scholarly journals Functional dynamics underlying near-threshold perception of facial emotions: a magnetoencephalography investigation

2018 ◽  
Author(s):  
Diljit Singh Kajal ◽  
Chiara Fioravanti ◽  
Adham Elshahabi ◽  
Sergio Ruiz ◽  
Ranganatha Sitaram ◽  
...  
Keyword(s):  
Visual Stimulation ◽  
Gamma Band ◽  
Gamma Activity ◽  
Hemispheric Dominance ◽  
Conscious Perception ◽  
Backward Masking ◽  
Top Down ◽  
Bottom Up ◽  
Facial Emotions ◽  
Perceptual Threshold

AbstractConscious perception of emotional valence of faces has been proposed to involve top-down and bottom-up information processing. Yet, the underlying neuronal mechanisms of these two processes and the implementation of their cooperation is still unclear. We hypothesized that the networks activated during the interaction of top-down and bottom-up processes are the key substrates responsible for perception. We assessed the participation of neural networks involved in conscious perception of emotional stimuli near the perceptual threshold using a visual-backward-masking paradigm in 12 healthy individuals using magnetoencephalography. Providing visual stimulation near the perceptual threshold enabled us to compare correctly and incorrectly recognized facial emotions and assess differences in top-down modulation for these stimuli using coherence analysis. We found a fronto-parietal network oscillating in the lower gamma band and exerting top-down control as determined by the causality measure of phase slope index. We demonstrated that correct recognition of facial emotions involved high-beta and low-gamma activity in parietal networks, Incorrect recognition was associated with enhanced coupling in the gamma band between left frontal and right parietal regions. Our results indicate that fronto-parietal control of the perception of emotional face stimuli relies on the right-hemispheric dominance of synchronized gamma band activity.

scholarly journals Top-down inhibition of irrelevant information indexed by alpha rhythms is disrupted in migraine

2021 ◽  
Author(s):  
Rémy Masson ◽  
Hesham A ElShafei ◽  
Geneviève Demarquay ◽  
Lesly Fornoni ◽  
Yohana Lévêque ◽  
...  
Keyword(s):  
Cognitive Processing ◽  
Gamma Activity ◽  
Auditory Target ◽  
Alpha Power ◽  
Top Down ◽  
Significant Group ◽  
Bottom Up ◽  
Power Increase ◽  
Visual Areas ◽  
Healthy Participants

There is growing evidence that migraine is associated with attentional abnormalities, both during and outside migraine attacks, which would impact the cognitive processing of sensory stimulation. However, these attention alterations are poorly characterized and their neurophysiological basis is still unclear. Nineteen migraineurs without aura and nineteen healthy participants were recruited to perform a task which used visually-cued auditory targets and distracting sounds to evaluate conjointly top-down and bottom-up attention mechanisms. Magnetoencephalography (MEG) signals were recorded. We investigated anticipatory alpha activity (power increase and decrease) and distractor-induced gamma activity as markers for top-down (inhibition and facilitation) and bottom-up attention, respectively. Compared to healthy participants, migraineurs presented a significantly less prominent alpha power increase in visual areas in anticipation of the auditory target, indexing a reduced inhibition of task-irrelevant visual areas. However, there was no significant group difference regarding the alpha power decrease in the relevant auditory cortices in anticipation of the target, nor regarding the distractor-induced gamma power increase in the ventral attention network. These results in the alpha band suggest that top-down inhibitory processes in the visual cortices are deficient in migraine but there is no clear evidence supporting a disruption of top-down facilitatory attentional processes. This relative inability to suppress irrelevant sensory information may be underlying the self-reported increased distractibility and contribute to sensory disturbances in migraine.

scholarly journals Bottom-up sensory processing can decrease activity and functional connectivity in the default mode like network in rats

2018 ◽  
Author(s):  
Rukun Hinz ◽  
Lore M. B. Peeters ◽  
Disha Shah ◽  
Stephan Missault ◽  
Michaël Belloy ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Sensory Processing ◽  
Large Scale ◽  
Visual Stimulation ◽  
Block Design ◽  
Brain State ◽  
Top Down ◽  
Similar Reduction ◽  
Bottom Up ◽  
Default Mode

AbstractThe default mode network is a large-scale brain network that is active during rest and internally focused states and deactivates as well as desynchronizes during externally oriented (top-down) attention demanding cognitive tasks. However, it is not sufficiently understood if unpredicted salient stimuli, able to trigger bottom-up attentional processes, could also result in similar reduction of activity and functional connectivity in the DMN. In this study, we investigated whether bottom-up sensory processing could influence the default mode like network (DMLN) in rats. DMLN activity was examined using block-design visual functional magnetic resonance imaging (fMRI) while its synchronization was investigated by comparing functional connectivity during a resting versus a continuously stimulated brain state by unpredicted light flashes. We demonstrated that activity in DMLN regions was decreased during visual stimulus blocks and increased during blanks. Furthermore, decreased inter-network functional connectivity between the DMLN and visual networks as well as decreased intra-network functional connectivity within the DMLN was observed during the continuous visual stimulation. These results suggest that triggering of bottom-up attention mechanisms in anesthetized rats can lead to a cascade similar to top-down orienting of attention in humans and is able to deactivate and desynchronize the DMLN.

scholarly journals DMT alters cortical travelling waves

2020 ◽  
Author(s):  
Andrea Alamia ◽  
Christopher Timmermann ◽  
Rufin VanRullen ◽  
Robin L. Carhart-Harris
Keyword(s):  
Visual Stimulation ◽  
Travelling Waves ◽  
Travelling Wave ◽  
Cortical Activation ◽  
Altered States ◽  
Top Down ◽  
Bottom Up ◽  
Eyes Closed ◽  
Psychedelic Drugs ◽  
Spatio Temporal

AbstractPsychedelic drugs are potent modulators of conscious states and therefore powerful tools for investigating their neurobiology. N,N, Dimethyltryptamine (DMT) is a particularly interesting serotonergic psychedelic that can rapidly induce an extremely immersive state of consciousness characterized by vivid and elaborate visual imagery. In the present study, we investigated the electrophysiological correlates of the DMT-induced altered state, by recording EEG signals from a pool of participants receiving DMT and (separately) placebo (saline), intravenously, while instructed to keep their eyes closed (i.e. ‘resting state’). Consistent with our prior hypotheses, results revealed a spatio-temporal pattern of cortical activation (i.e., travelling waves) similar to that elicited by visual stimulation. Moreover, the typical top-down alpha-band rhythms of closed-eyes rest (i.e. a backward travelling wave) were significantly decreased, while the bottom-up ‘forward travelling wave’, was significantly increased. These results support a recent model proposing that psychedelics reduce the ‘precision-weighting of priors’, thus altering the balance of top-down versus bottom-up information passing, where properties of backward waves are considered correlates of this precision weighting. The robust hypothesis-confirming nature of the present findings imply the discovery of an important mechanistic principle underpinning psychedelic-induced altered states – i.e. reduced backward and increased forward travelling waves - and lend further support to prior assumptions about the functional significance of cortical travelling waves.

Early interaction between bottom-up and top-down processes in the beta-gamma band during ultra-rapid visual object detection

NeuroImage ◽  
2009 ◽  
Vol 47 ◽  
pp. S155
Author(s):  
A.V. Medvedev ◽  
S.B. Borisov ◽  
J. Kainerstorfer ◽  
J. VanMeter
Keyword(s):  
Object Detection ◽  
Gamma Band ◽  
Visual Object ◽  
Top Down ◽  
Bottom Up ◽  
Early Interaction

scholarly journals Top-down beta enhances bottom-up gamma

2016 ◽  
Author(s):  
Craig G. Richter ◽  
William H. Thompson ◽  
Conrado A. Bosman ◽  
Pascal Fries
Keyword(s):  
Gamma Band ◽  
Visual Area ◽  
Beta Band ◽  
Top Down ◽  
Bottom Up ◽  
Area V4 ◽  
Frequency Interaction ◽  
Area 7A ◽  
Alpha Beta ◽  
Band Activity

AbstractSeveral recent studies have demonstrated that the bottom-up signaling of a visual stimulus is subserved by interareal gamma-band synchronization, whereas top-down influences are mediated by alpha-beta band synchronization. These processes may implement top-down control of stimulus processing if top-down and bottom-up mediating rhythms are coupled via cross-frequency interaction. To test this possibility, we investigated Granger-causal influences among awake male macaque primary visual area V1, higher visual area V4 and parietal control area 7a during attentional task performance. Top-down 7a-to-V1 beta-band influences enhanced visually driven V1-to-V4 gamma-band influences. This enhancement was spatially specific and largest when beta-band activity preceded gamma-band activity by ∼0.1 s, suggesting a causal effect of top-down processes on bottom-up processes. We propose that this cross-frequency interaction mechanistically subserves the attentional control of stimulus selection.Significance StatementContemporary research indicates that the alpha-beta frequency band underlies top-down control, while the gamma-band mediates bottom-up stimulus processing. This arrangement inspires an attractive hypothesis, which posits that top-down beta-band influences directly modulate bottom-up gamma band influences via cross-frequency interaction. We evaluate this hypothesis determining that beta-band top-down influences from parietal area 7a to visual area V1 are correlated with bottom-up gamma frequency oscillations from V1 to area V4, in a spatially specific manner, and that this correlation is maximal when top-down activity precedes bottom-up activity. These results show that for top-down processes such as spatial attention, elevated top-down beta-band influences directly enhance feedforward stimulus induced gamma-band processing, leading to enhancement of the selected stimulus.

scholarly journals Frontal and parietal alpha oscillations reflect attentional modulation of cross-modal matching

2018 ◽  
Author(s):  
Jonas Misselhorn ◽  
Uwe Friese ◽  
Andreas K. Engel
Keyword(s):  
Gamma Activity ◽  
Multisensory Perception ◽  
Top Down ◽  
Bottom Up ◽  
Alpha Oscillations ◽  
Sensory Inputs ◽  
Gamma Power ◽  
Sensory Cortices ◽  
Underlying Mechanisms ◽  
Selection Of

Multisensory perception is shaped by both attentional selection of relevant sensory inputs and exploitation of stimulus-driven factors that promote cross-modal binding. Underlying mechanisms of both top-down and bottom-up modulations have been linked to changes in alpha/gamma dynamics in primary sensory cortices and temporoparietal cortex. Accordingly, it has been proposed that alpha oscillations provide pulsed inhibition for gamma activity and thereby dynamically route cortical information flow. In this study, we employed a recently introduced multisensory paradigm incorporating both bottom-up and top-down aspects of cross-modal attention in an EEG study. The same trimodal stimuli were presented in two distinct attentional conditions, focused on visual-tactile or audio-visual components, for which cross-modal congruence of amplitude changes had to be evaluated. Neither top-down nor bottom-up cross-modal attention modulated alpha or gamma power in primary sensory cortices. Instead, we found alpha band effects in bilateral frontal and right parietal cortex. We propose that frontal alpha oscillations reflect the origin of top-down control regulating perceptual gains and that modulations of parietal alpha oscillations relates to intersensory re-orienting. Taken together, we suggest that the idea of selective cortical routing via alpha oscillations can be extended from sensory cortices to the frontoparietal attention network.

scholarly journals DMT alters cortical travelling waves

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Andrea Alamia ◽  
Christopher Timmermann ◽  
David J Nutt ◽  
Rufin VanRullen ◽  
Robin L Carhart-Harris
Keyword(s):  
Visual Stimulation ◽  
Travelling Waves ◽  
Cortical Activation ◽  
Altered States ◽  
Altered State ◽  
Top Down ◽  
Bottom Up ◽  
Eyes Closed ◽  
Psychedelic Drugs ◽  
Spatio Temporal

Psychedelic drugs are potent modulators of conscious states and therefore powerful tools for investigating their neurobiology. N,N, Dimethyltryptamine (DMT) can rapidly induce an extremely immersive state of consciousness characterized by vivid and elaborate visual imagery. Here, we investigated the electrophysiological correlates of the DMT-induced altered state from a pool of participants receiving DMT and (separately) placebo (saline) while instructed to keep their eyes closed. Consistent with our hypotheses, results revealed a spatio-temporal pattern of cortical activation (i.e. travelling waves) similar to that elicited by visual stimulation. Moreover, the typical top-down alpha-band rhythms of closed-eyes rest were significantly decreased, while the bottom-up forward wave was significantly increased. These results support a recent model proposing that psychedelics reduce the ‘precision-weighting of priors’, thus altering the balance of top-down versus bottom-up information passing. The robust hypothesis-confirming nature of these findings imply the discovery of an important mechanistic principle underpinning psychedelic-induced altered states.

Function-Related Gamma Oscillations and Conscious Perception

2010 ◽  
Vol 24 (2) ◽  
pp. 102-106 ◽  
Author(s):  
Simone Carozzo ◽  
Sergio Garbarino ◽  
Sebastiano Serra ◽  
Walter G. Sannita
Keyword(s):  
Gamma Oscillations ◽  
Inhibitory Interneuron ◽  
Gamma Band ◽  
Gamma Activity ◽  
Conscious Perception ◽  
Visuomotor Integration ◽  
Neural Processes ◽  
Frequency Domain Techniques ◽  
And Function ◽  
Brain Processing

Frequency-domain techniques describe oscillations as a fundamental behavior of neurons and brain signals. Oscillations synchronize over large portions of cortex and mediate in the spatiotemporally coherent activation of neuron assemblies required for brain processing to occur. Oscillations in the gamma band (~20.0–80.0 Hz) originate from the tonic excitation of inhibitory interneuron networks, sustain rhythms and frequency constancy, and are enhanced during sensory, motor, or “cognitive” processes through frequency-dependent and function-related neuronal synchronization. Experimental work indicates a role of gamma activity in conscious perception. Further investigation is, nevertheless, warranted as gamma-band synchronization plays a functional role in low-level phase coding as well as in high-complexity neural processes related to perception, such as selective attention, focused arousal, multistable or ambiguous perceptive conditions, visuomotor integration, and associative learning.

Time-frequency analysis of target detection reveals an early interface between bottom-up and top-down processes in the gamma-band

NeuroImage ◽  
2006 ◽  
Vol 29 (4) ◽  
pp. 1106-1116 ◽  
Author(s):  
Niko A. Busch ◽  
Jeanette Schadow ◽  
Ingo Fründ ◽  
Christoph S. Herrmann
Keyword(s):  
Target Detection ◽  
Frequency Analysis ◽  
Gamma Band ◽  
Top Down ◽  
Bottom Up ◽  
Time Frequency Analysis ◽  
Time Frequency

scholarly journals Impaired conscious access and abnormal attentional amplification in schizophrenia

2017 ◽  
Author(s):  
L Berkovitch ◽  
A Del Cul ◽  
M Maheu ◽  
S Dehaene
Keyword(s):  
Brain Activity ◽  
Event Related Potentials ◽  
Focused Attention ◽  
Conscious Perception ◽  
Top Down ◽  
Bottom Up ◽  
Essentially Normal ◽  
Related Potentials ◽  
P3 Component ◽  
The Brain

AbstractPrevious research suggests that the conscious perception of a masked stimulus is impaired in schizophrenia, while unconscious bottom-up processing of the same stimulus, as assessed by subliminal priming, can be preserved. Here, we test this postulated dissociation between intact bottom-up and impaired top-down processing and evaluate its brain mechanisms using high-density recordings of event-related potentials. Sixteen patients with schizophrenia and sixteen controls were exposed to peripheral digits with various degrees of visibility, under conditions of either focused attention or distraction by another task. In the distraction condition, the brain activity evoked by masked digits was drastically reduced in both groups, but early bottom-up visual activation could still be detected and did not differ between patients and controls. By contrast, under focused top-down attention, a major impairment was observed: in patients, contrary to controls, the late non-linear ignition associated with the P3 component was reduced. Interestingly, the patients showed an essentially normal attentional amplification of the PI and N2 components. These results suggest that some but not all top-down attentional amplification processes are impaired in schizophrenia, while bottom-up processing seems to be preserved.

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