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Neural correlates of consciousness

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https://www.readbyqxmd.com/read/29234817/neural-plasticity-and-its-initiating-conditions-in-tinnitus
#1
REVIEW
L E Roberts
BACKGROUND AND OBJECTIVE: Deafferentation caused by cochlear pathology (which can be hidden from the audiogram) activates forms of neural plasticity in auditory pathways, generating tinnitus and its associated conditions including hyperacusis. This article discusses tinnitus mechanisms and suggests how these mechanisms may relate to those involved in normal auditory information processing. MATERIALS AND METHODS: Research findings from animal models of tinnitus and from electromagnetic imaging of tinnitus patients are reviewed which pertain to the role of deafferentation and neural plasticity in tinnitus and hyperacusis...
December 12, 2017: HNO
https://www.readbyqxmd.com/read/29232704/do-early-neural-correlates-of-visual-consciousness-show-the-oblique-effect-a-binocular-rivalry-and-event-related-potential-study
#2
Bradley N Jack, Urte Roeber, Robert P O'Shea
When dissimilar images are presented one to each eye, we do not see both images; rather, we see one at a time, alternating unpredictably. This is called binocular rivalry, and it has recently been used to study brain processes that correlate with visual consciousness, because perception changes without any change in the sensory input. Such studies have used various types of images, but the most popular have been gratings: sets of bright and dark lines of orthogonal orientations presented one to each eye. We studied whether using cardinal rival gratings (vertical, 0°, and horizontal, 90°) versus oblique rival gratings (left-oblique, -45°, and right-oblique, 45°) influences early neural correlates of visual consciousness, because of the oblique effect: the tendency for visual performance to be greater for cardinal gratings than for oblique gratings...
2017: PloS One
https://www.readbyqxmd.com/read/29225064/intracranial-high-%C3%AE-connectivity-distinguishes-wakefulness-from-sleep
#3
Ezequiel Mikulan, Eugenia Hesse, Lucas Sedeño, Tristán Bekinschtein, Mariano Sigman, María Del Carmen García, Walter Silva, Carlos Ciraolo, Adolfo M García, Agustín Ibáñez
Neural synchrony in the γ-band is considered a fundamental process in cortical computation and communication and it has also been proposed as a crucial correlate of consciousness. However, the latter claim remains inconclusive, mainly due to methodological limitations, such as the spectral constraints of scalp-level electroencephalographic recordings or volume-conduction confounds. Here, we circumvented these caveats by comparing γ-band connectivity between two global states of consciousness via intracranial electroencephalography (iEEG), which provides the most reliable measurements of high-frequency activity in the human brain...
December 7, 2017: NeuroImage
https://www.readbyqxmd.com/read/29196672/network-properties-in-transitions-of-consciousness-during-propofol-induced-sedation
#4
Minji Lee, Robert D Sanders, Seul-Ki Yeom, Dong-Ok Won, Kwang-Suk Seo, Hyun Jeong Kim, Giulio Tononi, Seong-Whan Lee
Reliable electroencephalography (EEG) signatures of transitions between consciousness and unconsciousness under anaesthesia have not yet been identified. Herein we examined network changes using graph theoretical analysis of high-density EEG during patient-titrated propofol-induced sedation. Responsiveness was used as a surrogate for consciousness. We divided the data into five states: baseline, transition into unresponsiveness, unresponsiveness, transition into responsiveness, and recovery. Power spectral analysis showed that delta power increased from responsiveness to unresponsiveness...
December 1, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29180950/dissociable-electroencephalograph-correlates-of-visual-awareness-and-feature-based-attention
#5
Yifan Chen, Xiaochun Wang, Yanglan Yu, Ying Liu
Background: The relationship between awareness and attention is complex and controversial. A growing body of literature has shown that the neural bases of consciousness and endogenous attention (voluntary attention) are independent. The important role of exogenous attention (reflexive attention) on conscious experience has been noted in several studies. However, exogenous attention can also modulate subliminal processing, suggesting independence between the two processes. The question of whether visual awareness and exogenous attention rely on independent mechanisms under certain circumstances remains unanswered...
2017: Frontiers in Neuroscience
https://www.readbyqxmd.com/read/29176808/initial-state-dependent-robust-transient-neural-dynamics-encode-conscious-visual-perception
#6
Alexis T Baria, Brian Maniscalco, Biyu J He
Recent research has identified late-latency, long-lasting neural activity as a robust correlate of conscious perception. Yet, the dynamical nature of this activity is poorly understood, and the mechanisms governing its presence or absence and the associated conscious perception remain elusive. We applied dynamic-pattern analysis to whole-brain slow (< 5 Hz) cortical dynamics recorded by magnetoencephalography (MEG) in human subjects performing a threshold-level visual perception task. Up to 1 second before stimulus onset, brain activity pattern across widespread cortices significantly predicted whether a threshold-level visual stimulus was later consciously perceived...
November 27, 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/29170071/cortical-networks-for-auditory-detection-with-and-without-informational-masking-task-effects-and-implications-for-conscious-perception
#7
Katrin Wiegand, Sabine Heiland, Christian H Uhlig, Andrew R Dykstra, Alexander Gutschalk
Ambiguous and masked stimuli have been used to study conscious perception by comparing neural activity during different percepts of identical physical stimuli. One limitation of this approach is that it typically requires a reporting task that may engage neural processes beyond those required for conscious perception. Here, we explored potential fMRI correlates of auditory conscious perception with and without overt report. In experiment 1, regular tone patterns were presented as targets under informational masking, and participants reported their percepts on each trial...
November 21, 2017: NeuroImage
https://www.readbyqxmd.com/read/29160232/direct-electrical-stimulation-of-human-cortex-evokes-high-gamma-activity-that-predicts-conscious-somatosensory-perception
#8
Leah Muller, John D Rolston, Neal P Fox, Robert Knowlton, Vikram Rao, Edward F Chang
OBJECTIVE: Direct electrical stimulation (DES) is a clinical gold standard for human brain mapping and readily evokes conscious percepts, yet the neurophysiological changes underlying these percepts are not well understood. APPROACH: To determine the neural correlates of DES, we stimulated the somatosensory cortex of ten human participants at frequency-amplitude combinations that both elicited and failed to elicit conscious percepts, meanwhile recording neural activity directly surrounding the stimulation site...
November 21, 2017: Journal of Neural Engineering
https://www.readbyqxmd.com/read/29159190/divergent-neural-responses-to-narrative-speech-in-disorders-of-consciousness
#9
Ivan Iotzov, Brian C Fidali, Agustin Petroni, Mary M Conte, Nicholas D Schiff, Lucas C Parra
Objective: Clinical assessment of auditory attention in patients with disorders of consciousness is often limited by motor impairment. Here, we employ intersubject correlations among electroencephalography responses to naturalistic speech in order to assay auditory attention among patients and healthy controls. Methods: Electroencephalographic data were recorded from 20 subjects with disorders of consciousness and 14 healthy controls during of two narrative audio stimuli, presented both forwards and time-reversed...
November 2017: Annals of Clinical and Translational Neurology
https://www.readbyqxmd.com/read/29158992/hrv-derived-data-similarity-and-distribution-index-based-on-ensemble-neural-network-for-measuring-depth-of-anaesthesia
#10
Quan Liu, Li Ma, Ren-Chun Chiu, Shou-Zen Fan, Maysam F Abbod, Jiann-Shing Shieh
Evaluation of depth of anaesthesia (DoA) is critical in clinical surgery. Indices derived from electroencephalogram (EEG) are currently widely used to quantify DoA. However, there are known to be inaccurate under certain conditions; therefore, experienced anaesthesiologists rely on the monitoring of vital signs such as body temperature, pulse rate, respiration rate, and blood pressure to control the procedure. Because of the lack of an ideal approach for quantifying level of consciousness, studies have been conducted to develop improved methods of measuring DoA...
2017: PeerJ
https://www.readbyqxmd.com/read/29122959/prefrontal-oxygenation-correlates-to-the-responses-in-facial-skin-blood-flows-during-exposure-to-pleasantly-charged-movie
#11
Kanji Matsukawa, Kana Endo, Ryota Asahara, Miho Yoshikawa, Shinya Kusunoki, Tomoko Ishida
Our laboratory reported that facial skin blood flow may serve as a sensitive tool to assess an emotional status. Cerebral neural correlates during emotional interventions should be sought in relation to the changes in facial skin blood flow. To test the hypothesis that prefrontal activity has positive relation to the changes in facial skin blood flow during emotionally charged stimulation, we examined the dynamic changes in prefrontal oxygenation (with near-infrared spectroscopy) and facial skin blood flows (with two-dimensional laser speckle and Doppler flowmetry) during emotionally charged audiovisual challenges for 2 min (by viewing comedy, landscape, and horror movie) in 14 subjects...
November 2017: Physiological Reports
https://www.readbyqxmd.com/read/29121298/human-neural-correlates-of-sevoflurane-induced-unconsciousness
#12
B J A Palanca, M S Avidan, G A Mashour
Sevoflurane, a volatile anaesthetic agent well-tolerated for inhalation induction, provides a useful opportunity to elucidate the processes whereby halogenated ethers disrupt consciousness and cognition. Multiple molecular targets of sevoflurane have been identified, complementing imaging and electrophysiologic markers for the mechanistically obscure progression from wakefulness to unconsciousness. Recent investigations have more precisely detailed scalp EEG activity during this transition, with practical clinical implications...
October 1, 2017: British Journal of Anaesthesia
https://www.readbyqxmd.com/read/29121293/brain-functional-connectivity-differentiates-dexmedetomidine-from-propofol-and-natural-sleep
#13
P Guldenmund, A Vanhaudenhuyse, R D Sanders, J Sleigh, M A Bruno, A Demertzi, M A Bahri, O Jaquet, J Sanfilippo, K Baquero, M Boly, J F Brichant, S Laureys, V Bonhomme
Background: We used functional connectivity measures from brain resting state functional magnetic resonance imaging to identify human neural correlates of sedation with dexmedetomidine or propofol and their similarities with natural sleep. Methods: Connectivity within the resting state networks that are proposed to sustain consciousness generation was compared between deep non-rapid-eye-movement (N3) sleep, dexmedetomidine sedation, and propofol sedation in volunteers who became unresponsive to verbal command...
October 1, 2017: British Journal of Anaesthesia
https://www.readbyqxmd.com/read/29118218/consciousness-regained-disentangling-mechanisms-brain-systems-and-behavioral-responses
#14
Johan F Storm, Mélanie Boly, Adenauer G Casali, Marcello Massimini, Umberto Olcese, Cyriel M A Pennartz, Melanie Wilke
How consciousness (experience) arises from and relates to material brain processes (the "mind-body problem") has been pondered by thinkers for centuries, and is regarded as among the deepest unsolved problems in science, with wide-ranging theoretical, clinical, and ethical implications. Until the last few decades, this was largely seen as a philosophical topic, but not widely accepted in mainstream neuroscience. Since the 1980s, however, novel methods and theoretical advances have yielded remarkable results, opening up the field for scientific and clinical progress...
November 8, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/29111359/role-of-spontaneous-brain-activity-in-explicit-and-implicit-aspects-of-cognitive-flexibility-under-socially-conflicting-situations-a-resting-state-fmri-study-using-fractional-amplitude-of-low-frequency-fluctuations
#15
Junya Fujino, Shisei Tei, Kathryn F Jankowski, Ryosaku Kawada, Toshiya Murai, Hidehiko Takahashi
We are constantly exposed to socially conflicting situations in everyday life, and cognitive flexibility is essential for adaptively coping with such difficulties. Flexible goal choice and pursuit are not exclusively conscious, and therefore cognitive flexibility involves both explicit and implicit forms of processing. However, it is unclear how individual differences in explicit and implicit aspects of flexibility are associated with neural activity in a resting state. Here, we measured intrinsic fractional amplitude of low-frequency fluctuations (fALFF) by resting-state functional magnetic resonance imaging (RS-fMRI) as an indicator of regional brain spontaneous activity, together with explicit and implicit aspects of cognitive flexibility using the Cognitive Flexibility Scale (CFS) and Implicit Association Test (IAT)...
October 27, 2017: Neuroscience
https://www.readbyqxmd.com/read/29105672/-sinus-bradycardia-and-syncope-what-pathophysiological-mechanism-and-what-management-of-the-patient
#16
Paolo Alboni, Nicola Stucci, Claudia Parisi
Sick sinus syndrome (SSS) can be diagnosed only when there is a clear correlation between symptoms and sinus node dysfunction. In the absence of such correlation, the mechanism of undocumented intermittent symptoms such as syncopal spells in patients with permanent mild sinus bradycardia remains uncertain. Some clinical data suggest that a reflex mechanism is likely to be involved in many patients with syncope and sinus bradycardia: the course of syncopal recurrences is very variable from patient to patient and transient loss of consciousness does not recur in more than half of unpaced patients during an observation period of several years...
November 2017: Giornale Italiano di Cardiologia
https://www.readbyqxmd.com/read/29100736/single-neuron-correlates-of-awareness-during-attentional-blinks
#17
Zhongzheng Fu, Ueli Rutishauser
A recent single-neuron study revealed an anatomical anterior-to-posterior gradient of awareness-related responses by 'concept neurons' in the human medial temporal lobe (MTL). Delayed and weaker responses were indicative of the failure of a stimulus to reach awareness, suggesting that reliable fast responses are a critical aspect of the neural mechanisms of consciousness.
October 31, 2017: Trends in Cognitive Sciences
https://www.readbyqxmd.com/read/29075226/why-and-how-the-future-of-the-central-questions-of-consciousness
#18
REVIEW
Marek Havlík, Eva Kozáková, Jiří Horáček
In this review, we deal with two central questions of consciousness how and why, and we outline their possible future development. The question how refers to the empirical endeavor to reveal the neural correlates and mechanisms that form consciousness. On the other hand, the question why generally refers to the "hard problem" of consciousness, which claims that empirical science will always fail to provide a satisfactory answer to the question why is there conscious experience at all. Unfortunately, the hard problem of consciousness will probably never completely disappear because it will always have its most committed supporters...
2017: Frontiers in Psychology
https://www.readbyqxmd.com/read/28986208/dynamic-functional-connectivity-and-brain-metastability-during-altered-states-of-consciousness
#19
REVIEW
Federico Cavanna, Martina G Vilas, Matías Palmucci, Enzo Tagliazucchi
The scientific study of human consciousness has greatly benefited from the development of non-invasive brain imaging methods. The quest to identify the neural correlates of consciousness combined psychophysical experimentation with neuroimaging tools such as functional magnetic resonance imaging (fMRI) to map the changes in neural activity associated with conscious vs. unconscious percepts. Different neuroimaging methods have also been applied to characterize spontaneous brain activity fluctuations during altered states of consciousness, and to develop quantitative metrics for the level of consciousness...
October 3, 2017: NeuroImage
https://www.readbyqxmd.com/read/28981609/neural-evidence-for-non-conscious-working-memory
#20
Fredrik Bergström, Johan Eriksson
Recent studies have found that non-consciously perceived information can be retained for several seconds, a feat that has been attributed to non-conscious working memory processes. However, these studies have mainly relied on subjective measures of visual experience, and the neural processes responsible for non-conscious short-term retention remains unclear. Here we used continuous flash suppression to render stimuli non-conscious in a delayed match-to-sample task together with fMRI to investigate the neural correlates of non-conscious short-term (5-15 s) retention...
August 2, 2017: Cerebral Cortex
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