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Neural correlates of consciousness

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https://www.readbyqxmd.com/read/28544942/behavioural-and-neural-evidence-for-the-impact-of-fluency-context-on-conscious-memory
#1
Carlos Alexandre Gomes, Axel Mecklinger, Hubert Zimmer
It has been recently suggested that fluency may impact recognition memory performance when the fluency context varies from trial-to-trial. Surprisingly, such an effect has proved difficult to detect in the masked priming paradigm, one of the most popular means to increase fluency-based memory judgements. We conducted a functional magnetic resonance imaging (fMRI) experiment in which participants encoded words at study and, at test, performed a recognition memory task within a masked priming procedure. In order to optimise the chances of finding priming effects on recognition memory performance, we used low-frequency words, which have been shown to increase hits relative to false alarms and enhance masked priming effects...
April 21, 2017: Cortex; a Journal Devoted to the Study of the Nervous System and Behavior
https://www.readbyqxmd.com/read/28538517/greater-corticostriatal-activation-associated-with-facial-motor-imagery-compared-with-motor-execution-a-functional-mri-study
#2
Meena M Makary, Seulgi Eun, Kyungmo Park
Motor imagery (MI) relies on conscious mental simulation of a motor act without overt motor output and can promote motor skill acquisition and facilitate rehabilitation for patients with stroke or neurological conditions. Although a plethora of neuroimaging studies have investigated the neural network of MI regarding different body parts, exploration of the neural correlates to facial MI remains warranted. Here, we used functional MRI with a large cohort of 41 participants who underwent motor execution (ME) and MI runs of mouth-stretching tasks...
May 19, 2017: Neuroreport
https://www.readbyqxmd.com/read/28505152/a-predictive-coding-account-of-bistable-perception-a-model-based-fmri-study
#3
Veith Weilnhammer, Heiner Stuke, Guido Hesselmann, Philipp Sterzer, Katharina Schmack
In bistable vision, subjective perception wavers between two interpretations of a constant ambiguous stimulus. This dissociation between conscious perception and sensory stimulation has motivated various empirical studies on the neural correlates of bistable perception, but the neurocomputational mechanism behind endogenous perceptual transitions has remained elusive. Here, we recurred to a generic Bayesian framework of predictive coding and devised a model that casts endogenous perceptual transitions as a consequence of prediction errors emerging from residual evidence for the suppressed percept...
May 15, 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/28473797/reorganization-of-the-connectivity-between-elementary-functions-a-model-relating-conscious-states-to-neural-connections
#4
Jesper Mogensen, Morten Overgaard
In the present paper it is argued that the "neural correlate of consciousness" (NCC) does not appear to be a separate "module" - but an aspect of information processing within the neural substrate of various cognitive processes. Consequently, NCC can only be addressed adequately within frameworks that model the general relationship between neural processes and mental states - and take into account the dynamic connectivity of the brain. We presently offer the REFGEN (general reorganization of elementary functions) model as such a framework...
2017: Frontiers in Psychology
https://www.readbyqxmd.com/read/28444975/dissociation-between-the-neural-correlates-of-conscious-face-perception-and-visual-attention
#5
Joaquin Navajas, Aleksander W Nitka, Rodrigo Quian Quiroga
Given the higher chance to recognize attended compared to unattended stimuli, the specific neural correlates of these two processes, attention and awareness, tend to be intermingled in experimental designs. In this study, we dissociated the neural correlates of conscious face perception from the effects of visual attention. To do this, we presented faces at the threshold of awareness and manipulated attention through the use of exogenous prestimulus cues. We show that the N170 component, a scalp EEG marker of face perception, was modulated independently by attention and by awareness...
April 26, 2017: Psychophysiology
https://www.readbyqxmd.com/read/28442276/investigating-the-effects-of-nitrous-oxide-sedation-on-frontal-parietal-interactions
#6
Ji-Ho Ryu, Pil-Jong Kim, Hong-Gee Kim, Yong-Seo Koo, Teo Jeon Shin
Although functional connectivity has received considerable attention in the study of consciousness, few studies have investigated functional connectivity limited to the sedated state where consciousness is maintained but impaired. The aim of the present study was to investigate changes in functional connectivity of the parietal-frontal network resulting from nitrous oxide-induced sedation, and to determine the neural correlates of cognitive impairment during consciousness transition states. Electroencephalography was acquired from healthy adult patients who underwent nitrous oxide inhalation to induce cognitive impairment, and was analyzed using Granger causality (GC)...
April 23, 2017: Neuroscience Letters
https://www.readbyqxmd.com/read/28422113/increased-spontaneous-meg-signal-diversity-for-psychoactive-doses-of-ketamine-lsd-and-psilocybin
#7
Michael M Schartner, Robin L Carhart-Harris, Adam B Barrett, Anil K Seth, Suresh D Muthukumaraswamy
What is the level of consciousness of the psychedelic state? Empirically, measures of neural signal diversity such as entropy and Lempel-Ziv (LZ) complexity score higher for wakeful rest than for states with lower conscious level like propofol-induced anesthesia. Here we compute these measures for spontaneous magnetoencephalographic (MEG) signals from humans during altered states of consciousness induced by three psychedelic substances: psilocybin, ketamine and LSD. For all three, we find reliably higher spontaneous signal diversity, even when controlling for spectral changes...
April 19, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28398813/neural-correlates-of-consciousness-at-near-electrocerebral-silence-in-an-asphyxial-cardiac-arrest-model
#8
Donald E Lee, Lauren G Lee, Danny Siu, Afsheen K Bazrafkan, Maryam H Farahabadi, Tin J Dinh, Josue Orellana, Wei Xiong, Beth A Lopour, Yama Akbari
Recent electrophysiological studies have suggested surges in electrical correlates of consciousness (i.e., elevated gamma power and connectivity) after cardiac arrest (CA). This study examines electrocorticogram (ECoG) activity and coherence of the dying brain during asphyxial CA. Male Wistar rats (n = 16) were induced with isoflurane anesthesia, which was washed out before asphyxial CA. Mean phase coherence and ECoG power were compared during different stages of the asphyxial period to assess potential neural correlates of consciousness...
April 2017: Brain Connectivity
https://www.readbyqxmd.com/read/28394322/the-neural-correlates-of-dreaming
#9
Francesca Siclari, Benjamin Baird, Lampros Perogamvros, Giulio Bernardi, Joshua J LaRocque, Brady Riedner, Melanie Boly, Bradley R Postle, Giulio Tononi
Consciousness never fades during waking. However, when awakened from sleep, we sometimes recall dreams and sometimes recall no experiences. Traditionally, dreaming has been identified with rapid eye-movement (REM) sleep, characterized by wake-like, globally 'activated', high-frequency electroencephalographic activity. However, dreaming also occurs in non-REM (NREM) sleep, characterized by prominent low-frequency activity. This challenges our understanding of the neural correlates of conscious experiences in sleep...
June 2017: Nature Neuroscience
https://www.readbyqxmd.com/read/28392004/-paradox-of-slow-frequencies-are-slow-frequencies-in-upper-cortical-layers-a-neural-predisposition-of-the-level-state-of-consciousness-npc
#10
Georg Northoff
Consciousness research has much focused on faster frequencies like alpha or gamma while neglecting the slower ones in the infraslow (0.001-0.1Hz) and slow (0.1-1Hz) frequency range. These slower frequency ranges have a "bad reputation" though; their increase in power can observed during the loss of consciousness as in sleep, anesthesia, and vegetative state. However, at the same time, slower frequencies have been conceived instrumental for consciousness. The present paper aims to resolve this paradox which I describe as "paradox of slow frequencies"...
April 5, 2017: Consciousness and Cognition
https://www.readbyqxmd.com/read/28283789/cerebral-metabolic-changes-related-to-clinical-parameters-in-idiopathic-anosmic-patients-during-olfactory-stimulation-a-pilot-investigation
#11
Alessandro Micarelli, Agostino Chiaravalloti, Roberta Danieli, Orazio Schillaci, Marco Alessandrini
Idiopathic olfactory loss neural consequences have been studied especially by means of magnetic resonance imaging. Since other functional neuroimaging technique findings are lacking in the literature, present study used a validated (18)F-2-fluoro-2-deoxy-D-glucose (FDG) functional positron emission tomography procedure under olfactory stimulation (OS) to assess brain changes in idiopathic anosmic patients (IAPs) in comparison with healthy subjects (HS). A voxel-based analysis between these groups was used to evaluate FDG uptake in the brain and perform a correlation analysis between metabolic responses and the Sniffin' stick test as well as intensity visuo-analogue scores and disease duration (DD)...
March 10, 2017: European Archives of Oto-rhino-laryngology
https://www.readbyqxmd.com/read/28258035/raising-the-alarm-individual-differences-in-the-perceptual-awareness-of-masked-facial-expressions
#12
Ljubica Damjanovic, Marcel Meyer, Francisco Sepulveda
A theoretical concern in addressing the unconscious perception of emotion is the extent to which participants can access experiential properties of masked facial stimuli. Performance on a two alternative forced choice (2AFC) task as a measure of objective awareness was compared with a new measure developed to access experiential phenomena of the target-mask transition, the perceptual contrast-change sensitivity (PCCS) measure in a backward-masking paradigm with angry, happy and neutral facial expressions. Whilst 2AFC performance indicated that the targets were successfully masked, PCCS values were significantly higher in the happy-neutral face condition than in the angry-neutral face and the neutral-neutral face conditions (Experiment 1)...
June 2017: Brain and Cognition
https://www.readbyqxmd.com/read/28215463/markers-of-tms-evoked-visual-conscious-experience-in-a-patient-with-altitudinal-hemianopia
#13
Chiara Mazzi, Gaetano Mazzeo, Silvia Savazzi
Transcranial magnetic stimulation (TMS) of the occipital and parietal cortices can induce phosphenes, i.e. visual sensations of light without light entering the eyes. In this paper, we adopted a TMS-EEG interactive co-registration approach with a patient (AM) showing altitudinal hemianopia. Occipital and parietal cortices in both hemispheres were stimulated while concurrently recording EEG signal. Results showed that, for all sites, neural activity differentially encoding for the presence vs. absence of a conscious experience could be found in a cluster of electrodes close to the stimulation site at an early (70ms) time-period after TMS...
February 16, 2017: Consciousness and Cognition
https://www.readbyqxmd.com/read/28195526/regulating-the-access-to-awareness-brain-activity-related-to-probe-related-and-spontaneous-reversals-in-binocular-rivalry
#14
Brian A Metzger, Kyle E Mathewson, Evelina Tapia, Monica Fabiani, Gabriele Gratton, Diane M Beck
Research on the neural correlates of consciousness (NCC) has implicated an assortment of brain regions, ERP components, and network properties associated with visual awareness. Recently, the P3b ERP component has emerged as a leading NCC candidate. However, typical P3b paradigms depend on the detection of some stimulus change, making it difficult to separate brain processes elicited by the stimulus itself from those associated with updates or changes in visual awareness. Here we used binocular rivalry to ask whether the P3b is associated with changes in awareness even in the absence of changes in the object of awareness...
June 2017: Journal of Cognitive Neuroscience
https://www.readbyqxmd.com/read/28165171/less-is-more-neural-activity-during-very-brief-and-clearly-visible-exposure-to-phobic-stimuli
#15
Paul Siegel, Richard Warren, Zhishun Wang, Jie Yang, Don Cohen, Jason F Anderson, Lilly Murray, Bradley S Peterson
Research on automatic processes in fear has emphasized the provocation of fear responses rather than their attenuation. We have previously shown that the repeated presentation of feared images without conscious awareness via backward masking reduces avoidance of a live tarantula in spider-phobic participants. Herein we investigated the neural basis for these adaptive effects of masked exposure. 21 spider-phobic and 21 control participants, identified by a psychiatric interview, fear questionnaire, and approaching a live tarantula, viewed stimuli in each of three conditions: (1) very brief exposure (VBE) to masked images of spiders, severely limited awareness; (2) clearly visible exposure (CVE) to spiders, full awareness; and (3) masked images of flowers (control), severely limited awareness...
May 2017: Human Brain Mapping
https://www.readbyqxmd.com/read/28110456/facial-skin-blood-flow-responses-during-exposures-to-emotionally-charged-movies
#16
Kanji Matsukawa, Kana Endo, Kei Ishii, Momoka Ito, Nan Liang
The changes in regional facial skin blood flow and vascular conductance have been assessed for the first time with noninvasive two-dimensional laser speckle flowmetry during audiovisually elicited emotional challenges for 2 min (comedy, landscape, and horror movie) in 12 subjects. Limb skin blood flow and vascular conductance and systemic cardiovascular variables were simultaneously measured. The extents of pleasantness and consciousness for each emotional stimulus were estimated by the subjective rating from -5 (the most unpleasant; the most unconscious) to +5 (the most pleasant; the most conscious)...
January 21, 2017: Journal of Physiological Sciences: JPS
https://www.readbyqxmd.com/read/28107727/neural-correlates-of-subliminally-presented-visual-sexual-stimuli
#17
Martina Wernicke, Corinna Hofter, Kirsten Jordan, Peter Fromberger, Peter Dechent, Jürgen L Müller
In the context of forensic psychiatry, it is crucial that diagnoses of deviant sexual interests are resistant to manipulation. In a first attempt to promote the development of such tools, the current fMRI study focusses on the examination of hemodynamic responses to preferred, in contrast to non-preferred, sexual stimuli with and without explicit sexual features in 24 healthy heterosexual subjects. The subliminal stimulus presentation of sexual stimuli could be a new approach to reduce vulnerability to manipulation...
March 2017: Consciousness and Cognition
https://www.readbyqxmd.com/read/28092321/dexmedetomidine-disrupts-the-local-and-global-efficiencies-of-large-scale-brain-networks
#18
Javeria A Hashmi, Marco L Loggia, Sheraz Khan, Lei Gao, Jieun Kim, Vitaly Napadow, Emery N Brown, Oluwaseun Akeju
BACKGROUND: A clear understanding of the neural basis of consciousness is fundamental to research in clinical and basic neuroscience disciplines and anesthesia. Recently, decreased efficiency of information integration was suggested as a core network feature of propofol-induced unconsciousness. However, it is unclear whether this finding can be generalized to dexmedetomidine, which has a different molecular target. METHODS: Dexmedetomidine was administered as a 1-μg/kg bolus over 10 min, followed by a 0...
March 2017: Anesthesiology
https://www.readbyqxmd.com/read/28072803/neural-correlates-of-maladaptive-pain-behavior-in-chronic-neck-pain-a-single-case-control-fmri-study
#19
Konstantin Beinert, Audrey Mouthon, Martin Keller, Michael Mouthon, Jean-Marie Annoni, Wolfgang Taube
Chronic neck pain patients display functional impairments like decreased range of motion, decreased strength, and reduced sensorimotor function. In patients without structural damage, the reason for the persistence of pain is not well understood. Therefore, it is assumed that in chronic pain states, memory processes play an important role. We have now detected and tested a patient that might help us to better understand the neural correlates of maladaptive pain expectation/memory. This patient displays chronic neck pain and restricted unilateral motion of the cervical spine to the left...
January 2017: Pain Physician
https://www.readbyqxmd.com/read/28069540/multi-modal-analysis-of-functional-connectivity-and-cerebral-blood-flow-reveals-shared-and-unique-effects-of-propofol-in-large-scale-brain-networks
#20
Maolin Qiu, Dustin Scheinost, Ramachandran Ramani, R Todd Constable
Anesthesia-induced changes in functional connectivity and cerebral blow flow (CBF) in large-scale brain networks have emerged as key markers of reduced consciousness. However, studies of functional connectivity disagree on which large-scale networks are altered or preserved during anesthesia, making it difficult to find a consensus amount studies. Additionally, pharmacological alterations in CBF could amplify or occlude changes in connectivity due to the shared variance between CBF and connectivity. Here, we used data-driven connectivity methods and multi-modal imaging to investigate shared and unique neural correlates of reduced consciousness for connectivity in large-scale brain networks...
March 1, 2017: NeuroImage
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