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1.
Neuroimage ; 294: 120647, 2024 Jul 01.
Article in English | MEDLINE | ID: mdl-38761552

ABSTRACT

Mental representation is a key concept in cognitive science; nevertheless, its neural foundations remain elusive. We employed non-invasive electrical brain stimulation and functional magnetic resonance imaging to address this. During this process, participants perceived flickering red and green visual stimuli, discerning them either as distinct, non-fused colours or as a mentally generated, fused colour (orange). The application of transcranial alternating current stimulation to the medial prefrontal region (a key node of the default-mode network) suppressed haemodynamic activation in higher-order subthalamic and central executive networks associated with the perception of fused colours. This implies that higher-order thalamocortical and default-mode networks are crucial in humans' conscious perception of mental representation.


Subject(s)
Consciousness , Magnetic Resonance Imaging , Transcranial Direct Current Stimulation , Humans , Male , Female , Adult , Transcranial Direct Current Stimulation/methods , Consciousness/physiology , Young Adult , Prefrontal Cortex/physiology , Prefrontal Cortex/diagnostic imaging , Color Perception/physiology , Brain Mapping/methods , Brain/physiology , Brain/diagnostic imaging , Default Mode Network/physiology , Default Mode Network/diagnostic imaging , Photic Stimulation/methods
2.
Hum Brain Mapp ; 45(7): e26703, 2024 May.
Article in English | MEDLINE | ID: mdl-38716714

ABSTRACT

The default mode network (DMN) lies towards the heteromodal end of the principal gradient of intrinsic connectivity, maximally separated from the sensory-motor cortex. It supports memory-based cognition, including the capacity to retrieve conceptual and evaluative information from sensory inputs, and to generate meaningful states internally; however, the functional organisation of DMN that can support these distinct modes of retrieval remains unclear. We used fMRI to examine whether activation within subsystems of DMN differed as a function of retrieval demands, or the type of association to be retrieved, or both. In a picture association task, participants retrieved semantic associations that were either contextual or emotional in nature. Participants were asked to avoid generating episodic associations. In the generate phase, these associations were retrieved from a novel picture, while in the switch phase, participants retrieved a new association for the same image. Semantic context and emotion trials were associated with dissociable DMN subnetworks, indicating that a key dimension of DMN organisation relates to the type of association being accessed. The frontotemporal and medial temporal DMN showed a preference for emotional and semantic contextual associations, respectively. Relative to the generate phase, the switch phase recruited clusters closer to the heteromodal apex of the principal gradient-a cortical hierarchy separating unimodal and heteromodal regions. There were no differences in this effect between association types. Instead, memory switching was associated with a distinct subnetwork associated with controlled internal cognition. These findings delineate distinct patterns of DMN recruitment for different kinds of associations yet common responses across tasks that reflect retrieval demands.


Subject(s)
Default Mode Network , Emotions , Magnetic Resonance Imaging , Mental Recall , Semantics , Humans , Male , Female , Adult , Young Adult , Emotions/physiology , Default Mode Network/physiology , Default Mode Network/diagnostic imaging , Mental Recall/physiology , Cerebral Cortex/physiology , Cerebral Cortex/diagnostic imaging , Nerve Net/physiology , Nerve Net/diagnostic imaging , Brain Mapping , Pattern Recognition, Visual/physiology
4.
Brain Lang ; 252: 105405, 2024 May.
Article in English | MEDLINE | ID: mdl-38579461

ABSTRACT

This review examines whether and how the "default mode" network (DMN) contributes to semantic processing. We review evidence implicating the DMN in the processing of individual word meanings and in sentence- and discourse-level semantics. Next, we argue that the areas comprising the DMN contribute to semantic processing by coordinating and integrating the simultaneous activity of local neuronal ensembles across multiple unimodal and multimodal cortical regions, creating a transient, global neuronal ensemble. The resulting ensemble implements an integrated simulation of phenomenological experience - that is, an embodied situation model - constructed from various modalities of experiential memory traces. These situation models, we argue, are necessary not only for semantic processing but also for aspects of cognition that are not traditionally considered semantic. Although many aspects of this proposal remain provisional, we believe it provides new insights into the relationships between semantic and non-semantic cognition and into the functions of the DMN.


Subject(s)
Cognition , Semantics , Humans , Cognition/physiology , Default Mode Network/physiology , Default Mode Network/diagnostic imaging , Brain/physiology
5.
J Neurosci ; 44(20)2024 May 15.
Article in English | MEDLINE | ID: mdl-38589231

ABSTRACT

The default mode network (DMN) typically deactivates to external tasks, yet supports semantic cognition. It comprises medial temporal (MT), core, and frontotemporal (FT) subsystems, but its functional organization is unclear: the requirement for perceptual coupling versus decoupling, input modality (visual/verbal), type of information (social/spatial), and control demands all potentially affect its recruitment. We examined the effect of these factors on activation and deactivation of DMN subsystems during semantic cognition, across four task-based human functional magnetic resonance imaging (fMRI) datasets, and localized these responses in whole-brain state space defined by gradients of intrinsic connectivity. FT showed activation consistent with a central role across domains, tasks, and modalities, although it was most responsive to abstract, verbal tasks; this subsystem uniquely showed more "tuned" states characterized by increases in both activation and deactivation when semantic retrieval demands were higher. MT also activated to both perceptually coupled (scenes) and decoupled (autobiographical memory) tasks and showed stronger responses to picture associations, consistent with a role in scene construction. Core DMN consistently showed deactivation, especially to externally oriented tasks. These diverse contributions of DMN subsystems to semantic cognition were related to their location on intrinsic connectivity gradients: activation was closer to the sensory-motor cortex than deactivation, particularly for FT and MT, while activation for core DMN was distant from both visual cortex and cognitive control. These results reveal distinctive yet complementary DMN responses: MT and FT support different memory-based representations that are accessed externally and internally, while deactivation in core DMN is associated with demanding, external semantic tasks.


Subject(s)
Cognition , Default Mode Network , Magnetic Resonance Imaging , Semantics , Humans , Male , Female , Adult , Cognition/physiology , Default Mode Network/physiology , Default Mode Network/diagnostic imaging , Young Adult , Nerve Net/physiology , Nerve Net/diagnostic imaging , Brain Mapping/methods , Brain/physiology , Brain/diagnostic imaging
6.
J Neurosci ; 44(22)2024 May 29.
Article in English | MEDLINE | ID: mdl-38527807

ABSTRACT

Adaptive behavior relies both on specific rules that vary across situations and stable long-term knowledge gained from experience. The frontoparietal control network (FPCN) is implicated in the brain's ability to balance these different influences on action. Here, we investigate how the topographical organization of the cortex supports behavioral flexibility within the FPCN. Functional properties of this network might reflect its juxtaposition between the dorsal attention network (DAN) and the default mode network (DMN), two large-scale systems implicated in top-down attention and memory-guided cognition, respectively. Our study tests whether subnetworks of FPCN are topographically proximal to the DAN and the DMN, respectively, and how these topographical differences relate to functional differences: the proximity of each subnetwork is anticipated to play a pivotal role in generating distinct cognitive modes relevant to working memory and long-term memory. We show that FPCN subsystems share multiple anatomical and functional similarities with their neighboring systems (DAN and DMN) and that this topographical architecture supports distinct interaction patterns that give rise to different patterns of functional behavior. The FPCN acts as a unified system when long-term knowledge supports behavior but becomes segregated into discrete subsystems with different patterns of interaction when long-term memory is less relevant. In this way, our study suggests that the topographical organization of the FPCN and the connections it forms with distant regions of cortex are important influences on how this system supports flexible behavior.


Subject(s)
Brain , Nerve Net , Humans , Male , Female , Adult , Nerve Net/physiology , Nerve Net/diagnostic imaging , Brain/physiology , Magnetic Resonance Imaging , Attention/physiology , Young Adult , Default Mode Network/physiology , Default Mode Network/diagnostic imaging , Memory, Long-Term/physiology , Brain Mapping/methods , Parietal Lobe/physiology , Memory, Short-Term/physiology
7.
J Cogn Neurosci ; 36(6): 1021-1036, 2024 06 01.
Article in English | MEDLINE | ID: mdl-38527069

ABSTRACT

Autobiographical memory (AM) is episodic memory for personally experienced events, in which self-representation is more important than that in laboratory-based memory. Theoretically, self-representation in a social context is categorized as the interpersonal self (IS) referred to in a social interaction with a person or the social-valued self (SS) based on the reputation of the self in the surrounding society. Although functional neuroimaging studies have demonstrated the involvement of the default mode network (DMN) in self-representation, little is known about how the DMN subsystems contribute differentially to IS-related and SS-related AMs. To elucidate this issue, we used fMRI to scan healthy young adults during the recollection of AMs. We performed multivariate pattern analysis (MVPA) and assessed functional connectivity in the DMN subsystems: the midline core, medial temporal lobe (MTL), and dorsomedial pFC (dmPFC) subsystems. The study yielded two main sets of findings. First, MVPA revealed that all DMN subsystems showed significant classification accuracy between IS-related and nonsocial-self-related AMs, and IS-related functional connectivity of the midline core regions with the retrosplenial cortex of the MTL subsystem and the dmPFC of the dmPFC subsystem was significant. Second, MVPA significantly distinguished between SS-related and nonsocial-self-related AMs in the midline core and dmPFC subsystems but not in the MTL subsystem, and SS-related functional connectivity with the midline core regions was significant in the temporal pole and TPJ of the dmPFC subsystem. Thus, dissociable neural mechanisms in the DMN could contribute to different aspects of self-representation in social AMs.


Subject(s)
Default Mode Network , Magnetic Resonance Imaging , Memory, Episodic , Humans , Default Mode Network/physiology , Default Mode Network/diagnostic imaging , Male , Young Adult , Female , Adult , Mental Recall/physiology , Self Concept , Brain Mapping , Brain/physiology , Brain/diagnostic imaging
8.
Cereb Cortex ; 33(8): 4553-4561, 2023 04 04.
Article in English | MEDLINE | ID: mdl-36130087

ABSTRACT

Suppression of the brain's default mode network (DMN) during external goal-directed cognitive tasks has been consistently observed in neuroimaging studies. However, emerging insights suggest the DMN is not a monolithic "task-negative" network but is comprised of subsystems that show functional heterogeneity. Despite considerable research interest, no study has investigated the consistency of DMN activity suppression across multiple cognitive tasks within the same individuals. In this study, 85 healthy 15- to 25-year-olds completed three functional magnetic resonance imaging tasks that were designed to reliably map DMN suppression from a resting baseline. Our findings revealed a distinct suppression subnetwork across the three tasks that comprised traditional DMN and adjacent regions. Specifically, common suppression was observed in the medial prefrontal cortex, the dorsal-to-mid posterior cingulate cortex extending to the precuneus, and the posterior insular cortex and parietal operculum. Further, we found the magnitude of suppression of these regions were significantly correlated within participants across tasks. Overall, our findings indicate that externally oriented cognitive tasks elicit common suppression of a distinct subnetwork of the broader DMN. The consistency to which the DMN is suppressed within individuals suggests a domain-general mechanism that may reflect a stable feature of cognitive function that optimizes external goal-directed behavior.


Subject(s)
Cognition , Default Mode Network , Adolescent , Adult , Female , Humans , Male , Young Adult , Attention/physiology , Cognition/physiology , Default Mode Network/physiology , Emotions , Facial Expression , Goals , Gyrus Cinguli/physiology , Intelligence Tests , Magnetic Resonance Imaging , Parietal Lobe/physiology , Prefrontal Cortex/physiology , Reaction Time , Task Performance and Analysis , Photic Stimulation
9.
Neuroimage ; 249: 118854, 2022 04 01.
Article in English | MEDLINE | ID: mdl-34971767

ABSTRACT

Canonical Correlation Analysis (CCA) and its regularised versions have been widely used in the neuroimaging community to uncover multivariate associations between two data modalities (e.g., brain imaging and behaviour). However, these methods have inherent limitations: (1) statistical inferences about the associations are often not robust; (2) the associations within each data modality are not modelled; (3) missing values need to be imputed or removed. Group Factor Analysis (GFA) is a hierarchical model that addresses the first two limitations by providing Bayesian inference and modelling modality-specific associations. Here, we propose an extension of GFA that handles missing data, and highlight that GFA can be used as a predictive model. We applied GFA to synthetic and real data consisting of brain connectivity and non-imaging measures from the Human Connectome Project (HCP). In synthetic data, GFA uncovered the underlying shared and specific factors and predicted correctly the non-observed data modalities in complete and incomplete data sets. In the HCP data, we identified four relevant shared factors, capturing associations between mood, alcohol and drug use, cognition, demographics and psychopathological measures and the default mode, frontoparietal control, dorsal and ventral networks and insula, as well as two factors describing associations within brain connectivity. In addition, GFA predicted a set of non-imaging measures from brain connectivity. These findings were consistent in complete and incomplete data sets, and replicated previous findings in the literature. GFA is a promising tool that can be used to uncover associations between and within multiple data modalities in benchmark datasets (such as, HCP), and easily extended to more complex models to solve more challenging tasks.


Subject(s)
Behavior , Brain , Connectome/methods , Default Mode Network , Mental Processes , Models, Theoretical , Nerve Net , Bayes Theorem , Behavior/physiology , Brain/diagnostic imaging , Brain/physiology , Datasets as Topic , Default Mode Network/diagnostic imaging , Default Mode Network/physiology , Factor Analysis, Statistical , Humans , Magnetic Resonance Imaging , Mental Processes/physiology , Nerve Net/diagnostic imaging , Nerve Net/physiology
10.
Neuroimage ; 246: 118763, 2022 02 01.
Article in English | MEDLINE | ID: mdl-34863961

ABSTRACT

Relating brain dynamics acting on time scales that differ by at least an order of magnitude is a fundamental issue in brain research. The same is true for the observation of stable dynamical structures in otherwise highly non-stationary signals. The present study addresses both problems by the analysis of simultaneous resting state EEG-fMRI recordings of 53 patients with epilepsy. Confirming previous findings, we observe a generic and temporally stable average correlation pattern in EEG recordings. We design a predictor for the General Linear Model describing fluctuations around the stationary EEG correlation pattern and detect resting state networks in fMRI data. The acquired statistical maps are contrasted to several surrogate tests and compared with maps derived by spatial Independent Component Analysis of the fMRI data. By means of the proposed EEG-predictor we observe core nodes of known fMRI resting state networks with high specificity in the default mode, the executive control and the salience network. Our results suggest that both, the stationary EEG pattern as well as resting state fMRI networks are different expressions of the same brain activity. This activity is interpreted as the dynamics on (or close to) a stable attractor in phase space that is necessary to maintain the brain in an efficient operational mode. We discuss that this interpretation is congruent with the theoretical framework of complex systems as well as with the brain's energy balance.


Subject(s)
Cerebral Cortex/physiology , Connectome/methods , Default Mode Network/physiology , Electroencephalography/methods , Executive Function/physiology , Magnetic Resonance Imaging/methods , Nerve Net/physiology , Adolescent , Adult , Aged , Cerebral Cortex/diagnostic imaging , Default Mode Network/diagnostic imaging , Female , Humans , Male , Middle Aged , Nerve Net/diagnostic imaging , Young Adult
11.
Hum Brain Mapp ; 43(2): 773-786, 2022 02 01.
Article in English | MEDLINE | ID: mdl-34652882

ABSTRACT

Many individuals spend a significant amount of their time "mind-wandering". Mind-wandering often includes spontaneous, nonintentional thought, and a neural correlate of this kind of thought is the default mode network (DMN). Thoughts during mind-wandering can have positive or negative valence, but only little is known about the neural correlates of positive or negative thoughts. We used resting-state functional magnetic resonance imaging (fMRI) and music to evoke mind-wandering in n = 33 participants, with positive-sounding music eliciting thoughts with more positive valence and negative-sounding music eliciting thoughts with more negative valence. Applying purely data-driven analysis methods, we show that medial orbitofrontal cortex (mOFC, part of the ventromedial prefrontal cortex) and the posterior cingulate sulcus (likely area 23c of the posterior cingulate cortex), two sub-regions of the DMN, modulate the valence of thought-contents during mind-wandering. In addition, across two independent experiments, we observed that the posterior cingulate sulcus, a region involved in pain, shows valence-specific functional connectivity with core regions of the brain's putative pain network. Our results suggest that two DMN regions (mOFC and posterior cingulate sulcus) support the formation of negative spontaneous, nonintentional thoughts, and that the interplay between these structures with regions of the putative pain network forms a neural mechanism by which thoughts can become painful.


Subject(s)
Auditory Perception/physiology , Connectome , Default Mode Network/physiology , Emotions/physiology , Gyrus Cinguli/physiology , Music , Nerve Net/physiology , Pain/physiopathology , Prefrontal Cortex/physiology , Thinking/physiology , Adult , Default Mode Network/diagnostic imaging , Female , Gyrus Cinguli/diagnostic imaging , Humans , Magnetic Resonance Imaging , Male , Nerve Net/diagnostic imaging , Pain/diagnostic imaging , Prefrontal Cortex/diagnostic imaging , Young Adult
12.
Behav Brain Res ; 417: 113586, 2022 01 24.
Article in English | MEDLINE | ID: mdl-34536430

ABSTRACT

The cerebellum plays an important role in cognitive functions through connecting with the cerebral cortical areas. However, the relationship between the resting-state functional connectivity (FC) pattern of human cerebro-cerebellar circuits and cognition is not fully understood. The present study investigated the FC patterns of human cerebro-cerebellar circuits and their associations with verbal working memory performance (an n-back task with three subtasks: 0-back, 1-back, and 2-back) through resting-state functional magnetic resonance imaging (fMRI) data from 34 healthy subjects. The whole-brain connectivity analysis was used to identify the cortical hubs as regions of interest (ROI). Then ROI-based FC analysis was performed to investigate the connectivity characteristics within the key cortical hubs and their associations with n-back task performance. The results showed that the bilateral cerebellum lobule VI as central hubs had increased FC with the default mode network (DMN) node (e.g., right posterior cingulate cortex) and salient network (SN) node (e.g., right anterior cingulate cortex), while decreased FC with the executive control network (ECN) node (e.g., the bilateral superior frontal gyrus). Furthermore, FC values of the cerebellum lobule VI with DMN and ECN nodes correlated with verbal working memory performance (response time of 2-back task). The results suggest that the cerebro-cerebellar circuits involve the underlying neural basis of verbal working memory processing during the resting state.


Subject(s)
Cerebellum/physiology , Cerebral Cortex/physiology , Cognition/physiology , Memory, Short-Term/physiology , Adult , Brain/physiology , Default Mode Network/physiology , Female , Healthy Volunteers , Humans , Magnetic Resonance Imaging , Male , Reaction Time , Verbal Learning/physiology , Young Adult
13.
Hum Brain Mapp ; 43(3): 985-997, 2022 02 15.
Article in English | MEDLINE | ID: mdl-34713955

ABSTRACT

A common finding in the aging literature is that of the brain's decreased within- and increased between-network functional connectivity. However, it remains unclear what is causing this shift in network organization with age. Given the essential role of the ascending arousal system (ARAS) in cortical activation and previous findings of disrupted ARAS functioning with age, it is possible that age differences in ARAS functioning contribute to disrupted cortical connectivity. We test this possibility here using resting state fMRI data from over 500 individuals across the lifespan from the Cambridge Center for Aging and Neuroscience (Cam-CAN) population-based cohort. Our results show that ARAS-cortical connectivity declines with age and, consistent with our expectations, significantly mediates some age-related differences in connectivity within and between association networks (specifically, within the default mode and between the default mode and salience networks). Additionally, connectivity between the ARAS and association networks predicted cognitive performance across several tasks over and above the effects of age and connectivity within the cortical networks themselves. These findings suggest that age differences in cortical connectivity may be driven, at least in part, by altered arousal signals from the brainstem and that ARAS-cortical connectivity relates to cognitive performance with age.


Subject(s)
Arousal/physiology , Brain Stem/physiology , Cerebral Cortex/physiology , Cognitive Aging/physiology , Connectome , Default Mode Network/physiology , Nerve Net/physiology , Adolescent , Adult , Age Factors , Aged , Aged, 80 and over , Brain Stem/diagnostic imaging , Cerebral Cortex/diagnostic imaging , Default Mode Network/diagnostic imaging , Female , Humans , Magnetic Resonance Imaging , Male , Middle Aged , Nerve Net/diagnostic imaging , Young Adult
14.
Hum Brain Mapp ; 43(2): 647-664, 2022 02 01.
Article in English | MEDLINE | ID: mdl-34738276

ABSTRACT

Music is known to induce emotions and activate associated memories, including musical memories. In adults, it is well known that music activates both working memory and limbic networks. We have recently discovered that as early as during the newborn period, familiar music is processed differently from unfamiliar music. The present study evaluates music listening effects at the brain level in newborns, by exploring the impact of familiar or first-time music listening on the subsequent resting-state functional connectivity in the brain. Using a connectome-based framework, we describe resting-state functional connectivity (RS-FC) modulation after music listening in three groups of newborn infants, in preterm infants exposed to music during their neonatal-intensive-care-unit (NICU) stay, in control preterm, and full-term infants. We observed modulation of the RS-FC between brain regions known to be implicated in music and emotions processing, immediately following music listening in all newborn infants. In the music exposed group, we found increased RS-FC between brain regions known to be implicated in familiar and emotionally arousing music and multisensory processing, and therefore implying memory retrieval and associative memory. We demonstrate a positive correlation between the occurrence of the prior music exposure and increased RS-FC in brain regions implicated in multisensory and emotional processing, indicating strong engagement of musical memories; and a negative correlation with the Default Mode Network, indicating disengagement due to the aforementioned cognitive processing. Our results describe the modulatory effect of music listening on brain RS-FC that can be linked to brain correlates of musical memory engrams in preterm infants.


Subject(s)
Amygdala/physiology , Auditory Perception/physiology , Cerebral Cortex/physiology , Connectome , Default Mode Network/physiology , Emotions/physiology , Infant, Premature/physiology , Music , Recognition, Psychology/physiology , Thalamus/physiology , Amygdala/diagnostic imaging , Cerebral Cortex/diagnostic imaging , Default Mode Network/diagnostic imaging , Female , Humans , Infant, Newborn , Magnetic Resonance Imaging , Male , Thalamus/diagnostic imaging
15.
Neuroimage ; 246: 118760, 2022 02 01.
Article in English | MEDLINE | ID: mdl-34875381

ABSTRACT

Control processes allow us to constrain the retrieval of semantic information from long-term memory so that it is appropriate for the task or context. Control demands are influenced by the strength of the target information itself and by the circumstances in which it is retrieved, with more control needed when relatively weak aspects of knowledge are required and after the sustained retrieval of related concepts. To investigate the neurocognitive basis of individual differences in these aspects of semantic control, we used resting-state fMRI to characterise the intrinsic connectivity of left ventrolateral prefrontal cortex (VLPFC), implicated in controlled retrieval, and examined associations on a paced serial semantic task, in which participants were asked to detect category members amongst distractors. This task manipulated both the strength of target associations and the requirement to sustain retrieval within a narrow semantic category over time. We found that individuals with stronger connectivity between VLPFC and medial prefrontal cortex within the default mode network (DMN) showed better retrieval of strong associations (which are thought to be recalled more automatically). Stronger connectivity between the same VLPFC seed and another DMN region in medial parietal cortex was associated with larger declines in retrieval over the course of the category. In contrast, participants with stronger connectivity between VLPFC and cognitive control regions within the ventral attention network (VAN) had better controlled retrieval of weak associations and were better able to sustain their comprehension throughout the category. These effects overlapped in left insular cortex within the VAN, indicating that a common pattern of connectivity is associated with different aspects of controlled semantic retrieval induced by both the structure of long-term knowledge and the sustained retrieval of related information.


Subject(s)
Connectome , Default Mode Network/physiology , Executive Function/physiology , Individuality , Mental Recall/physiology , Nerve Net/physiology , Prefrontal Cortex/physiology , Adolescent , Adult , Default Mode Network/diagnostic imaging , Female , Humans , Male , Nerve Net/diagnostic imaging , Prefrontal Cortex/diagnostic imaging , Semantics , Young Adult
16.
Neuroimage ; 245: 118758, 2021 12 15.
Article in English | MEDLINE | ID: mdl-34838949

ABSTRACT

The default mode network (DMN) mediates self-awareness and introspection, core components of human consciousness. Therapies to restore consciousness in patients with severe brain injuries have historically targeted subcortical sites in the brainstem, thalamus, hypothalamus, basal forebrain, and basal ganglia, with the goal of reactivating cortical DMN nodes. However, the subcortical connectivity of the DMN has not been fully mapped, and optimal subcortical targets for therapeutic neuromodulation of consciousness have not been identified. In this work, we created a comprehensive map of DMN subcortical connectivity by combining high-resolution functional and structural datasets with advanced signal processing methods. We analyzed 7 Tesla resting-state functional MRI (rs-fMRI) data from 168 healthy volunteers acquired in the Human Connectome Project. The rs-fMRI blood-oxygen-level-dependent (BOLD) data were temporally synchronized across subjects using the BrainSync algorithm. Cortical and subcortical DMN nodes were jointly analyzed and identified at the group level by applying a novel Nadam-Accelerated SCAlable and Robust (NASCAR) tensor decomposition method to the synchronized dataset. The subcortical connectivity map was then overlaid on a 7 Tesla 100 µm ex vivo MRI dataset for neuroanatomic analysis using automated segmentation of nuclei within the brainstem, thalamus, hypothalamus, basal forebrain, and basal ganglia. We further compared the NASCAR subcortical connectivity map with its counterpart generated from canonical seed-based correlation analyses. The NASCAR method revealed that BOLD signal in the central lateral nucleus of the thalamus and ventral tegmental area of the midbrain is strongly correlated with that of the DMN. In an exploratory analysis, additional subcortical sites in the median and dorsal raphe, lateral hypothalamus, and caudate nuclei were correlated with the cortical DMN. We also found that the putamen and globus pallidus are negatively correlated (i.e., anti-correlated) with the DMN, providing rs-fMRI evidence for the mesocircuit hypothesis of human consciousness, whereby a striatopallidal feedback system modulates anterior forebrain function via disinhibition of the central thalamus. Seed-based analyses yielded similar subcortical DMN connectivity, but the NASCAR result showed stronger contrast and better spatial alignment with dopamine immunostaining data. The DMN subcortical connectivity map identified here advances understanding of the subcortical regions that contribute to human consciousness and can be used to inform the selection of therapeutic targets in clinical trials for patients with disorders of consciousness.


Subject(s)
Basal Ganglia/physiology , Brain Mapping , Brain Stem/physiology , Consciousness/physiology , Default Mode Network/physiology , Hypothalamus/physiology , Mesencephalon/physiology , Thalamus/physiology , Adult , Basal Ganglia/diagnostic imaging , Brain Mapping/methods , Brain Stem/diagnostic imaging , Connectome , Default Mode Network/diagnostic imaging , Echo-Planar Imaging/methods , Humans , Hypothalamus/diagnostic imaging , Mesencephalon/diagnostic imaging , Thalamus/diagnostic imaging
17.
J Neurosci ; 41(48): 9944-9956, 2021 12 01.
Article in English | MEDLINE | ID: mdl-34675087

ABSTRACT

Human brains interpret external stimuli based on internal representations. One untested hypothesis is that the default-mode network (DMN), widely considered responsible for internally oriented cognition, can decode external information. Here, we posit that the unique structural and functional fingerprint of the precuneus (PCu) supports a prominent role for the posterior part of the DMN in this process. By analyzing the imaging data of 100 participants performing two attention-demanding tasks, we found that the PCu is functionally divided into dorsal and ventral subdivisions. We then conducted a comprehensive examination of their connectivity profiles and found that at rest, both the ventral PCu (vPCu) and dorsal PCu (dPCu) are mainly connected with the DMN but also are differentially connected with internally oriented networks (IoN) and externally oriented networks (EoN). During tasks, the double associations between the v/dPCu and the IoN/EoN are correlated with task performance and can switch depending on cognitive demand. Furthermore, dynamic causal modeling (DCM) revealed that the strength and direction of the effective connectivity (EC) between v/dPCu is modulated by task difficulty in a manner potentially dictated by the balance of internal versus external cognitive demands. Our study provides evidence that the posterior medial part of the DMN may drive interactions between large-scale networks, potentially allowing access to stored representations for moment-to-moment interpretation of an ever-changing environment.SIGNIFICANCE STATEMENT The default-mode network (DMN) is widely known for its association with internalized thinking processes, e.g., spontaneous thoughts, which is the most interesting but least understood component in human consciousness. The precuneus (PCu), a posteromedial DMN hub, is thought to play a role in this, but a mechanistic explanation has not yet been established. In this study we found that the associations between ventral PCu (vPCu)/dorsal PCu (dPCu) subdivisions and internally oriented network (IoN)/externally oriented network (EoN) are flexibly modulated by cognitive demand and correlate with task performance. We further propose that the recurrent causal connectivity between the ventral and dorsal PCu supports conscious processing by constantly interpreting external information based on an internal model, meanwhile updating the internal model with the incoming information.


Subject(s)
Attention/physiology , Default Mode Network/physiology , Parietal Lobe/physiology , Adult , Brain Mapping , Female , Humans , Magnetic Resonance Imaging , Male
18.
Neuroimage ; 240: 118382, 2021 10 15.
Article in English | MEDLINE | ID: mdl-34252524

ABSTRACT

Self-construal (orientations of independence and interdependence) is a fundamental concept that guides human behaviour, and it is linked to a large number of brain regions. However, understanding the connectivity of these regions and the critical principles underlying these self-functions are lacking. Because brain activity linked to self-related processes are intrinsic, the resting-state method has received substantial attention. Here, we focused on resting-state functional connectivity matrices based on brain asymmetry as indexed by the differential partition of the connectivity located in mirrored positions of the two hemispheres, hemispheric specialization measured using the intra-hemispheric (left or right) connectivity, brain communication via inter-hemispheric interactions, and global connectivity as the sum of the two intra-hemispheric connectivity. Combining machine learning techniques with hypothesis-driven network mapping approaches, we demonstrated that orientations of independence and interdependence were best predicted by the asymmetric matrix compared to brain communication, hemispheric specialization, and global connectivity matrices. The network results revealed that there were distinct asymmetric connections between the default mode network, the salience network and the executive control network which characterise independence and interdependence. These analyses shed light on the importance of brain asymmetry in understanding how complex self-functions are optimally represented in the brain networks.


Subject(s)
Brain/physiology , Default Mode Network/physiology , Executive Function/physiology , Functional Laterality/physiology , Machine Learning , Magnetic Resonance Imaging/methods , Adolescent , Adult , Brain/diagnostic imaging , Default Mode Network/diagnostic imaging , Female , Humans , Male , Young Adult
19.
Nat Rev Neurosci ; 22(8): 503-513, 2021 08.
Article in English | MEDLINE | ID: mdl-34226715

ABSTRACT

The default mode network (DMN) is a set of widely distributed brain regions in the parietal, temporal and frontal cortex. These regions often show reductions in activity during attention-demanding tasks but increase their activity across multiple forms of complex cognition, many of which are linked to memory or abstract thought. Within the cortex, the DMN has been shown to be located in regions furthest away from those contributing to sensory and motor systems. Here, we consider how our knowledge of the topographic characteristics of the DMN can be leveraged to better understand how this network contributes to cognition and behaviour.


Subject(s)
Brain/physiology , Cognition/physiology , Default Mode Network/physiology , Brain/diagnostic imaging , Brain Mapping , Default Mode Network/diagnostic imaging , Humans , Magnetic Resonance Imaging
20.
J Neurosci ; 41(35): 7372-7387, 2021 09 01.
Article in English | MEDLINE | ID: mdl-34301824

ABSTRACT

Human language learning differs significantly across individuals in the process and ultimate attainment. Although decades of research exploring the neural substrates of language learning have identified distinct and overlapping neural networks subserving learning of different components, the neural mechanisms that drive the large interindividual differences are still far from being understood. Here we examine to what extent the neural dynamics of multiple brain networks in men and women across sessions of training contribute to explaining individual differences in learning multiple linguistic components (i.e., vocabulary, morphology, and phrase and sentence structures) of an artificial language in a 7 d training and imaging paradigm with functional MRI. With machine-learning and predictive modeling, neural activation patterns across training sessions were highly predictive of individual learning success profiles derived from the four components. We identified four neural learning networks (i.e., the Perisylvian, frontoparietal, salience, and default-mode networks) and examined their dynamic contributions to the learning success prediction. Moreover, the robustness of the predictions systematically changes across networks depending on specific training phases and the learning components. We further demonstrate that a subset of network nodes in the inferior frontal, insular, and frontoparietal regions increasingly represent newly acquired language knowledge, while the multivariate connectivity between these representation regions is enhanced during learning for more successful learners. These findings allow us to understand why learners differ and are the first to attribute not only the degree of success but also patterns of language learning across components, to neural fingerprints summarized from multiple neural network dynamics.SIGNIFICANCE STATEMENT Individual differences in learning a language are widely observed not only within the same component of language but also across components. This study demonstrates that the dynamics of multiple brain networks across four imaging sessions of a 7 d artificial language training contribute to individual differences in learning-outcome profiles derived from four language components. With machine-learning predictive modeling, we identified four neural learning networks, including the Perisylvian, frontoparietal, salience, and default-mode networks, that contribute to predicting individual learning-outcome profiles and revealed language-component-general and component-specific prediction patterns across training sessions. These findings provide significant insights in understanding training-dependent neural dynamics underlying individual differences in learning success across language components.


Subject(s)
Brain Mapping , Cerebral Cortex/physiology , Individuality , Language Development , Learning/physiology , Nerve Net/physiology , Neural Pathways/physiology , Adult , Connectome , Default Mode Network/physiology , Female , Humans , Language , Language Tests , Machine Learning , Magnetic Resonance Imaging , Male , Memory, Long-Term/physiology , Mental Recall/physiology , Mental Status and Dementia Tests , Models, Neurological , Young Adult
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