scholarly journals The Role of Dendritic Signaling in the Anesthetic Suppression of Consciousness

2015 ◽  
Vol 122 (6) ◽  
pp. 1415-1431 ◽  
Author(s):  
Kaspar Meyer
Keyword(s):  
Pyramidal Neurons ◽  
Physiological Mechanism ◽  
Anatomical Site ◽  
General Anesthetics ◽  
Top Down ◽  
Theoretical Frameworks ◽  
Cortical Pyramidal Neurons ◽  
Sensory Cortices ◽  
The Brain

Abstract Despite considerable progress in the identification of the molecular targets of general anesthetics, it remains unclear how these drugs affect the brain at the systems level to suppress consciousness. According to recent proposals, anesthetics may achieve this feat by interfering with corticocortical top–down processes, that is, by interrupting information flow from association to early sensory cortices. Such a view entails two immediate questions. First, at which anatomical site, and by virtue of which physiological mechanism, do anesthetics interfere with top–down signals? Second, why does a breakdown of top–down signaling cause unconsciousness? While an answer to the first question can be gleaned from emerging neurophysiological evidence on dendritic signaling in cortical pyramidal neurons, a response to the second is offered by increasingly popular theoretical frameworks that place the element of prediction at the heart of conscious perception.

scholarly journals The use of viral gene transfer in studies of brainstem noradrenergic and serotonergic neurons

2009 ◽  
Vol 364 (1529) ◽  
pp. 2565-2576 ◽  
Author(s):  
S. Kasparov ◽  
A. G. Teschemacher
Keyword(s):  
Viral Vectors ◽  
Pyramidal Neurons ◽  
Viral Gene ◽  
Volume Transmission ◽  
Neuronal Populations ◽  
Central Neurons ◽  
Wide Range ◽  
Cortical Pyramidal Neurons ◽  
The Brain

In contrast to some other neuronal populations, for example hippocampal or cortical pyramidal neurons, mechanisms of synaptic integration and transmitter release in central neurons that contain noradrenaline (NA) and serotonin (5HT) are not well understood. These cells, crucial for a wide range of autonomic and behavioural processes, have long un-myelinated axons with hundreds of varicosities where transmitters are synthesized and released. Both seem to signal mostly in ‘volume transmission’ mode. Very little is known about the rules that apply to this type of transmission in the brain and the factors that regulate the release of NA and 5HT. We discuss some of our published studies and more recent experiments in which viral vectors were used to investigate the physiology of these neuronal populations. We also focus on currently unresolved issues concerning the mechanism of volume transmission by NA and 5HT in the brain. We suggest that clarifying the role of astroglia in this process could be essential for our understanding of central noradrenergic and 5HT signalling.

scholarly journals The cutaneous borders of interoception: Active and social inference of pain and pleasure on the skin

2018 ◽  
Author(s):  
Mariana von Mohr ◽  
Aikaterini Fotopoulou
Keyword(s):  
Social Factors ◽  
Predictive Coding ◽  
Active Inference ◽  
Top Down ◽  
Bottom Up ◽  
Social Inference ◽  
Brain Levels ◽  
The Brain

Pain and pleasant touch have been recently classified as interoceptive modalities. This reclassification lies at the heart of long-standing debates questioning whether these modalities should be defined as sensations on their basis of neurophysiological specificity at the periphery or as homeostatic emotions on the basis of top-down convergence and modulation at the spinal and brain levels. Here, we outline the literature on the peripheral and central neurophysiology of pain and pleasant touch. We next recast this literature within a recent Bayesian predictive coding framework, namely active inference. This recasting puts forward a unifying model of bottom-up and top-down determinants of pain and pleasant touch and the role of social factors in modulating the salience of peripheral signals reaching the brain.

Dendritic integration theory: A thalamo-cortical theory of state and content of consciousness

2020 ◽  
Vol 1 (II) ◽  
Author(s):  
Talis Bachmann ◽  
Mototaka Suzuki ◽  
Jaan Aru
Keyword(s):  
Pyramidal Neurons ◽  
Conscious Experience ◽  
Pyramidal Cells ◽  
Neural Mechanisms ◽  
Integration Theory ◽  
Thalamic Nuclei ◽  
Cortical Pyramidal Neurons ◽  
Cortical System ◽  
Work Done

The idea that the thalamo-cortical system is the crucial constituent of the neurobiological mechanisms of consciousness has a long history. For the last few decades, however, consciousness research has to a large extent overlooked the interplay between the cortex and thalamus. Here we revive an integrated view of the neurobiology of consciousness by presenting and discussing several recent major findings about the role of the thalamocortical interactions in consciousness. Based on these findings we propose a specific cellular mechanism how thalamic nuclei modulate the integration of different processing streams within single cortical pyramidal neurons. This theory is inspired by recent work done in rodents, but it integrates decades of work conducted on various species. We illustrate how this new view readily explains various properties and experimental phenomena associated with conscious experience. We discuss the implications of this idea and some of the experiments that need to be done in order to test it. Our view bridges two long-standing perspectives on the neural mechanisms of consciousness and proposes that cortical and thalamo-cortical processing interact at the level of single pyramidal cells.

scholarly journals Active Forgetting: Adaptation of Memory by Prefrontal Control

2021 ◽  
Vol 72 (1) ◽  
pp. 1-36 ◽  
Author(s):  
Michael C. Anderson ◽  
Justin C. Hulbert
Keyword(s):  
Emotional State ◽  
Memory Loss ◽  
Brain Structures ◽  
Past Century ◽  
Top Down ◽  
The Past ◽  
New Findings ◽  
Nonhuman Animals ◽  
The Brain

Over the past century, psychologists have discussed whether forgetting might arise from active mechanisms that promote memory loss to achieve various functions, such as minimizing errors, facilitating learning, or regulating one's emotional state. The past decade has witnessed a great expansion in knowledge about the brain mechanisms underlying active forgetting in its varying forms. A core discovery concerns the role of the prefrontal cortex in exerting top-down control over mnemonic activity in the hippocampus and other brain structures, often via inhibitory control. New findings reveal that such processes not only induce forgetting of specific memories but also can suppress the operation of mnemonic processes more broadly, triggering windows of anterograde and retrograde amnesia in healthy people. Recent work extends active forgetting to nonhuman animals, presaging the development of a multilevel mechanistic account that spans the cognitive, systems, network, and even cellular levels. This work reveals how organisms adapt their memories to their cognitive and emotional goals and has implications for understanding vulnerability to psychiatric disorders.

scholarly journals The Role of the Primary Sensory Cortices in Early Language Processing

2017 ◽  
Vol 29 (10) ◽  
pp. 1755-1765 ◽  
Author(s):  
Andrew C. Papanicolaou ◽  
Marina Kilintari ◽  
Roozbeh Rezaie ◽  
Shalini Narayana ◽  
Abbas Babajani-Feremi
Keyword(s):  
Left Hemisphere ◽  
Language Processing ◽  
Stimulus Onset ◽  
Linguistic Processing ◽  
Feature Processing ◽  
Sensory Cortices ◽  
Linguistic Analyses ◽  
The Brain ◽  
Language Network

The results of this magnetoencephalography study challenge two long-standing assumptions regarding the brain mechanisms of language processing: First, that linguistic processing proper follows sensory feature processing effected by bilateral activation of the primary sensory cortices that lasts about 100 msec from stimulus onset. Second, that subsequent linguistic processing is effected by left hemisphere networks outside the primary sensory areas, including Broca's and Wernicke's association cortices. Here we present evidence that linguistic analysis begins almost synchronously with sensory, prelinguistic verbal input analysis and that the primary cortices are also engaged in these linguistic analyses and become, consequently, part of the left hemisphere language network during language tasks. These findings call for extensive revision of our conception of linguistic processing in the brain.

scholarly journals Towards better hypothesis tests in oxytocin research: Evaluating the validity of auxiliary assumptions

2021 ◽  
Author(s):  
Daniel S Quintana
Keyword(s):  
Experimental Design ◽  
Hypothesis Testing ◽  
Small Sample ◽  
Social Cues ◽  
The Body ◽  
Theoretical Frameworks ◽  
Small Sample Sizes ◽  
The Brain ◽  
Behavior And Cognition

Various factors have been attributed to the inconsistent reproducibility of human oxytocin research in the cognitive and behavioral sciences. These factors include small sample sizes, a lack of pre-registered studies, and the absence of overarching theoretical frameworks that can account for oxytocin’s effects over a broad range of contexts. While there have been efforts to remedy these issues, there has been very little systematic scrutiny of the role of auxiliary assumptions, which are claims that are not central for testing a hypothesis but nonetheless critical for testing theories. For instance, the hypothesis that oxytocin increases the salience of social cues is predicated on the assumption that intranasally administered oxytocin increases oxytocin levels in the brain. Without robust auxiliary assumptions, it is unclear whether a hypothesis testing failure is due to an incorrect hypothesis or weak auxiliary assumptions. Consequently, weak auxiliary assumptions can be blamed for hypothesis failure, thereby safeguarding theories from falsification. In this article, I will evaluate the body of evidence for key auxiliary assumptions in human behavioral oxytocin research in terms of theory, experimental design, and statistical inference, and highlight assumptions that require stronger evidence. Strong auxiliary assumptions will leave hypotheses vulnerable for falsification, which will improve hypothesis testing and consequently advance our understanding of oxytocin’s role in behavior and cognition.

scholarly journals Pain and Attention

2018 ◽  
Author(s):  
Dimiti van Ryckeghem ◽  
Geert Crombez
Keyword(s):  
Contextual Factors ◽  
Critical Role ◽  
Daily Activities ◽  
Pivotal Role ◽  
Future Research ◽  
Clinical Implications ◽  
Top Down ◽  
Theoretical Frameworks ◽  
The Relationship

Attention plays a pivotal role in the experience of pain and its impact upon daily activities. Accordingly, research on the interplay between attention and pain has a long scientific history. This chapter discusses the theoretical frameworks that aim to explain the relationship between attention and pain. It argues for a motivational perspective on pain that highlights the critical role of cognitive, affective, and contextual factors in explaining the interplay between attention and pain. To substantiate this argument, the chapter provides an overview of available research addressing the bottom-up capture of attention by pain and the top-down modulation (both inhibition and facilitation) of attention for pain. It concludes with guidelines and suggestions for future research and discusses clinical implications of adopting a motivational perspective on pain.

scholarly journals Assessing interactions in the brain with exact low-resolution electromagnetic tomography

2011 ◽  
Vol 369 (1952) ◽  
pp. 3768-3784 ◽  
Author(s):  
Roberto D. Pascual-Marqui ◽  
Dietrich Lehmann ◽  
Martha Koukkou ◽  
Kieko Kochi ◽  
Peter Anderer ◽  
...  
Keyword(s):  
Current Density ◽  
Pyramidal Neurons ◽  
Phase Synchronization ◽  
High Time Resolution ◽  
Low Resolution ◽  
Electromagnetic Tomography ◽  
Cortical Pyramidal Neurons ◽  
Invasive Method ◽  
Electric Potentials ◽  
The Brain

Scalp electric potentials (electroencephalogram; EEG) are contingent to the impressed current density unleashed by cortical pyramidal neurons undergoing post-synaptic processes. EEG neuroimaging consists of estimating the cortical current density from scalp recordings. We report a solution to this inverse problem that attains exact localization: exact low-resolution brain electromagnetic tomography (eLORETA). This non-invasive method yields high time-resolution intracranial signals that can be used for assessing functional dynamic connectivity in the brain, quantified by coherence and phase synchronization. However, these measures are non-physiologically high because of volume conduction and low spatial resolution. We present a new method to solve this problem by decomposing them into instantaneous and lagged components, with the lagged part having almost pure physiological origin.

scholarly journals Dynamic interactions between top-down expectations and conscious awareness

2017 ◽  
Author(s):  
Erik L. Meijs ◽  
Heleen A. Slagter ◽  
Floris P. de Lange ◽  
Simon van Gaal
Keyword(s):  
Attentional Blink ◽  
Conscious Awareness ◽  
Prediction Errors ◽  
Top Down ◽  
Dynamic Interactions ◽  
Electrophysiological Recordings ◽  
Stimulus Perception ◽  
The Relationship ◽  
The Brain

AbstractIt is well known that top-down expectations affect perceptual processes. Yet, remarkably little is known about the relationship between expectations and conscious awareness We address three crucial questions that are outstanding: 1) How do predictions affect the likelihood of conscious stimulus perception?; 2) Does the brain register violations of predictions nonconsciously?; and 3) Do predictions need to be conscious to influence perceptual decisions? We performed three experiments in which we manipulated stimulus predictability within the attentional blink paradigm, while combining visual psychophysics with electrophysiological recordings. We found that valid stimulus expectations increase the likelihood of conscious access of stimuli. Furthermore, our findings suggest a clear dissociation in the interaction between expectations and consciousness: conscious awareness seems crucial for the implementation of top-down predictions, but not for the bottom-up generation of stimulus-evoked prediction errors. These results constrain and update influential theories about the role of consciousness in the predictive brain.

The Synergy Between Neuroscience and Control Theory: The Nervous System as Inspiration for Hard Control Challenges

2020 ◽  
Vol 3 (1) ◽  
pp. 243-267 ◽  
Author(s):  
Manu S. Madhav ◽  
Noah J. Cowan
Keyword(s):  
Nervous System ◽  
Control Theory ◽  
Control Systems ◽  
Neural Control ◽  
Theoretic Model ◽  
Top Down ◽  
Engineering Control ◽  
And Control ◽  
The Brain

Here, we review the role of control theory in modeling neural control systems through a top-down analysis approach. Specifically, we examine the role of the brain and central nervous system as the controller in the organism, connected to but isolated from the rest of the animal through insulated interfaces. Though biological and engineering control systems operate on similar principles, they differ in several critical features, which makes drawing inspiration from biology for engineering controllers challenging but worthwhile. We also outline a procedure that the control theorist can use to draw inspiration from the biological controller: starting from the intact, behaving animal; designing experiments to deconstruct and model hierarchies of feedback; modifying feedback topologies; perturbing inputs and plant dynamics; using the resultant outputs to perform system identification; and tuning and validating the resultant control-theoretic model using specially engineered robophysical models.

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