Abstract
Brain Connectivity has expanded its remit to provide comprehensive coverage of articles in clinical neurology, neuroscience, and neuroimaging. While neuroimaging plays an important role in the diagnosis and management of different neurological disorders, by integrating neuroimaging with articles focusing on clinical neurology and neuroscience gives an opportunity for the journal audience to have a comprehensive knowledge of topics covered in Brain Connectivity. Involvement of the brain in different neurological diseases is accompanied by different molecular changes and neuropathological processes. Pathological substrates such as amyloid deposition, tau deposition, microglial activation, synuclein pathology, astrocyte activation, mitochondrial function, and other changes in structural and functional connectivity are closely inter-related. By expanding the remit of Brain Connectivity, we hope to provide comprehensive cover of individual pathological process in different neurological disorders.
The multiorgan involvement in COVID-19 causes significant involvement of the brain. The damage caused by the virus directly or indirectly can lead to disruption of the integrity of structural and functional connectivity by different mechanisms. The impact of COVID-19 on the nervous system needs further evaluation. At Brain Connectivity, being one of the leading journals in the field of neuroscience, we are now inviting articles addressing central nervous system involvement in COVID-19.
After the expansion of the remit of Brain Connectivity, we are now inviting articles of a translational nature in the field of clinical neurology, neuroscience, and neuroimaging by focusing on four special issues on
Neurological complications of COVID-19
Alzheimer's disease
Stroke
Parkinson's disease and other movement disorders.
We invite you to submit articles focusing on the aforementioned theme. Any of the following themes will be of huge interest: Clinical and translational research and review articles Novel positron emission tomography (PET) and magnetic resonance imaging (MRI) biomarkers in neurodegenerative diseases and stroke Influence of genetic and epigenetic factors on structural and functional connectivity in brain disorders Multimodal imaging in brain disorders in both human subjects and animal models Experimental techniques combining MRI (connectivity), electroencephalography, magnetoencephalography, PET, single photon emission computed tomography, and other new and evolving methods.
For more information about the journal, including scope and instructions for authors, please visit our website
In this issue, you will find several high-quality articles by experts in their fields.
Altered Metabolic Interrelationships in the Cortico-Limbic Circuitry in Military Service Members with Persistent Post-Traumatic Stress Disorder Symptoms Following Mild Traumatic Brain Injury (https://doi.org/10.1089/brain.2021.0036 )
The aim of this study is to investigate brain metabolic inter-relationships in service members with and without persistent Post-Traumatic Stress Disorder (PTSD) symptoms after mild traumatic brain injury (mTBI) using 18F-fluorodeoxyglucose PET. In this study, Chihwa Song and Grant H. Bonavia along with their colleagues studied large number of service members diagnosed with mTBI. Participants were divided into two groups based on DSM-IV-TR criteria for PTSD, and structural equation modeling was performed to test a priori hypotheses on metabolic inter-relationships among the brain regions in the cortico-limbic circuitry responsible for top-down control and bottom-up emotional processing.
FDG (F-fluorodeoxyglucose) uptake in the temporo-limbic system was positively correlated with postconcussive and hyperarousal symptoms. For the bottom-up emotional processing, the insula and amygdala-hippocampal complex in PTSD-present group had stronger metabolic inter-relationships with the bilateral rostral anterior cingulate, left lingual, right lateral occipital, and left superior temporal cortices, but a weaker relationship with the right precuneus cortex, compared with PTSD-absent group. For the top-down control, PTSD-present group had decreased metabolic engagements of the dorsolateral prefrontal cortex (DLPFC) on the amygdala.
The authors conclude that altered metabolic inter-relationships in the cortico-limbic circuitry in mTBI subjects with persistent PTSD symptoms may underlie the pathophysiological mechanism in these patients.
Multimodel Order Independent Component Analysis: A Data-Driven Method for Evaluating Brain Functional Network Connectivity Within and Between Multiple Spatial Scales (https://doi.org/10.1089/brain.2021.0079 )
Functional connectivity is widely studied; however, there has been little work studying functional connectivity at different spatial scales. In this study, Xing Meng, Vince D. Calhoun along with their colleagues proposed an independent component analysis (ICA)-based approach to capture information at multiple model orders (component numbers) and to evaluate functional network connectivity (FNC) both within and between model orders. They studied group differences in the context of a study of resting functional MRI (rsfMRI) data collected from schizophrenia (SZ) individuals and healthy controls (HC). The predictive ability of FNC at multiple spatial scales was assessed using support vector machine-based classification.
They observed that the FNC between model order 25 and 50 maintained the highest predictive information between HC and SZ. In addition to consistent predictive patterns at both multiple-model orders and single-model orders, unique predictive information was seen at multiple-model orders and in the interaction between model orders. Results highlighted the predictive ability of the somatomotor and visual domains both within and between model orders compared with other functional domains. They conclude that multimodel order ICA provides a more comprehensive way to study FNC, produces meaningful results that are applicable to future studies.
Stress-Induced Changes in Effective Connectivity During Regulation of the Emotional Response to Threat (https://doi.org/10.1089/brain.2021.0062 )
Stress-related disruption of emotion regulation appears to involve the PFC and amygdala. However, the interactions between brain regions that mediate stress-induced changes in emotion regulation remain unclear. Adam M. Goodman and David C. knight along with their colleagues investigated the effective connectivity between brain regions. In this study, participants completed the Montreal Imaging Stress Task followed by a Pavlovian fear conditioning procedure during fMRI. Stress ratings and psychophysiological responses were used to assess stress reactivity. Effective connectivity during fear conditioning was identified using multivariate autoregressive modeling.
The authors have demonstrated that a neural hub within the dorsomedial PFC (dmPFC) showed greater effective connectivity to other PFC regions, inferior parietal lobule, insula, and amygdala during predictable than unpredictable threat. The dmPFC also showed greater connectivity to different DLPFC and amygdala regions during unpredictable than predictable threat. Stress ratings varied with connectivity differences from the dmPFC to the amygdala. They conclude that acute stress disrupts connectivity underlying top-down emotion regulation of the threat response. Furthermore, increased connectivity between the dmPFC and amygdala may play a critical role in stress-induced changes in the emotional response to threat.
Functional Interactions Between Neural Substrates of Socio-cognitive Mechanisms Involved in Simple Deception and Manipulative Truth (https://doi.org/10.1089/brain.2021.0063 )
The organization of functional interactions underlying simple deception and manipulative truth remains unclear. In this study, Maya Zheltyakova and Maxim Kireev along with their colleagues performed psychophysiological interaction analysis for a key node in the theory of mind (TOM) system, the right temporoparietal junction (rTPJ), using fMRI data obtained from volunteers during the sender–receiver game. During the game, participants send true, simple deceptive, or manipulative truthful messages to another player according to their own choice. A Bayesian approach to statistics was employed to perform statistical inference.
They observed increased functional interactions between nodes of the TOM system (bilateral TPJ, left precuneus, left dmPFC, and right superior temporal sulcus) characterizing both forms of deception. They identified an increment in functional interactions of the rTPJ with the left TPJ (lTPJ) and right precuneus associated with manipulative truth. They demonstrated that a higher rate of manipulative truthful actions was associated with weaker functional interactions between the rTPJ and lTPJ, left precuneus, and left dmPFC.
They conclude that compared with simple deception, manipulative truth is associated with a higher demand for socio-cognitive processes, which contributes to the cognitive load of this form of deception.
Thalamo-Cortical and Thalamo-Thalamic Coupling During Sleep and Wakefulness in Rats (https://doi.org/10.1089/brain.2021.0052 )
The thalamus is involved in the generation of sleep-related thalamo-cortical oscillations. Higher-order nuclei might possess a distinct function compared with first-order nuclei in brain communication. Ilya V. Sysoev and Annika Lüttjohann and their colleagues investigated whether this distinction can also be found during the process of falling asleep and deepening of slow-wave sleep.
A nonlinear version of Granger causality was used to describe changes in directed network activity between somatosensory-cortex and rostral reticular-thalamic-nucleus (rRTN) and caudal reticular-thalamic-nucleus (cRTN), the higher-order posterior- and anterior-thalamic nuclei and the first-order ventral-postero-medial thalamic nucleus as assessed in local-field-potentials recordings acquired during passive-wakefulness (PW), light and deep slow-wave sleep (LSWS, DSWS) in freely behaving rats. Surrogate statistics were used to assess significance.
The authors found decreases in cortico-thalamo-cortical couplings. In contrast, multiple increases in intrathalamic couplings were also observed. In particular, the rRTN increased its inhibition on the anterior (ATN) from PW to LSWS, and this was further strengthened from LSWS to DSWS. The cRTN increased its coupling to ventro-postero-medial thalamic nucleus (VPM) and posterior thalamic nucleus (PO) from PW to LSWS, but the coupling from cRTN to VPM weakened at the transition from LSWS to DSWS, whereas its coupling to PO strengthened. The authors conclude that higher-order (ATN and PO) and first-order nuclei (VPM) are differentially inhibited during DSWS, which might be relevant for a proper functioning of sleep-related processes.
Abnormal Brain Activation During Verbal Memory Encoding in Postacute Anti-N-Methyl-d -Aspartate Receptor Encephalitis (https://doi.org/10.1089/brain.2021.0046 )
Patients with postacute anti-N-methyl-
They recruited patients with anti-NMDA receptor encephalitis past the acute stage and HCs. fMRI data were collected when they completed an episodic memory task. Patients showed higher brain activation than the HCs in the bilateral hippocampus/parahippocampus (HG/PHG), right superior temporal gyrus, and right thalamus during memory encoding. The patients also showed worse memory retrieval performance than the HCs. Importantly, greater brain activation in the left HG/PHG during memory encoding was significantly associated with worse memory retrieval performance among the patients.
Their findings indicate that postacute anti-NMDA receptor encephalitis is likely related to altered brain activation during memory encoding. Particularly, less memory retrieval performance often observed in patients with postacute anti-NMDA receptor encephalitis may result from abnormal activation in hippocampus during encoding.
Dynamic Causal Modeling of the Prefrontal/Amygdala Network During Processing of Emotional Faces (https://doi.org/10.1089/brain.2021.0073 )
The importance of the amygdala—medial orbitofrontal cortex (OFC) network during processing of emotional stimuli, emotional faces in particular, is well established. However, there is missing evidence from human brain connectivity studies that the OFC and no other prefrontal brain areas such as the DLPFC or ventrolateral PFC (VLPFC) are responsible for amygdala regulation in the functional context of emotional face stimuli.
In this study, Ronald Sladky and Christian Windischberger along with their colleagues performed dynamic causal modeling of ultrahigh field functional MRI data acquired at 7 Tesla in healthy subjects and a well-established paradigm for emotional face processing was used to assess the central role of the OFC to provide empirical validation for the assumed network architecture.
Using Bayesian model selection, they demonstrated that indeed the OFC, and not the VLPFC and the DLPFC, downregulates amygdala activation during the emotion discrimination task. In addition, Bayesian model averaging group results were rigorously tested using bootstrapping, further corroborating these findings and providing an estimator for robustness and optimal sample sizes. They conclude that VLPFC and DLPFC are relevant for the processing of emotional faces and are connected to the OFC; the OFC appears to be a central hub for prefrontal–amygdala interaction.
Finally, I would like to thank all the researchers and all the staff at Mary Ann Liebert, Inc., publishers, editors, and reviewers of Brain Connectivity who are dedicated to advance research and improve our lives in every corner of the world.