scholarly journals Top-down contribution to motor network reorganization during action preparation

2021 ◽  
Author(s):  
Alberto Pisoni ◽  
Valentina Bianco ◽  
Eleonora Arrigoni ◽  
Francesco Di Russo ◽  
Leonor Josefina Romero Lauro
Keyword(s):  
Functional Connectivity ◽  
Time Course ◽  
Cortical Excitability ◽  
Stimulus Onset ◽  
Functional Networks ◽  
Beta Band ◽  
Top Down ◽  
Action Preparation ◽  
Eeg Recordings ◽  
Changes Over Time

It is unclear whether the Bereitschaftspotential (BP) recorded in humans during action preparation mirrors motor areas activation escalation, or if its early and late phases reflect the engagement of different functional networks. Here, we aimed at recording the TMS evoked-potentials (TEP) stimulating the supplementary motor area (SMA) to assess whether and how cortical excitability and functional connectivity of this region change as the BP increases. We hypothesize that, at later stages, the SMA functional network should become more connected to regions relevant for the implementation of the final motor plan. We performed TMS-EEG recordings on fourteen healthy subjects during the performance of a visuomotor Go/No-go task, eliciting and recording cortical activity and functional connectivity at -700 ms and -300 ms before the onset of visual stimuli over the SMA. When approaching stimulus onset, and thus BP peak, the SMA increased its functional connectivity with movement-related structures in the gamma and alpha bands, indicating a regional top-down preparation to implement the motor act. Beta-band connectivity, instead, was maintained constant for the whole BP time-course, being potentially related to sustained attention required by the experimental task. These findings reveal that the BP is not a mere result of increased activation of the SMA, but the functional networks in which this region is involved qualitatively changes over time, becoming more related to the execution of the motor act.

scholarly journals Infant functional networks are modulated by state of consciousness and circadian rhythm

2021 ◽  
pp. 1-36
Author(s):  
Rachel J. Smith ◽  
Ehsan Alipourjeddi ◽  
Cristal Garner ◽  
Amy L. Maser ◽  
Daniel W. Shrey ◽  
...  
Keyword(s):  
Circadian Rhythm ◽  
Functional Connectivity ◽  
Principal Component ◽  
Time Of Day ◽  
Clustering Coefficient ◽  
Functional Networks ◽  
Temporal Properties ◽  
Healthy Infants ◽  
Infant Brain ◽  
Eeg Recordings

Abstract Functional connectivity networks are valuable tools for studying development, cognition, and disease in the infant brain. In adults, such networks are modulated by the state of consciousness and the circadian rhythm; however, it is unknown if infant brain networks exhibit similar variation, given the unique temporal properties of infant sleep and circadian patterning. To address this, we analyzed functional connectivity networks calculated from long-term EEG recordings (average duration 20.8 hours) from 19 healthy infants. Networks were subjectspecific, as inter-subject correlations between weighted adjacency matrices were low. However, within individual subjects, both sleep and wake networks were stable over time, with stronger functional connectivity during sleep than wakefulness. Principal component analysis revealed the presence of two dominant networks; visual sleep scoring confirmed that these corresponded to sleep and wakefulness. Lastly, we found that network strength, degree, clustering coefficient, and path length significantly varied with time of day, when measured in either wakefulness or sleep at the group level. Together, these results suggest that modulation of healthy functional networks occurs over ~24 hours and is robust and repeatable. Accounting for such temporal periodicities may improve the physiological interpretation and use of functional connectivity analysis to investigate brain function in health and disease.

scholarly journals Age-dependent differences in functional brain networks are atypical in Tourette syndrome

2020 ◽  
Author(s):  
Ashley N. Nielsen ◽  
Caterina Gratton ◽  
Soyoung Kim ◽  
Jessica A. Church ◽  
Kevin J. Black ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Tourette Syndrome ◽  
Time Course ◽  
Neurodevelopmental Disorder ◽  
Developmental Differences ◽  
Functional Networks ◽  
Functional Neuroanatomy ◽  
Brain Structure And Function ◽  
Functional Brain Networks ◽  
And Function

AbstractTourette syndrome (TS) is a neurodevelopmental disorder characterized by motor and vocal tics. TS is complex, with symptoms that involve sensory, motor, and top-down control processes and that fluctuate over the course of development. While many have studied atypical brain structure and function associated with TS, the neural substrates supporting the complex range and time-course of symptoms is largely understudied. Here, we used functional connectivity MRI to examine functional networks across the whole-brain in children and adults with TS. To investigate the functional neuroanatomy of childhood and adulthood TS, we separately considered the sets of connections within each functional network and those between each pair of functional networks. We tested whether developmental stage (child, adult), diagnosis (TS, control), or an interaction between these factors was present among these connections. We found that developmental changes for most functional networks in TS were unaltered (i.e., developmental differences in TS were similar to those in typically developing children and adults). However, there were several within-network and cross-network connections that exhibited either “divergent” or “attenuated” development in TS. Connections involving the somatomotor, cingulo-opercular, auditory, dorsal attention, and default mode networks diverged from typical development in TS, demonstrating enhanced functional connectivity in adulthood TS. In contrast, connections involving the basal ganglia, thalamus, cerebellum, auditory, visual, reward, and ventral attention networks showed attenuated developmental differences in TS. These results suggest that adulthood TS is characterized by increased functional connectivity among functional networks that support cognitive control and attention, which may be implicated in suppressing, producing, and attending to tics. In contrast, subcortical systems that have been implicated in the initiation and production of tics may be immature in adulthood TS. Jointly, our results reveal how several cortical and subcortical functional networks interact and differ across development in TS.

Dynamic modulation of intrinsic functional connectivity by transcranial direct current stimulation

2012 ◽  
Vol 108 (12) ◽  
pp. 3253-3263 ◽  
Author(s):  
Bernhard Sehm ◽  
Alexander Schäfer ◽  
Judy Kipping ◽  
Daniel Margulies ◽  
Virginia Conde ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Healthy Subjects ◽  
Time Course ◽  
Cortical Excitability ◽  
Eigenvector Centrality ◽  
Resting State Functional Connectivity ◽  
Brain Areas ◽  
Direct Current Stimulation

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique capable of modulating cortical excitability and thereby influencing behavior and learning. Recent evidence suggests that bilateral tDCS over both primary sensorimotor cortices (SM1) yields more prominent effects on motor performance in both healthy subjects and chronic stroke patients than unilateral tDCS over SM1. To better characterize the underlying neural mechanisms of this effect, we aimed to explore changes in resting-state functional connectivity during both stimulation types. In a randomized single-blind crossover design, 12 healthy subjects underwent functional magnetic resonance imaging at rest before, during, and after 20 min of unilateral, bilateral, and sham tDCS stimulation over SM1. Eigenvector centrality mapping (ECM) was used to investigate tDCS-induced changes in functional connectivity patterns across the whole brain. Uni- and bilateral tDCS over SM1 resulted in functional connectivity changes in widespread brain areas compared with sham stimulation both during and after stimulation. Whereas bilateral tDCS predominantly modulated changes in primary and secondary motor as well as prefrontal regions, unilateral tDCS affected prefrontal, parietal, and cerebellar areas. No direct effect was seen under the stimulating electrode in the unilateral condition. The time course of changes in functional connectivity in the respective brain areas was nonlinear and temporally dispersed. These findings provide evidence toward a network-based understanding regarding the underpinnings of specific tDCS interventions.

Seeing the Same Words Differently: The Time Course of Automaticity and Top–Down Intention in Reading

2015 ◽  
Vol 27 (8) ◽  
pp. 1542-1551 ◽  
Author(s):  
Kristof Strijkers ◽  
Daisy Bertrand ◽  
Jonathan Grainger
Keyword(s):  
Language Processing ◽  
High Frequency ◽  
Time Course ◽  
Lexical Processing ◽  
Low Frequency ◽  
Stimulus Onset ◽  
Top Down ◽  
Electrophysiological Response ◽  
The Brain

We investigated how linguistic intention affects the time course of visual word recognition by comparing the brain's electrophysiological response to a word's lexical frequency, a well-established psycholinguistic marker of lexical access, when participants actively retrieve the meaning of the written input (semantic categorization) versus a situation where no language processing is necessary (ink color categorization). In the semantic task, the ERPs elicited by high-frequency words started to diverge from those elicited by low-frequency words as early as 120 msec after stimulus onset. On the other hand, when categorizing the colored font of the very same words in the color task, word frequency did not modulate ERPs until some 100 msec later (220 msec poststimulus onset) and did so for a shorter period and with a smaller scalp distribution. The results demonstrate that, although written words indeed elicit automatic recognition processes in the brain, the speed and quality of lexical processing critically depends on the top–down intention to engage in a linguistic task.

Prestimulus Oscillations in the Alpha Band of the EEG Are Modulated by the Difficulty of Feature Discrimination and Predict Activation of a Sensory Discrimination Process

2014 ◽  
Vol 26 (8) ◽  
pp. 1615-1628 ◽  
Author(s):  
Daniel M. Roberts ◽  
John R. Fedota ◽  
George A. Buzzell ◽  
Raja Parasuraman ◽  
Craig G. McDonald
Keyword(s):  
Spatial Attention ◽  
Cortical Excitability ◽  
Control Process ◽  
Discrimination Performance ◽  
Stimulus Onset ◽  
Time On Task ◽  
Alpha Power ◽  
Top Down ◽  
Alpha Oscillation ◽  
Selection Tasks

Recent work has demonstrated that the occipital–temporal N1 component of the ERP is sensitive to the difficulty of visual discrimination, in a manner that cannot be explained by simple differences in low-level visual features, arousal, or time on task. These observations provide evidence that the occipital–temporal N1 component is modulated by the application of top–down control. However, the timing of this control process remains unclear. Previous work has demonstrated proactive, top–down modulation of cortical excitability for cued spatial attention or feature selection tasks. Here, the possibility that a similar top–down process facilitates performance of a difficult stimulus discrimination task is explored. Participants performed an oddball task at two levels of discrimination difficulty, with difficulty manipulated by modulating the similarity between target and nontarget stimuli. Discrimination processes and cortical excitability were assessed via the amplitude of the occipital–temporal N1 component and prestimulus alpha oscillation of the EEG, respectively. For correct discriminations, prestimulus alpha power was reduced, and the occipital–temporal N1 was enhanced in the hard relative to the easy condition. Furthermore, within the hard condition, prestimulus alpha power was reduced, and the occipital–temporal N1 was enhanced for correct relative to incorrect discriminations. The generation of ERPs contingent on relative prestimulus alpha power additionally suggests that diminished alpha power preceding stimulus onset is related to enhancement of the occipital–temporal N1. As in spatial attention, proactive control appears to enhance cortical excitability and facilitate discrimination performance in tasks requiring nonspatial, feature-based attention, even in the absence of competing stimulus features.

scholarly journals Characterization of young and old adult brains: An EEG functional connectivity analysis

2018 ◽  
Author(s):  
Bahar Moezzi ◽  
Latha Madhuri Pratti ◽  
Brenton Hordacre ◽  
Lynton Graetz ◽  
Carolyn Berryman ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Resting State ◽  
Older Age ◽  
Support Vector ◽  
Functional Networks ◽  
Svm Classifier ◽  
Age Group ◽  
Beta Band ◽  
Machine Learning Classification ◽  
Functional Connections

Brain connectivity studies have reported that functional networks change with older age. We aim to (1) investigate whether electroencephalography (EEG) data can be used to distinguish between individual functional networks of young and old adults; and (2) identify the functional connections that contribute to this classification. Two eyes-open resting-state EEG recording sessions with 64 electrodes for each of 22 younger adults (19-37 years) and 22 older adults (63-85 years) were conducted. For each session, imaginary coherence matrices in theta, alpha, beta and gamma bands were computed. A range of machine learning classification methods were utilized to distinguish younger and older adult brains. A support vector machine (SVM) classifier was 94% accurate in classifying the brains by age group. We report decreased functional connectivity with older age in theta, alpha and gamma bands, and increased connectivity with older age in beta band. Most connections involving frontal, temporal, and parietal electrodes, and approximately two-thirds of connections involving occipital electrodes, showed decreased connectivity with older age. Just over half of the connections involving central electrodes showed increased connectivity with older age. Functional connections showing decreased strength with older age had significantly longer electrode-to-electrode distance than those that increased with older age. Most of the connections used by the classifier to distinguish participants by age group belonged to the alpha band. Findings suggest a decrease in connectivity in key networks and frequency bands associated with attention and awareness, and an increase in connectivity of the sensorimotor functional networks with ageing during a resting state.

Functional Anatomy of Intensity Aspects of Attention

2003 ◽  
Vol 14 (3) ◽  
pp. 181-190 ◽  
Author(s):  
Walter Sturm
Keyword(s):  
Right Hemisphere ◽  
Functional Anatomy ◽  
Fmri Data ◽  
Functional Networks ◽  
Top Down ◽  
Stimulus Modality ◽  
Spatial Orienting ◽  
Phasic Alertness ◽  
Co Activation ◽  
Attention System

Abstract: Behavioral and PET/fMRI-data are presented to delineate the functional networks subserving alertness, sustained attention, and vigilance as different aspects of attention intensity. The data suggest that a mostly right-hemisphere frontal, parietal, thalamic, and brainstem network plays an important role in the regulation of attention intensity, irrespective of stimulus modality. Under conditions of phasic alertness there is less right frontal activation reflecting a diminished need for top-down regulation with phasic extrinsic stimulation. Furthermore, a high overlap between the functional networks for alerting and spatial orienting of attention is demonstrated. These findings support the hypothesis of a co-activation of the posterior attention system involved in spatial orienting by the anterior alerting network. Possible implications of these findings for the therapy of neglect are proposed.

Engaging regularly with fiction influences connectivity in cortical areas for language and mentalizing

2017 ◽  
Author(s):  
Roel M. Willems ◽  
Franziska Hartung
Keyword(s):  
Functional Connectivity ◽  
Time Course ◽  
Language Skills ◽  
Brain Regions ◽  
Brain Areas ◽  
Daily Lives ◽  
Cortical Areas ◽  
Social Abilities ◽  
Behavioral Evidence ◽  
Amount Of Reading

Behavioral evidence suggests that engaging with fiction is positively correlated with social abilities. The rationale behind this link is that engaging with fictional narratives offers a ‘training modus’ for mentalizing and empathizing. We investigated the influence of the amount of reading that participants report doing in their daily lives, on connections between brain areas while they listened to literary narratives. Participants (N=57) listened to two literary narratives while brain activation was measured with fMRI. We computed time-course correlations between brain regions, and compared the correlation values from listening to narratives to listening to reversed speech. The between-region correlations were then related to the amount of fiction that participants read in their daily lives. Our results show that amount of fiction reading is related to functional connectivity in areas known to be involved in language and mentalizing. This suggests that reading fiction influences social cognition as well as language skills.

scholarly journals Synaptic Molecular and Neurophysiological Markers Are Independent Predictors of Progression in Alzheimer’s Disease

2021 ◽  
pp. 1-12
Author(s):  
Una Smailovic ◽  
Ingemar Kåreholt ◽  
Thomas Koenig ◽  
Nicholas J. Ashton ◽  
Bengt Winblad ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Global Field ◽  
Prognostic Indicators ◽  
Early Event ◽  
Functional Markers ◽  
Beta Band ◽  
Global Field Power ◽  
Synaptic Markers ◽  
Eeg Recordings

Background: Cerebrospinal fluid (CSF) neurogranin and quantitative electroencephalography (qEEG) are potential molecular and functional markers of synaptic pathology in Alzheimer’s disease (AD). Synaptic markers have emerged as candidate prognostic indicators of AD since synaptic degeneration was shown to be an early event and the best correlate of cognitive deficits in patients along the disease continuum. Objective: The present study investigated the association between CSF neurogranin and qEEG measures as well as their potential to predict clinical deterioration in mild cognitive impairment (MCI) patients. Methods: Patients diagnosed with MCI (n = 99) underwent CSF conventional AD biomarkers and neurogranin analysis and resting-state EEG recordings. The study population was further stratified into stable (n = 41) and progressive MCI (n = 31), based on the progression to AD dementia during two years follow-up. qEEG analysis included computation of global field power and global field synchronization in four conventional frequency bands. Results: CSF neurogranin levels were associated with theta power and synchronization in the progressive MCI group. CSF neurogranin and qEEG measures were significant predictors of progression to AD dementia, independent of baseline amyloid status in MCI patients. A combination of CSF neurogranin with global EEG power in theta and global EEG synchronization in beta band exhibited the highest classification accuracy as compared to either of these markers alone. Conclusion: qEEG and CSF neurogranin are independent predictors of progression to AD dementia in MCI patients. Molecular and neurophysiological synaptic markers may have additive value in a multimodal diagnostic and prognostic approach to dementia.

scholarly journals Cerebral functional networks during sleep in young and older individuals

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Véronique Daneault ◽  
Pierre Orban ◽  
Nicolas Martin ◽  
Christian Dansereau ◽  
Jonathan Godbout ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Brain Plasticity ◽  
Network Connectivity ◽  
Sleep Stages ◽  
Functional Networks ◽  
Older Individuals ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Age Related ◽  
Light Sleep

AbstractEven though sleep modification is a hallmark of the aging process, age-related changes in functional connectivity using functional Magnetic Resonance Imaging (fMRI) during sleep, remain unknown. Here, we combined electroencephalography and fMRI to examine functional connectivity differences between wakefulness and light sleep stages (N1 and N2 stages) in 16 young (23.1 ± 3.3y; 7 women), and 14 older individuals (59.6 ± 5.7y; 8 women). Results revealed extended, distributed (inter-between) and local (intra-within) decreases in network connectivity during sleep both in young and older individuals. However, compared to the young participants, older individuals showed lower decreases in connectivity or even increases in connectivity between thalamus/basal ganglia and several cerebral regions as well as between frontal regions of various networks. These findings reflect a reduced ability of the older brain to disconnect during sleep that may impede optimal disengagement for loss of responsiveness, enhanced lighter and fragmented sleep, and contribute to age effects on sleep-dependent brain plasticity.

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