scholarly journals The Rapid Extraction of Gist—Early Neural Correlates of High-level Visual Processing

2012 ◽  
Vol 24 (2) ◽  
pp. 521-529 ◽  
Author(s):  
Frank Oppermann ◽  
Uwe Hassler ◽  
Jörg D. Jescheniak ◽  
Thomas Gruber
Keyword(s):  
Visual Processing ◽  
Time Course ◽  
Occipital Cortex ◽  
Stimulus Onset ◽  
Gamma Band ◽  
Oscillatory Activity ◽  
Rapid Extraction ◽  
The Right ◽  
High Level ◽  
Individual Objects

The human cognitive system is highly efficient in extracting information from our visual environment. This efficiency is based on acquired knowledge that guides our attention toward relevant events and promotes the recognition of individual objects as they appear in visual scenes. The experience-based representation of such knowledge contains not only information about the individual objects but also about relations between them, such as the typical context in which individual objects co-occur. The present EEG study aimed at exploring the availability of such relational knowledge in the time course of visual scene processing, using oscillatory evoked gamma-band responses as a neural correlate for a currently activated cortical stimulus representation. Participants decided whether two simultaneously presented objects were conceptually coherent (e.g., mouse–cheese) or not (e.g., crown–mushroom). We obtained increased evoked gamma-band responses for coherent scenes compared with incoherent scenes beginning as early as 70 msec after stimulus onset within a distributed cortical network, including the right temporal, the right frontal, and the bilateral occipital cortex. This finding provides empirical evidence for the functional importance of evoked oscillatory activity in high-level vision beyond the visual cortex and, thus, gives new insights into the functional relevance of neuronal interactions. It also indicates the very early availability of experience-based knowledge that might be regarded as a fundamental mechanism for the rapid extraction of the gist of a scene.

Time-course of Posterior Parietal and Occipital Cortex Contribution to Sound Localization

2008 ◽  
Vol 20 (8) ◽  
pp. 1454-1463 ◽  
Author(s):  
Olivier Collignon ◽  
Marco Davare ◽  
Anne G. De Volder ◽  
Colline Poirier ◽  
Etienne Olivier ◽  
...  
Keyword(s):  
Time Course ◽  
Posterior Parietal Cortex ◽  
Space Perception ◽  
Occipital Cortex ◽  
Stimulus Onset ◽  
Spatial Processing ◽  
Auditory Space ◽  
Posterior Parietal ◽  
The Right ◽  
Precise Time

It has been suggested that both the posterior parietal cortex (PPC) and the extrastriate occipital cortex (OC) participate in the spatial processing of sounds. However, the precise time-course of their contribution remains unknown, which is of particular interest, considering that it could give new insights into the mechanisms underlying auditory space perception. To address this issue, we have used event-related transcranial magnetic stimulation (TMS) to induce virtual lesions of either the right PPC or right OC at different delays in subjects performing a sound lateralization task. Our results confirmed that these two areas participate in the spatial processing of sounds. More precisely, we found that TMS applied over the right OC 50 msec after the stimulus onset significantly impaired the localization of sounds presented either to the right or to the left side. Moreover, right PPC virtual lesions induced 100 and 150 msec after sound presentation led to a rightward bias for stimuli delivered on the center and on the left side, reproducing transiently the deficits commonly observed in hemineglect patients. The finding that the right OC is involved in sound processing before the right PPC suggests that the OC exerts a feedforward influence on the PPC during auditory spatial processing.

Interhemispheric EEG asymmetries during unilateral bright-light exposure and subsequent sleep in humans

2008 ◽  
Vol 294 (3) ◽  
pp. R1053-R1060 ◽  
Author(s):  
Christian Cajochen ◽  
Rosalba Di Biase ◽  
Makoto Imai
Keyword(s):  
Visual Cortex ◽  
Time Course ◽  
Visual Stimulation ◽  
Light Exposure ◽  
Bright Light ◽  
Occipital Cortex ◽  
Alpha Activity ◽  
Hemispheric Dominance ◽  
Eeg Activity ◽  
The Right

We tested whether evening exposure to unilateral photic stimulation has repercussions on interhemispheric EEG asymmetries during wakefulness and later sleep. Because light exerts an alerting response in humans, which correlates with a decrease in waking EEG theta/alpha-activity and a reduction in sleep EEG delta activity, we hypothesized that EEG activity in these frequency bands show interhemispheric asymmetries after unilateral bright light (1,500 lux) exposure. A 2-h hemi-field light exposure acutely suppressed occipital EEG alpha activity in the ipsilateral hemisphere activated by light. Subjects felt more alert during bright light than dim light, an effect that was significantly more pronounced during activation of the right than the left visual cortex. During subsequent sleep, occipital EEG activity in the delta and theta range was significantly reduced after activation of the right visual cortex but not after stimulation of the left visual cortex. Furthermore, hemivisual field light exposure was able to shift the left predominance in occipital spindle EEG activity toward the stimulated hemisphere. Time course analysis revealed that this spindle shift remained significant during the first two sleep cycles. Our results reflect rather a hemispheric asymmetry in the alerting action of light than a use-dependent recovery function of sleep in response to the visual stimulation during prior waking. However, the observed shift in the spindle hemispheric dominance in the occipital cortex may still represent subtle local use-dependent recovery functions during sleep in a frequency range different from the delta range.

Neuronal Synchronization and Selective Color Processing in the Human Brain

2004 ◽  
Vol 16 (3) ◽  
pp. 503-522 ◽  
Author(s):  
Matthias M. Müller ◽  
Andreas Keil
Keyword(s):  
Large Scale ◽  
Time Course ◽  
Time Window ◽  
Brain Activity ◽  
Stimulus Onset ◽  
Gamma Band ◽  
Event Related Potential ◽  
Alpha Band ◽  
Color Processing ◽  
The Time Domain

In the present study, subjects selectively attended to the color of checkerboards in a feature-based attention paradigm. Induced gamma band responses (GBRs), the induced alpha band, and the event-related potential (ERP) were analyzed to uncover neuronal dynamics during selective feature processing. Replicating previous ERP findings, the selection negativity (SN) with a latency of about 160 msec was extracted. Furthermore, and similarly to previous EEG studies, a gamma band peak in a time window between 290 and 380 msec was found. This peak had its major energy in the 55to 70-Hz range and was significantly larger for the attended color. Contrary to previous human induced gamma band studies, a much earlier 40to 50-Hz peak in a time window between 160 and 220 msec after stimulus onset and, thus, concurrently to the SN was prominent with significantly more energy for attended as opposed to unattended color. The induced alpha band (9.8–11.7 Hz), on the other hand, exhibited a marked suppression for attended color in a time window between 450 and 600 msec after stimulus onset. A comparison of the time course of the 40to 50-Hz and 55to 70-Hz induced GBR, the induced alpha band, and the ERP revealed temporal coincidences for changes in the morphology of these brain responses. Despite these similarities in the time domain, the cortical source configuration was found to discriminate between induced GBRs and the SN. Our results suggest that large-scale synchronous high-frequency brain activity as measured in the human GBR play a specific role in attentive processing of stimulus features.

scholarly journals Monitoring the haemodynamic response to visual stimulation in glaucoma patients

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
R. Re ◽  
D. Messenio ◽  
G. Marano ◽  
L. Spinelli ◽  
I. Pirovano ◽  
...  
Keyword(s):  
Time Course ◽  
Near Infrared ◽  
Visual Stimulation ◽  
Open Angle Glaucoma ◽  
Occipital Cortex ◽  
Stimulus Onset ◽  
Ease Of Use ◽  
Haemodynamic Response ◽  
Functional Near Infrared Spectroscopy ◽  
Domain Functional

AbstractIn this paper, we used time-domain functional near infrared spectroscopy (TD-fNIRS) to evaluate the haemodynamic response function (HRF) in the occipital cortex following visual stimulation in glaucomatous eyes as compared to healthy eyes. A total of 98 subjects were enrolled in the study and clinically classified as healthy subjects, glaucoma patients (primary open-angle glaucoma) and mixed subjects (i.e. with a different classification for the two eyes). After quality check data were used from HRF of 73 healthy and 62 glaucomatous eyes. The amplitudes of the oxygenated and deoxygenated haemoglobin concentrations, together with their latencies with respect to the stimulus onset, were estimated by fitting their time course with a canonical HRF. Statistical analysis showed that the amplitudes of both haemodynamic parameters show a significant association with the pathology and a significant discriminating ability, while no significant result was found for latencies. Overall, our findings together with the ease of use and noninvasiveness of TD-NIRS, make this technique a promising candidate as a supporting tool for a better evaluation of the glaucoma pathology.

scholarly journals Spatial attention follows category-based attention during naturalistic visual search: evidence from MEG decoding

2018 ◽  
Author(s):  
Elisa Battistoni ◽  
Daniel Kaiser ◽  
Clayton Hickey ◽  
Marius V. Peelen
Keyword(s):  
Visual Search ◽  
Time Course ◽  
Target Location ◽  
Daily Life ◽  
Stimulus Onset ◽  
Target Presence ◽  
Object Categories ◽  
Search Experiment ◽  
Category Search ◽  
High Level

AbstractIn daily life, attention is often directed to high-level object attributes, such as when we look out for cars before crossing a road. Previous work used MEG decoding to investigate the influence of such category-based attention on the time course of object category representations. Attended object categories were more strongly represented than unattended categories from 180 ms after scene onset. In the present study, we used a similar approach to determine when, relative to this category-level modulation, attention is spatially focused on the target. Participants completed two tasks. In the first, they detected cars and people at varying locations in photographs of real-world scenes. In the second, they detected a cross that appeared at salient locations in an array of lines. Multivariate classifiers were trained on data of the artificial salience experiment and tested on data of the naturalistic visual search experiment. Results showed that the location of both target and distracter objects could be accurately decoded shortly after scene onset (50 ms). However, the emergence of spatial attentional selection - reflected in better decoding of target location than distracter location - emerged only later in time (240 ms). Target presence itself (irrespective of location and category) could be decoded from 180 ms after stimulus onset. Combined with earlier work, these results indicate that naturalistic category search operates through an initial spatially-global modulation of category processing that then guides attention to the location of the target.

TMS of the right angular gyrus modulates priming of pop-out in visual search: combined TMS-ERP evidence

2011 ◽  
Vol 106 (6) ◽  
pp. 3001-3009 ◽  
Author(s):  
Paul C. J. Taylor ◽  
Neil G. Muggleton ◽  
Roger Kalla ◽  
Vincent Walsh ◽  
Martin Eimer
Keyword(s):  
Visual Search ◽  
Visual Processing ◽  
Critical Role ◽  
Stimulus Onset ◽  
Event Related Potential ◽  
Angular Gyrus ◽  
Previous Trial ◽  
Search Array ◽  
Feature Target ◽  
The Right

During priming of pop-out, performance at discriminating a pop-out feature target in visual search is affected by whether the target on the previous trial was defined by the same feature as on the upcoming trial. Recent studies suggest that priming of pop-out relies on attentional processes. With the use of simultaneous, combined transcranial magnetic stimulation and event-related potential recording (TMS-ERP), we tested for any critical role of the right angular gyrus (rANG) and left and right frontal eye fields (FEFs)—key attentional sites—in modulating both performance and the ERPs evoked by such visual events. Intertrial TMS trains were applied while participants discriminated the orientation of a color pop-out element in a visual search array. rANG TMS disrupted priming of pop-out, reducing reaction time costs on switch trials and speeding responses when the color of the pop-out target switched. rANG TMS caused a negativity in the ERP elicited in response to the visual stimulus array, starting 210 ms after stimulus onset. Both behavioral and ERP effects were apparent only after rANG TMS, on switch trials, and when the target in the visual search array was presented in the left visual field, with no effects after left or right FEF TMS. These results provide evidence for an attentional reorienting mechanism, which originates in the rANG and is modulated by the implicit memory of the previous trial. The rANG plays a causal role on switch trials during priming of pop-out by interacting with visual processing, particularly in the ipsilateral hemisphere representing the contralateral hemifield.

scholarly journals Contextual and spatial associations between objects interactively modulate visual processing

2020 ◽  
Author(s):  
Genevieve L. Quek ◽  
Marius V. Peelen
Keyword(s):  
Visual Processing ◽  
Perceptual Grouping ◽  
Spatial Configuration ◽  
Stimulus Onset ◽  
Object Identity ◽  
Identity Integration ◽  
Object Processing ◽  
Spatial Associations ◽  
Spatial Configurations ◽  
High Level

AbstractMuch of what we know about object recognition arises from the study of isolated objects. In the real world, however, we commonly encounter groups of contextually-associated objects (e.g., teacup, saucer), often in stereotypical spatial configurations (e.g., teacup above saucer). Here we used EEG to test whether identity-based associations between objects (e.g., teacup-saucer vs. teacup-stapler) are encoded jointly with their typical relative positioning (e.g., teacup above saucer vs. below saucer). Observers viewed a 2.5Hz image stream of contextually-associated object pairs intermixed with non-associated pairs as every fourth image. The differential response to non-associated pairs (measurable at 0.625Hz in 28/37 participants), served as an index of contextual integration, reflecting the association of object identities in each pair. Over right occipitotemporal sites, this signal was larger for typically-positioned object streams, indicating that spatial configuration facilitated the extraction of the objects’ contextual association. This high-level influence of spatial configuration on object identity integration arose ∼320ms post stimulus onset, with lower-level perceptual grouping (shared with inverted displays) present at ∼130ms. These results demonstrate that contextual and spatial associations between objects interactively influence object processing. We interpret these findings as reflecting the high-level perceptual grouping of objects that frequently co-occur in highly stereotyped relative positions.

Detection of a Weak Somatosensory Stimulus: Role of the Prestimulus Mu Rhythm and Its Top–Down Modulation

2010 ◽  
Vol 22 (2) ◽  
pp. 307-322 ◽  
Author(s):  
Yan Zhang ◽  
Mingzhou Ding
Keyword(s):  
Field Potential ◽  
Electrical Stimulus ◽  
Stimulus Onset ◽  
Oscillatory Activity ◽  
Somatosensory Processing ◽  
Causality Analysis ◽  
Mu Rhythm ◽  
Potential Oscillations ◽  
Scalp Electroencephalogram ◽  
The Right

The ongoing neural activity in human primary somatosensory cortex (SI) is characterized by field potential oscillations in the 7–13 Hz range known as the mu rhythm. Recent work has shown that the magnitude of the mu oscillation immediately preceding the onset of a weak stimulus has a significant impact on its detection. The neural mechanisms mediating this impact remain not well understood. In particular, whether and how somatosensory mu rhythm is modulated by executive areas prior to stimulus onset for improved behavioral performance has not been investigated. We addressed these issues by recording 128-channel scalp electroencephalogram from normal volunteers performing a somatosensory perception experiment in which they reported the detection of a near-threshold electrical stimulus (∼50% detection rate) delivered to the right index finger. Three results were found. First, consistent with numerous previous reports, the N1 component (∼140 msec) of the somatosensory-evoked potential was significantly enhanced for perceived stimulus compared to unperceived stimulus. Second, the prestimulus mu power and the evoked N1 amplitude exhibited an inverted-U relationship, suggesting that an intermediate level of prestimulus mu oscillatory activity is conducive to stimulus processing and perception. Third, a Granger causality analysis revealed that the prestimulus causal influence in the mu band from prefrontal cortex to SI was significantly higher for perceived stimulus than for unperceived stimulus, indicating that frontal executive structures, via ongoing mu oscillations, exert cognitive control over posterior sensory cortices to facilitate somatosensory processing.

scholarly journals Hemispheric differences in altered reactivity of brain oscillations at rest after posterior lesions

2021 ◽  
Author(s):  
Jessica Gallina ◽  
Mattia Pietrelli ◽  
Marco Zanon ◽  
Caterina Bertini
Keyword(s):  
Visual System ◽  
Resting State ◽  
Visual Processing ◽  
Right Hemisphere ◽  
Oscillatory Activity ◽  
Alpha Oscillations ◽  
Eyes Closed ◽  
Eyes Open ◽  
The Right ◽  
Theta Range

AbstractA variety of evidence supports the dominance of the right hemisphere in perceptual and visuo-spatial processing. Although growing evidence shows a strong link between alpha oscillations and the functionality of the visual system, asymmetries in alpha oscillatory patterns still need to be investigated. Converging findings indicate that the typical alpha desynchronization occurring in the transition from the eyes-closed to the eyes-open resting state might represent an index of reactivity of the visual system. Thus, investigating hemispheric asymmetries in EEG reactivity at the opening of the eyes in brain-lesioned patients may shed light on the contribution of specific cortical sites and each hemisphere in regulating the oscillatory patterns reflecting the functionality of the visual system. To this aim, EEG signal was recorded during eyes-closed and eyes-open resting state in hemianopic patients with posterior left or right lesions, patients without hemianopia with anterior lesions and healthy controls. Hemianopics with both left and right posterior lesions showed a reduced alpha reactivity at the opening of the eyes, suggesting that posterior cortices have a pivotal role in the functionality of alpha oscillations. However, right-lesioned hemianopics showed a greater dysfunction, demonstrated by a reactivity reduction more distributed over the scalp, compared to left-lesioned hemianopics. Moreover, they also revealed impaired reactivity in the theta range. This favors the hypothesis of a specialized role of the right hemisphere in orchestrating oscillatory patterns, both coordinating widespread alpha oscillatory activity and organizing focal processing in the theta range, to support visual processing at the opening of the eyes.

Timing Spatial Conflict within the Parietal Cortex: A TMS Study

2011 ◽  
Vol 23 (12) ◽  
pp. 3998-4007 ◽  
Author(s):  
Sami Schiff ◽  
Lara Bardi ◽  
Demis Basso ◽  
Daniela Mapelli
Keyword(s):  
Parietal Cortex ◽  
Visual Information ◽  
Motor Response ◽  
Time Course ◽  
Posterior Parietal Cortex ◽  
Simon Task ◽  
Single Pulse ◽  
Stimulus Onset ◽  
Parietal Lobes ◽  
The Right

Orienting and motor attention are known to recruit different regions within right and left parietal lobes. However, the time course and the role played by these modules when visual information competes for different motor response are still unknown. To deal with this issue, single-pulse TMS was applied over the angular (AG) and the supramarginal (SMG) gyri of both hemispheres at several time intervals during the execution of a Simon task. Suppression of the conflict between stimulus and response positions (i.e., the Simon effect) was found when TMS pulse was applied 130 msec after stimulus onset over the right AG and after 160 msec when applied over the left AG and SMG. Interestingly, only stimulation of the left SMG suppressed the asymmetry in conflict magnitude between left- and right-hand responses, usually observed in the Simon task. The present data show that orienting attention and motor attention processes are temporally, functionally, and spatially separated in the posterior parietal cortex, and both contribute to prime motor response during spatial conflict.

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