Posterior Medial Cortex Research Articles

Neuroimaging studies of resting-state functional magnetic resonance imaging in eating disorders

Eating disorders (EDs), including anorexia nervosa (AN), bulimia nervosa (BN), binge-eating disorder (BED), and pica, are psychobehavioral conditions characterized by abnormal eating behaviors and an excessive preoccupation with weight and body shape. This review examines changes in brain regions and functional connectivity in ED patients over the past decade (2013–2023) using resting-state functional magnetic resonance imaging (rs-fMRI). Key findings highlight alterations in brain networks such as the default mode network (DMN), central executive network (CEN), and emotion regulation network (ERN). In individuals with AN, there is reduced functional connectivity in areas associated with facial information processing and social cognition, alongside increased connectivity in regions linked to sensory stimulation, aesthetic judgment, and social anxiety. Conversely, BED patients show diminished connectivity in the dorsal anterior cingulate cortex within the salience network and increased connectivity in the posterior cingulate cortex and medial prefrontal cortex within the DMN. These findings suggest that rs-fMRI could serve as a valuable biomarker for assessing brain function and predicting treatment outcomes in EDs, paving the way for personalized therapeutic strategies.

Leveraging Input-Level Feature Deformation with Guided-Attention for Sulcal Labeling.

The identification of cortical sulci is key for understanding functional and structural development of the cortex. While large, consistent sulci (or primary/secondary sulci) receive significant attention in most studies, the exploration of smaller and more variable sulci (or putative tertiary sulci) remains relatively under-investigated. Despite its importance, automatic labeling of cortical sulci is challenging due to (1) the presence of substantial anatomical variability, (2) the relatively small size of the regions of interest (ROIs) compared to unlabeled regions, and (3) the scarcity of annotated labels. In this paper, we propose a novel end-to-end learning framework using a spherical convolutional neural network (CNN). Specifically, the proposed method learns to effectively warp geometric features in a direction that facilitates the labeling of sulci while mitigating the impact of anatomical variability. Moreover, we introduce a guided-attention mechanism that takes into account the extent of deformation induced by the learned warping. This extracts discriminative features that emphasize sulcal ROIs, while suppressing irrelevant information of unlabeled regions. In the experiments, we evaluate the proposed method on 8 sulci of the posterior medial cortex. Our method outperforms existing methods particularly in the putative tertiary sulci. The code is publicly available at https://github.com/Shape-Lab/DSPHARM-Net.

Neural correlates of the experience of ugliness.

Previous studies have shown that the experience of beauty is dependent upon the co-activity of field A1 of the medial frontal cortex and sensory areas. This leaves us with the question of ugliness; are the same neural mechanisms involved in this experience, including neural activity patterns, or are different mechanisms at play? This question arises because ugliness, although often regarded as the opposite of beauty, could possibly be a distinct aesthetic category. Subjects were asked to rate faces according to how ugly they found them to be while their brain activity was measured with functional magnetic resonance imaging. There was moderate agreement in the experience of ugliness of faces among subjects. Univariate parametric analyses did not reveal any brain regions with increasing activity as the declared intensity of the experience of ugliness increased. In contrast, increasing activity appeared in the striatum and posterior medial orbitofrontal cortex with decreasing levels of ugliness. As with studies on facial beauty, representational similarity analysis revealed distinct neural activity patterns with the experience of facial ugliness in sensory areas relevant for face processing and in the medial orbitofrontal cortex. Thus, similar neural mechanisms appear to be involved in the experience of facial beauty and ugliness, the difference being the level and distribution of activity within the neural network. This suggests that ugliness and beauty are on the same aesthetic continuum.

Suspending the Embodied Self in Meditation Attenuates Beta Oscillations in the Posterior Medial Cortex.

Human experience is imbued by the sense of being an embodied agent. The investigation of such basic self-consciousness has been hampered by the difficulty of comprehensively modulating it in the laboratory while reliably capturing ensuing subjective changes. The present preregistered study fills this gap by combining advanced meditative states with principled phenomenological interviews: 46 long-term meditators (19 female, 27 male) were instructed to modulate and attenuate their embodied self-experience during magnetoencephalographic monitoring. Results showed frequency-specific (high-beta band) activity reductions in frontoparietal and posterior medial cortices (PMC). Importantly, PMC reductions were driven by a subgroup describing radical embodied self-disruptions, including suspension of agency and dissolution of a localized first-person perspective. Neural changes were correlated with lifetime meditation and interview-derived experiential changes, but not with classical self-reports. The results demonstrate the potential of integrating in-depth first-person methods into neuroscientific experiments. Furthermore, they highlight neural oscillations in the PMC as a central process supporting the embodied sense of self.

Mixed anxiety-depressive disorder in Parkinson's disease associated with worse resting state functional response to deep brain stimulation of subthalamic nucleus

BackgroundParkinson's disease (PD), even though generally perceived as a dominantly motor disorder, is associated with a wide range of non-motor symptoms, including mixed anxiety-depressive disorder (MADD). ObjectivesThe aim of the presented study was to determine whether deep brain stimulation (DBS) of the subthalamic nucleus (STN) brings the functional characteristics of non-motor networks closer to the condition detected in healthy population and whether pre-DBS presence of MADD in PD patients was associated with different reaction to this therapeutic modality. MethodsResting-state fMRI signature elicited by STN DBS activation and deactivation in 81 PD patients was compared against healthy controls, with the focus on measures of efficiency of information processing and localised subnetwork differences. ResultsWhile all the MRI metrics showed statistically significant differences between PD patients in DBS OFF condition and healthy controls, none were detected in such a comparison against DBS ON condition. Furthermore, in the post-DBS evaluation, PD patients with MADD in the pre-DBS stage showed no differences in depression scales compared to pre-DBS psychiatrically intact PD patients, but still exhibited lower DBS-related connectivity in a subnetwork encompassing anterior and posterior cingulate, dorsolateral prefrontal and medial temporal cortices. ConclusionsSTN DBS improved all the metrics of interest towards the healthy state, normalising the resting-state MRI signature of PD. Furthermore, pre-DBS presence of MADD, even though clinically silent at post-DBS MRI acquisition, was associated with lower DBS effect in areas highly relevant for depression. This finding points to a possibly latent nature of post-DBS MADD, calling for caution in further follow-up of these patients.

Lamination, Borders, and Thalamic Projections of the Primary Visual Cortex in Human, Non-Human Primate, and Rodent Brains.

The primary visual cortex (V1) is one of the most studied regions of the brain and is characterized by its specialized and laminated layer 4 in human and non-human primates. However, studies aiming to harmonize the definition of the cortical layers and borders of V1 across rodents and primates are very limited. This article attempts to identify and harmonize the molecular markers and connectional patterns that can consistently link corresponding cortical layers of V1 and borders across mammalian species and ages. V1 in primates has at least two additional and unique layers (L3b2 and L3c) and two sublayers of layer 4 (L4a and L4b) compared to rodent V1. In all species examined, layers 4 and 3b of V1 receive strong inputs from the (dorsal) lateral geniculate nucleus, and V1 is mostly surrounded by the secondary visual cortex except for one location where V1 directly abuts area prostriata. The borders of primate V1 can also be clearly identified at mid-gestational ages using gene markers. In rodents, a novel posteromedial extension of V1 is identified, which expresses V1 marker genes and receives strong inputs from the lateral geniculate nucleus. This V1 extension was labeled as the posterior retrosplenial cortex and medial secondary visual cortex in the literature and brain atlases. Layer 6 of the rodent and primate V1 originates corticothalamic projections to the lateral geniculate, lateral dorsal, and reticular thalamic nuclei and the lateroposterior-pulvinar complex with topographic organization. Finally, the direct geniculo-extrastriate (particularly the strong geniculo-prostriata) projections are probably major contributors to blindsight after V1 lesions. Taken together, compared to rodents, primates, and humans, V1 has at least two unique middle layers, while other layers are comparable across species and display conserved molecular markers and similar connections with the visual thalamus with only subtle differences.

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.

Heart failure causally affects the brain cortical structure: a Mendelian randomization study.

The effects of heart failure (HF) on cortical brain structure remain unclear. Therefore, the present study aimed to investigate the causal effects of heart failure on cortical structures in the brain using Mendelian randomization (MR) analysis. We conducted a two-sample MR analysis utilizing genetically-predicted HF trait, left ventricular ejection fraction (LVEF), and N-terminal prohormone brain natriuretic peptide (NT-proBNP) levels to examine their effects on the cortical surface area (SA) and thickness (TH) across 34 cortical brain regions. Genome-wide association study summary data were extracted from studies by Rasooly (1,266,315 participants) for HF trait, Schmidt (36,548 participants) for LVEF, the SCALLOP consortium (21,758 participants) for NT-proBNP, and the ENIGMA Consortium (51,665 participants) for cortical SA and TH. A series of MR analyses were employed to exclude heterogeneity and pleiotropy, ensuring the stability of the results. Given the exploratory nature of the study, p-values between 1.22E-04 and 0.05 were considered suggestive of association, and p-values below 1.22E-04 were defined as statistically significant. In this study, we found no significant association between HF and cortical TH or SA (all p > 1.22E-04). We found that the HF trait and elevated NT-proBNP levels were not associated with cortical SA, but were suggested to decrease cortical TH in the pars orbitalis, lateral orbitofrontal cortex, temporal pole, lingual gyrus, precuneus, and supramarginal gyrus. Reduced LVEF was primarily suggested to decrease cortical SA in the isthmus cingulate gyrus, frontal pole, postcentral gyrus, cuneus, and rostral middle frontal gyrus, as well as TH in the postcentral gyrus. However, it was suggested to causally increase in the SA of the posterior cingulate gyrus and medial orbitofrontal cortex and the TH of the entorhinal cortex and superior temporal gyrus. We found 15 brain regions potentially affected by HF, which may lead to impairments in cognition, emotion, perception, memory, language, sensory processing, vision, and executive control in HF patients.

Associations of APOE4 and Alzheimer’s disease biomarkers with cortical reinstatement and episodic memory in clinically unimpaired older adults

AbstractBackgroundCortical reinstatement is a key neural correlate of episodic remembering across the lifespan and explains significant variability in memory performance among older adults. We assessed whether Alzheimer’s disease (AD) risk factors – cerebrospinal fluid (CSF) Aβ42/Aβ40, CSF pTau181, plasma pTau181, and APOE genotype – impact cortical reinstatement in clinically unimpaired older adults.MethodParticipants were 150 clinically unimpaired older adults enrolled in the Stanford Aging and Memory Study (SAMS). APOE genotype was determined from whole‐genome sequencing and participants were classified as ε4 carriers (N = 38) or non‐carriers (N = 112). CSF Aβ42/Aβ40 and pTau181 and plasma pTau181 were quantified using the automated Lumipulse G system. Cortical reinstatement was quantified during successful retrieval of word‐picture associations using fMRI multivoxel pattern analysis (MVPA) in five regions of interest, including parahippocampal gyrus (PHG), ventral temporal cortex (VTC), middle temporal gyrus (MTG), angular gyrus (ANG), and posterior medial cortex (PMC). Regression analyses examined cross‐sectional relationships between regional cortical reinstatement and a) APOE genotype (N = 150), b) CSF Aβ42/Aβ40 and pTau181 (N = 113), and (c) plasma pTau181 (N = 140), as well as associations of these variables with associative memory discrimination (d’). All models included age, sex, and regional MVPA classifier accuracy during memory encoding.ResultAPOE ε4 genotype was negatively associated with reinstatement strength in VTC (β = ‐0.54, p < .005), MTG (β = ‐0.32, p < .05), and ANG (β = ‐0.32, p < .05) and CSF Aβ42/Aβ40 burden was linked to weaker reinstatement in ANG (β = 0.16, p < .05). In VTC, the effect of APOE ε4 on reinstatement remained significant after controlling for CSF Aβ42/Aβ40 (β = ‐0.47, p < .05); a similar pattern was observed in MTG and ANG. Although CSF pTau181 was unrelated to reinstatement strength, both pTau181 and cortical reinstatement explained unique variance in memory performance (pTau181: β = ‐0.26, p < .005, reinstVTC: β = 0.39, p < .001). Analogous findings were observed with plasma pTau181.ConclusionThese results suggest that APOE ε4 impacts cortical reinstatement, and that this effect may be independent of amyloid burden. These effects of APOE ε4 may be distinct from tau‐mediated effects on episodic memory in human aging.

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.

The human posterior cingulate, retrosplenial, and medial parietal cortex effective connectome, and implications for memory and navigation.

The human posterior cingulate, retrosplenial, and medial parietal cortex are involved in memory and navigation. The functional anatomy underlying these cognitive functions was investigated by measuring the effective connectivity of these Posterior Cingulate Division (PCD) regions in the Human Connectome Project-MMP1 atlas in 171 HCP participants, and complemented with functional connectivity and diffusion tractography. First, the postero-ventral parts of the PCD (31pd, 31pv, 7m, d23ab, and v23ab) have effective connectivity with the temporal pole, inferior temporal visual cortex, cortex in the superior temporal sulcus implicated in auditory and semantic processing, with the reward-related vmPFC and pregenual anterior cingulate cortex, with the inferior parietal cortex, and with the hippocampal system. This connectivity implicates it in hippocampal episodic memory, providing routes for "what," reward and semantic schema-related information to access the hippocampus. Second, the antero-dorsal parts of the PCD (especially 31a and 23d, PCV, and also RSC) have connectivity with early visual cortical areas including those that represent spatial scenes, with the superior parietal cortex, with the pregenual anterior cingulate cortex, and with the hippocampal system. This connectivity implicates it in the "where" component for hippocampal episodic memory and for spatial navigation. The dorsal-transitional-visual (DVT) and ProStriate regions where the retrosplenial scene area is located have connectivity from early visual cortical areas to the parahippocampal scene area, providing a ventromedial route for spatial scene information to reach the hippocampus. These connectivities provide important routes for "what," reward, and "where" scene-related information for human hippocampal episodic memory and navigation. The midcingulate cortex provides a route from the anterior dorsal parts of the PCD and the supracallosal part of the anterior cingulate cortex to premotor regions.

Aberrant brain functional hubs convergence in the acute severe traumatic brain injury patients with rapidly recovering.

We aimed to identify the aberrant functional hubs in patients with acute severe traumatic brain injury (sTBI) and investigate whether they could help inform prognosis. Twenty-eight sTBI patients and health controls underwent imaging scanning. The graph-theoretical measure of degree centrality (DC) was applied to identify the abnormal brain functional hubs and conjoined with regions of interest-based analysis to investigate their interaction and impact on whole-brain. We further split sTBI patients into two subgroups according to their recovery to explore whether the fractional amplitude of low-frequency fluctuation (fALFF) roles in functional connectivity (FC) differential areas to help inform the patients' long-term prognosis. We identified the part of prefrontal cortex (PFC), precentral and postcentral gyrus (Pre-/Post-CG), cingulate gyrus (CgG), posterior medial cortex (PMC), and brainstem that could be core hubs whose DC was significantly increased in patients with acute sTBI. The interaction strength of the paired hubs could be enhanced (CG-PFC, CgG-PFC, CG-brainstem, CgG-brainstem, PMC-brainstem, and PFC-brainstem) and weakened (CG-CgG, CG-PMC, CgG-PMC, and PMC-PFC), compared with healthy controls. We also found abnormal FC in 5 hubs to whole-brain. The spontaneous brain activities in the FC differential regions [e.g., the fALFF and mean fALFF value] were valid to predict outcome at 6-month in patients with sTBI. We demonstrated a compensatory mechanism that part of brain regions will converge into abnormal functional hubs in patients with acute sTBI, which provides a potential approach to objectively predicting patients' long-term outcome.

Contextual Expectations Shape Cortical Reinstatement of Sensory Representations.

When making a turn at a familiar intersection, we know what items and landmarks will come into view. These perceptual expectations, or predictions, come from our knowledge of the context, however it’s unclear how memory and perceptual systems interact to support the prediction and reactivation of sensory details in cortex. To address this, human participants learned the spatial layout of animals positioned in a cross maze. During fMRI, participants of both sexes navigated between animals to reach a target, and in the process saw a predictable sequence of five animal images. Critically, to isolate activity patterns related to item predictions, rather than bottom-up inputs, one quarter of trials ended early, with a blank screen presented instead. Using multivariate pattern similarity analysis, we reveal that activity patterns in early visual cortex, posterior medial regions, and the posterior hippocampus showed greater similarity when seeing the same item compared to different items. Further, item effects in posterior hippocampus were specific to the sequence context. Critically, activity patterns associated with seeing an item in visual cortex and posterior medial cortex, were also related to activity patterns when an item was expected, but omitted, suggesting sequence predictions were reinstated in these regions. Finally, multivariate connectivity showed that patterns in the posterior hippocampus at one position in the sequence were related to patterns in early visual cortex and posterior medial cortex at a later position. Together, our results support the idea that hippocampal representations facilitate sensory processing by modulating visual cortical activity in anticipation of expected items.

A generalized cortical activity pattern at internally generated mental context boundaries during unguided narrative recall.

Current theory and empirical studies suggest that humans segment continuous experiences into events based on the mismatch between predicted and actual sensory inputs; detection of these 'event boundaries' evokes transient neural responses. However, boundaries can also occur at transitions between internal mental states, without relevant external input changes. To what extent do such 'internal boundaries' share neural response properties with externally driven boundaries? We conducted an fMRI experiment where subjects watched a series of short movies and then verbally recalled the movies, unprompted, in the order of their choosing. During recall, transitions between movies thus constituted major boundaries between internal mental contexts, generated purely by subjects' unguided thoughts. Following the offset of each recalled movie, we observed stereotyped spatial activation patterns in the default mode network, especially the posterior medial cortex, consistent across different movie contents and even across the different tasks of movie watching and recall. Surprisingly, the between-movie boundary patterns did not resemble patterns at boundaries between events within a movie. Thus, major transitions between mental contexts elicit neural phenomena shared across internal and external modes and distinct from within-context event boundary detection, potentially reflecting a cognitive state related to the flushing and reconfiguration of situation models.

Perspective-taking is associated with increased discriminability of affective states in the ventromedial prefrontal cortex.

Recent work using multivariate-pattern analysis (MVPA) on functional magnetic resonance imaging (fMRI) data has found that distinct affective states produce correspondingly distinct patterns of neural activity in the cerebral cortex. However, it is unclear whether individual differences in the distinctiveness of neural patterns evoked by affective stimuli underlie empathic abilities such as perspective-taking (PT). Accordingly, we examined whether we could predict PT tendency from the classification of blood-oxygen-level-dependent (BOLD) fMRI activation patterns while participants (n = 57) imagined themselves in affectively charged scenarios. We used an MVPA searchlight analysis to map where in the brain activity patterns permitted the classification of four affective states: happiness, sadness, fear and disgust. Classification accuracy was significantly above chance levels in most of the prefrontal cortex and in the posterior medial cortices. Furthermore, participants' self-reported PT was positively associated with classification accuracy in the ventromedial prefrontal cortex and insula. This finding has implications for understanding affective processing in the prefrontal cortex and for interpreting the cognitive significance of classifiable affective brain states. Our multivariate approach suggests that PT ability may rely on the grain of internally simulated affective representations rather than simply the global strength.