scholarly journals Audio-visual synchrony and spatial attention enhance processing of dynamic visual stimulation independently and in parallel: a frequency-tagging study

2017 ◽  
Author(s):  
Amra Covic ◽  
Christian Keitel ◽  
Emanuele Porcu ◽  
Erich Schröger ◽  
Matthias M Müller
Keyword(s):  
Spatial Attention ◽  
Visual Stimulus ◽  
Visual Processing ◽  
Visual Stimulation ◽  
Visual Fields ◽  
Tone Presentation ◽  
Neural Processing ◽  
Brain Responses ◽  
Neural Processes ◽  
Steady State Responses

ABSTRACTThe neural processing of a visual stimulus can be facilitated by attending to its position or by a co-occurring auditory tone. Using frequency-tagging we investigated whether facilitation by spatial attention and audio-visual synchrony rely on similar neural processes. Participants attended to one of two flickering Gabor patches (14.17 and 17 Hz) located in opposite lower visual fields. Gabor patches further “pulsed” (i.e. showed smooth spatial frequency variations) at distinct rates (3.14 and 3.63 Hz). Frequency-modulating an auditory stimulus at the pulse-rate of one of the visual stimuli established audio-visual synchrony. Flicker and pulsed stimulation elicited stimulus-locked rhythmic electrophysiological brain responses that allowed tracking the neural processing of simultaneously presented stimuli. These steady-state responses (SSRs) were quantified in the spectral domain to examine visual stimulus processing under conditions of synchronous vs. asynchronous tone presentation and when respective stimulus positions were attended vs. unattended. Strikingly, unique patterns of effects on pulse- and flicker driven SSRs indicated that spatial attention and audiovisual synchrony facilitated early visual processing in parallel and via different cortical processes. We found attention effects to resemble the classical top-down gain effect facilitating both, flicker and pulse-driven SSRs. Audio-visual synchrony, in turn, only amplified synchrony-producing stimulus aspects (i.e. pulse-driven SSRs) possibly highlighting the role of temporally co-occurring sights and sounds in bottom-up multisensory integration.

scholarly journals Stimulus-driven brain rhythms within the alpha band: The attentional-modulation conundrum

2018 ◽  
Author(s):  
Christian Keitel ◽  
Anne Keitel ◽  
Christopher SY Benwell ◽  
Christoph Daube ◽  
Gregor Thut ◽  
...  
Keyword(s):  
Spatial Attention ◽  
Visual Processing ◽  
Visual Stimulation ◽  
Brain Activity ◽  
Gain Control ◽  
Sensory Stimulation ◽  
Alpha Band ◽  
Visual Evoked Response ◽  
Brain Rhythms ◽  
Inhibitory Function

Two largely independent research lines use rhythmic sensory stimulation to study visual processing. Despite the use of strikingly similar experimental paradigms, they differ crucially in their notion of the stimulus-driven periodic brain responses: One regards them mostly as synchronised (entrained) intrinsic brain rhythms; the other assumes they are predominantly evoked responses (classically termed steady-state responses, or SSRs) that add to the ongoing brain activity. This conceptual difference can produce contradictory predictions about, and interpretations of, experimental outcomes. The effect of spatial attention on brain rhythms in the alpha-band (8-13 Hz) is one such instance: alpha-range SSRs have typically been found to increase in power when participants focus their spatial attention on laterally presented stimuli, in line with a gain control of the visual evoked response. In nearly identical experiments, retinotopic decreases in entrained alpha-band power have been reported, in line with the inhibitory function of intrinsic alpha. Here we reconcile these contradictory findings by showing that they result from a small but far-reaching difference between two common approaches to EEG spectral decomposition. In a new analysis of previously published EEG data, recorded during bilateral rhythmic visual stimulation, we find the typical SSR gain effect when emphasising stimulus-locked neural activity and the typical retinotopic alpha suppression when focusing on ongoing rhythms. These opposite but parallel effects suggest that spatial attention may bias the neural processing of dynamic visual stimulation via two complementary neural mechanisms.

Spatial and Cross-Modal Attention Alter Responses to Unattended Sensory Information in Early Visual and Auditory Human Cortex

2007 ◽  
Vol 98 (4) ◽  
pp. 2399-2413 ◽  
Author(s):  
Vivian M. Ciaramitaro ◽  
Giedrius T. Buračas ◽  
Geoffrey M. Boynton
Keyword(s):  
Spatial Attention ◽  
Auditory Stimulus ◽  
Visual Stimulus ◽  
Visual Information ◽  
Visual Stimuli ◽  
Sensory Information ◽  
Visual Area ◽  
Auditory Stimuli ◽  
Auditory Information ◽  
Brain Responses

Attending to a visual or auditory stimulus often requires irrelevant information to be filtered out, both within the modality attended and in other modalities. For example, attentively listening to a phone conversation can diminish our ability to detect visual events. We used functional magnetic resonance imaging (fMRI) to examine brain responses to visual and auditory stimuli while subjects attended visual or auditory information. Although early cortical areas are traditionally considered unimodal, we found that brain responses to the same ignored information depended on the modality attended. In early visual area V1, responses to ignored visual stimuli were weaker when attending to another visual stimulus, compared with attending to an auditory stimulus. The opposite was true in more central visual area MT+, where responses to ignored visual stimuli were weaker when attending to an auditory stimulus. Furthermore, fMRI responses to the same ignored visual information depended on the location of the auditory stimulus, with stronger responses when the attended auditory stimulus shared the same side of space as the ignored visual stimulus. In early auditory cortex, responses to ignored auditory stimuli were weaker when attending a visual stimulus. A simple parameterization of our data can describe the effects of redirecting attention across space within the same modality (spatial attention) or across modalities (cross-modal attention), and the influence of spatial attention across modalities (cross-modal spatial attention). Our results suggest that the representation of unattended information depends on whether attention is directed to another stimulus in the same modality or the same region of space.

scholarly journals Spatial attention enhances cortical tracking of quasi-rhythmic visual stimuli

2019 ◽  
Author(s):  
D. Tabarelli ◽  
C. Keitel ◽  
J. Gross ◽  
D. Baldauf
Keyword(s):  
Spatial Attention ◽  
Dynamic Range ◽  
Temporal Dynamics ◽  
Visual Stimulation ◽  
Stimulus Frequency ◽  
Neural Representation ◽  
Neural Processing ◽  
Temporal Precision ◽  
Dynamic Stimuli ◽  
Visual Cortices

AbstractSuccessfully interpreting and navigating our natural visual environment requires us to track its dynamics constantly. Additionally, we focus our attention on behaviorally relevant stimuli to enhance their neural processing. Little is known, however, about how sustained attention affects the ongoing tracking of stimuli with rich natural temporal dynamics. Here, we used MRI-informed source reconstructions of magnetoencephalography (MEG) data to map to what extent various cortical areas track concurrent continuous quasi-rhythmic visual stimulation. Further, we tested how top-down visuo-spatial attention influences this tracking process. Our bilaterally presented quasi-rhythmic stimuli covered a dynamic range of 4 – 20Hz, subdivided into three distinct bands. As an experimental control, we also included strictly rhythmic stimulation (10 vs 12 Hz). Using a spectral measure of brain-stimulus coupling, we were able to track the neural processing of left vs. right stimuli independently, even while fluctuating within the same frequency range. The fidelity of neural tracking depended on the stimulation frequencies, decreasing for higher frequency bands. Both attended and non-attended stimuli were tracked beyond early visual cortices, in ventral and dorsal streams depending on the stimulus frequency. In general, tracking improved with the deployment of visuo-spatial attention to the stimulus location. Our results provide new insights into how human visual cortices process concurrent dynamic stimuli and provide a potential mechanism – namely increasing the temporal precision of tracking – for boosting the neural representation of attended input.

scholarly journals A neural signature of automatic lexical access in bilinguals

2021 ◽  
Author(s):  
Sabrina Aristei ◽  
Aliette Lochy ◽  
Bruno Rossion ◽  
Christine Schiltz
Keyword(s):  
Visual Processing ◽  
Word Processing ◽  
Visual Stimulation ◽  
Temporal Cortex ◽  
Visual Responses ◽  
Beneficial Effects ◽  
Brain Responses ◽  
Neural Signature ◽  
Language Exposure ◽  
Cross Language

Bilingualism is often associated with beneficial effects on cognitive control and top-down processes. The present study aimed at bypassing these processes to assess automatic visual word recognition in bilinguals. Using fast periodic visual stimulation, we recorded frequency-tagged word-selective EEG responses in French monolinguals and late bilinguals (German native, French as second language). Words were presented centrally within rapid (10 Hz) sequences of letter strings varying in word-likeness, i.e., consonant strings, non-words, pseudo-words, while participants performed an orthogonal task. Automatic word-selective brain responses in the occipito-temporal cortex arose almost exclusively for the languages mastered by participants: two in bilinguals vs. one in monolinguals. Importantly, the amplitude of bilinguals responses to words within consonant strings were unaffected by the native vs. late-learnt status of the language. Furthermore, for all and only known languages, word-selective responses were reduced by embedding them in pseudo-words relative to non-words, both derived from the same language as the words. This word-likeness effect highlights the lexical nature of the recorded brain visual responses. A cross-language word-likeness effect was observed only in bilinguals and only with pseudo-words derived from the native language, indicating an experience-based tuning to language. Taken together these findings indicate that the amount of exposure to a language determines the engagement of neural resources devoted to word processing in the occipito-temporal visual cortex. We conclude that automatic lexical coding occurs at early visual processing in bilinguals and monolinguals alike, and that language exposure determines the competition strength of a language.

Dissociating Effects of Movement Preparation and Spatial Attention on Visual Processing: Evidence from Event-Related Potentials

2014 ◽  
Vol 27 (2) ◽  
pp. 139-160 ◽  
Author(s):  
Pia Ley ◽  
Brigitte Röder
Keyword(s):  
Spatial Attention ◽  
Visual Stimulus ◽  
Visual Processing ◽  
Visual Stimuli ◽  
Event Related Potentials ◽  
Movement Preparation ◽  
Visual Spatial Attention ◽  
Visual Spatial ◽  
Sensory Motor ◽  
Related Potentials

The present study investigated whether effects of movement preparation and visual spatial attention on visual processing can be dissociated. Movement preparation and visual spatial attention were manipulated orthogonally in a dual-task design. Ten participants covertly prepared unimanual lateral arm movements to one hemifield, while attending to visual stimuli presented either in the same or in the hemifield opposite to the movement goal. Event-related potentials to task-irrelevant visual stimuli were analysed. Both joint and distinct modulations of visual ERPs by visual spatial attention and movement preparation were observed: The latencies of all analysed peaks (P1, N1, P2) were shorter for matching (in terms of direction of attention and movement) versus non-matching sensory–motor conditions. The P1 amplitude, as well, depended on the sensory–motor matching: The P1 was larger for non-matching compared to matching conditions. By contrast, the N1 amplitude showed additive effects of sensory attention and movement preparation: with attention and movement preparation directed towards the visual stimulus the N1 was largest, with both directed opposite to the stimulus the N1 was smallest. P2 amplitudes, instead, were only modulated by sensory attention. The present data show that movement preparation and sensory spatial attention are tightly linked and interrelated, showing joint modulations throughout stimulus processing. At the same time, however, our data argue against the idea of identity of the two systems. Instead, sensory spatial attention and movement preparation seem to be processed at least partially independently, though still exerting a combined influence on visual stimulus processing.

Visual Responses

2017 ◽  
pp. 214-226
Author(s):  
Riitta Hari ◽  
Aina Puce
Keyword(s):  
Visual Stimulus ◽  
Visual Angle ◽  
Visual Stimulation ◽  
Evoked Responses ◽  
Visual Responses ◽  
Visual Evoked Responses ◽  
Steady State Responses ◽  
Entire Visual Field ◽  
State Responses ◽  
Light Flashes

This chapter introduces visual evoked responses. Transient VEPs are maximal across the posterior scalp and consist of three main deflections—N75, P100, and N135. Magnetic VEFs also show a prominent occipital response peaking at around 100 ms. Visual stimulation can include light flashes, pattern onset/offsets, pattern reversals and natural images. The extent and eccentricity of the visual stimulus can selectively encompass foveal or extrafoveal regions, or include quadrants, hemifield or the entire visual field. Stimulus attributes such as visual angle, spatial frequency, luminance and contrast greatly affect VEF and VEP amplitudes and latencies. Selective responses in the dorsal and ventral visual streams can be elicited with carefully chosen stimuli. Steady-state responses to periodically varying visual stimuli can be used to frequency-tag different aspects of the visual stimulus.

Neural Processes Involved in Directing Attention

1989 ◽  
Vol 1 (3) ◽  
pp. 223-237 ◽  
Author(s):  
M. Russell Harter ◽  
Steven L. Miller ◽  
Natalie J. Price ◽  
Margaret E. LaLonde ◽  
Alvin L. Keyes
Keyword(s):  
Visual Field ◽  
Spatial Attention ◽  
Cortical Excitability ◽  
Visual Fields ◽  
Event Related Potential ◽  
Right Visual Field ◽  
Hemispheric Differences ◽  
Visual Spatial ◽  
Neural Processes ◽  
Directing Attention

Neural processes associated with two aspects of visual-spatial attention were investigated with event-related potential (ERPs): those that direct spatial attention to a given point in space and those that modulate the processing of sensory input after attention has been directed. The subjects were 6- to 9-year-old children (51 boys and 35 girls). An arrow cue directed attention from the central to peripheral visual field; targets were then flashed in the attended or ignored visual field 600 msec after the cue. The directing of attention to the left vs. right visual field was associated with hemispheric differences in slow potentials prior to the presentation of the targets. The earliest potential, which started about 200 msec after the cue and was negative over the hemisphere contralateral to the direction of attention, was greatest over the parietal area and appeared to reflect processes directing attention per se. The last potential, which peaked 60 msec after the target and was positive over the hemisphere contralateral to the direction of attention, was greatest over the occipital-parietal region. It appeared to reflect the modulation of cortical excitability in the regions receiving input from the relevant and irrelevant visual fields. The effects of spatial attention on P1, N1, and P3 ERP components following the targets replicated previous results. Boys appeared more aroused (as indicated by CNVs) and reflected faster and greater selective processing (as indicated by reaction time, and N1-P1 latency and amplitude) than girls.

scholarly journals Linking the Rapid Cascade of Visuo-Attentional Processes to Successful Memory Encoding

2020 ◽  
Author(s):  
B R Geib ◽  
R Cabeza ◽  
M G Woldorff
Keyword(s):  
Visual Processing ◽  
Memory Retrieval ◽  
Current Knowledge ◽  
High Temporal Resolution ◽  
Alpha Power ◽  
Attentional Orienting ◽  
Memory Encoding ◽  
Attentional Processes ◽  
Neural Processes ◽  
Dm Effect

Abstract While it is broadly accepted that attention modulates memory, the contribution of specific rapid attentional processes to successful encoding is largely unknown. To investigate this issue, we leveraged the high temporal resolution of electroencephalographic recordings to directly link a cascade of visuo-attentional neural processes to successful encoding: namely (1) the N2pc (peaking ~200 ms), which reflects stimulus-specific attentional orienting and allocation, (2) the sustained posterior-contralateral negativity (post-N2pc), which has been associated with sustained visual processing, (3) the contralateral reduction in oscillatory alpha power (contralateral reduction in alpha > 200 ms), which has also been independently related to attentionally sustained visual processing. Each of these visuo-attentional processes was robustly predictive of successful encoding, and, moreover, each enhanced memory independently of the classic, longer-latency, conceptually related, difference-due-to memory (Dm) effect. Early latency midfrontal theta power also promoted successful encoding, with at least part of this influence being mediated by the later latency Dm effect. These findings markedly expand current knowledge by helping to elucidate the intimate relationship between attentional modulations of perceptual processing and effective encoding for later memory retrieval.

scholarly journals Visual attention spreads broadly but selects information locally

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Satoshi Shioiri ◽  
Hajime Honjyo ◽  
Yoshiyuki Kashiwase ◽  
Kazumichi Matsumiya ◽  
Ichiro Kuriki
Keyword(s):  
Visual Attention ◽  
Spatial Attention ◽  
Visual Processing ◽  
Early Stage ◽  
Event Related Potential ◽  
Spatial Spread ◽  
Local Selection ◽  
Unified View ◽  
Behavioral Evidence ◽  
P3 Component

Abstract Visual attention spreads over a range around the focus as the spotlight metaphor describes. Spatial spread of attentional enhancement and local selection/inhibition are crucial factors determining the profile of the spatial attention. Enhancement and ignorance/suppression are opposite effects of attention, and appeared to be mutually exclusive. Yet, no unified view of the factors has been provided despite their necessity for understanding the functions of spatial attention. This report provides electroencephalographic and behavioral evidence for the attentional spread at an early stage and selection/inhibition at a later stage of visual processing. Steady state visual evoked potential showed broad spatial tuning whereas the P3 component of the event related potential showed local selection or inhibition of the adjacent areas. Based on these results, we propose a two-stage model of spatial attention with broad spread at an early stage and local selection at a later stage.

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