The Experts below are selected from a list of 33747 Experts worldwide ranked by ideXlab platform
Randy L Buckner - One of the best experts on this subject based on the ideXlab platform.
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The brain’s Default Network: updated anatomy, physiology and evolving insights
Nature Reviews Neuroscience, 2019Co-Authors: Randy L Buckner, Lauren DinicolaAbstract:Discoveries over the past two decades demonstrate that regions distributed throughout the association cortex, often called the Default Network, are suppressed during tasks that demand external attention and are active during remembering, envisioning the future and making social inferences. This Review describes progress in understanding the organization and function of Networks embedded within these association regions. Detailed high-resolution analyses of single individuals suggest that the Default Network is not a single Network, as historically described, but instead comprises multiple interwoven Networks. The multiple Networks share a common organizational motif (also evident in marmoset and macaque anatomical circuits) that might support a general class of processing function dependent on internally constructed rather than externally constrained representations, with each separate interwoven Network specialized for a distinct processing domain. Direct neuronal recordings in humans and monkeys reveal evidence for competitive relationships between the internally and externally oriented Networks. Findings from rodent studies suggest that the thalamus might be essential to controlling which Networks are engaged through specialized thalamic reticular neurons, including antagonistic subpopulations. These association Networks (and presumably thalamocortical circuits) are expanded in humans and might be particularly vulnerable to dysregulation implicated in mental illness. The brain’s Default Network is thought to comprise a set of regions in the association cortex. Randy Buckner and Lauren DiNicola review findings from humans, monkeys and rodents indicating that multiple subNetworks make up the Default Network and explore the implications of these observations.
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the brain s Default Network updated anatomy physiology and evolving insights
Nature Reviews Neuroscience, 2019Co-Authors: Randy L Buckner, Lauren DinicolaAbstract:Discoveries over the past two decades demonstrate that regions distributed throughout the association cortex, often called the Default Network, are suppressed during tasks that demand external attention and are active during remembering, envisioning the future and making social inferences. This Review describes progress in understanding the organization and function of Networks embedded within these association regions. Detailed high-resolution analyses of single individuals suggest that the Default Network is not a single Network, as historically described, but instead comprises multiple interwoven Networks. The multiple Networks share a common organizational motif (also evident in marmoset and macaque anatomical circuits) that might support a general class of processing function dependent on internally constructed rather than externally constrained representations, with each separate interwoven Network specialized for a distinct processing domain. Direct neuronal recordings in humans and monkeys reveal evidence for competitive relationships between the internally and externally oriented Networks. Findings from rodent studies suggest that the thalamus might be essential to controlling which Networks are engaged through specialized thalamic reticular neurons, including antagonistic subpopulations. These association Networks (and presumably thalamocortical circuits) are expanded in humans and might be particularly vulnerable to dysregulation implicated in mental illness. The brain’s Default Network is thought to comprise a set of regions in the association cortex. Randy Buckner and Lauren DiNicola review findings from humans, monkeys and rodents indicating that multiple subNetworks make up the Default Network and explore the implications of these observations.
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The brain's Default Network: origins and implications for the study of psychosis
Dialogues in clinical neuroscience, 2013Co-Authors: Randy L BucknerAbstract:The brain's Default Network is a set of regions that is spontaneously active during passive moments. The Network is also active during directed tasks that require participants to remember past events or imagine upcoming events. One hypothesis is that the Network facilitates construction of mental models (simulations) that can be used adaptively in many contexts. Extensive research has considered whether disruption of the Default Network may contribute to disease. While an intriguing possibility, a specific challenge to this notion is the fact that it is difficult to accurately measure the Default Network in patients where confounds of head motion and compliance are prominent. Nonetheless, some intriguing recent findings suggest that dysfunctional interactions between front-oparietal control systems and the Default Network contribute to psychosis. Psychosis may be a Network disturbance that manifests as disordered thought partly because it disrupts the fragile balance between the Default Network and competing brain systems.
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the serendipitous discovery of the brain s Default Network
NeuroImage, 2012Co-Authors: Randy L BucknerAbstract:Abstract One of the most unexpected findings by functional neuroimaging has been the discovery of the brain's Default Network — a set of brain regions that is spontaneously active during passive moments. The Default Network's discovery was a fortunate accident that occurred due to the inclusion of rest control conditions in early PET and functional MRI studies. At first, the Network was ignored. Later, its presence was shunned as evidence of an experimental confound. Finally, it emerged as a mainstream target of focused study. Here, I describe a personal perspective of the Default Network's serendipitous discovery.
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The serendipitous discovery of the brain's Default Network.
NeuroImage, 2011Co-Authors: Randy L BucknerAbstract:Abstract One of the most unexpected findings by functional neuroimaging has been the discovery of the brain's Default Network — a set of brain regions that is spontaneously active during passive moments. The Default Network's discovery was a fortunate accident that occurred due to the inclusion of rest control conditions in early PET and functional MRI studies. At first, the Network was ignored. Later, its presence was shunned as evidence of an experimental confound. Finally, it emerged as a mainstream target of focused study. Here, I describe a personal perspective of the Default Network's serendipitous discovery.
Sarah H. Lisanby - One of the best experts on this subject based on the ideXlab platform.
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Self-enhancement processing in the Default Network: a single-pulse TMS study
Experimental Brain Research, 2012Co-Authors: Bruce Luber, Julian P. Keenan, Sarah H. LisanbyAbstract:Much research has been done on positive self-evaluation and its relationship to mental health. However, little is known about its neural underpinnings. Imaging studies have suggested that the brain’s Default Network is involved with self-related processing and that one portion of the Default Network, medial prefrontal cortex (MPFC), is particularly involved with self-evaluation. Here, we used transcranial magnetic stimulation (TMS) to causally demonstrate that this Network, and particularly MPFC, is involved with self-evaluative processing. In a first experiment, 27 healthy volunteers judged whether adjectives, evenly divided between desirable and undesirable traits, described themselves or their best friends, and a robust self-enhancement bias effect was found. In a second experiment, single-pulse TMS was applied targeting three locations (MPFC and left and right parietal cortex) in a different group of healthy volunteers while they performed the adjective task. In each trial, TMS was applied at one of five different times relative to onset of the adjective ranging from 0 to 480 ms. TMS affected self-enhancement bias in a site- and latency-specific manner: at MPFC, the self-enhancement bias actually reversed at 160 ms, with subjects favoring their best friend over themselves. TMS may thus be of use in investigating areas of mental illness in which self-evaluation is abnormal, potentially as a diagnostic tool. In addition, the present study, combined with our previous reports (Lou et al., Proc Natl Acad Sci USA 101(17):6827–6832, 2004 , Exp Brain Res 207:27–38, 2010 ), causally demonstrates two kinds of self-related processing within the Default Network, one centered in parietal cortex and concerned with retrieval of self-related associations, and the other MPFC-centered and involved in self-evaluative processing.
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Self-specific processing in the Default Network: a single-pulse TMS study.
Experimental brain research, 2010Co-Authors: Hans C Lou, Bruce Luber, Arielle Stanford, Sarah H. LisanbyAbstract:In examining neural processing specific to the self, primarily by contrasting self-related stimuli with non-self-related stimuli (i.e., self vs. other), neuroimaging studies have activated a consistent set of regions, including medial prefrontal cortex (MPFC), precuneus, and right and left inferior parietal cortex. However, criticism has arisen that this Network may not be specific to self-related processing, but instead reflects a more general aspect of cortical processing. For example, it is almost identical to the active Network of the resting state, the "Default" mode, when the subject is free to think about anything at all. We tested the self-specificity of this Network by using transcranial magnetic stimulation (TMS) to briefly disrupt local cortical processing while subjects rated adjectives as like or unlike themselves or their best friend. Healthy volunteers show a self-reference effect (SRE) in this task, in which performance with self-related items is superior to that with other-related items. As individual adjectives appeared on a monitor, single-pulse TMS was applied at five different times relative to stimulus onset (SOA: stimulus onset asynchrony) ranging from 0 to 480 ms. In 18 subjects, TMS to left parietal cortex suppressed the SRE from 160 to 480 ms. SRE suppression occurred at later SOA with TMS to the right parietal cortex. In contrast, no effects were seen with TMS to MPFC. Together with our previous work, these results provide evidence for a self-specific processing system in which midline and lateral inferior parietal cortices, as elements of the Default Network, play a role in ongoing self-awareness.
Daniel L Schacter - One of the best experts on this subject based on the ideXlab platform.
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Default Network contributions to episodic and semantic processing during divergent creative thinking a representational similarity analysis
NeuroImage, 2020Co-Authors: Roger E. Beaty, Mathias Benedek, Paul J Silvia, Qunlin Chen, Alexander P Christensen, Yoed N Kenett, Daniel L SchacterAbstract:Abstract Cognitive and neuroimaging evidence suggests that episodic and semantic memory—memory for autobiographical events and conceptual knowledge, respectively—support different aspects of creative thinking, with a growing number of studies reporting activation of brain regions within the Default Network during performance on creative thinking tasks. The present research sought to dissociate neural contributions of these memory processes by inducing episodic or semantic retrieval orientations prior to performance on a divergent thinking task during fMRI. We conducted a representational similarity analysis (RSA) to identify multivoxel patterns of neural activity that were similar across induction (episodic and semantic) and idea generation. At the behavioral level, we found that semantic induction was associated with increased idea originality, assessed via computational estimates of semantic distance between concepts. RSA revealed that multivoxel patterns during semantic induction and subsequent idea generation were more similar (compared to episodic induction) within the left angular gyrus (AG), posterior cingulate cortex (PCC), and left anterior inferior parietal lobe (IPL). Conversely, activity patterns during episodic induction and subsequent generation were more similar within left parahippocampal gyrus and right anterior IPL. Together, the findings point to dissociable contributions of episodic and semantic memory processes to creative cognition and suggest that distinct regions within the Default Network support specific memory-related processes during divergent thinking.
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Creativity, Self-Generated Thought, and the Brain’s Default Network
The Creative Self, 2017Co-Authors: Roger E. Beaty, Daniel L SchacterAbstract:In this chapter, we explore emerging research from psychology and neuroscience on the contributions of self-generated thought and the brain’s Default Network in creative cognition. Self-generated thought encompasses a wide range of human cognition, from mind-wandering to memory retrieval. In general, self-generated thought is characterized by internally focused mental activity that occurs when the mind is not engaged with the external world. Neuroimaging research has identified the brain’s Default Network as the primary source of self-generated cognition. Increasing evidence suggests that the Default Network plays a critical role in creative thought, with several neuroimaging studies reporting activation of Default regions during both domain-general creative problem solving (e.g., divergent thinking) and domain-specific artistic performance (e.g., musical improvisation). In the chapter, we describe the various cognitive functions associated with the Default Network, with a focus on understanding how this Network may contribute to the production of creative ideas.
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Default Network and Aging: Beyond the Task-Negative Perspective
Trends in cognitive sciences, 2016Co-Authors: David Maillet, Daniel L SchacterAbstract:During cognitive tasks requiring externally directed attention, activation in the Default-Network (DN) typically decreases below baseline levels (‘deactivation'). Healthy aging is associated with reduced deactivation, which is usually attributed to a failure to suppress DN processes. Recent evidence instead suggests that older adults may be more reliant on DN than young adults when performing these tasks.
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Default Network Modulation and Large-Scale Network Interactivity in Healthy Young and Old Adults
Cerebral cortex (New York N.Y. : 1991), 2011Co-Authors: R. Nathan Spreng, Daniel L SchacterAbstract:We investigated age-related changes in Default, attention, and control Network activity and their interactions in young and old adults. Brain activity during autobiographical and visuospatial planning was assessed using multivariate analysis and with intrinsic connectivity Networks as regions of interest. In both groups, autobiographical planning engaged the Default Network while visuospatial planning engaged the attention Network, consistent with a competition between the domains of internalized and externalized cognition. The control Network was engaged for both planning tasks. In young subjects, the control Network coupled with the Default Network during autobiographical planning and with the attention Network during visuospatial planning. In old subjects, Default-to-control Network coupling was observed during both planning tasks, and old adults failed to deactivate the Default Network during visuospatial planning. This failure is not indicative of Default Network dysfunction per se, evidenced by Default Network engagement during autobiographical planning. Rather, a failure to modulate the Default Network in old adults is indicative of a lower degree of flexible Network interactivity and reduced dynamic range of Network modulation to changing task demands.
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Solving future problems: Default Network and executive activity associated with goal-directed mental simulations
NeuroImage, 2011Co-Authors: Kathy D. Gerlach, Adrian W Gilmore, R. Nathan Spreng, Daniel L SchacterAbstract:Mental simulations are often focused on a goal in the future or a problem to be solved. Recent neuroimaging studies have associated mental simulations of the future with Default Network activity, but the simulations in these studies were not typically directed toward achieving a particular goal. Goal-directed simulation requires cognitive control to maintain information, make decisions, and coordinate abstract action sequences. Therefore, it should recruit not only the Default Network, but also executive regions. To investigate whether Default Network and executive regions can be coactive in the context of goal-directed simulation, we designed a problem-solving task in which participants simulated solving several specific problems in imaginary scenarios while in the MRI scanner. We analyzed brain activity during simulation relative to a semantic elaboration task and found that goal-directed simulation engaged core regions of the Default Network and executive dorsolateral prefrontal cortex. A functional connectivity analysis with posterior cingulate and dorsolateral prefrontal cortex seeds revealed that activity in these regions was coupled throughout the goal-directed simulation period and associated with a distributed Network of other Default and executive regions, including medial prefrontal cortex, medial temporal, and parietal regions.
Bruce Luber - One of the best experts on this subject based on the ideXlab platform.
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Self-enhancement processing in the Default Network: a single-pulse TMS study
Experimental Brain Research, 2012Co-Authors: Bruce Luber, Julian P. Keenan, Sarah H. LisanbyAbstract:Much research has been done on positive self-evaluation and its relationship to mental health. However, little is known about its neural underpinnings. Imaging studies have suggested that the brain’s Default Network is involved with self-related processing and that one portion of the Default Network, medial prefrontal cortex (MPFC), is particularly involved with self-evaluation. Here, we used transcranial magnetic stimulation (TMS) to causally demonstrate that this Network, and particularly MPFC, is involved with self-evaluative processing. In a first experiment, 27 healthy volunteers judged whether adjectives, evenly divided between desirable and undesirable traits, described themselves or their best friends, and a robust self-enhancement bias effect was found. In a second experiment, single-pulse TMS was applied targeting three locations (MPFC and left and right parietal cortex) in a different group of healthy volunteers while they performed the adjective task. In each trial, TMS was applied at one of five different times relative to onset of the adjective ranging from 0 to 480 ms. TMS affected self-enhancement bias in a site- and latency-specific manner: at MPFC, the self-enhancement bias actually reversed at 160 ms, with subjects favoring their best friend over themselves. TMS may thus be of use in investigating areas of mental illness in which self-evaluation is abnormal, potentially as a diagnostic tool. In addition, the present study, combined with our previous reports (Lou et al., Proc Natl Acad Sci USA 101(17):6827–6832, 2004 , Exp Brain Res 207:27–38, 2010 ), causally demonstrates two kinds of self-related processing within the Default Network, one centered in parietal cortex and concerned with retrieval of self-related associations, and the other MPFC-centered and involved in self-evaluative processing.
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Self-specific processing in the Default Network: a single-pulse TMS study.
Experimental brain research, 2010Co-Authors: Hans C Lou, Bruce Luber, Arielle Stanford, Sarah H. LisanbyAbstract:In examining neural processing specific to the self, primarily by contrasting self-related stimuli with non-self-related stimuli (i.e., self vs. other), neuroimaging studies have activated a consistent set of regions, including medial prefrontal cortex (MPFC), precuneus, and right and left inferior parietal cortex. However, criticism has arisen that this Network may not be specific to self-related processing, but instead reflects a more general aspect of cortical processing. For example, it is almost identical to the active Network of the resting state, the "Default" mode, when the subject is free to think about anything at all. We tested the self-specificity of this Network by using transcranial magnetic stimulation (TMS) to briefly disrupt local cortical processing while subjects rated adjectives as like or unlike themselves or their best friend. Healthy volunteers show a self-reference effect (SRE) in this task, in which performance with self-related items is superior to that with other-related items. As individual adjectives appeared on a monitor, single-pulse TMS was applied at five different times relative to stimulus onset (SOA: stimulus onset asynchrony) ranging from 0 to 480 ms. In 18 subjects, TMS to left parietal cortex suppressed the SRE from 160 to 480 ms. SRE suppression occurred at later SOA with TMS to the right parietal cortex. In contrast, no effects were seen with TMS to MPFC. Together with our previous work, these results provide evidence for a self-specific processing system in which midline and lateral inferior parietal cortices, as elements of the Default Network, play a role in ongoing self-awareness.
James B. Brewer - One of the best experts on this subject based on the ideXlab platform.
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elaboration versus suppression of cued memories influence of memory recall instruction and success on parietal lobe Default Network and hippocampal activity
PLOS ONE, 2014Co-Authors: Sarah I Gimbel, James B. BrewerAbstract:Functional imaging studies of episodic memory retrieval consistently report task-evoked and memory-related activity in the medial temporal lobe, Default Network and parietal lobe subregions. Associated components of memory retrieval, such as attention-shifts, search, retrieval success, and post-retrieval processing also influence regional activity, but these influences remain ill-defined. To better understand how top-down control affects the neural bases of memory retrieval, we examined how regional activity responses were modulated by task goals during recall success or failure. Specifically, activity was examined during memory suppression, recall, and elaborative recall of paired-associates. Parietal lobe was subdivided into dorsal (BA 7), posterior ventral (BA 39), and anterior ventral (BA 40) regions, which were investigated separately to examine hypothesized distinctions in sub-regional functional responses related to differential attention-to-memory and memory strength. Top-down suppression of recall abolished memory strength effects in BA 39, which showed a task-negative response, and BA 40, which showed a task-positive response. The task-negative response in Default Network showed greater negatively-deflected signal for forgotten pairs when task goals required recall. Hippocampal activity was task-positive and was influenced by memory strength only when task goals required recall. As in previous studies, we show a memory strength effect in parietal lobe and hippocampus, but we show that this effect is top-down controlled and sensitive to whether the subject is trying to suppress or retrieve a memory. These regions are all implicated in memory recall, but their individual activity patterns show distinct memory-strength-related responses when task goals are varied. In parietal lobe, Default Network, and hippocampus, top-down control can override the commonly identified effects of memory strength.
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Erratum: search-related suppression of hippocampus and Default Network activity during associative memory retrieval
Frontiers in human neuroscience, 2013Co-Authors: Emilie T Reas, Sarah I Gimbel, Jena B Hales, James B. BrewerAbstract:Episodic memory retrieval involves the coordinated interaction of several cognitive processing stages such as mental search, access to a memory store, associative re-encoding, and post-retrieval monitoring. The neural response during memory retrieval is an integration of signals from multiple regions that may subserve supportive cognitive control, attention, sensory association, encoding, or working memory functions. It is particularly challenging to dissociate contributions of these distinct components to brain responses in regions such as the hippocampus, which lies at the interface between overlapping memory encoding and retrieval, and “Default” Networks. In the present study, event-related functional magnetic resonance imaging (fMRI) and measures of memory performance were used to differentiate brain responses to memory search from subcomponents of episodic memory retrieval associated with successful recall. During the attempted retrieval of both poorly and strongly remembered word pair associates, the hemodynamic response was negatively deflected below baseline in anterior hippocampus and regions of the Default Network. Activations in anterior hippocampus were functionally distinct from those in posterior hippocampus and negatively correlated with response times. Thus, relative to the pre-stimulus period, the hippocampus shows reduced activity during intensive engagement in episodic memory search. Such deactivation was most salient during trials that engaged only pre-retrieval search processes in the absence of successful recollection or post-retrieval processing. Implications for interpretation of hippocampal fMRI responses during retrieval are discussed. A model is presented to interpret such activations as representing modulation of encoding-related activity, rather than retrieval-related activity. Engagement in intensive mental search may reduce neural and attentional resources that are otherwise tonically devoted to encoding an individual’s stream of experience into episodic memory.
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Search-Related Suppression of Hippocampus and Default Network Activity during Associative Memory Retrieval.
Frontiers in human neuroscience, 2011Co-Authors: Emilie T Reas, Sarah I Gimbel, Jena B Hales, James B. BrewerAbstract:Episodic memory retrieval involves the coordinated interaction of several cognitive processing stages such as mental search, access to a memory store, associative re-encoding, and post-retrieval monitoring. The neural response during memory retrieval is an integration of signals from multiple regions that may subserve supportive cognitive control, attention, sensory association, encoding, or working memory functions. It is particularly challenging to dissociate contributions of these distinct components to brain responses in regions such as the hippocampus, which lies at the interface between overlapping memory encoding and retrieval, and "Default" Networks. In the present study, event-related functional magnetic resonance imaging (fMRI) and measures of memory performance were used to differentiate brain responses to memory search from subcomponents of episodic memory retrieval associated with successful recall. During the attempted retrieval of both poorly and strongly remembered word pair associates, the hemodynamic response was negatively deflected below baseline in anterior hippocampus and regions of the Default Network. Activations in anterior hippocampus were functionally distinct from those in posterior hippocampus and negatively correlated with response times. Thus, relative to the pre-stimulus period, the hippocampus shows reduced activity during intensive engagement in episodic memory search. Such deactivation was most salient during trials that engaged only pre-retrieval search processes in the absence of successful recollection or post-retrieval processing. Implications for interpretation of hippocampal fMRI responses during retrieval are discussed. A model is presented to interpret such activations as representing modulation of encoding-related activity, rather than retrieval-related activity. Engagement in intensive mental search may reduce neural and attentional resources that are otherwise tonically devoted to encoding an individual's stream of experience into episodic memory.
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Default Network correlations analyzed on native surfaces
Journal of neuroscience methods, 2011Co-Authors: Tyler M. Seibert, James B. BrewerAbstract:Disruptions of interregional correlations in the blood oxygenation level dependent fMRI signal have been reported in multiple diseases, including Alzheimer's disease and mild cognitive impairment. "Default Network" regions that overlap with areas of earliest amyloid deposition have been highlighted by these reports, and abnormal Default Network activity is also observed in unimpaired elderly subjects with high amyloid burden. However, one limitation of current methods for analysis of interregional correlations is that they rely on transformation of functional data to an atlas volume (e.g., Talairach-Tournoux or Montreal Neurological Institute atlases) and may not adequately account for anatomic variation between subjects, particularly in the presence of atrophy. We assessed the utility of the FreeSurfer cortical parcellation to analyze Default Network functional correlations on the native surfaces of individual subjects. Group-level quantitative analysis was accomplished by comparing correlations between equivalent structures in different subjects. The method was applied to resting-state fMRI data from young, healthy subjects; preliminary results were also obtained from cognitively unimpaired elderly subjects and patients with Alzheimer's disease, Parkinson's disease, Parkinson's disease dementia, and dementia with Lewy bodies.
