Biology subjects

Mangun, G. R.

Publications and source records attributed to Mangun, G. R..

10 recordsLinked to original sources

bioRxiv2025

Volitional Attention to Color: Breaking Willed Attention out of the Spatial Domain

Attention can be guided by either voluntary (top-down) or involuntary (bottom-up) influences. In real-world vision, voluntary attention can be directed by a wide range of influences such as reward, priming, meaning, experience, selection history, and volition. Laboratory studies of voluntary attention have commonly used attention-directing cues to induce or instruct human subjects to attend one class of stimuli while ignoring others. In recent years, free choice conditions of attention have been introduced, where self-generated volitional shifts of attention (willed attention) are possible (for a review, see Nadra & Mangun, 2023). Prior willed attention studies have focused on mechanisms of covert spatial attention, investigating the neurophysiological correlates of willed attention related to both post-decision processing, and the pre-decision brain activity patterns that predict participants free choices about where to attend. Much less work, however, has been done on willed non-spatial attention. In this study, in a fashion similar to prior willed spatial attention studies, we investigated willed attention to stimulus color. In a trial-by-trial cueing design, subjects were either cued what color to attend or were allowed to freely choose what color to attend, in order to subsequently discriminate visual features of the cued or willfully chosen target. Behavioral measures showed that the subjects were selectively attending the cued or willed color. Using support vector machine decoding on EEG alpha (8-12 Hz) signals, we found significant post-decision differences in alpha-band power and broadband EEG voltage when participants chose to attend to orange versus purple. However, in contrast to the findings in prior work on willed spatial attention, no pre-decision EEG signals could be identified that predicted which color participants would choose to attend to.

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bioRxiv2025

Discourse Focus and Memory Encoding: The Role of Trial-Level Alpha Power

The rapid, continuous flow of spoken language places strong demands on attention, and it is thought that listeners meet these demands by predicting when important information will occur and allocating attention accordingly. However, to date there is little direct evidence for the involvement of preparatory attention during language processing. In this study, we investigate preparatory attention during spoken language comprehension by measuring alpha neural activity with EEG, a known measure of temporal attentional preparation. Alpha activity leading up to target words that were either focused or defocused by a preceding discourse question did not vary as a function of focus, challenging the assumption that attention is pre-allocated to the timing of focused words. On the other hand, we found that trial-by-trial fluctuations in alpha activity predicted both the depth of processing and the subsequent memory for new information. Specifically, pre-target alpha modulated a centro-parietal Dm subsequent memory effect for focused words, linking preparatory attention to memory encoding during comprehension. Together, these findings bridge psycholinguistic studies on information structure and cognitive neuroscience research on temporal attention, offering novel insights into the role of alpha activity in attentional dynamics during spoken language processing.

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bioRxiv2025

The Ventral Attention Network Mediates Attentional Reorienting to Cross-Modal Expectancy Violations: Evidence from EEG and fMRI

Our daily interactions with the world are shaped by sensory expectations informed by context and prior experiences, which in turn influence how we allocate our attention. Prominent predictive coding models suggest that sensory expectancy and attention interact but disagree on the precise mechanisms. One possibility is that the Ventral Attention Network (VAN), may play a role by facilitating attentional reorienting when expectancy is violated. To test this, we employed an auditory-visual trial-by-trial cueing paradigm in three experiments integrating EEG and fMRI to investigate the VANs role in violations of cross-modal expectancy. Behavioral results showed faster responses to expected targets, confirming the efficacy of cue-induced expectations in orienting attention to the expected target modality. EEG analyses revealed differences in early ([~]100 ms latency) event-related potentials (ERPs) to both auditory and visual stimuli when expectations were violated. Unexpected stimuli elicited significantly larger early-latency negative ERPs, across both modalities. Source localization of these ERPs and subsequent fMRI evidence revealed activation in the right VAN. Functional connectivity analyses further showed greater coupling between VAN regions and sensory cortices, with modality-specific pathways involving superior temporal gyrus (STG) for auditory and fusiform gyrus (FG) for visual targets. These findings demonstrate that expectancy violations recruit the VAN to reorient attention and resolve sensory conflict. By coordinating top-down control and bottom-up sensory input, the VAN supports adaptive responses to unexpected stimuli. This work advances our understanding of predictive processing in multisensory perception and highlights the VANs central role in flexible cognitive control.

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bioRxiv2025

Unconscious Neural Activity Predicts Overt Attention in Visual Search

Unconscious neural activity has been shown to precede both motor and cognitive acts. In the present study, we investigated the neural antecedents of overt attention during visual search, where subjects make voluntary saccadic eye movements to search a cluttered stimulus array for a target item. Building on studies of both overt self-generated motor actions (Lau et al., 2004, Soon et al., 2008) and self-generated cognitive actions (Bengson et al., 2014, Soon et al., 2013), we hypothesized that brain activity prior to the onset of a search array would predict the direction of the first saccade during unguided visual search. Because both spatial attention and gaze are coordinated during visual search, both cognition and motor actions are coupled during visual search. A well-established finding in fMRI studies of willed action is that neural antecedents of the intention to make a motor act (e.g., reaching) can be identified seconds before the action occurs. Studies of the volitional control of covert spatial attention in EEG have shown that predictive brain activity is limited to only a few hundred milliseconds before a voluntary shift of covert spatial attention. In the present study, the visual search task and stimuli were designed so that subjects could not predict the onset of the search array. Perceptual task difficulty was high, such that they could not locate the target using covert attention alone, thus requiring overt shifts of attention (saccades) to carry out the visual search. If the first saccade to the array onset in unguided visual search shares mechanisms with willed shifts of covert attention, we expected predictive EEG alpha-band activity (8-12 Hz) immediately prior to the array onset (within 1 sec) (Bengson et al., 2014; Nadra et al., 2023). Alternatively, if they follow the principles of willed motor actions, predictive neural signals should be reflected in broadband EEG activity (Libet et al., 1983) and would likely emerge earlier (Soon et al., 2008). Applying support vector machine decoding, we found that the direction of the first saccade in an unguided visual search could be predicted up to two seconds preceding the search arrays onset in the broadband but not alpha-band EEG. These findings suggest that self-directed eye movements in visual search emerge from early preparatory neural activity more akin to willed motor actions than to covert willed attention. This highlights a distinct role for unconscious neural dynamics in shaping visual search behavior.

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bioRxiv2025

Neural mechanisms of object prioritization in vision

Selective attention is widely thought to be sensitive to visual objects. This is commonly demonstrated in cueing studies, which show that when attention is deployed to a known target location that happens to fall on a visual object, responses to targets that unexpectedly appear at other locations on that object are faster and more accurate, as if the object in its entirety has been visually prioritized. However, this notion has recently been challenged by results suggesting that putative object-based effects may reflect the influence of hemifield anisotropies in attentional deployment, or of unacknowledged influences of perceptual complexity and visual clutter. Studies employing measures of behaviour provide limited opportunity to address these challenges. Here, we used EEG to directly measure the influence of task-irrelevant objects on the deployment of visual attention. We had participants complete a simple visual cueing task involving identification of a target that appeared at either a cued location or elsewhere. Throughout each experimental trial, displays contained task-irrelevant rectangle stimuli that could be oriented horizontally or vertically. We derived two cue-elicited indices of attentional deployment-lateralized alpha oscillations and the ADAN component of the event-related potential-and found that these were sensitive to the otherwise irrelevant orientation of the rectangles. Our results demonstrate that the allocation of visual attention is influenced by objects boundaries, supporting models of object-based attentional prioritization.

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bioRxiv2024

Hierarchical Organization of Visual Feature Attention Control

Attention can be deployed in anticipation of visual stimuli based on features such as their color or direction of motion. This anticipatory feature-based attention involves top-down neural control signals from the frontoparietal network that bias visual cortex to enhance the processing of attended information and suppress distraction. So, for example, anticipatory attention control can enable effective selection based on stimulus color while ignoring distracting information about stimulus motion. But as well, anticipatory attention can be focused more narrowly, for example, to select specific colors or motion directions that define task-relevant events and objects. One important question that remains open is whether anticipatory attention control first biases broad feature dimensions such as color versus motion before biasing the specific feature attributes (e.g., blue vs. green). To investigate this, we recorded EEG activity during a task where participants were cued to either attend to a color (blue or green) or a motion direction (up or down) on a trial-by-trial basis. Applying multivariate decoding approaches to the EEG alpha band (8-12 Hz) activity during the attention control period (cue-target interval), we observed significant decoding for both the attended dimensions (color vs. motion) and specific feature attributes (blue vs. green; up vs. down). Importantly, the temporal onset of the dimension-level biasing (color vs. motion) preceded that of the attribute-level biasing (e.g., blue vs. green). These findings demonstrate that the top-down control of feature-based attention proceeds in a hierarchical fashion, first biasing the broad feature dimension, and then narrowing to the specific feature attribute. Significance StatementDuring voluntary feature-based attention, electrophysiological and neuroimaging studies have highlighted the role of anticipatory (top-down) biasing of the sensory cortex in enhancing the selection of attended stimulus attributes, but little is known about how this is achieved. In particular, it is not clear whether attending to an attribute such as a color (blue vs. green) or motion direction (up vs. down) first biases all neural structures coding that dimension (color/motion) before biasing the specific attribute, or if the top-down signals directly bias only the attended attribute. Using EEG and multivariate decoding, we report that top-down attention control follows a hierarchical organization: first, the broader attended feature dimension is biased, which is followed by the biasing of the specific feature attribute.

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bioRxiv2023

Top-Down Biasing of Visual Cortical Activity Encodes Attended Information and Facilitates Behavioral Performance in Visual Spatial Attention

In models of visual spatial attention control, it is commonly held that top-down control signals originate in the dorsal attention network, propagating to the visual cortex to modulate baseline neural activity and bias sensory processing. However, the precise distribution of these top-down influences across different levels of the visual hierarchy is debated. In addition, it is unclear whether these changes in baseline neural activity directly translate into improved performance. We analyzed attention-related baseline activity during the anticipatory period of a trial-by-trial voluntary spatial attention task, using two independent fMRI datasets, and two different analytic approaches. First, as in prior studies, univariate analysis showed that covert attention significantly enhanced baseline neural activity in higher-order visual areas contralateral to the attended visual hemifield, while effects in lower-order visual areas (e.g., V1) were weaker and more variable. Second, in contrast, multivariate pattern analysis (MVPA) revealed significant decoding of attention conditions across all visual cortical areas, with lower-order visual areas exhibiting higher decoding accuracies than higher-order areas. Third, decoding accuracy, rather than the magnitude of univariate activation, was a better predictor of a subjects stimulus discrimination performance. Finally, the MVPA results were replicated across two experimental conditions, where the direction of spatial attention was either externally instructed by a cue or based on the participants free choice decision about where to attend. Together, these findings offer new insights into the extent of attentional biases in the visual hierarchy under top-down control, and how these biases influence both sensory processing and behavioral performance. HighlightsO_LIMultivariate pattern analysis revealed the presence of top-down attentional biasing signals in all areas of the visual hierarchy whereas univariate analysis was not able to reveal the full extent of attentional biasing in the visual cortex. C_LIO_LIThe decoding accuracy derived from the MVPA analysis but not the magnitude difference derived from the univariate analysis predicted the subjects behavioral performance in stimulus discrimination. C_LIO_LIThe MVPA results were consistent across two experimental conditions where the direction of spatial attention was driven either by external instructions or from purely internal decisions. C_LI

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bioRxiv2022

The Temporal Dynamics of Willed Attention in Vision

Most models of attention distinguish between voluntary and involuntary attention, the latter being driven in a bottom-up fashion by salient sensory signals. Studies of voluntary visual-spatial attention have used informational or instructional cues, such as arrows, to induce or instruct observers to direct selective attention to relevant locations in visual space in order to detect or discriminate subsequent target stimuli. In everyday vision, however, voluntary attention is influenced by a host of factors, most of which are quite different from the laboratory paradigms that utilize attention-directing cues. These factors include priming, experience, reward, meaning, motivations, and high-level behavioral goals. Attention that is endogenously directed in the absence of external cues has been referred to as self-initiated attention, or in our prior work as "willed attention". Such studies typically replace attention-directing cues with a "prompt" that signals the subject when to choose where they will attend in preparation for the upcoming target stimulus. We used a novel paradigm that was designed to minimize external influences (i.e., cues or prompts) as to where, as well as when, spatial attention would be shifted and focused. Participants were asked to view bilateral dynamic dot motion displays, and to shift their covert spatial attention to either the left or right visual field patch at a time of their own choosing, thus allowing the participants to control both when and where they attended on each trial. The task was to discriminate and respond to a pattern in the attended dot motion patch. Our goal was to identify patterns of neural activity in the scalp-recorded EEG that revealed when and where attention was focused. Using machine learning methods to decode attention-related EEG alpha band activity, we were able to identify the onset of voluntary (willed) shifts of visual-spatial attention, and to determine where attention was focused. This work contributes to our understanding of the neural antecedents of voluntary attention, opening the door for improved models of attentional control, and providing steps toward development of brain-computer interfaces using non-invasive electrical recordings of brain activity.

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bioRxiv2022

Top-down control of the left visual field bias in cued visual spatial attention

A left visual field (LVF) bias in perceptual judgements, response speed and discrimination accuracy are well documented in humans. However, LVF bias can be modulated by perceptual and task demands. For example, cuing spatial attention can reduce or eliminate the LVF bias, suggesting that attentional control can compensate for the LVF bias. We investigated this possibility directly by recording pupillometry together with fMRI in a cued visual spatial attention task. Prior to the onset of a task-relevant target stimulus, we observed that the pupil was significantly more dilated following attend-right than attend-left cues even though task performance did not differ. This difference in pupil dilation was inversely related to the corresponding difference in later target-evoked pupil dilation and in the reaction times to those targets, suggesting that an increased attentional effort was triggered by the attend-right cues, and this offset the LVF bias, equating behavioral performance. The differences in pupil dilation to the right versus left hemifield were correlated with corresponding fMRI differences primarily in the right hemisphere, supporting the idea that the increased attentional effort for rightward attention is mediated by activity in right hemisphere networks, which illuminates how attentional control mediates attentional biases in vision.

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bioRxiv2020

Role of Inferior Frontal Junction (IFJ) in the Control of Feature vs Spatial Attention

Feature-based attention refers to preferential selection and processing of items and objects based on their non-spatial attributes such as color or shape. While it is intuitively an easier form of attention to relate to in our day to day lives, the neural mechanisms of feature-based attention are not well understood. Studies have long implicated the dorsal attention network as a key control system for voluntary spatial, feature and object-based attention. Recent studies have expanded on this model by focusing on the inferior frontal junction (IFJ), a region in the pre-frontal cortex to be the source of feature attention control, but not spatial attention control. However, the extent to which IFJ contributes to spatial attention remains a topic of debate. We investigated the role of IFJ in the control of feature versus spatial attention in a cued visual spatial (attend left or right) and feature attention (attend red or green) task using fMRI. Analyzing single-trial cue-evoked fMRI responses using univariate GLM and multi-voxel pattern analysis (MVPA), we observed the following. First, the univariate BOLD activation responses yielded no significant differences between feature and spatial cues. Second, MVPA analysis showed above chance level decoding in classifying feature attention (attend-red vs. attend-green) in both the left and right IFJ, whereas during spatial attention (attend-left vs. attend-right) decoding was at chance. Third, while the cue-evoked decoding accuracy was significant for both left and right IFJ during feature attention, target stimulus-evoked neural responses were not different. Importantly, only the connectivity patterns from the right IFJ was predictive of target-evoked activity in visual cortex (V4); this was true for both left and right V4. Finally, the strength of this connectivity between right IFJ and V4 (bilaterally) was found to be predictive of behavioral performance. These results support a model where the right IFJ plays a crucial role in top down control of feature but not spatial attention.

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