arXiv subjects

Eduardo C. Padovani

Publications and source records attributed to Eduardo C. Padovani.

4 recordsLinked to original sources

arXiv2023

Structure and Dynamics of Brain Lobe's Functional Networks at the Onset of Anesthesia-Induced Loss of Consciousness

Anesthetic agents are neurotropic drugs capable of inducing significant alterations in the thalamocortical system, promoting a profound decrease in awareness and level of consciousness. There is experimental evidence that general anesthesia affects large-scale functional networks, leading to alterations in the brain's state. However, the specific impact on the network structure assumed by functional connectivity locally in different cortical regions has not yet been reported. Within this context, the present study has sought to characterize the functional brain networks relative to the frontal, parietal, temporal, and occipital lobes. In this study, electrophysiological neural activity was recorded using a dense ECoG-electrode array placed directly on the cortical surface of an old-world monkey of the species Macaca fuscata. Networks were estimated serially over time every five seconds, while the animal model was under controlled experimental conditions of a Ketamine-Medetomidine anesthetic induction. In each of the four cortical brain lobes, noticeable alterations in distinct properties of the networks evidenced a transition in the network's architecture, which occurred within approximately one and a half minutes after administering the anesthetics. The characterization of functional brain networks performed in this study provides relevant experimental evidence that expands our understanding of the neural correlates of consciousness in terms of the structure and properties of the functional brain networks.

q-bio.NC↗

arXiv2023

Macaque's Cortical Functional Connectivity Dynamics at the Onset of Propofol-Induced Anesthesia

Propofol, when administered for general anesthesia, induces oscillatory dynamic brain states that are thought to underlie the drug's pharmacological effects. Despite the elucidation of propofol's mechanisms of action at the molecular level, its effects on neural circuits and overall cortical functioning, which eventually lead to unconsciousness, are still unclear. To identify possible mechanisms, the spatial-temporal patterns of functional connectivity established among specialized cortical areas in anesthetized subjects need to be described. Within this context, the present research involved the analysis of dense sub-dural ECoG electrode array recordings from macaques under propofol anesthetic induction. Granger causality methodology was used to infer functional connectivity interactions in five physiological frequency bands serially over time, every five seconds throughout the experiment. The time-resolved networks obtained permitted us to observe the unfolding of the anesthetic induction and compare the networks obtained under different experimental conditions. About one minute after administering propofol, functional connectivity started to increase for 4-5 minutes, then decreased until the LOC was achieved. A predominant Granger causality flow from the occipital and temporal areas towards the frontal and parietal regions was also evidenced during the transition. During general anesthesia, the local connectivity of the occipital lobe increased, as did the interactions between the occipital and temporal lobes. Conversely, the functional connectivity from the frontal and parietal lobes toward the temporal and occipital regions was mainly impaired. The research is one of the first studies to describe the dynamics of the functional connectivity during the transitional state that precedes the LOC.

q-bio.NC↗

arXiv2023

Characterization of Large-Scale Functional Brain Networks During Ketamine-Medetomidine Anesthetic Induction

Several experiments provide evidence that specialized brain regions functionally interact and reveal that the brain processes and integrates information in a specific and structured manner. Networks can be applied to model brain functional activities, providing means to characterize and quantify this structured form of organization. Reports substantiate that different physiological states or diseases that affect the central nervous system may be associated with alterations in these networks, which might be reflected in graphs of different architectures. However, the relationship between their structure and the organism's distinct physiological conditions is poorly comprehended. Therefore, experiments that estimate the functional neural networks of subjects exposed to different controlled conditions are highly relevant. Within this context, this research has sought to model large-scale functional brain networks during an anesthetic induction process. The experiment was based on intra-cranial recordings of the neural activities of an old-world macaque of the species Macaca fuscata. Neural activity was recorded during a Ketamine-Medetomidine anesthetic induction process, and networks were estimated sequentially in five-second intervals. One and a half minutes after administering the anesthetics, changes occurred in various network properties, revealing a transition in the network architecture. During general anesthesia, functional connectivity and network integration capabilities were reduced at both local and global levels. Additionally, it has been verified that the brain shifted to a highly specific and dynamic state. The results provide empirical evidence and report the relationship between the induced state of anesthesia and functional network properties, contributing to the elucidation of novel aspects of the neural correlates of consciousness.

q-bio.NC↗

arXiv2023

Characterization of the Community Structure of Large-Scale Functional Brain Networks During Ketamine-Medetomidine Anesthetic Induction

One of the main goals of neuroscience is to understand how an organism's cognitive capacities or physiological states are potentially related to brain activities that involve the interaction of multiple brain structures and cortical areas. A key feature of functional brain networks is that they are modularly structured, and this modular architecture is regarded as accounting for a range of properties and functional dynamics. In the neurobiological context, communities may indicate brain regions involved in the same activity, representing neural-segregated processes. Several studies have demonstrated the modular character of the organization of brain activities. However, empirical evidence regarding its dynamics and relation to different levels of consciousness has not yet been reported. In this context, this research sought to characterize the community structure of functional brain networks during an anesthetic induction process. The experiment was based on intracranial recordings of the neural activities of an old-world macaque of the species Macaca fuscata during a Ketamine-Medetomidine anesthetic induction process. Changes were observed within approximately one and a half minutes after administering the anesthetics, revealing a transition in the community structure. The awake state was characterized by large clusters involving the frontal and parietal regions. In contrast, the anesthetized state was marked by the presence of communities in the primary visual and motor cortices, while the areas of the secondary associative cortex were the most affected. The results report the influence of general anesthesia on the structure of functional clusters, contributing to understanding some novel aspects of the neural correlates of consciousness.

q-bio.NC↗