scholarly journals Global Enhancement but Local Suppression in Feature-based Attention

2017 ◽  
Vol 29 (4) ◽  
pp. 619-627 ◽  
Author(s):  
Norman Forschack ◽  
Søren K. Andersen ◽  
Matthias M. Müller
Keyword(s):  
No Reduction ◽  
Coherent Motion ◽  
Neural Dynamics ◽  
Focused Attention ◽  
Amplitude Increase ◽  
Early Visual Cortex ◽  
Feature Based ◽  
Left And Right ◽  
The One ◽  
Task Irrelevant

A key property of feature-based attention is global facilitation of the attended feature throughout the visual field. Previously, we presented superimposed red and blue randomly moving dot kinematograms (RDKs) flickering at a different frequency each to elicit frequency-specific steady-state visual evoked potentials (SSVEPs) that allowed us to analyze neural dynamics in early visual cortex when participants shifted attention to one of the two colors. Results showed amplification of the attended and suppression of the unattended color as measured by SSVEP amplitudes. Here, we tested whether the suppression of the unattended color also operates globally. To this end, we presented superimposed flickering red and blue RDKs in the center of a screen and a red and blue RDK in the left and right periphery, respectively, also flickering at different frequencies. Participants shifted attention to one color of the superimposed RDKs in the center to discriminate coherent motion events in the attended from the unattended color RDK, whereas the peripheral RDKs were task irrelevant. SSVEP amplitudes elicited by the centrally presented RDKs confirmed the previous findings of amplification and suppression. For peripherally located RDKs, we found the expected SSVEP amplitude increase, relative to precue baseline when color matched the one of the centrally attended RDK. We found no reduction in SSVEP amplitude relative to precue baseline, when the peripheral color matched the unattended one of the central RDK, indicating that, while facilitation in feature-based attention operates globally, suppression seems to be linked to the location of focused attention.

scholarly journals Dissociating Reward- and Attention-driven Biasing of Global Feature-based Selection in Human Visual Cortex

2019 ◽  
Vol 31 (4) ◽  
pp. 469-481 ◽  
Author(s):  
Haydee G. Garcia-Lazaro ◽  
Mandy V. Bartsch ◽  
Carsten N. Boehler ◽  
Ruth M. Krebs ◽  
Sarah E. Donohue ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Target Selection ◽  
Target Color ◽  
Selective Area ◽  
Early Visual Cortex ◽  
Feature Based ◽  
Irrelevant Color ◽  
Task Irrelevant ◽  
Open Question ◽  
Attention Demands

Objects that promise rewards are prioritized for visual selection. The way this prioritization shapes sensory processing in visual cortex, however, is debated. It has been suggested that rewards motivate stronger attentional focusing, resulting in a modulation of sensory selection in early visual cortex. An open question is whether those reward-driven modulations would be independent of similar modulations indexing the selection of attended features that are not associated with reward. Here, we use magnetoencephalography in human observers to investigate whether the modulations indexing global color-based selection in visual cortex are separable for target- and (monetary) reward-defining colors. To assess the underlying global color-based activity modulation, we compare the event-related magnetic field response elicited by a color probe in the unattended hemifield drawn either in the target color, the reward color, both colors, or a neutral task-irrelevant color. To test whether target and reward relevance trigger separable modulations, we manipulate attention demands on target selection while keeping reward-defining experimental parameters constant. Replicating previous observations, we find that reward and target relevance produce almost indistinguishable gain modulations in ventral extratriate cortex contralateral to the unattended color probe. Importantly, increasing attention demands on target discrimination increases the response to the target-defining color, whereas the response to the rewarded color remains largely unchanged. These observations indicate that, although task relevance and reward influence the very same feature-selective area in extrastriate visual cortex, the associated modulations are largely independent.

scholarly journals Early Visual Cortex Dynamics during Top–Down Modulated Shifts of Feature-Selective Attention

2016 ◽  
Vol 28 (4) ◽  
pp. 643-655 ◽  
Author(s):  
Matthias M. Müller ◽  
Mireille Trautmann ◽  
Christian Keitel
Keyword(s):  
Visual Cortex ◽  
Selective Attention ◽  
Time Course ◽  
Temporal Dynamics ◽  
Behavioral Data ◽  
Coherent Motion ◽  
Neural Dynamics ◽  
Early Visual Cortex ◽  
Time Courses ◽  
Feature Dimension

Shifting attention from one color to another color or from color to another feature dimension such as shape or orientation is imperative when searching for a certain object in a cluttered scene. Most attention models that emphasize feature-based selection implicitly assume that all shifts in feature-selective attention underlie identical temporal dynamics. Here, we recorded time courses of behavioral data and steady-state visual evoked potentials (SSVEPs), an objective electrophysiological measure of neural dynamics in early visual cortex to investigate temporal dynamics when participants shifted attention from color or orientation toward color or orientation, respectively. SSVEPs were elicited by four random dot kinematograms that flickered at different frequencies. Each random dot kinematogram was composed of dashes that uniquely combined two features from the dimensions color (red or blue) and orientation (slash or backslash). Participants were cued to attend to one feature (such as color or orientation) and respond to coherent motion targets of the to-be-attended feature. We found that shifts toward color occurred earlier after the shifting cue compared with shifts toward orientation, regardless of the original feature (i.e., color or orientation). This was paralleled in SSVEP amplitude modulations as well as in the time course of behavioral data. Overall, our results suggest different neural dynamics during shifts of attention from color and orientation and the respective shifting destinations, namely, either toward color or toward orientation.

Test anxiety, evaluative stress, and susceptibility to distraction from threat

2001 ◽  
Vol 15 (2) ◽  
pp. 123-141 ◽  
Author(s):  
Edmund Keogh ◽  
Christopher C. French
Keyword(s):  
Test Anxiety ◽  
Educational Practice ◽  
Focused Attention ◽  
Attentional Resources ◽  
Specific Trait ◽  
Selective Search ◽  
Task Irrelevant ◽  
High Test ◽  
Specific Susceptibility

Examinations are perhaps one of the main methods of assessment in education. Unfortunately, there are some individuals who are so fearful of such events that performance is impaired. Test anxiety is believed to be the trait that predisposes individuals to react negatively to examinations and tests. One way in which it is believed that test anxiety affects performance is by increasing susceptibility to distraction from task‐irrelevant material. However, few studies have directly investigated this impairment. An experiment was therefore conducted to investigate susceptibility to distraction in high and low test‐anxious students. The task used was based on one developed by Mathews, May, Mogg and Eysenck (1990), which distinguishes between focused attention and selective search. In order to determine whether a specific susceptibility to distraction exists, the distractors were varied in terms of valence and relevance to examinations. Since test anxiety is a situation‐specific trait, an evaluation‐related stressor was used to trigger test‐anxious reactions. A specific susceptibility to distraction from threat was found amongst high test‐anxious participants who received the evaluation‐related stressor. However, this effect was only found when participants were using focused attention. This suggests that the disturbed performance often found to be associated with test anxiety might be due to an inability to ignore threatening material when attempting to focus attentional resources. These results are discussed in light of current theories of test anxiety and implications for educational practice. Copyright © 2001 John Wiley & Sons, Ltd.

scholarly journals The fate of task-irrelevant visual motion: Perceptual load versus feature-based attention

2009 ◽  
Vol 9 (12) ◽  
pp. 12-12 ◽  
Author(s):  
S. Taya ◽  
W. J. Adams ◽  
E. W. Graf ◽  
N. Lavie
Keyword(s):  
Visual Motion ◽  
Perceptual Load ◽  
Feature Based ◽  
Task Irrelevant

WIGNER THEORY OF THE NAMBU STRING: (II) THE CLOSED STRING

1992 ◽  
Vol 07 (17) ◽  
pp. 4107-4148 ◽  
Author(s):  
F. COLOMO ◽  
L. LUSANNA
Keyword(s):  
Minkowski Space ◽  
Canonical Basis ◽  
Open String ◽  
Closed String ◽  
Zero Modes ◽  
Left And Right ◽  
The One

A set of relative variables for the closed string with P2>0 is found, which has Wigner covariance properties. They allow one to obtain global Lorentz-invariant abelianizations of the constraints, like for the open string, and then global Lorentz-invariant canonically conjugated gauge variables are found. But now there are two extra zero modes in the constraints and in the gauge variables, related to the gauge arbitrariness of the origin σ0 of the circle σ∈(−n, π) embedded in Minkowski space, σ↦xμ(σ). By means of the multitemporal approach a noncanonical redundant set of Dirac observables for the left and right modes is defined; they transform as spin-1 Wigner vectors and satisfy constraints of the same kind as in σ models. The quantization is not made, because a canonical basis of observables is still lacking, but the program to be followed to find them is just the same as the one delineated for the case of the open string.

scholarly journals Monocular mechanisms determine plaid motion coherence

1996 ◽  
Vol 13 (4) ◽  
pp. 615-626 ◽  
Author(s):  
David Alais ◽  
Maarten J. van der Smagt ◽  
Frans A. J. Verstraten ◽  
W. A. van de Grind
Keyword(s):  
Cortical Area ◽  
The Other ◽  
Coherent Motion ◽  
Spatial Period ◽  
Two Dimensional ◽  
Middle Temporal ◽  
Spatial Frequencies ◽  
Motion Coherence ◽  
Plaid Motion ◽  
Feature Based

AbstractAlthough the neural location of the plaid motion coherence process is not precisely known, the middle temporal (MT) cortical area has been proposed as a likely candidate. This claim rests largely on the neurophysiological findings showing that in response to plaid stimuli, a subgroup of cells in area MT responds to the pattern direction, whereas cells in area V1 respond only to the directions of the component gratings. In Experiment 1, we report that the coherent motion of a plaid pattern can be completely abolished following adaptation to a grating which moves in the plaid direction and has the same spatial period as the plaid features (the so-called “blobs”). Interestingly, we find this phenomenon is monocular: monocular adaptation destroys plaid coherence in the exposed eye but leaves it unaffected in the other eye. Experiment 2 demonstrates that adaptation to a purely binocular (dichoptic) grating does not affect perceived plaid coherence. These data suggest several conclusions: (1) that the mechanism determining plaid coherence responds to the motion of plaid features, (2) that the coherence mechanism is monocular, and thus (3), that it is probably located at a relatively low level in the visual system and peripherally to the binocular mechanisms commonly presumed to underlie two-dimensional (2-D) motion perception. Experiment 3 examines the spatial tuning of the monocular coherence mechanism and our results suggest it is broadly tuned with a preference for lower spatial frequencies. In Experiment 4, we examine whether perceived plaid direction is determined by the motion of the grating components or the features. Our data strongly support a feature-based model.

scholarly journals Corrigendum to “Neural dynamics underlying coherent motion perception in children and adults” [Dev. Cogn. Neurosci. 38 (August) (2019) 100670]

2020 ◽  
Vol 41 ◽  
pp. 100748
Author(s):  
Catherine Manning ◽  
Blair Kaneshiro ◽  
Peter J. Kohler ◽  
Mihaela Duta ◽  
Gaia Scerif ◽  
...  
Keyword(s):  
Motion Perception ◽  
Coherent Motion ◽  
Neural Dynamics

scholarly journals High Dimensional Feature for Hyperspectral Image Classification

2018 ◽  
Vol 246 ◽  
pp. 03041
Author(s):  
Cailing Wang ◽  
Hongwei Wang ◽  
Yinyong Zhang ◽  
Jia Wen ◽  
Fan Yang
Keyword(s):  
Image Classification ◽  
Hyperspectral Image ◽  
Texture Feature ◽  
High Dimensional ◽  
Support Vector ◽  
Hyperspectral Image Classification ◽  
Feature Based ◽  
Pca Method ◽  
The One ◽  
Low Dimensional

Making a high dimensional (e.g., 100k-dim) feature for hyperspectral image classification seems not a good idea because it will bring difficulties on consequent training, computation, and storage. In this paper, we study the performance of a high-dimensional feature by texture feature. The texture feature based on multi-local binary pattern descriptor, can achieve significant improvements over both its tradition version and the one we proposed in our previous work. We also make the high-dimensional feature practical, we employ the PCA method for dimension reduction and support vector machine for hyperspectral image classification. The two real hyperspectral image datasets are employed. Our experimental results with real hyperspectral images indicate that the high dimensional feature can enhance the classification accuracy than some low dimensional.

Modification of V2O5-WO3/TiO2 Catalysts Supported on SiC Filter for NO Reduction at Low Temperature

2007 ◽  
Vol 124-126 ◽  
pp. 1713-1716 ◽  
Author(s):  
Youn Gae Kim ◽  
Joo Hong Choi ◽  
Liang Yu ◽  
Young Cheoul Bak
Keyword(s):  
No Reduction ◽  
Catalyst System ◽  
Ceramic Filter ◽  
Commercial Catalyst ◽  
Scr Catalyst ◽  
Catalytic Filter ◽  
Temperature Window ◽  
Face Velocity ◽  
The One ◽  
Optimum Working

The catalytic filter, a ceramic filter supported SCR catalyst, is a promising material for treating particulates and NOX simultaneously. Recently, it is found that a SiC filter supported V2O5- WO3-TiO2 [commercial catalyst system] shows a reasonable SCR activity around 320 °C [1]. In order to improve its catalytic activity at low temperatures, the effects of Pt and MnOX addition on the catalytic filter are investigated. The macro-porous TiO2 film was firstly coated on the pore surface of SiC filter element using the solution composed of the preformed TiO2 particles (P25). Catalytic filters were prepared by the impregnation of TiO2 coated-SiC filter in the solution containing the catalyst components. The MnOX-added catalytic filter showed very wide temperature window from 150-340 °C, providing NX slip concentration less than 20 ppm for the treatment of 700 ppm NO at a face velocity of 2 cm/s. Pt added-catalytic filter shifted the optimum working temperature towards the lower temperatures (180-240 °C) compared to the one without Pt (280-330 °C). It is understood that MnOX in the catalyst system roles as the main catalyst component while Pt rose as a electron modification additive.

Alpha Oscillations Correlate with the Successful Inhibition of Unattended Stimuli

2011 ◽  
Vol 23 (9) ◽  
pp. 2494-2502 ◽  
Author(s):  
Barbara F. Händel ◽  
Thomas Haarmeier ◽  
Ole Jensen
Keyword(s):  
Visual System ◽  
Alpha Activity ◽  
Coherent Motion ◽  
Motion Processing ◽  
Alpha Power ◽  
Motion Direction ◽  
Alpha Oscillations ◽  
Visual Hemifield ◽  
Left And Right ◽  
Visual Hemifields

Because the human visual system is continually being bombarded with inputs, it is necessary to have effective mechanisms for filtering out irrelevant information. This is partly achieved by the allocation of attention, allowing the visual system to process relevant input while blocking out irrelevant input. What is the physiological substrate of attentional allocation? It has been proposed that alpha activity reflects functional inhibition. Here we asked if inhibition by alpha oscillations has behavioral consequences for suppressing the perception of unattended input. To this end, we investigated the influence of alpha activity on motion processing in two attentional conditions using magneto-encephalography. The visual stimuli used consisted of two random-dot kinematograms presented simultaneously to the left and right visual hemifields. Subjects were cued to covertly attend the left or right kinematogram. After 1.5 sec, a second cue tested whether subjects could report the direction of coherent motion in the attended (80%) or unattended hemifield (20%). Occipital alpha power was higher contralateral to the unattended side than to the attended side, thus suggesting inhibition of the unattended hemifield. Our key finding is that this alpha lateralization in the 20% invalidly cued trials did correlate with the perception of motion direction: Subjects with pronounced alpha lateralization were worse at detecting motion direction in the unattended hemifield. In contrast, lateralization did not correlate with visual discrimination in the attended visual hemifield. Our findings emphasize the suppressive nature of alpha oscillations and suggest that processing of inputs outside the field of attention is weakened by means of increased alpha activity.

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