Bidirectionally connected cores in a mouse connectome: Towards extracting the brain subnetworks essential for consciousness

Where in the brain consciousness resides remains unclear. It has been suggested that the subnetworks supporting consciousness should be bidirectionally (recurrently) connected because both feed-forward and feedback processing are necessary for conscious experience. Accordingly, evaluating which subnetworks are bidirectionally connected and the strength of these connections would likely aid the identification of regions essential to consciousness. Here, we propose a method for hierarchically decomposing a network into cores with different strengths of bidirectional connection, as a means of revealing the structure of the complex brain network. We applied the method to a whole-brain mouse connectome. We found that cores with strong bidirectional connections consisted of regions presumably essential to consciousness (e.g., the isocortical and thalamic regions, and claustrum) and did not include regions presumably irrelevant to consciousness (e.g., cerebellum). Contrarily, we could not find such correspondence between cores and consciousness when we applied other simple methods which ignored bidirectionality. These findings suggest that our method provides a novel insight into the relation between bidirectional brain network structures and consciousness.

Focused attention meditation changes the boundary and configuration of functional networks in the brain

Scientific Reports ◽

10.1038/s41598-020-75396-9 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Shogo Kajimura ◽

Naoki Masuda ◽

Johnny King L. Lau ◽

Kou Murayama

Keyword(s):

Network Architecture ◽

Single Case ◽

Brain Networks ◽

Brain Network ◽

Focused Attention ◽

Community Size ◽

Whole Brain ◽

Motor Network ◽

Functional Brain Networks ◽

Abstract Research has shown that focused attention meditation not only improves our cognitive and motivational functioning (e.g., attention, mental health), it influences the way our brain networks [e.g., default mode network (DMN), fronto-parietal network (FPN), and sensory-motor network (SMN)] function and operate. However, surprisingly little attention has been paid to the possibility that meditation alters the architecture (composition) of these functional brain networks. Here, using a single-case experimental design with intensive longitudinal data, we examined the effect of mediation practice on intra-individual changes in the composition of whole-brain networks. The results showed that meditation (1) changed the community size (with a number of regions in the FPN being merged into the DMN after meditation) and (2) led to instability in the community allegiance of the regions in the FPN. These results suggest that, in addition to altering specific functional connectivity, meditation leads to reconfiguration of whole-brain network architecture. The reconfiguration of community architecture in the brain provides fruitful information about the neural mechanisms of meditation.

Spatial constancy mechanisms in motor control

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2010.0089 ◽

2011 ◽

Vol 366 (1564) ◽

pp. 476-491 ◽

Cited By ~ 44

Author(s):

W. Pieter Medendorp

Keyword(s):

Motor Control ◽

Eye Movements ◽

Three Dimensional ◽

Spatial Updating ◽

Feedback Processing ◽

Feed Forward ◽

Motor Information ◽

Induced Motion ◽

Forward Process ◽

The success of the human species in interacting with the environment depends on the ability to maintain spatial stability despite the continuous changes in sensory and motor inputs owing to movements of eyes, head and body. In this paper, I will review recent advances in the understanding of how the brain deals with the dynamic flow of sensory and motor information in order to maintain spatial constancy of movement goals. The first part summarizes studies in the saccadic system, showing that spatial constancy is governed by a dynamic feed-forward process, by gaze-centred remapping of target representations in anticipation of and across eye movements. The subsequent sections relate to other oculomotor behaviour, such as eye–head gaze shifts, smooth pursuit and vergence eye movements, and their implications for feed-forward mechanisms for spatial constancy. Work that studied the geometric complexities in spatial constancy and saccadic guidance across head and body movements, distinguishing between self-generated and passively induced motion, indicates that both feed-forward and sensory feedback processing play a role in spatial updating of movement goals. The paper ends with a discussion of the behavioural mechanisms of spatial constancy for arm motor control and their physiological implications for the brain. Taken together, the emerging picture is that the brain computes an evolving representation of three-dimensional action space, whose internal metric is updated in a nonlinear way, by optimally integrating noisy and ambiguous afferent and efferent signals.

Functional Connectivity within and beyond the Face Network Is Related to Reduced Discrimination of Degraded Faces in Young and Older Adults

Cerebral Cortex ◽

10.1093/cercor/bhaa179 ◽

2020 ◽

Vol 30 (12) ◽

pp. 6206-6223

Author(s):

Cheryl L Grady ◽

Jenny R Rieck ◽

Daniel Nichol ◽

Douglas D Garrett

Keyword(s):

Older Adults ◽

Functional Connectivity ◽

Brain Networks ◽

Brain Network ◽

Whole Brain ◽

The Face ◽

Brain Correlates ◽

Brain And Behavior ◽

Face Stimuli ◽

Abstract Degrading face stimuli reduces face discrimination in both young and older adults, but the brain correlates of this decline in performance are not fully understood. We used functional magnetic resonance imaging to examine the effects of degraded face stimuli on face and nonface brain networks and tested whether these changes would predict the linear declines seen in performance. We found decreased activity in the face network (FN) and a decrease in the similarity of functional connectivity (FC) in the FN across conditions as degradation increased but no effect of age. FC in whole-brain networks also changed with increasing degradation, including increasing FC between the visual network and cognitive control networks. Older adults showed reduced modulation of this whole-brain FC pattern. The strongest predictors of within-participant decline in accuracy were changes in whole-brain network FC and FC similarity of the FN. There was no influence of age on these brain-behavior relations. These results suggest that a systems-level approach beyond the FN is required to understand the brain correlates of performance decline when faces are obscured with noise. In addition, the association between brain and behavior changes was maintained into older age, despite the dampened FC response to face degradation seen in older adults.

Focused attention meditation changes the boundary and configuration of functional networks in the brain

10.1101/664573 ◽

2019 ◽

Author(s):

Shogo Kajimura ◽

Naoki Masuda ◽

Johnny King Lau ◽

Kou Murayama

Keyword(s):

Single Case ◽

Brain Networks ◽

Brain Regions ◽

Brain Network ◽

Health It ◽

Community Size ◽

Whole Brain ◽

Motor Network ◽

Functional Brain Networks ◽

AbstractResearch has shown that meditation not only improves our cognitive and motivational functioning (e.g., attention, mental health), it influences the way how our brain networks [e.g., default mode network (DMN), fronto-parietal network (FPN), and sensory-motor network (SMN)] function and operate. However, surprisingly little attention has been paid to the possibility that meditation alters the structure (composition) of these functional brain networks. Here, using a single-case experimental design with longitudinal intensive data, we examined the effect of mediation practice on intra-individual changes in the composition of whole-brain networks. The results showed that meditation (1) changed the community size (with a number of regions in the FPN being merged into the DMN after meditation), (2) changed the brain regions composing the SMN community without changing its size, and (3) led to instability in the community allegiance of the regions in the FPN. These results suggest that, in addition to altering specific functional connectivity, meditation leads to reconfiguration of whole-brain network structure. The reconfiguration of community structure in the brain provides fruitful information about the neural mechanisms of meditation.

Psilocybin-induced changes in brain network integrity and segregation correlate with plasma psilocin level and psychedelic experience

10.1101/2021.02.03.429325 ◽

2021 ◽

Author(s):

Martin K. Madsen ◽

Dea S. Stenbæk ◽

Albin Arvidsson ◽

Sophia Armand ◽

Maja R. Marstrand-Joergensen ◽

...

Keyword(s):

Time Course ◽

Subjective Experience ◽

Brain Network ◽

Executive Control Network ◽

Neural Processes ◽

Dorsal Attention Network ◽

Induced Changes ◽

Serotonin 2A ◽

The Brain ◽

AbstractThe emerging novel therapeutic psilocybin produces psychedelic effects via engagement of cerebral serotonergic targets by psilocin (active metabolite). The serotonin 2A receptor critically mediates these effects by altering distributed neural processes that manifest as increased entropy, reduced functional connectivity (FC) within discrete brain networks (i.e., reduced integrity) and increased FC between networks (i.e., reduced segregation). Reduced integrity of the default mode network (DMN) is proposed to play a particularly prominent role in psychedelic phenomenology, including perceived ego-dissolution. Here, we investigate the effects of a psychoactive oral dose of psilocybin (0.2-0.3 mg/kg) on plasma psilocin level (PPL), subjective drug intensity (SDI) and their association in fifteen healthy individuals. We further evaluate associations between these measures and resting-state FC, measured with functional magnetic resonance imaging, acquired over the course of five hours after psilocybin administration. We show that PPL and SDI correlate negatively with measures of network integrity (including DMN) and segregation, both spatially constrained and unconstrained. We also find that the executive control network and dorsal attention network desegregate, increasing connectivity with other networks and throughout the brain as a function of PPL and SDI. These findings provide direct evidence that psilocin critically shapes the time course and magnitude of changes in the cerebral functional architecture and subjective experience following psilocybin administration. Our findings provide novel insight into the neurobiological mechanisms underlying profound perceptual experiences evoked by this emerging transnosological therapeutic and implicate the expression of network integrity and segregation in the psychedelic experience and consciousness.

COMP-03. TUMOR CONNECTOME: INSIGHT INTO THE IMPACT OF CNS NEOPLASIA AND THERAPY ON THE BRAIN NETWORK

Neuro-Oncology ◽

10.1093/neuonc/noy148.258 ◽

2018 ◽

Vol 20 (suppl_6) ◽

pp. vi64-vi64

Author(s):

Drew Parker ◽

Jacob Alappatt ◽

Mark Elliott ◽

Steven Brem ◽

Ragini Verma

Keyword(s):

Brain Network ◽

The Impact ◽

The Brain ◽

Causal evidence of network communication in whole-brain dynamics through a multiplexed neural code

10.1101/2020.06.09.142695 ◽

2020 ◽

Author(s):

Piergiorgio Salvan ◽

Alberto Lazari ◽

Diego Vidaurre ◽

Francesca Mandino ◽

Heidi Johansen-Berg ◽

...

Keyword(s):

Brain Network ◽

Network Communication ◽

Markov Modeling ◽

Whole Brain ◽

Hidden Markov Modeling ◽

Route Information ◽

Information Streams ◽

Brain Fmri ◽

The Brain ◽

Selective Information

AbstractAn important question in neuroscience is how local activity can be flexibly and selectively routed across the brain network. A proposed mechanism to flexibly route information is frequency division multiplexing: selective readout can be achieved by segregating the signal into non-overlapping frequency bands. Here, in wild-type mice and in a transgenic model (3xTgAD) of Alzheimer’s Disease (AD), we use optogenetic activation of the entorhinal cortex, concurrent whole-brain fMRI, and hidden Markov modeling. We demonstrate how inducing neuronal spiking with different theta frequencies causes spatially distinct states of brain network dynamics to emerge and to preferentially respond to one frequency, showing how selective information streams can arise from a single neuronal source of activity. This theta modulation mechanism, however, is impaired in the AD model. This work demonstrates that neuronal multiplexing is a sufficient mechanism to enable flexible brain network communication, and provides insight into the aberrant mechanisms underlying cognitive decline.

Individualized event structure drives individual differences in whole-brain functional connectivity

10.1101/2021.03.12.435168 ◽

2021 ◽

Author(s):

Richard F. Betzel ◽

Sarah A. Cutts ◽

Sarah Greenwell ◽

Olaf Sporns

Keyword(s):

Functional Connectivity ◽

Developmental State ◽

High Amplitude ◽

Brain Network ◽

Resting State Functional Connectivity ◽

Whole Brain ◽

Brain Functional Connectivity ◽

Dense Sampling ◽

Resting-state functional connectivity is typically modeled as the correlation structure of whole-brain regional activity. It is studied widely, both to gain insight into the brain’s intrinsic organization but also to develop markers sensitive to changes in an individual’s cognitive, clinical, and developmental state. Despite this, the origins and drivers of functional connectivity, especially at the level of densely sampled individuals, remain elusive. Here, we leverage novel methodology to decompose functional connectivity into its precise framewise contributions. Using two dense sampling datasets, we investigate the origins of individualized functional connectivity, focusing specifically on the role of brain network “events” – short-lived and peaked patterns of high-amplitude cofluctuations. Here, we develop a statistical test to identify events in empirical recordings. We show that the patterns of cofluctuation expressed during events are repeated across multiple scans of the same individual and represent idiosyncratic variants of template patterns that are expressed at the group level. Lastly, we propose a simple model of functional connectivity based on event cofluctuations, demonstrating that group-averaged cofluctuations are suboptimal for explaining participant-specific connectivity. Our work complements recent studies implicating brief instants of high-amplitude cofluctuations as the primary drivers of static, whole-brain functional connectivity. Our work also extends those studies, demonstrating that cofluctuations during events are individualized, positing a dynamic basis for functional connectivity.