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Geraint Rees - One of the best experts on this subject based on the ideXlab platform.
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distinct meg correlates of Conscious Experience perceptual reversals and stabilization during binocular rivalry
NeuroImage, 2014Co-Authors: Morten Overgaard, Kristian Sandberg, Bahador Bahrami, Ryota Kanai, Gareth R Barnes, Geraint ReesAbstract:During binocular rivalry, visual perception alternates spontaneously between two different monocular images. Such perceptual reversals are slowed or halted if stimuli are presented intermittently with inter-stimulus intervals larger than ~ 400 ms — a phenomenon called stabilization. Often, the neural correlates of reversal and stabilization are studied separately, and both phenomena in turn are studied separately from the neural correlates of Conscious perception. To distinguish the neural correlates of perceptual content, stabilization and reversal, we recorded MEG signals associated with each in the same group of healthy humans observing repeated trials of intermittent presentation of a dichoptic stimulus. Perceptual content correlated mainly with modulation of stimulus-specific activity in occipital/temporal areas 150–270 ms after stimulus onset, possibly reflecting inhibition of the neural populations representing the suppressed image. Stability of perception reflected a gradual build-up of this modulation across at least 10 trials and was also, to some extent, associated with parietal activity 40–90 ms and 220–270 ms after stimulus onset. Perceptual reversals, in contrast, were associated with parietal (150–270 ms) and temporal (150–210 ms) activity on the trial before the reversal and a gradual change in perception-specific activity in occipital (150–270 ms) and temporal (220–420 ms) areas across at least 10 trials leading up to a reversal. Mechanistically, these findings suggest that stability of perception during rivalry is maintained by modulation of activity related to the two monocular images, and gradual adaptation of neuronal populations leads to instability that is eventually resolved by signals from parietal and late sensory cortices.
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early visual responses predict Conscious face perception within and between subjects during binocular rivalry
Journal of Cognitive Neuroscience, 2013Co-Authors: Kristian Sandberg, Morten Overgaard, Bahador Bahrami, Ryota Kanai, Gareth R Barnes, Geraint ReesAbstract:Previous studies indicate that Conscious face perception may be related to neural activity in a large time window around 170-800 msec after stimulus presentation, yet in the majority of these studies changes in Conscious Experience are confounded with changes in physical stimulation. Using multivariate classification on MEG data recorded when participants reported changes in Conscious perception evoked by binocular rivalry between a face and a grating, we showed that only MEG signals in the 120-320 msec time range, peaking at the M170 around 180 msec and the P2m at around 260 msec, reliably predicted Conscious Experience. Conscious perception could not only be decoded significantly better than chance from the sensors that showed the largest average difference, as previous studies suggest, but also from patterns of activity across groups of occipital sensors that individually were unable to predict perception better than chance. In addition, source space analyses showed that sources in the early and late visual system predicted Conscious perception more accurately than frontal and parietal sites, although Conscious perception could also be decoded there. Finally, the patterns of neural activity associated with Conscious face perception generalized from one participant to another around the times of maximum prediction accuracy. Our work thus demonstrates that the neural correlates of particular Conscious contents here, faces are highly consistent in time and space within individuals and that these correlates are shared to some extent between individuals.
Kristian Sandberg - One of the best experts on this subject based on the ideXlab platform.
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distinct meg correlates of Conscious Experience perceptual reversals and stabilization during binocular rivalry
NeuroImage, 2014Co-Authors: Morten Overgaard, Kristian Sandberg, Bahador Bahrami, Ryota Kanai, Gareth R Barnes, Geraint ReesAbstract:During binocular rivalry, visual perception alternates spontaneously between two different monocular images. Such perceptual reversals are slowed or halted if stimuli are presented intermittently with inter-stimulus intervals larger than ~ 400 ms — a phenomenon called stabilization. Often, the neural correlates of reversal and stabilization are studied separately, and both phenomena in turn are studied separately from the neural correlates of Conscious perception. To distinguish the neural correlates of perceptual content, stabilization and reversal, we recorded MEG signals associated with each in the same group of healthy humans observing repeated trials of intermittent presentation of a dichoptic stimulus. Perceptual content correlated mainly with modulation of stimulus-specific activity in occipital/temporal areas 150–270 ms after stimulus onset, possibly reflecting inhibition of the neural populations representing the suppressed image. Stability of perception reflected a gradual build-up of this modulation across at least 10 trials and was also, to some extent, associated with parietal activity 40–90 ms and 220–270 ms after stimulus onset. Perceptual reversals, in contrast, were associated with parietal (150–270 ms) and temporal (150–210 ms) activity on the trial before the reversal and a gradual change in perception-specific activity in occipital (150–270 ms) and temporal (220–420 ms) areas across at least 10 trials leading up to a reversal. Mechanistically, these findings suggest that stability of perception during rivalry is maintained by modulation of activity related to the two monocular images, and gradual adaptation of neuronal populations leads to instability that is eventually resolved by signals from parietal and late sensory cortices.
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early visual responses predict Conscious face perception within and between subjects during binocular rivalry
Journal of Cognitive Neuroscience, 2013Co-Authors: Kristian Sandberg, Morten Overgaard, Bahador Bahrami, Ryota Kanai, Gareth R Barnes, Geraint ReesAbstract:Previous studies indicate that Conscious face perception may be related to neural activity in a large time window around 170-800 msec after stimulus presentation, yet in the majority of these studies changes in Conscious Experience are confounded with changes in physical stimulation. Using multivariate classification on MEG data recorded when participants reported changes in Conscious perception evoked by binocular rivalry between a face and a grating, we showed that only MEG signals in the 120-320 msec time range, peaking at the M170 around 180 msec and the P2m at around 260 msec, reliably predicted Conscious Experience. Conscious perception could not only be decoded significantly better than chance from the sensors that showed the largest average difference, as previous studies suggest, but also from patterns of activity across groups of occipital sensors that individually were unable to predict perception better than chance. In addition, source space analyses showed that sources in the early and late visual system predicted Conscious perception more accurately than frontal and parietal sites, although Conscious perception could also be decoded there. Finally, the patterns of neural activity associated with Conscious face perception generalized from one participant to another around the times of maximum prediction accuracy. Our work thus demonstrates that the neural correlates of particular Conscious contents here, faces are highly consistent in time and space within individuals and that these correlates are shared to some extent between individuals.
Morten Overgaard - One of the best experts on this subject based on the ideXlab platform.
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emotional priming depends on the degree of Conscious Experience
Neuropsychologia, 2017Co-Authors: Michael Lohse, Morten OvergaardAbstract:Abstract Most experiments in Consciousness research assume that awareness is a dichotomous 'either/or' phenomenon. However, participants can distinguish multiple levels of subjective Experience of simple features (colour, shape etc.), which correlate with their performance in different tasks. As experiments showing multiple levels of perceptual awareness question the widespread idea that many forms of perception can occur unConsciously, we investigated emotional priming combined with methods able to measure small variations in subjective Experience. We show awareness of emotional faces is gradual rather than dichotomous, and that the effects of emotional priming are predicted by the level of perceptual awareness of emotional faces, with no effects when reported unseen. The results question how much unConscious perceptions can influence behaviour. As priming is one of the most well-established phenomena believed to occur unConsciously, the results expand the growing body of evidence that questions the contributions of unConscious processing on behaviour.
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distinct meg correlates of Conscious Experience perceptual reversals and stabilization during binocular rivalry
NeuroImage, 2014Co-Authors: Morten Overgaard, Kristian Sandberg, Bahador Bahrami, Ryota Kanai, Gareth R Barnes, Geraint ReesAbstract:During binocular rivalry, visual perception alternates spontaneously between two different monocular images. Such perceptual reversals are slowed or halted if stimuli are presented intermittently with inter-stimulus intervals larger than ~ 400 ms — a phenomenon called stabilization. Often, the neural correlates of reversal and stabilization are studied separately, and both phenomena in turn are studied separately from the neural correlates of Conscious perception. To distinguish the neural correlates of perceptual content, stabilization and reversal, we recorded MEG signals associated with each in the same group of healthy humans observing repeated trials of intermittent presentation of a dichoptic stimulus. Perceptual content correlated mainly with modulation of stimulus-specific activity in occipital/temporal areas 150–270 ms after stimulus onset, possibly reflecting inhibition of the neural populations representing the suppressed image. Stability of perception reflected a gradual build-up of this modulation across at least 10 trials and was also, to some extent, associated with parietal activity 40–90 ms and 220–270 ms after stimulus onset. Perceptual reversals, in contrast, were associated with parietal (150–270 ms) and temporal (150–210 ms) activity on the trial before the reversal and a gradual change in perception-specific activity in occipital (150–270 ms) and temporal (220–420 ms) areas across at least 10 trials leading up to a reversal. Mechanistically, these findings suggest that stability of perception during rivalry is maintained by modulation of activity related to the two monocular images, and gradual adaptation of neuronal populations leads to instability that is eventually resolved by signals from parietal and late sensory cortices.
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early visual responses predict Conscious face perception within and between subjects during binocular rivalry
Journal of Cognitive Neuroscience, 2013Co-Authors: Kristian Sandberg, Morten Overgaard, Bahador Bahrami, Ryota Kanai, Gareth R Barnes, Geraint ReesAbstract:Previous studies indicate that Conscious face perception may be related to neural activity in a large time window around 170-800 msec after stimulus presentation, yet in the majority of these studies changes in Conscious Experience are confounded with changes in physical stimulation. Using multivariate classification on MEG data recorded when participants reported changes in Conscious perception evoked by binocular rivalry between a face and a grating, we showed that only MEG signals in the 120-320 msec time range, peaking at the M170 around 180 msec and the P2m at around 260 msec, reliably predicted Conscious Experience. Conscious perception could not only be decoded significantly better than chance from the sensors that showed the largest average difference, as previous studies suggest, but also from patterns of activity across groups of occipital sensors that individually were unable to predict perception better than chance. In addition, source space analyses showed that sources in the early and late visual system predicted Conscious perception more accurately than frontal and parietal sites, although Conscious perception could also be decoded there. Finally, the patterns of neural activity associated with Conscious face perception generalized from one participant to another around the times of maximum prediction accuracy. Our work thus demonstrates that the neural correlates of particular Conscious contents here, faces are highly consistent in time and space within individuals and that these correlates are shared to some extent between individuals.
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Consciousness and modality on the possible preserved visual Consciousness in blindsight subjects
Consciousness and Cognition, 2011Co-Authors: Morten Overgaard, Thor GrunbaumAbstract:In a recent paper, Brogaard (2011) presents counter-arguments to the conclusions of an experiment with blindsight subject GR. She argues that contrary to the apparent findings that GR’s preserved visual abilities relate to degraded visual Experiences, she is in fact fully unConscious of the stimuli she correctly identifies. In this paper, we present arguments and evidence why Brogaard’s argument does not succeed in its purpose. We suggest that not only is relevant empirical evidence in opposition to Brogaard’s argument, her argument misconstrues necessary criteria to decide whether a Conscious Experience is visual or not visual.
Giulio Tononi - One of the best experts on this subject based on the ideXlab platform.
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causal connectivity according to Conscious Experience in non rapid eye movement sleep
Systems Man and Cybernetics, 2019Co-Authors: Minji Lee, Giulio Tononi, Benjamin Baird, Olivia Gosseries, Jaakko O Nieminen, Melanie Boly, Seongwhan LeeAbstract:The understanding of human Consciousness based on brain connectivity is considered important for brain- machine interfacing. In this study, we investigated changes in causal connectivity in electroencephalography data related to Conscious and unConscious Experiences during non-rapid eye movement sleep after parietal transcranial magnetic stimulation (TMS). A serial awakening paradigm was used to determine whether subjects had had a Conscious Experience or not. We calculated direct transfer function (DTF) as a measure of effective connectivity in five frequency bands focusing on frontal and parietal-occipital regions. The DTF showed significant differences in frontal-to-parietal flow between reported unConsciousness and Consciousness. During the first 100 ms after TMS, the outward links of the parietal region at low frequencies were higher in no Conscious Experience than in Conscious Experience. During the next 100 ms, however, the outward links of the frontal region were higher in the Conscious Experience than the no Conscious Experience at low frequencies. Changes with causal connectivity over time after TMS indicate that the spatial roles in brain regions associated with Consciousness are different. These findings may help clarify the cortical mechanisms related to Conscious Experience.
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graph theoretical analysis of cortical networks based on Conscious Experience
International Conference of the IEEE Engineering in Medicine and Biology Society, 2019Co-Authors: Minji Lee, Giulio Tononi, Benjamin Baird, Olivia Gosseries, Jaakko O Nieminen, Melanie Boly, Seongwhan LeeAbstract:The aim of the study was to investigate differences in cortical networks based on the state of Consciousness. Five subjects performed a serial-awakening paradigm with electroencephalography (EEG) recordings. We considered four states of Consciousness: (1) non-rapid eye movement (NREM) sleep with no Conscious Experience, (2) NREM sleep with Conscious Experience, (3) rapid eye movement (REM) sleep with Conscious Experience, and (4) wakefulness. We applied graph theoretical analysis to explore the cortical connectivity and network properties in five frequency bands. Connectivity between EEG channels was evaluated with the weighted phase lag index (wPLI). The characteristic path length, transitivity, and clustering coefficient were computed to evaluate functional integration and segregation of the associated brain network. There were no significant differences in wPLI among the four states of Consciousness. In the beta band, functional integration in wakefulness was higher than in NREM sleep. Regarding functional segregation, in the theta band, transitivity and clustering coefficient in NREM sleep with no Conscious Experience were stronger than in wakefulness or REM sleep, but clustering in the beta band showed an opposite effect. The observed differences may be related to cortical bistability and add to previously observed neural correlates of Consciousness.
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spatio temporal analysis of eeg signal during Consciousness using convolutional neural network
2018 6th International Conference on Brain-Computer Interface (BCI), 2018Co-Authors: Seulki Yeom, Benjamin Baird, Olivia Gosseries, Jakko O Nieminen, Giulio TononiAbstract:Electroencephalogram (EEG) measurement could help to distinguish the level of Consciousness in an individual without requiring a behavioral response, which could be useful as a diagnostic aid in patients with disorders of Consciousness. In this study, we explored the EEG-evoked perturbation and analyzed Consciousness using event-related spectral perturbation and convolutional neural network. We observed a novel EEG neurophysiological signature that can be used to monitor brain activity during unConsciousness. Also, the performance accuracy in the parietal region was higher than in the frontal region. The sensitivity for Conscious Experience was 90.9%, whereas sensitivity for unConscious Experience was at the chance level in the parietal region. These results could be evidence for the importance of the posterior hot zone and could help shed light on the internal neural dynamics related to Conscious Experience.
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an information integration theory of Consciousness
BMC Neuroscience, 2004Co-Authors: Giulio TononiAbstract:Background: Consciousness poses two main problems. The first is understanding the conditions that determine to what extent a system has Conscious Experience. For instance, why is our Consciousness generated by certain parts of our brain, such as the thalamocortical system, and not by other parts, such as the cerebellum? And why are we Conscious during wakefulness and much less so during dreamless sleep? The second problem is understanding the conditions that determine what kind of Consciousness a system has. For example, why do specific parts of the brain contribute specific qualities to our Conscious Experience, such as vision and audition? Presentation of the hypothesis: This paper presents a theory about what Consciousness is and how it can be measured. According to the theory, Consciousness corresponds to the capacity of a system to integrate information. This claim is motivated by two key phenomenological properties of Consciousness: differentiation – the availability of a very large number of Conscious Experiences; and integration – the unity of each such Experience. The theory states that the quantity of Consciousness available to a system can be measured as the Φ value of a complex of elements. Φ is the amount of causally effective information that can be integrated across the informational weakest link of a subset of elements. A complex is a subset of elements with Φ>0 that is not part of a subset of higher Φ. The theory also claims that the quality of Consciousness is determined by the informational relationships among the elements of a complex, which are specified by the values of effective information among them. Finally, each particular Conscious Experience is specified by the value, at any given time, of the variables mediating informational interactions among the elements of a complex. Testing the hypothesis: The information integration theory accounts, in a principled manner, for several neurobiological observations concerning Consciousness. As shown here, these include the association of Consciousness with certain neural systems rather than with others; the fact that neural processes underlying Consciousness can influence or be influenced by neural processes that remain unConscious; the reduction of Consciousness during dreamless sleep and generalized seizures; and the time requirements on neural interactions that support Consciousness. Implications of the hypothesis: The theory entails that Consciousness is a fundamental quantity, that it is graded, that it is present in infants and animals, and that it should be possible to build Conscious artifacts.
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information measures for Conscious Experience
Archives Italiennes De Biologie, 2001Co-Authors: Giulio TononiAbstract:This paper argues that Consciousness is integrated information, and introduces measures to assess it. These measures lead to the prediction that a physical system such as the brain gives rise to Consciousness when some of its elements constitute a complex having high minimum information midpartition (MID) complexity.
Patrick Haggard - One of the best experts on this subject based on the ideXlab platform.
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volition and the brain revisiting a classic experimental study
Trends in Neurosciences, 2018Co-Authors: Patrick Haggard, Chris D FrithAbstract:In 1983 Libet et al. demonstrated that brain activity associated with a voluntary act precedes Conscious Experience of the intention to act by several hundred milliseconds. The implication that it is the brain, rather than 'free will', that initiates voluntary acts has been discussed ever since by philosophers and lawyers, as well as by scientists. We show here how Libet's original study gave rise to an entire research field of experimental investigations of volition.
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abnormal sense of intention preceding voluntary movement in patients with psychogenic tremor
Neuropsychologia, 2011Co-Authors: Mark J Edwards, Giovanna Moretto, Petra Schwingenschuh, Petra Katschnig, Kailash P Bhatia, Patrick HaggardAbstract:Psychogenic tremor is the commonest psychogenic movement disorder, yet little is known of its pathophysiology. Given the presence of movements that appear from their physiological properties to be voluntarily produced, and yet are not Experienced as such by the patients, we hypothesised that patients might have an abnormal Conscious Experience of volition with regard to self-generated movement. Nine patients with psychogenic tremor were asked to judge the timing of a self-paced button press relative to a clock displayed on a computer screen. In separate trials they were asked to judge the timing of their internal feeling of intention to move. These results were compared to those of healthy control participants. Patients with psychogenic tremor judged their feeling of intention to move significantly later compared to control participants. As a result, the interval between the perceived time of intention and the perceived time of action, which was highly significant in the control participants, was numerically smaller and non-significant in the patients. This study provides novel data that the sense of volition prior to movement is impaired in patients with psychogenic tremor. This fits with a pathophysiological explanation for this disorder based on an impairment of neural mechanisms that generate the Conscious Experience of action: actions that are voluntary in terms of their physiological origin might be Experienced as involuntary.
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intentional action Conscious Experience and neural prediction
Consciousness and Cognition, 2003Co-Authors: Patrick Haggard, Samuel J ClarkAbstract:Abstract Intentional action involves both a series of neural events in the motor areas of the brain, and also a distinctive Conscious Experience that “I” am the author of the action. This paper investigates some possible ways in which these neural and phenomenal events may be related. Recent models of motor prediction are relevant to the Conscious Experience of action as well as to its neural control. Such models depend critically on matching the actual consequences of a movement against its internally predicted effects. However, it remains unclear whether our Conscious Experience of action depends on a precise matching process, or a retrospective inference that “I” must have been responsible for a particular event. We report an experiment in which normal subjects judged the perceived time of either intentional actions, involuntary movements, or subsequent effects (auditory tones) of these. We found that the subject’s intention to produce the auditory tone produced an intentional binding between the perceived times of the subject’s action and the tone. However, if the intention was interrupted by an imposed involuntary movement, followed by the identical tone, no such binding occurred. The phenomenology of intentional action requires an appropriate predictive link between intentions and effects, rather than a retrospective inference that “I” caused the effect.