Beta and theta oscillations differentially support free versus forced control over multiple-target search

AbstractMany important situations require human observers to simultaneously search for more than one object. Despite a long history of research into visual search, the behavioral and neural mechanisms associated with multiple-target search are poorly understood. Here we test the novel theory that the efficiency of looking for multiple targets critically depends on the mode of cognitive control the environment affords to the observer. We used an innovative combination of EEG and eye tracking while participants searched for two targets, within two different contexts: Either both targets were present in the search display and observers were free to prioritize either one of them, thus enabling proactive control over selection; or only one of the two targets would be present in each search display, which requires reactive control to reconfigure selection when the wrong target is prioritized. During proactive control, both univariate and multivariate signals of beta-band (15–35 Hz) power suppression prior to display onset predicted switches between target selections. This signal originated over midfrontal and sensorimotor regions and has previously been associated with endogenous state changes. In contrast, imposed target selections requiring reactive control elicited prefrontal power enhancements in the delta/theta-band (2–8 Hz), but only after display onset. This signal predicted individual differences in associated oculomotor switch costs, reflecting reactive reconfiguration of target selection. The results provide compelling evidence that multiple target representations are differentially prioritized during visual search, and for the first time reveal distinct neural mechanisms underlying proactive and reactive control over multiple-target search.Significance StatementSearching for more than one object in complex visual scenes can be detrimental for search performance. While perhaps annoying in daily life, this can have severe consequences in professional settings such as medical and security screening. Previous research has not yet resolved whether multiple-target search involves changing priorities in what people attend to, and how such changes are controlled. We approached these questions by concurrently measuring cortical activity and eye movements using EEG and eye tracking, while observers searched for multiple possible targets. Our findings provide the first unequivocal support for the existence of two modes of control during multiple-target search, which are expressed in qualitatively distinct time-frequency signatures of the EEG both before and after visual selection.

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The Role of Proactive and Reactive Cognitive Control for Target Selection in Multiple-Target Search

10.1101/559500 ◽

2019 ◽

Cited By ~ 2

Author(s):

Eduard Ort ◽

Johannes J. Fahrenfort ◽

Reshanne Reeder ◽

Stefan Pollmann ◽

Christian N. L. Olivers

Keyword(s):

Cognitive Control ◽

Target Selection ◽

Multiple Target ◽

Proactive Control ◽

Reactive Control ◽

Target Search ◽

Switch Costs ◽

Control Switch ◽

Frontoparietal Control Network

AbstractCognitive control can involve proactive (preparatory) and reactive (corrective) mechanisms. Using a gaze-contingent eye tracking paradigm combined with fMRI, we investigated the involvement of these different modes of control and their underlying neural networks, when switching between different targets in multiple-target search. Participants simultaneously searched for two possible targets presented among distractors, and selected one of them. In one condition, only one of the targets was available in each display, so that the choice was imposed, and reactive control would be required. In the other condition, both targets were present, giving observers free choice over target selection, and allowing for proactive control. Switch costs emerged only when targets were imposed and not when target selection was free. We found differential levels of activity in the frontoparietal control network depending on whether target switches were free or imposed. Furthermore, we observed core regions of the default mode network to be active during target repetitions, indicating reduced control on these trials. Free and imposed switches jointly activated parietal and posterior frontal cortices, while free switches additionally activated anterior frontal cortices. These findings highlight unique contributions of proactive and reactive control during visual search.

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Neural Dynamics of Cognitive Control over Working Memory Capture of Attention

Journal of Cognitive Neuroscience ◽

10.1162/jocn_a_01409 ◽

2019 ◽

Vol 31 (7) ◽

pp. 1079-1090 ◽

Cited By ~ 2

Author(s):

Peter S. Whitehead ◽

Mathilde M. Ooi ◽

Tobias Egner ◽

Marty G. Woldorff

Keyword(s):

Working Memory ◽

Visual Search ◽

Cognitive Control ◽

Attentional Capture ◽

Search Display ◽

Neural Mechanisms ◽

High Temporal Resolution ◽

Control Mechanisms ◽

Attentional Orienting ◽

Behavioral Studies

The contents of working memory (WM) guide visual attention toward matching features, with visual search being faster when the target and a feature of an item held in WM spatially overlap (validly cued) than when they occur at different locations (invalidly cued). Recent behavioral studies have indicated that attentional capture by WM content can be modulated by cognitive control: When WM cues are reliably helpful to visual search (predictably valid), capture is enhanced, but when reliably detrimental (predictably invalid), capture is attenuated. The neural mechanisms underlying this effect are not well understood, however. Here, we leveraged the high temporal resolution of ERPs time-locked to the onset of the search display to determine how and at what processing stage cognitive control modulates the search process. We manipulated predictability by grouping trials into unpredictable (50% valid/invalid) and predictable (100% valid, 100% invalid) blocks. Behavioral results confirmed that predictability modulated WM-related capture. Comparison of ERPs to the search arrays showed that the N2pc, a posteriorly distributed signature of initial attentional orienting toward a lateralized target, was not impacted by target validity predictability. However, a longer latency, more anterior, lateralized effect—here, termed the “contralateral attention-related negativity”—was reduced under predictable conditions. This reduction interacted with validity, with substantially greater reduction for invalid than valid trials. These data suggest cognitive control over attentional capture by WM content does not affect the initial attentional-orienting process but can reduce the need to marshal later control mechanisms for processing relevant items in the visual world.

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Effects of Image Segmentation and Target Number on Visual Search: An Eye-Tracking Study

Proceedings of the Human Factors and Ergonomics Society Annual Meeting ◽

10.1177/1541931218621450 ◽

2018 ◽

Vol 62 (1) ◽

pp. 1987-1991

Author(s):

Kaifeng Liu ◽

Calvin Ka-lun Or

Keyword(s):

Image Segmentation ◽

Visual Search ◽

Eye Tracking ◽

Repeated Measures ◽

Fixation Duration ◽

Search Time ◽

Search Performance ◽

Target Number ◽

Lower Accuracy ◽

Time Accuracy

This is an eye-tracking study examining the effects of image segmentation and target number on visual search performance. A two-way repeated-measures computer-based visual search test was used for data collection. Thirty students participated in the test, in which they were asked to search for all of the Landolt Cs in 80 arrays of closed rings. The dependent variables were search time, accuracy, fixation count, and average fixation duration. Our principal findings were that some of the segmentation methods significantly improved accuracy, and reduced search time, fixation count, and average fixation duration, compared with the no-segmentation condition. Increased target number was found to be associated with longer search time, lower accuracy, more fixations, and longer average fixation duration. Our study indicates that although visual search tasks with multiple targets are relatively difficult, the visual search accuracy and efficiency can potentially be improved with the aid of image segmentation.

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Lack of Free Choice Reveals the Cost of Having to Search for More Than One Object

Psychological Science ◽

10.1177/0956797617705667 ◽

2017 ◽

Vol 28 (8) ◽

pp. 1137-1147 ◽

Cited By ~ 17

Author(s):

Eduard Ort ◽

Johannes J. Fahrenfort ◽

Christian N. L. Olivers

Keyword(s):

Cognitive Control ◽

Eye Tracking ◽

Crucial Role ◽

Free Choice ◽

The Other ◽

Multiple Target ◽

Proactive Control ◽

Switch Costs ◽

The Cost ◽

Reactive Mechanism

It is debated whether people can actively search for more than one object or whether this results in switch costs. Using a gaze-contingent eye-tracking paradigm, we revealed a crucial role for cognitive control in multiple-target search. We instructed participants to simultaneously search for two target objects presented among distractors. In one condition, both targets were available, which gave the observer free choice of what to search for and allowed for proactive control. In the other condition, only one of the two targets was available, so that the choice was imposed, and a reactive mechanism would be required. No switch costs emerged when target choice was free, but switch costs emerged reliably when targets were imposed. Bridging contradictory findings, the results are consistent with models of visual selection in which only one attentional template actively drives selection and in which the efficiency of switching targets depends on the type of cognitive control allowed for by the environment.

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Studying visual search without an eye tracker: an assessment of artificial foveation

Cognitive Research Principles and Implications ◽

10.1186/s41235-021-00304-2 ◽

2021 ◽

Vol 6 (1) ◽

Author(s):

Laura E. Matzen ◽

Mallory C. Stites ◽

Zoe. N. Gastelum

Keyword(s):

Visual Search ◽

Eye Tracking ◽

Human Cognition ◽

Nuclear Safeguards ◽

Search Performance ◽

Eye Tracker ◽

Comparison Task ◽

List Condition ◽

Computer Based ◽

Verification Process

AbstractEye tracking is a useful tool for studying human cognition, both in the laboratory and in real-world applications. However, there are cases in which eye tracking is not possible, such as in high-security environments where recording devices cannot be introduced. After facing this challenge in our own work, we sought to test the effectiveness of using artificial foveation as an alternative to eye tracking for studying visual search performance. Two groups of participants completed the same list comparison task, which was a computer-based task designed to mimic an inventory verification process that is commonly performed by international nuclear safeguards inspectors. We manipulated the way in which the items on the inventory list were ordered and color coded. For the eye tracking group, an eye tracker was used to assess the order in which participants viewed the items and the number of fixations per trial in each list condition. For the artificial foveation group, the items were covered with a blurry mask except when participants moused over them. We tracked the order in which participants viewed the items by moving their mouse and the number of items viewed per trial in each list condition. We observed the same overall pattern of performance for the various list display conditions, regardless of the method. However, participants were much slower to complete the task when using artificial foveation and had more variability in their accuracy. Our results indicate that the artificial foveation method can reveal the same pattern of differences across conditions as eye tracking, but it can also impact participants’ task performance.

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Alpha Oscillatory Activity Associated with Impaired Visual Search in Cerebral Visual Impairment

10.21203/rs.3.rs-107877/v1 ◽

2020 ◽

Author(s):

Christopher Bennett ◽

Corinna Bauer ◽

Peter Bex ◽

Davide Bottari ◽

LOTFI MERABET

Keyword(s):

Visual Search ◽

Visual Impairment ◽

Spatial Processing ◽

Oscillatory Activity ◽

Search Performance ◽

Success Rates ◽

Thalamic Nuclei ◽

Time Frequency ◽

Visual Spatial ◽

Visual Spatial Processing

Abstract Cerebral (cortical) visual impairment (CVI) is associated with perinatal damage to retrochiasmatic pathways and cerebral structures. Individuals with CVI often present with impairments in visual spatial processing and attention. However, the neural correlates associated with these higher order perceptual deficits remain unknown. In this study, we investigated visual search performance using a novel virtual reality based task combined with electroencephalography (EEG) and time frequency decomposition of recorded oscillatory activity. We found that CVI participants showed impaired visual search performance (indexed by both decreased success rates and increased reaction times) compared to age matched controls. Furthermore, analysis of captured EEG activity revealed that posterior alpha desynchronization (typically associated with coordinating neural activity in perceptual and cognitive tasks) was greatly impaired in CVI compared to control participants. Finally, exploratory analysis suggested a potential association between amplitude of oscillations in the alpha range and morphometric anatomical measures. Specifically, less alpha desynchronization following stimulus onset was correlated with decreased volume of specific thalamic nuclei. These results suggest that in the setting of early neurological damage to retrochiasmatic visual pathways, alpha desynchronization remains greatly impaired and may be related to deficits in visual spatial processing and attention commonly observed in this population.

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What eye-tracking can tell us about multiple-target visual search

Journal of Vision ◽

10.1167/12.9.1010 ◽

2012 ◽

Vol 12 (9) ◽

pp. 1010-1010 ◽

Cited By ~ 2

Author(s):

M. S. Cain ◽

S. H. Adamo ◽

S. R. Mitroff

Keyword(s):

Visual Search ◽

Eye Tracking ◽

Multiple Target

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Distractor Heterogeneity versus Linear Separability in Colour Visual Search

Perception ◽

10.1068/p251281 ◽

1996 ◽

Vol 25 (11) ◽

pp. 1281-1293 ◽

Cited By ~ 38

Author(s):

Ben Bauer ◽

Pierre Jolicoeur ◽

William B Cowan

Keyword(s):

Visual Search ◽

Search Display ◽

Search Performance ◽

Set Size ◽

Linear Separability

D'Zmura, and Bauer, Jolicoeur, and Cowan demonstrated that a target whose chromaticity was linearly separable from distractor chromaticities was relatively easy to detect in a search display, whereas a target that was not linearly separable from the distractor chromaticities resulted in steep search slopes. This linear separability effect suggests that efficient colour visual search is mediated by a chromatically linear mechanism. Failure of this mechanism leads to search performance strongly influenced by number of search items (set size). In their studies, linear separability was confounded with distractor heterogeneity and thus the results attributed to linear separability were also consistent with the model of visual search proposed by Duncan and Humphreys in which search performance is determined in part by distractor heterogeneity. We contrasted the predictions based on linear separability and on the Duncan and Humphreys model by varying the ratios of the quantities of the two distractors and demonstrated the potent effects of linear separability in a design that deconfounded linear separability and distractor heterogeneity.

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