Cerebral Cortex
April 9, 2008
M. D. Greicius, K. Supekar, V. Menon et al.
2,227 citations
Resting-state functional connectivity MRI, which measures correlated brain activity while a person lies quietly in a scanner, has been questioned as possibly reflecting noise rather than true neural connections. By combining diffusion tensor imaging tractography with resting-state functional connectivity MRI, this work tested whether the functional correlations correspond to actual structural pathways. Focusing on the default mode network—a set of brain regions involved in memory, including the medial prefrontal cortex, medial temporal lobes, and posterior cingulate/retrosplenial cortex—the analysis found that structural connections matched the functional connectivity maps. Medial temporal lobes connected to retrosplenial cortex, while medial prefrontal cortex connected to posterior cingulate cortex. The results demonstrate that resting-state functional connectivity reflects structural connectivity, and combining methods can deepen understanding of brain networks.
Cerebral Cortex
February 17, 2011
Philipp G. Sämann, Renate Wehrle, David Hoehn et al.
408 citations
As people fall asleep, the brain's default mode network (DMN) and its anticorrelated network (ACN) break down. In 25 healthy participants, functional connectivity between key brain regions—especially the posterior cingulate cortex, parahippocampal gyrus, and medial prefrontal cortex—decreased with deeper non-REM sleep. The loss of synchronization between the posterior and anterior midline nodes of the DMN, and between the DMN and ACN, suggests that preserved corticocortical connectivity is necessary for maintaining internal and external awareness. The posterior cingulate/retrosplenial cortex appears particularly important for regulating consciousness.
Cerebral Cortex
March 7, 2011
Elizabeth C. Mormino, Andre Smiljic, Amynta O. Hayenga et al.
349 citations
Beta-amyloid deposition, a hallmark of Alzheimer's disease, is also common in cognitively normal older adults. Using Pittsburgh compound-B PET imaging, the study found that greater beta-amyloid burden in normal controls is associated with altered functional connectivity within the default mode network during rest. Connectivity decreased in regions critical for episodic memory, including posteromedial cortex, ventral medial prefrontal cortex, and angular gyrus, while increases appeared in dorsal and anterior medial prefrontal and lateral temporal cortices. The decreases align with known vulnerability of memory-related areas in Alzheimer's disease, and the increases may reflect compensatory mechanisms.
Cerebral Cortex
November 29, 2012
John D. Murray, Alan Anticevic, Mark G. Gancsos et al.
278 citations
Disruption of the balance between excitation and inhibition in the prefrontal cortex is thought to underlie cognitive problems in schizophrenia. A computational model of spatial working memory showed that disinhibition—caused by perturbing NMDA receptors on interneurons—broadens the tuning of memory-related neural activity, leading to more variable and less precise stored information and a reduced ability to filter out distractions. This prediction was tested with behavioral data from humans given ketamine, which induces disinhibition, and ketamine increased errors as the model predicted. The model also showed that restoring excitation-inhibition balance could reverse these working memory deficits, pointing to new experimental approaches for studying memory problems in schizophrenia.
Cerebral Cortex
December 15, 2011
Tim Gard, Britta K. Hölzel, Alexander T. Sack et al.
275 citations
Pain can be modulated by mindfulness, but the underlying brain mechanisms differ from those of other cognitive techniques. Mindfulness practitioners reduced pain unpleasantness by 22% and anticipatory anxiety by 29% during a mindful state, while controls did not. In the brain, this reduction was associated with decreased activation in the lateral prefrontal cortex and increased activation in the right posterior insula during stimulation, and increased rostral anterior cingulate cortex activation during pain anticipation. These findings indicate a unique mechanism of pain modulation involving increased sensory processing and decreased cognitive control, contrasting with established mechanisms.
Cerebral Cortex
April 24, 2012
Renaud Jardri, Pierre Thomas, Christine Delmaire et al.
180 citations
Hallucinations in psychosis may arise when the brain's default-mode network (DMN) disengages abnormally, similar to its response to real external stimuli. In 20 drug-free adolescents with brief psychotic disorder, multimodal MRI showed that during auditory, visual, and multisensory hallucinations, cortical thickness was reduced and blood oxygen level-dependent signal increased in modality-dependent association sensory cortices, while primary sensory cortex recruitment was not systematic and linked to greater vividness. DMN disengagement coincided with hallucinations, and spatial and temporal instabilities of the DMN correlated with hallucination severity and persisted even without symptoms. This suggests hallucinations emerge from spontaneous DMN withdrawal, offering a model beyond the auditory modality.
Cerebral Cortex
June 21, 2018
Verity Smith, Daniel J Mitchell, John Duncan
173 citations
The default mode network (DMN) is typically thought to support internally focused thought, but a new brain imaging study shows it also activates during certain external task switches. Using fMRI, 24 participants performed a task-switching experiment. The DMN increased activity not only during task switches, replicating prior findings, but also during brief rests and task restarts after rest. These results challenge theories that restrict DMN function to internal or self-directed cognition. The authors propose that the DMN encodes scene, episode, or context by integrating spatial, self-referential, and temporal information. Context representations are strong at rest, but re-reference to context also occurs at major cognitive transitions.
Cerebral Cortex
November 10, 2004
G. Honey, R. Honey, C. O'Loughlin et al.
116 citations
Ketamine, a drug that blocks NMDA receptors, impairs episodic memory. Using fMRI, brain activity was measured in healthy volunteers during memory encoding and retrieval under two intravenous doses of ketamine in a double-blind, placebo-controlled, randomized, within-subjects design. Encoding and retrieval were separated across two study-test cycles to isolate drug effects on each process. Results suggest that ketamine increases left frontal activation when elaborative semantic processing is needed during encoding, and successful encoding on the drug relies on additional incidental non-verbal processing. At retrieval, ketamine appears to impair access to contextual features of studied items. Even when behavior appears normal, ketamine alters recruitment of key brain regions for episodic memory.
Cerebral Cortex
August 8, 2012
André Schmidt, Andreea O. Diaconescu, Michael Kometer et al.
110 citations
Using dynamic causal modeling and Bayesian model selection on data from a double-blind, placebo-controlled, crossover ketamine study, the authors investigated how the NMDA-receptor antagonist ketamine reduces mismatch negativity (MMN) amplitudes. Guided by a predictive coding framework that unifies adaptation and model adjustment theories, they compared models allowing different expressions of neuronal adaptation and synaptic plasticity. Results replicated that both adaptation and short-term plasticity are necessary for MMN generation. Ketamine significantly affected synaptic plasticity but not adaptation, with a selective effect on the forward connection from left primary auditory cortex to superior temporal gyrus. This model-based estimate of ketamine's effect on synaptic plasticity correlated with ratings of ketamine-induced impairments in cognition and control, suggesting a concrete mechanism linking ketamine effects on MMN to drug-induced psychopathology.
Cerebral Cortex
July 10, 2013
Gustavo Deco, P. Hagmann, Anthony G. Hudetz et al.
99 citations
The transition from wakefulness to sleep involves gradual neural changes rather than an abrupt shift. Local slow waves appear during wakefulness and increase as arousal-promoting neuromodulation decreases, while resting-state brain networks maintain their overall organization. Only when neuromodulation drops to very low levels do slow waves become global and resting-state networks merge into a single synchronized network.
Cerebral Cortex
May 14, 2018
Lisa Miller, Iris M. Balodis, Clayton H. Mcclintock et al.
65 citations
People across cultures and throughout history report spiritual experiences that involve a sense of union transcending the ordinary self, but their neural mechanisms are poorly understood. Using an individualized guided-imagery task, the authors compared brain activity during personally meaningful spiritual experiences with that during stressful and neutral-relaxing experiences. During spiritual experiences, the left inferior parietal lobule showed reduced activity compared to neutral-relaxing experiences, suggesting this region contributes to perceptual processing and self-other representations. Compared to stress cues, spiritual cues reduced activity in the medial thalamus and caudate, regions linked to sensory and emotional processing. The findings point to neural mechanisms underlying broadly defined, personally experienced spirituality.
Cerebral Cortex
June 10, 2021
Patricia Duerler, Silvia Brem, Gorka Fraga González et al.
64 citations
Psilocybin reduces brain responses to surprising tactile stimuli, altering the sense of body and self. In a combined EEG-fMRI study, psilocybin decreased activity in frontal regions, visual cortex, and cerebellum during unexpected touch, and reduced mismatch negativity signals at frontal electrodes. These changes were linked to altered body- and self-experience. The findings highlight the role of the 5-HT2A receptor system in processing unexpected bodily sensations and integrating them with self-awareness, which may inform treatments for psychiatric disorders involving distorted body perception.
Cerebral Cortex
July 16, 2013
Fosco Bernasconi, André Schmidt, Thomas Pokorny et al.
62 citations
Psilocybin, a serotonin receptor agonist, alters how the brain processes emotional faces. Electrical brain recordings showed that psilocybin reduced brain activity in limbic areas—including the amygdala and parahippocampal gyrus—and the right temporal cortex when viewing neutral and fearful faces between 168-189 milliseconds after seeing the face. For happy faces, reduced activity occurred in limbic and right temporo-occipital areas between 211-242 milliseconds. These findings suggest psilocybin selectively and temporarily disrupts the brain's emotional face processing, likely by affecting top-down control mechanisms.
Cerebral Cortex
September 12, 2017
Frederick S. Barrett, Katrin H. Preller, Marcus Herdener et al.
52 citations
Classic psychedelic drugs that activate serotonin 2A receptors alter how the brain responds to the changing tonal structure of music. In 25 healthy adults, brain imaging after placebo, LSD, and LSD combined with a serotonin 2A blocker showed that serotonin 2A signaling changes neural activity in regions for basic and higher-level music processing, memory, emotion, and self-referential thought. This signaling appears critical for tracking musical tonality and for the heightened emotionality, connectedness, and meaningfulness people often report after taking psychedelics. The findings clarify the neuropsychopharmacology of music perception and why music can feel profoundly altered during psychedelic experiences.
Cerebral Cortex
December 16, 2019
Danielle D. DeSouza, Katy H. Stimpson, Laima Baltusis et al.
26 citations
Hypnotizability, a stable trait in adulthood, is linked to the concentration of the neurotransmitter GABA in the anterior cingulate cortex (ACC). In healthy individuals, higher ACC GABA levels were positively associated with higher hypnotizability scores measured by the Hypnotic Induction Profile. An exploratory analysis also found a negative relationship between glutamate levels and the absorption and imaginative involvement subscale of the Dissociative Experiences Scale. These findings suggest a neurobiological basis for individual differences in hypnotic responsiveness, which may help explain variability in treatment outcomes for hypnosis-based psychotherapies.
Cerebral Cortex
September 6, 2018
Gregory M. James, Gregor Gryglewski, Thomas Vanicek et al.
16 citations
The cerebral cortex can be divided into distinct areas based on the density of proteins involved in the serotonin system. Using positron emission tomography in healthy participants, the study quantified serotonin 1A receptors (n = 30), 5-HT2A receptors (n = 22), the serotonin-degrading enzyme monoamine oxidase A (n = 32), and the serotonin transporter (n = 24). Clustering analysis identified five optimal clusters of cortical regions defined by these molecular profiles. These clusters explained the effects of psychotropic drugs acting on serotonin, such as antidepressants and psychedelics, suggesting the method is useful for integrating multimodal imaging data in neuropharmacology and psychiatry.
Cerebral Cortex
July 1, 2024
Yupeng Han, Lizhao Du, Qiyun Huang et al.
Long-term meditation experience produces detectable neurophysiological changes in brain activity, possibly enhancing functional segregation and specialization. Electroencephalogram data from 20 long-term meditators and 20 nonmeditators during cognitive tasks and a relaxed state showed that meditators had higher classification accuracy and calculation efficiency. During a calculation task, both the power and global phase synchronism of gamma response decreased in meditators compared to their relaxation state, while no such change occurred in nonmeditators. These findings suggest meditation improves brain flexibility through neural plastic mechanisms.
Cerebral Cortex
May 4, 2023
Xinying Wang, Hui Zhou, Yuzheng Hu
Cannabis-dependent individuals show an unusual link between negative emotions and poor cognitive performance, unlike healthy controls. Analyzing resting-state fMRI data from the Human Connectome Project, the authors found opposite brain-behavior associations in the two groups: in healthy controls, better cognitive performance correlated with stronger within-network connectivity and segregation of the cognitive network, but these correlations were reversed in cannabis-dependent individuals. In cannabis-dependent individuals, better cognitive performance correlated with stronger within-network effective connectivity and integration, associations not significant in controls. Effective connectivity within the cognition network also mediated the behavioral coupling between emotional state and cognitive performance. The results suggest disorganization of the cognitive network in cannabis dependence.
Cerebral Cortex
November 1, 2022
Menglu Chen, Ying He, Lei Hao et al.
The default mode network (DMN) and the frontal parietal network (FPN) mature at different rates in children, with the DMN reaching adult-like levels earlier than the FPN. In a longitudinal developmental fMRI study using an n-back task with 528 children and 103 young adults, children showed greater improvement over time but still performed worse than adults. Children had weaker DMN deactivation and FPN activation but stronger coupling between DMN and FPN regions. The coupling between the posterior cingulate cortex and dorsolateral prefrontal cortex mediated the relationship between age and working memory-related functional coupling, and together with task-invoked PCC activity, accounted for children's behavioral improvement. The DMN appears to provide a scaffolding effect supporting the immature FPN during executive function development.
Cerebral Cortex
December 18, 2019
M. Owens, D. Yuan, S. Hahn et al.
preprint
The default mode network (DMN) and dorsal attention network (DAN) typically show an 'anticorrelation' in healthy adults, reflecting a separation between internal and external thought. Reduced separation of these networks has been proposed as a mechanism for cognitive deficits in psychiatric disorders, but this link had rarely been tested in pre-adolescent children. Using data from the Adolescent Brain Cognitive Development study, the largest sample to date of 9- to 10-year-old children (N=6543), the analysis examined the relationship between DMN/DAN anticorrelation strength and psychiatric symptoms.