scholarly journals Control of Visual Selection during Visual Search in the Human Brain

2007 ◽  
Vol 1 (1) ◽  
Author(s):  
Manuel C. Olma ◽  
Tobias H. Donner ◽  
Stephan A. Brandt
Keyword(s):  
Visual Search ◽  
Human Brain ◽  
Feature Binding ◽  
Conjunction Search ◽  
Search Process ◽  
Intraparietal Sulcus ◽  
Neural Basis ◽  
Feature Search ◽  
Active Search ◽  
Salient Features

How do we find a target object in a cluttered visual scene? Targets carrying unique salient features can be found in parallel without directing attention, whereas targets defined by feature conjunctions or non-salient features need to be scrutinized in a serial attentional process in order to be identified. In this article, we review a series of experiments in which we used fMRI to probe the neural basis of this active search process in the human brain. In all experiments, we compared the fMRI signal between a difficult and an easy visual search (each performed without eye movements) in order to isolate neural activity reflecting the search process from other components such as stimulus responses and movement-related activity. The difficult search was either a conjunction search or a hard feature search and compared with an easy feature search, matched in visual stimulation and motor requirements. During both, the conjunction search and the hard feature search the frontal eye fields (FEF) and three parietal regions located in the intraparietal sulcus (IPS) were differentially activated: the anterior and posterior part of the intraparietal sulcus (AIPS, PIPS) as well as the junction of the intraparietal with the transverse occipital sulcus (IPTO). Only in PIPS, the modulation strength was most indistinguishable between conjunction and hard feature search. In a further experiment we showed that AIPS and IPTO are involved in visual conjunction search even in the absence of distractors; by contrast, the involvement of PIPS seems to depend on the presence of distractors. Taken together, these findings from these experiments demonstrate that all four key nodes of the human ’frontoparietal attention network’ are generally engaged in the covert selection process of visual search. But they also suggest that these areas play differential roles, perhaps reflecting different sub-processes in active search. We conclude by discussing a number of such sub-processes, such as the direction of spatial attention, visual feature binding, and the active suppression of distractors.

scholarly journals Saccade target selection in macaque during feature and conjunction visual search

1999 ◽  
Vol 16 (1) ◽  
pp. 81-89 ◽  
Author(s):  
NARCISSE P. BICHOT ◽  
JEFFREY D. SCHALL
Keyword(s):  
Visual Search ◽  
Computational Models ◽  
Selection Process ◽  
Target Selection ◽  
Conjunction Search ◽  
Saccade Target ◽  
Experimental Session ◽  
Shape Information ◽  
Feature Search ◽  
The Individual

To gain insight into how vision guides eye movements, monkeys were trained to make a single saccade to a specified target stimulus during feature and conjunction search with stimuli discriminated by color and shape. Monkeys performed both tasks at levels well above chance. The latencies of saccades to the target in conjunction search exhibited shallow positive slopes as a function of set size, comparable to slopes of reaction time of humans during target present/absent judgments, but significantly different than the slopes in feature search. Properties of the selection process were revealed by the occasional saccades to distractors. During feature search, errant saccades were directed more often to a distractor near the target than to a distractor at any other location. In contrast, during conjunction search, saccades to distractors were guided more by similarity than proximity to the target; monkeys were significantly more likely to shift gaze to a distractor that had one of the target features than to a distractor that had none. Overall, color and shape information were used to similar degrees in the search for the conjunction target. However, in single sessions we observed an increased tendency of saccades to a distractor that had been the target in the previous experimental session. The establishment of this tendency across sessions at least a day apart and its persistence throughout a session distinguish this phenomenon from the short-term (<10 trials) perceptual priming observed in this and earlier studies using feature visual search. Our findings support the hypothesis that the target in at least some conjunction visual searches can be detected efficiently based on visual similarity, most likely through parallel processing of the individual features that define the stimuli. These observations guide the interpretation of neurophysiological data and constrain the development of computational models.

Search for Capacity-Limited and Super-Capacity Search

2017 ◽  
Vol 64 (3) ◽  
pp. 149-158 ◽  
Author(s):  
Suk Won Han
Keyword(s):  
Visual Search ◽  
Conjunction Search ◽  
Search Process ◽  
Search Performance ◽  
Capacity Limitations ◽  
Singleton Search ◽  
Series Of Experiments ◽  
Feature Target ◽  
Limited Process ◽  
Singleton Target

Abstract. The present study investigated capacity limitations of visual search. In a series of experiments, participants searched for a singleton target among homogenous distractors, a conjunction target defined by combination of two features, or a feature target among heterogeneous distractors. Using the simultaneous-sequential paradigm, I found that singleton search proceeded in a capacity-unlimited manner. By contrast, the performance of the conjunction search was found to depend on a capacity-limited process. For feature searches, the performance of searching for a specific color was not affected by how the stimuli were presented, while the orientation search performance was enhanced as the number of distractors simultaneously presented with the target increased. These results imply that distinct colors are individually coded, whereas multiple orientations are encoded as an ensemble in a structured way. Taken together, the present study clarifies which type of search process are capacity-limited and reveals how this limit can be overcome.

Evidence for Attentional Capture by a Surprising Color Singleton in Visual Search

2002 ◽  
Vol 13 (6) ◽  
pp. 499-505 ◽  
Author(s):  
Gernot Horstmann
Keyword(s):  
Visual Search ◽  
Reaction Time ◽  
Target Letter ◽  
Attentional Capture ◽  
Search Task ◽  
Color Singleton ◽  
Conjunction Search ◽  
Feature Search ◽  
Set Size ◽  
And Performance

Three experiments were conducted to investigate whether surprising color singletons capture attention. Participants performed a visual search task in which a target letter had to be detected among distractor letters. Experiments 1 and 2 assessed accuracy as the dependent variable. In Experiment 1, the unannounced presentation of a color singleton 500 ms prior to the letters (and in the same position as the target letter) resulted in better performance than in the preceding conjunction search segment, in which no singleton was presented, and performance was as good in this surprise-singleton trial as in the following feature search segment, in which the singleton always coincided with the target. In contrast, no improvement was observed when the color singleton was presented simultaneously with the letters in Experiment 2, indicating that attentional capture occurred later in the surprise trial than in the feature search segment. In Experiment 3, set size was varied, and reaction time was the dependent variable. Reaction time depended on set size in the conjunction search segment, but not in the surprise trial nor in the feature search segment. The results of the three experiments support the view that surprising color singletons capture attention independently of a corresponding attentional set.

scholarly journals Causal Evidence for the Role of Neuronal Oscillations in Top–Down and Bottom–Up Attention

2019 ◽  
Vol 31 (5) ◽  
pp. 768-779 ◽  
Author(s):  
Justin Riddle ◽  
Kai Hwang ◽  
Dillan Cellier ◽  
Sofia Dhanani ◽  
Mark D'Esposito
Keyword(s):  
Visual Field ◽  
Conjunction Search ◽  
Intraparietal Sulcus ◽  
Top Down ◽  
Neuronal Oscillations ◽  
Bottom Up ◽  
Search Condition ◽  
Gamma Frequency ◽  
Task Conditions ◽  
Beta Frequency

Beta and gamma frequency neuronal oscillations have been implicated in top–down and bottom–up attention. In this study, we used rhythmic TMS to modulate ongoing beta and gamma frequency neuronal oscillations in frontal and parietal cortex while human participants performed a visual search task that manipulates bottom–up and top–down attention (single feature and conjunction search). Both task conditions will engage bottom–up attention processes, although the conjunction search condition will require more top–down attention. Gamma frequency TMS to superior precentral sulcus (sPCS) slowed saccadic RTs during both task conditions and induced a response bias to the contralateral visual field. In contrary, beta frequency TMS to sPCS and intraparietal sulcus decreased search accuracy only during the conjunction search condition that engaged more top–down attention. Furthermore, beta frequency TMS increased trial errors specifically when the target was in the ipsilateral visual field for the conjunction search condition. These results indicate that beta frequency TMS to sPCS and intraparietal sulcus disrupted top–down attention, whereas gamma frequency TMS to sPCS disrupted bottom–up, stimulus-driven attention processes. These findings provide causal evidence suggesting that beta and gamma oscillations have distinct functional roles for cognition.

scholarly journals Reading problems and their connection with visual search and attention: The search for a cause continues

2021 ◽  
Author(s):  
Heida Maria Sigurdardottir ◽  
Hilma Ros Omarsdóttir ◽  
Anna Sigridur Valgeirsdottir
Keyword(s):  
Visual Search ◽  
Internal Control ◽  
Search Task ◽  
Conjunction Search ◽  
Reading Problems ◽  
Visual Stream ◽  
Attentional Processes ◽  
Search Tasks ◽  
Reading Abilities ◽  
Gating Mechanism

Attention has been hypothesized to act as a sequential gating mechanism for the orderly processing of letters in words. These same visuo-attentional processes are assumed to partake in some but not all visual search tasks. In the current study, 60 adults with varying degrees of reading abilities, ranging from expert readers to severely impaired dyslexic readers, completed an attentionally demanding visual conjunction search task thought to heavily rely on the dorsal visual stream. A visual feature search task served as an internal control. According to the dorsal view of dyslexia, reading problems should go hand in hand with specific problems in visual conjunction search – particularly elevated conjunction search slopes (time per search item) – which would be interpreted as a problem with visual attention. Results showed that reading problems were associated with slower visual search, especially conjunction search. However, problems with reading were not associated with increased conjunction search slopes but instead with increased conjunction search intercepts, traditionally not interpreted as reflecting attentional processes. Our data are hard to reconcile with hypothesized problems in dyslexia with the serial moving of an attentional spotlight across a visual scene or a page of text.

Linking brain imaging signals to visual perception

2013 ◽  
Vol 30 (5-6) ◽  
pp. 229-241 ◽  
Author(s):  
ANDREW E. WELCHMAN ◽  
ZOE KOURTZI
Keyword(s):  
Human Brain ◽  
Brain Imaging ◽  
Imaging Data ◽  
Neural Basis ◽  
3D Perception ◽  
Multimodal Data ◽  
Psychological States ◽  
Perceptual Judgments ◽  
Brain Circuits ◽  
Brain Imaging Data

AbstractThe rapid advances in brain imaging technology over the past 20 years are affording new insights into cortical processing hierarchies in the human brain. These new data provide a complementary front in seeking to understand the links between perceptual and physiological states. Here we review some of the challenges associated with incorporating brain imaging data into such “linking hypotheses,” highlighting some of the considerations needed in brain imaging data acquisition and analysis. We discuss work that has sought to link human brain imaging signals to existing electrophysiological data and opened up new opportunities in studying the neural basis of complex perceptual judgments. We consider a range of approaches when using human functional magnetic resonance imaging to identify brain circuits whose activity changes in a similar manner to perceptual judgments and illustrate these approaches by discussing work that has studied the neural basis of 3D perception and perceptual learning. Finally, we describe approaches that have sought to understand the information content of brain imaging data using machine learning and work that has integrated multimodal data to overcome the limitations associated with individual brain imaging approaches. Together these approaches provide an important route in seeking to understand the links between physiological and psychological states.

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