The Experts below are selected from a list of 564 Experts worldwide ranked by ideXlab platform
Logothetis N. - One of the best experts on this subject based on the ideXlab platform.
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Decoding the contents of consciousness from prefrontal ensembles
'Cold Spring Harbor Laboratory', 2020Co-Authors: Dwarakanath A., Safavi S., Werner J., Besserve M., Panagiotaropoulos F., Logothetis N.Abstract:Multiple theories attribute to the primate prefrontal cortex a critical role in conscious Perception. However, opposing views caution that prefrontal activity could reflect other cognitive variables during paradigms investigating consciousness, such as decision-making, monitoring and motor reports. To resolve this ongoing debate, we recorded from prefrontal ensembles of macaque monkeys during a no-report paradigm of binocular rivalry that instigates internally driven transitions in conscious Perception. We could decode the contents of consciousness from prefrontal ensemble activity during binocular rivalry with an accuracy similar to when these stimuli were presented without competition. Oculomotor signals, used to infer conscious content, were not the only source of these representations since visual input could be significantly decoded when eye movements were suppressed. Our results suggest that the collective dynamics of prefrontal cortex populations reflect internally generated changes in the content of consciousness during Multistable Perception
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Low frequency oscillatory bursts in the macaque prefrontal cortex predict spontaneous transitions in the content of consciousness
2019Co-Authors: Dwarakanath A., Safavi S., Werner J., Logothetis N., Fedorov L., Hatsopoulos N., Panagiotaropoulos T.Abstract:In Multistable Perception, the content of consciousness alternates spontaneously between mutually exclusive or mixed interpretations of competing representations. Identifying neural signals predictive of such intrinsically driven perceptual transitions is fundamental in resolving the mechanism and localizing the brain areas giving rise to visual consciousness. Here we employed a no-report paradigm of binocular motion rivalry based on the optokinetic nystagmus reflex read-out of spontaneous perceptual transitions coupled with multielectrode recordings of local field potentials and single neuron discharges in the macaque prefrontal cortex. We show that an increase of oscillatory bursts in the delta-theta (1-9 Hz), and a decrease in the beta (20-40 Hz) bands, along with significant perceptual modulation of single neurons during periods of dominance and perceptual switches, are predictive of spontaneous transitions in the content of visual consciousness. These results suggest that the balance of stochastic prefrontal fluctuations is critical in refreshing conscious Perception, casting doubt on a posterior cortical mechanism for visual awareness
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Cortical microcircuit dynamics in visual awareness
2012Co-Authors: Theodoni P., Logothetis N., Panagiotaropoulos T., Deco G.Abstract:When a subject is dichoptically presented with two conflicting images, only one image is perceived at a time while the other is suppressed from awareness; this paradigm of Multistable Perception, is known as Binocular Rivalry (BR). Perception, therefore, alternates between the two visual patterns allowing a dissociation of sensory stimulation from conscious visual Perception. From a theoretical point of view, most of the computational models proposed to account for BR are rate-like models. The need is nevertheless apparent to employ biophysically plausible neuronal network models in order to connect psychophysics experiments with neurophysiological data. Here we adopted a spiking network with biophysically realistic AMPA, NMDA, and GABA receptor-mediated synaptic dynamics, as well as spike-frequency adaptation mechanisms based on Ca++-activated K+ after-hyperpolarization currents. Noise due to the probabilistic spike times of neurons is crucial for rivalry. It has been shown that competition models based on cross-inhibition and adaptation explain the observed alternations in Perception when noise operates in balance with adaptation. In order to gain insights into the cortical microcircuit dynamics mediating spontaneous perceptual alternations in BR, we derived a consistently reduced four-variable population rate model from a recurrent attractorbased biologically realistic spiking network used to model working memory, attention, and decision-making, where neuronal adaptation is implemented, using mean-field techniques. The model accounts for experimental data, collected from human subjects during BR, such as mean dominance duration, coefficient of variation, shape parameter of the gamma distribution of dominance durations and agrees with Levelt’s second and fourth proposition. The model replicates the observed data when it operates near the bifurcation that separates the noise-driven-transitions from the adaptation-driven-oscillations dynamical regime. Moreover, we show that spike-frequency adaptation of interneurons is not crucial for the spontaneous perceptual alternations, but affects the optimal parametric space of the system by decreasing the overall level of neuronal adaptation necessary for the bifurcation to occur and generates oscillations in resting state, such as in the absence of external stimuli. Furthermore, we consider recent experimental data from the macaque lateral prefrontal cortex collected during Binocular Flash Suppression a paradigm of externally induced perceptual alternation. They show a decrease in correlated variability across pairs of neurons sharing similar stimulus preferences when their preferred stimulus is perceived during rivalrous visual stimulation compared to the magnitude of correlation when the same stimulus is perceived without competition. Employing the biophysically plausible spiking network with spike-frequency adaptation, we explore distinct possible computational strategies responsible for the noise correlation decrease under visual competition
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The role of parietal visual cortex in perceptual transitions during bistable Perception
'Association for Research in Vision and Ophthalmology (ARVO)', 2012Co-Authors: Bahmani H., Logothetis N., Keliris G.Abstract:Several imaging studies in humans have shown the involvement of a frontoparietal network of cortical areas in perceptual transitions during bistable Perception. To investigate further the possible role of parietal visual areas in perceptual alternations, we recorded extracellular neural activity in the lateral intraparietal area (LIP) of the rhesus macaque. The subject was initially presented with congruent patterns to the two eyes. Then the stimulus was switched for either one or both eyes (binocular flash suppression versus physical alternation), both resulting in Perception of the newly presented stimulus. The recorded cells typically showed an initial burst of activity at stimulus onsets as well as stimulus switches. In contrast to previous reports by a number of fMRI studies, we found strong transient activity during physical alternations at the single cell level. This signal was also present during binocular flash suppression but to a lesser extent. Importantly, the amplitude of the signal dropped substantially in control conditions where physical changes were introduced in the stimuli but did not induce concomitant changes in Perception. The transient response of the recorded neurons was followed by a tonic response which exhibited independent dynamics. Interestingly, this sustained activity was significantly lower during incongruent versus congruent stimulation. We conjecture that areas at the high end of the dorsal pathway might be involved in Multistable Perception in a different way in comparison with feature and object selective areas of the ventral pathway. The transient signal recorded in LIP neurons during perceptual transitions could potentially trigger reorganization of activity in constellations of feature selective neurons in the ventral pathway. In addition, the suppression of the sustained activity in LIP during incongruent stimulation may reflect inhibitory processes involved in the resolution of conflict between the two stimuli or indicate a failure to bind the sensory input into a coherent percept
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Neural activity during stable Perception of ambiguous displays in monkey visual cortex
2002Co-Authors: Maier A., Leopold D., Logothetis N.Abstract:Multistable Perception is generally considered to be the inevitable consequence of prolonged inspection of ambiguous displays. We have recently demonstrated that in human observers perceptual alternation can be strongly retarded, and in some cases nearly eliminated, when the inducing pattern is perceived intermittently rather than continuously (Leopold et al., Nat. Neurosci. 2002). The present study extends these results to the macaque monkey (macaca mulatta), and examines what types of neural mechanisms might underlie such stabilization. We recorded broad-band signals with multiple electrodes from the early visual areas of a rhesus monkey trained to report his percepts during perceptual rivalry. Ambiguous patterns were presented intermittently with “on” and “off” periods each lasting 1-5 seconds. Given our previous finding that under these conditions Perception of such patterns can become stable, and a perceptual configuration can predominate over many subsequent presentations, we examined whether neural activity during the blank periods (i.e. delay-period activity) might reflect such a prolonged perceptual bias. We will present our initial results on this topic, with emphasis on how immediate perceptual history might affect subsequent activity in the early visual areas
Tomas Knapen - One of the best experts on this subject based on the ideXlab platform.
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Multistable Perception and the role of the frontoparietal cortex in perceptual inference
Annual Review of Psychology, 2018Co-Authors: Jan W Brascamp, Philipp Sterzer, Randolph Blake, Tomas KnapenAbstract:A given pattern of optical stimulation can arise from countless possible real-world sources, creating a dilemma for vision: What in the world actually gives rise to the current pattern? This dilemma was pointed out centuries ago by the astronomer and mathematician Ibn Al-Haytham and was forcefully restated 150 years ago when von Helmholtz characterized Perception as unconscious inference. To buttress his contention, von Helmholtz cited Multistable Perception: recurring changes in Perception despite unchanging sensory input. Recent neuroscientific studies have exploited Multistable Perception to identify brain areas uniquely activated in association with these perceptual changes, but the specific roles of those activations remain controversial. This article provides an overview of theoretical models of Multistable Perception, a review of recent neuroimaging and brain stimulation studies focused on mechanisms associated with these perceptual changes, and a synthesis of available evidence within the context of current notions about Bayesian inference that find their historical roots in von Helmholtz's work.
Jan W Brascamp - One of the best experts on this subject based on the ideXlab platform.
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Multistable Perception and the role of the frontoparietal cortex in perceptual inference
Annual Review of Psychology, 2018Co-Authors: Jan W Brascamp, Philipp Sterzer, Randolph Blake, Tomas KnapenAbstract:A given pattern of optical stimulation can arise from countless possible real-world sources, creating a dilemma for vision: What in the world actually gives rise to the current pattern? This dilemma was pointed out centuries ago by the astronomer and mathematician Ibn Al-Haytham and was forcefully restated 150 years ago when von Helmholtz characterized Perception as unconscious inference. To buttress his contention, von Helmholtz cited Multistable Perception: recurring changes in Perception despite unchanging sensory input. Recent neuroscientific studies have exploited Multistable Perception to identify brain areas uniquely activated in association with these perceptual changes, but the specific roles of those activations remain controversial. This article provides an overview of theoretical models of Multistable Perception, a review of recent neuroimaging and brain stimulation studies focused on mechanisms associated with these perceptual changes, and a synthesis of available evidence within the context of current notions about Bayesian inference that find their historical roots in von Helmholtz's work.
Fürstenau Norbert - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear dynamics model for simulation of Multistable Perception using reentrant Perception-attention-memory coupling
Universität Dresden, 2008Co-Authors: Fürstenau Norbert, Mittendorf MonikaAbstract:Simulation results of Multistable Perception due to ambiguous visual stimuli are presented which are obtained with a behavioral nonlinear dynamics model using Perception–attention–memory coupling. The basic model couples the dynamics of a macroscopic Perception state order parameter with an adaptive attention control parameter with reentrant delay T and additive band limited white noise. Quasiperiodic perceptual switching is induced by attention fatigue coupled to the Perception state, corresponding to Ditzinger and Haken (1989). As a new feature memory effects are introduced by allowing for the slow adaptation of the Perception bias parameter via coupling to the Perception state. The simulations exhibit long range correlations of the perceptual duration times in agreement with recent experimental results of Gao et al. (2006). They are determined via the self similarity (Hurst) parameter H of the reversal time series (H > 0.5). Deviations of the simulated reversal time statistics from the Gamma-distribution as typically observed in experiments, increase with decreasing memory time constant and attention noise. Mean perceptual duration times of 2 – 5 s are predicted in agreement with experimental results reported in the literature, if a feedback delay T of 40 ms is assumed which is typical for Thalamo-cortical reentrant loops. Numerically determined perceptual transition times of 3 – 5 T are in reasonable agreement with stimulus–conscious Perception delay of 150 – 200 ms. Initial periodic stimulus simulations yields the reversal rate variation as a function of stimulus off-time in surprisingly good quantitative agreement with experimental results of Orbach et.al.(1966)
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Modelling and Simulation of Spontaneous Perception Switching with Ambiguous Visual Stimuli in Augmented Vision Systems
'Springer Fachmedien Wiesbaden GmbH', 2006Co-Authors: Fürstenau NorbertAbstract:A behavioral nonlinear dynamics model of Multistable Perception due to ambiguous visual stimuli is presented. The Perception state is formalized as the phase variable (order parameter) of a recursive cosinuidal map with the two control parameters μ= difference of meaning and G ~ attention. μ controls the transition between unambiguous and ambiguous stimuli, e.g. from stimulus off to stimulus on, by means of a node bifurcation. Neuronal mean field interference with delayed phase feedback, with gain G, delay T, and damping time τ enables transitions between chaotic and limit cycle attractors representing the Perception states. Quasiperiodic perceptual reversals are induced by attention satiation (fatigue) G(t) with time constant γ and attention bias which determines the relative duration of the different percepts. The coupled attention – percep-tion dynamics with an additive stochastic attention noise term reproduces the experimentally observed Γ-distribution of the reversal time statistics. Mean reversal times of typically 3 – 5 s as reported in the literature, are correctly predicted if T is associated with the delay of 40 ms between stimulus onset and primary visual cortex (V1) response. Numerically determined perceptual transition times of 3 – 5 T are in reasonable agreement with stimulus – conscious Perception delay of 150 – 200 ms [11]. Eigenfrequencies of the limit cycle oscillations are in the range of 10 – 100 Hz, in agreement with typical EEG frequencies
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A nonlinear dynamics phase oscillator model for the simulation of Multistable Perception
Edizioni Goliardiche, 2005Co-Authors: Fürstenau NorbertAbstract:A nonlinear dynamics model of Multistable Perception and numerical simulations of the quasiperiodic Perception reversals due to ambiguous stimuli are presented. The Perception state is formalized as the phase variable (order parameter) of a recursive cosinuidal map with the two control parameters μ= difference of meaning and G ~ attention. The mapping function is closely related to the neuronal mean field phase oscillator theory of temporal binding. Mean field interference with delayed phase feedback with gain ∼ G, delay T, and damping time τ enables transitions between chaotic and limit cycle attractors representing the Perception states. Quasiperiodic perceptual reversals are induced by attention satiation (fatigue) G(t) with time constant γ. The coupled attention – Perception dynamics reproduces the experimentally observed Γ-distribution of the reversal time statistics if a stochastic noise term is added to the attention equation. Mean reversal times of typically 3 – 5 s as reported in the literature, are correctly predicted if T is associated with the delay of 40 ms between stimulus onset and primary visual cortex (V1) response. Numerically determined perceptual transition times of 3 – 5 T are in reasonable agreement with stimulus – conscious Perception delay of 150 – 200 ms (Lamme 2003). Eigenfrequencies of the limit cycle oscillations are in the range of 10 – 100 Hz, in agreement with typical EEG frequencies
David Lehmann - One of the best experts on this subject based on the ideXlab platform.
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subsecond changes of global brain state in illusory Multistable motion Perception
Journal of Neural Transmission, 2005Co-Authors: T Muller, Th Koenig, Jiri Wackermann, Peter Kalus, Andreas J Fallgatter, Werner Strik, David LehmannAbstract:This study explored transient changes in EEG microstates and spatial Omega complexity associated with changes in Multistable Perception. 21-channel EEG was recorded from 13 healthy subjects viewing an alternating dot pattern that induced illusory motion with ambiguous direction. Baseline epochs with stable motion direction were compared to epochs immediately preceding stimuli that were perceived with changed motion direction (‘reference stimuli’). About 750 ms before reference stimuli, Omega complexity decreased as compared to baseline, and two of four classes of EEG microstates changed their probability of occurrence. About 300 ms before reference stimuli, Omega complexity increased and the previous deviations of EEG microstates were reversed. Given earlier results on Omega complexity and microstates, these sub-second EEG changes might parallel longer-lasting fluctuations in vigilance. Assumedly, the discontinuities of illusory motion thus occur during sub-second dips in arousal, and the following reconstruction of the illusion coincides with a state of relative over-arousal.
