalar connections strongly overlap across all layers, especially in A25. In the dorsal ACC, outputs to dPMC and the amygdala strongly overlap in deep layers. However, dPMC input to the dorsal ACC was densest in deep layers, while amygdalar inputs predominantly localized in upper layers. These connection patterns are consistent with diverse roles of the dorsal ACC in motor evaluation and the ventral ACC in affective and contextual memory. Further, distinct laminar circuits suggest unique interactions within specific ACC compartments that are likely important for the temporal integration of motor and limbic information during flexible goal-directed behavior.

Abnormal functional connectivity based on nodes of the default mode network in first-episode drug-naive early-onset schizophrenia.

Schizophrenia is considered a connectivity disorder. Further, the functional connectivity (FC) of the default-mode network (DMN) has gained the interest of researchers. However, few studies have been conducted on the abnormal connectivity of DMN in early-onset schizophrenia (EOS). In this study, the key brain regions of the DMN were used as seed regions to analyze the FC of the whole brain in EOS. When the seed was located in the medial prefrontal cortex (mPFC), patients with EOS exhibited decreased FC between mPFC and other brain regions compared with healthy controls (voxel P value < 0.001, cluster P value < 0.05, Gaussian random field corrected). When the seed was located in the posterior cingulate cortex (PCC), the FC between PCC and other brain regions was enhanced and weakened (voxel P value < 0.001, cluster P value < 0.05, Gaussian random field corrected), and PCC connectivity with the right parahippocampal gyrus was associated with Positive and Negative Syndrome Scale scores for the general score (r = -0.315, P = 0.02). The results showed that the FC within the DMN and that between DMN and visual networks were abnormal, suggesting that the DMN might be involved in the pathogenesis of EOS.

Income is associated with hippocampal/amygdala and education with cingulate cortex grey matter volume.

Income and education are both elements of a person's socioeconomic status, which is predictive of a broad range of life outcomes. The brain's gray matter volume (GMV) is influenced by socioeconomic status and mediators related to an unhealthy life style. We here investigated two independent general population samples comprising 2838 participants (all investigated with the same MRI-scanner) with regard to the association of indicators of the socioeconomic status and gray matter volume. Voxel-based morphometry without prior hypotheses revealed that years of education were positively associated with GMV in the anterior cingulate cortex and net-equivalent income with gray matter volume in the hippocampus/amygdala region. Analyses of possible mediators (alcohol, cigarettes, body mass index (BMI), stress) revealed that the relationship between income and GMV in the hippocampus/amygdala region was partly mediated by self-reported stressors, and the association of years of education with GMV in the anterior cingulate cortex by BMI. These results corrected for whole brain effects (and therefore not restricted to certain brain areas) do now offer possibilities for more detailed hypotheses-driven approaches.

Sulcal Pattern Variability and Dorsal Anterior Cingulate Cortex Functional Connectivity Across Adult Age.

Background: The dorsal anterior cingulate cortex (dACC) is a key network hub for cognitive control and environmental adaptation. Previous studies have shown that task-based functional activity in this area is constrained by individual differences in sulcal pattern, a morphologic feature of cortex anatomy determined during fetal life and stable throughout development. Methods: By using anatomical magnetic resonance imaging and seed-based resting-state functional connectivity (rsFC), we explored the influence of sulcal pattern variability on the functional architecture of the dACC in a sample of healthy adults aged 20-80 years (n = 173). Results: Overall, rsFC was associated with individual differences in sulcal pattern. Furthermore, rsFC was modulated by the age-sulcal pattern interaction. Conclusion: Our results suggest a relationship between brain structure and function that partly traces back to early stages of brain development. The modulation of rsFC by the age-sulcal pattern interaction indicates that the effects of sulcal pattern variability on the functional architecture of the dACC may change over adulthood, with potential repercussions for brain network efficiency and cognitive function in aging.

Functional differentiation in the human ventromedial frontal lobe: A data-driven parcellation.

Ventromedial regions of the frontal lobe (vmFL) are thought to play a key role in decision-making and emotional regulation. However, aspects of this area's functional organization, including the presence of a multiple subregions, their functional and anatomical connectivity, and the cross-species homologies of these subregions with those of other species, remain poorly understood. To address this uncertainty, we employed a two-stage parcellation of the region to identify six distinct structures within the region on the basis of data-driven classification of functional connectivity patterns obtained using the meta-analytic connectivity modeling (MACM) approach. From anterior to posterior, the derived subregions included two lateralized posterior regions, an intermediate posterior region, a dorsal and ventral central region, and a single anterior region. The regions were characterized further by functional connectivity derived using resting-state fMRI and functional decoding using the Brain Map database. In general, the regions could be differentiated on the basis of different patterns of functional connectivity with canonical "default mode network" regions and/or subcortical regions such as the striatum. Together, the findings suggest the presence of functionally distinct neural structures within vmFL, consistent with data from experimental animals as well prior demonstrations of anatomical differences within the region. Detailed correspondence with the anterior cingulate, medial orbitofrontal cortex, and rostroventral prefrontal cortex, as well as specific animal homologs are discussed. The findings may suggest future directions for resolving potential functional and structural correspondence of subregions within the frontal lobe across behavioral contexts, and across mammalian species.