scholarly journals Depth of sedation with dexmedetomidine modulates cortical excitability non-linearly

2021 ◽  
Author(s):  
Paolo Cardone ◽  
Olivier Bodart ◽  
Murielle Kirsch ◽  
Julien Sanfilippo ◽  
Alessandra Virgilitto ◽  
...  
Keyword(s):  
Brain Region ◽  
Cortical Excitability ◽  
Future Research ◽  
Negative Peak ◽  
Anaesthetic Agents ◽  
Neuronavigation System ◽  
Light Sedation ◽  
Conscious Processes ◽  
Parietal Cortices ◽  
Dose Dependent Increase

Background: Cortical excitability changes across conscious states, being higher in unconsciousness compared to normal wakefulness. Anaesthesia offers controlled manipulation to investigate conscious processes and underlying brain dynamics. Among commonly used anaesthetic agents, dexmedetomidine (DEX) effects are not completely known. In this study, we investigated cortical excitability as a function of DEX sedation depth. Methods: Transcranial magnetic stimulation coupled with electroencephalography was recorded in 20 healthy subjects undergoing DEX sedation in four conditions (baseline, light sedation, deep sedation, recovery). Frontal and parietal cortices were stimulated using a neuronavigation system. Cortical excitability was inferred by slope, amplitude, positive and negative peak latencies of the first component (0-30 ms) of the TMS-evoked potential. Four Generalized Linear Mixed Models (GLMM) were used to test the effect of condition and brain region over cortical excitability. Results: Dexmedetomidine modulated amplitude (P<0.001), slope (P=0.0001) and positive peak (P=0.042), while the targeted brain region affected amplitude (P<0.001), slope (P<0.001), and negative peak (P=0.001). The interaction between dexmedetomidine and region had an effect over amplitude (P=0.004), and slope (P=0.009) such that cortical excitability was higher during all conditions where DEX was present as compared to the baseline. Conclusions: Cortical excitability changes non-linearly as a function of the depth of DEX sedation, with a paradoxical non dose-dependent increase. The effect is region-specific, being present in the frontal but not in the parietal region. Future research should extend the current results with other anaesthetics to better understand the link between cortical excitability and depth of sedation.

scholarly journals A review of literature on substance abuse among anaesthesia providers

2019 ◽  
Vol 24 (8) ◽  
pp. 587-600
Author(s):  
Stephanie DeFord ◽  
Julie Bonom ◽  
Terri Durbin
Keyword(s):  
Substance Abuse ◽  
Literature Review ◽  
Registered Nurse ◽  
High Stress ◽  
Future Research ◽  
Educational Setting ◽  
Preventive Strategies ◽  
Nurse Anaesthetist ◽  
Anaesthetic Agents ◽  
American Society

Background Research has demonstrated that anaesthesia providers are susceptible to substance abuse. Several preventive measures are being implemented in certified registered nurse anaesthetist programmes to educate future providers about substance abuse. Given the continued prevalence and impact of the problem, more research is needed about the prevalence of substance abuse among student registered nurse anaesthetists and the implementation of preventive strategies in the educational setting. Aims The purpose of this narrative literature review was to examine the state of the science related to substance abuse among US certified anaesthesia providers. This literature review covered abuse of alcohol, tobacco, recreational drugs, opioids and anaesthetic agents. Methods This narrative review was conducted using the following search terms: anaesthesia, student, wellness, stress, substance abuse, satisfaction, personality, depression, nurse, nurse anaesthetist, propofol, isoflurane and fentanyl. References were identified using PubMed, CINAHL, Google Scholar, and the American Society of Anesthesiologists and American Association of Nurse Anesthetists websites. A total of 36 articles were identified as relevant to this literature review based on content and country of publication. This literature review was limited to articles published in the past 15 years. With one exception, our search was limited to manuscripts from the US. Results The literature underscored that various risk factors contribute to substance abuse. Board-certified anaesthesia providers fall prey to substance abuse due to ease of access, the high stress associated with administering anaesthesia, and the propensity to become addicted to opioids and other anaesthetics. A gap in the science exists about the prevalence of substance abuse among student registered nurse anaesthetists and the effectiveness of preventive strategies in the educational setting. Conclusions Anaesthesia providers are at high risk of abusing substances. To create a safer environment, future research should explore the prevalence of substance abuse among student registered nurse anaesthetists and emphasise the integration of effective preventive strategies in the educational setting.

scholarly journals Evaluation and Treatment of Vascular Cognitive Impairment by Transcranial Magnetic Stimulation

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Mariagiovanna Cantone ◽  
Giuseppe Lanza ◽  
Francesco Fisicaro ◽  
Manuela Pennisi ◽  
Rita Bella ◽  
...  
Keyword(s):  
Cognitive Impairment ◽  
Synaptic Plasticity ◽  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Cortical Excitability ◽  
Disease Process ◽  
Vascular Cognitive Impairment ◽  
Future Research ◽  
Disease Modifying Drugs

The exact relationship between cognitive functioning, cortical excitability, and synaptic plasticity in dementia is not completely understood. Vascular cognitive impairment (VCI) is deemed to be the most common cognitive disorder in the elderly since it encompasses any degree of vascular-based cognitive decline. In different cognitive disorders, including VCI, transcranial magnetic stimulation (TMS) can be exploited as a noninvasive tool able to evaluate in vivo the cortical excitability, the propension to undergo neural plastic phenomena, and the underlying transmission pathways. Overall, TMS in VCI revealed enhanced cortical excitability and synaptic plasticity that seem to correlate with the disease process and progression. In some patients, such plasticity may be considered as an adaptive response to disease progression, thus allowing the preservation of motor programming and execution. Recent findings also point out the possibility to employ TMS to predict cognitive deterioration in the so-called “brains at risk” for dementia, which may be those patients who benefit more of disease-modifying drugs and rehabilitative or neuromodulatory approaches, such as those based on repetitive TMS (rTMS). Finally, TMS can be exploited to select the responders to specific drugs in the attempt to maximize the response and to restore maladaptive plasticity. While no single TMS index owns enough specificity, a panel of TMS-derived measures can support VCI diagnosis and identify early markers of progression into dementia. This work reviews all TMS and rTMS studies on VCI. The aim is to evaluate how cortical excitability, plasticity, and connectivity interact in the pathophysiology of the impairment and to provide a translational perspective towards novel treatments of these patients. Current pitfalls and limitations of both studies and techniques are also discussed, together with possible solutions and future research agenda.

scholarly journals Cerebral perturbations during exercise in hypoxia

2012 ◽  
Vol 302 (8) ◽  
pp. R903-R916 ◽  
Author(s):  
Samuel Verges ◽  
Thomas Rupp ◽  
Marc Jubeau ◽  
Bernard Wuyam ◽  
François Esteve ◽  
...  
Keyword(s):  
Exercise Performance ◽  
Cerebral Oxygenation ◽  
Cortical Excitability ◽  
Muscle Metabolism ◽  
Voluntary Activation ◽  
Whole Body ◽  
Future Research ◽  
Motor Drive ◽  
Impaired Performance ◽  
Central Drive

Reduction of aerobic exercise performance observed under hypoxic conditions is mainly attributed to altered muscle metabolism due to impaired O2 delivery. It has been recently proposed that hypoxia-induced cerebral perturbations may also contribute to exercise performance limitation. A significant reduction in cerebral oxygenation during whole body exercise has been reported in hypoxia compared with normoxia, while changes in cerebral perfusion may depend on the brain region, the level of arterial oxygenation and hyperventilation induced alterations in arterial CO2. With the use of transcranial magnetic stimulation, inconsistent changes in cortical excitability have been reported in hypoxia, whereas a greater impairment in maximal voluntary activation following a fatiguing exercise has been suggested when arterial O2 content is reduced. Electromyographic recordings during exercise showed an accelerated rise in central motor drive in hypoxia, probably to compensate for greater muscle contractile fatigue. This accelerated development of muscle fatigue in moderate hypoxia may be responsible for increased inhibitory afferent signals to the central nervous system leading to impaired central drive. In severe hypoxia (arterial O2 saturation <70–75%), cerebral hypoxia per se may become an important contributor to impaired performance and reduced motor drive during prolonged exercise. This review examines the effects of acute and chronic reduction in arterial O2 (and CO2) on cerebral blood flow and cerebral oxygenation, neuronal function, and central drive to the muscles. Direct and indirect influences of arterial deoxygenation on central command are separated. Methodological concerns as well as future research avenues are also considered.

scholarly journals The claustrum: Considerations regarding its anatomy, functions and a programme for research

2017 ◽  
Vol 1 ◽  
pp. 239821281771896 ◽  
Author(s):  
Christopher M. Dillingham ◽  
Maciej M. Jankowski ◽  
Ruchi Chandra ◽  
Bethany E. Frost ◽  
Shane M. O’Mara
Keyword(s):  
Decision Making ◽  
Information Processing ◽  
Brain Region ◽  
Spatial Information ◽  
Mammalian Brain ◽  
Future Research ◽  
Subcortical Structures ◽  
Present Evidence ◽  
Open Questions ◽  
Extensive Range

The claustrum is a highly conserved but enigmatic structure, with connections to the entire cortical mantle, as well as to an extended and extensive range of heterogeneous subcortical structures. Indeed, the human claustrum is thought to have the highest number of connections per millimetre cubed of any other brain region. While there have been relatively few functional investigations of the claustrum, many theoretical suggestions have been put forward, including speculation that it plays a key role in the generation of consciousness in the mammalian brain. Other claims have been more circumspect, suggesting that the claustrum has a particular role in, for example, orchestrating cortical activity, spatial information processing or decision making. Here, we selectively review certain key recent anatomical, electrophysiological and behavioural experimental advances in claustral research and present evidence that calls for a reassessment of its anatomical boundaries in the rodent. We conclude with some open questions for future research.

scholarly journals Investigating Parietal and Premotor Influence on Motor Cortical Excitability Associated with Visuomotor Associative Plasticity

2021 ◽  
Vol 11 (4) ◽  
pp. 452
Author(s):  
Paul J. Wolfe ◽  
Lynea B. Kaethler ◽  
W. Richard Staines
Keyword(s):  
Repeated Measures ◽  
Cortical Excitability ◽  
Occipital Cortex ◽  
Long Term Potentiation ◽  
Future Research ◽  
Reaching Movement ◽  
Repeated Measures Design ◽  
Term Potentiation ◽  
Motor Cortex Excitability

The brain changes in response to sensory signals it is exposed to. It has been shown that long term potentiation-like neuroplasticity can be experimentally induced via visual paired-associative stimulation (V-PAS). V-PAS combines afferent visual stimuli with a transcranial magnetic stimulation pulse to induce plasticity. Preparation of a reaching movement to generate activity in superior parietal occipital cortex (SPOC) was used in this study as an additional afferent contributor to modulate the resultant plasticity. We hypothesized that V-PAS with a reaching movement would induce greater cortical excitability than V-PAS alone and would exhibit facilitated SPOC to M1 projections. All four experiments enrolled groups of 10 participants to complete variations of V-PAS in a repeated measures design. SPOC to M1 projections facilitated motor cortex excitability following V-PAS regardless of intervention received. We did not observe evidence indicating extra afferent information provided an additive effect to participants. Investigation of PMd to M1 projections confirmed disinhibition and suggested interneuronal populations within M1 may be mechanistically involved. Future research should look to rule out the existence of an upper limit for effective afference during V-PAS and investigate the average influence of V-PAS on cortical excitability in the larger population.

Is The Cerebral Cortex Hyperexcitable or Hyperresponsive in Migraine?

Cephalalgia ◽  
2007 ◽  
Vol 27 (12) ◽  
pp. 1427-1439 ◽  
Author(s):  
G Coppola ◽  
F Pierelli ◽  
J Schoenen
Keyword(s):  
Cerebral Cortex ◽  
Magnetic Stimulation ◽  
Cortical Excitability ◽  
Future Research ◽  
Evoked Responses ◽  
Cortical Hyperexcitability ◽  
Sensory Modalities ◽  
Sensory Cortices ◽  
Methodological Approaches ◽  
External Stimuli

Although migraineurs appear in general to be hypersensitive to external stimuli, they maybe also have increased daytime sleepiness and complain of fatigue. Neurophisiological studies between attacks have shown that for a number of different sensory modalities the migrainous brain is characterised by a lack of habituation of evoked responses. Whether this is due to increased cortical hyperexcitability, possibly due to decreased inhibition, or to an abnormal responsivity of the cortex due a decreased preactivation level remains disputed. Studies using transcranial magnetic stimulation in particular have yielded contradictory results. We will review here the available data on cortical excitability obtained with different methodological approaches in patients over the migraine cycle. We will show that these data congruently indicate that the sensory cortices of migraineurs react excessively to repetitive, but not to single, stimuli and that the controversy above hyper- versus hypo-excitability is merely a semantic misunderstanding. Describing the migrainous brain as ‘hyperresponsive’ would fit most of the available data. Deciphering the precise cellular and molecular underpinnings of this hyperresponsivity remains a challenge for future research. We propose, as a working hypothesis, that a thalamo-cortical dysrhythmia might be the culprit.

scholarly journals Default mode network activity in bipolar disorder

2020 ◽  
Vol 29 ◽  
Author(s):  
Niccolò Zovetti ◽  
Maria Gloria Rossetti ◽  
Cinzia Perlini ◽  
Eleonora Maggioni ◽  
Pietro Bontempi ◽  
...  
Keyword(s):  
Bipolar Disorder ◽  
Default Mode Network ◽  
Psychiatric Patients ◽  
Network Activity ◽  
Current Evidence ◽  
Future Research ◽  
Research Directions ◽  
Default Mode ◽  
Future Research Directions ◽  
Parietal Cortices

Abstract Since its discovery in 1997, the default mode network (DMN) and its components have been extensively studied in both healthy individuals and psychiatric patients. Several studies have investigated possible DMN alterations in specific mental conditions such as bipolar disorder (BD). In this review, we describe current evidence from resting-state functional magnetic resonance imaging studies with the aim to understand possible changes in the functioning of the DMN in BD. Overall, several types of analyses including seed-based and independent component have been conducted on heterogeneous groups of patients highlighting different results. Despite the differences, findings seem to indicate that BD is associated with alterations in both frontal and posterior DMN structures, mainly in the prefrontal, posterior cingulate and inferior parietal cortices. We conclude this review by suggesting possible future research directions.

scholarly journals Brain structural connectivity predicts brain functional complexity: DTI derived centrality accounts for variance in fractal properties of fMRI signal

2019 ◽  
Author(s):  
Josh Neudorf ◽  
Chelsea Ekstrand ◽  
Shaylyn Kress ◽  
Ron Borowsky
Keyword(s):  
Brain Region ◽  
Current Flow ◽  
Diffusion Tensor ◽  
Brain Activity ◽  
Structural Connectivity ◽  
Brain Network ◽  
Centrality Measures ◽  
Future Research ◽  
Sources Of Information ◽  
Complex Activity

AbstractThe complexity of brain activity has recently been investigated using the Hurst (H) exponent, which describes the extent to which functional magnetic resonance imaging (fMRI) blood oxygen-level dependent (BOLD) activity is self-similar vs. complex. For example, research has demonstrated that fMRI activity is more complex before than after consumption of alcohol and during task than resting state. The measurement of H in fMRI is a novel method that requires the investigation of additional factors contributing to complexity. Graph theory metrics of centrality can assess how centrally important to the brain network each region is, based on diffusion tensor imaging (DTI) counts of probabilistic white matter (WM) tracts. DTI derived centrality was hypothesized to account for the complexity of functional activity, based on the supposition that more sources of information to integrate should result in more complex activity. FMRI BOLD complexity as measured by H was associated with five brain region centrality measures: degree, eigenvector, PageRank, current flow betweenness, and current flow closeness centrality. Multiple regression analyses demonstrated that degree centrality was the most robust predictor of complexity, whereby greater centrality was associated with increased complexity (lower H). Regions known to be highly connected, including the thalamus and hippocampus, notably were among the highest in centrality and complexity. This research has led to a greater understanding of how brain region characteristics such as DTI centrality relate to the novel Hurst exponent approach for assessing brain activity complexity, and implications for future research that employ these measures are discussed.

scholarly journals Intrinsic connectivity reveals functionally distinct cortico-hippocampal networks in the human brain

PLoS Biology ◽  
2021 ◽  
Vol 19 (6) ◽  
pp. e3001275
Author(s):  
Alexander J. Barnett ◽  
Walter Reilly ◽  
Halle R. Dimsdale-Zucker ◽  
Eda Mizrak ◽  
Zachariah Reagh ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Episodic Memory ◽  
Medial Temporal Lobe ◽  
Meta Analysis ◽  
Critical Role ◽  
Future Research ◽  
Intrinsic Connectivity ◽  
Using Data ◽  
Hippocampal Networks ◽  
Parietal Cortices

Episodic memory depends on interactions between the hippocampus and interconnected neocortical regions. Here, using data-driven analyses of resting-state functional magnetic resonance imaging (fMRI) data, we identified the networks that interact with the hippocampus—the default mode network (DMN) and a “medial temporal network” (MTN) that included regions in the medial temporal lobe (MTL) and precuneus. We observed that the MTN plays a critical role in connecting the visual network to the DMN and hippocampus. The DMN could be further divided into 3 subnetworks: a “posterior medial” (PM) subnetwork comprised of posterior cingulate and lateral parietal cortices; an “anterior temporal” (AT) subnetwork comprised of regions in the temporopolar and dorsomedial prefrontal cortex; and a “medial prefrontal” (MP) subnetwork comprised of regions primarily in the medial prefrontal cortex (mPFC). These networks vary in their functional connectivity (FC) along the hippocampal long axis and represent different kinds of information during memory-guided decision-making. Finally, a Neurosynth meta-analysis of fMRI studies suggests new hypotheses regarding the functions of the MTN and DMN subnetworks, providing a framework to guide future research on the neural architecture of episodic memory.

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