Biology subjects

Van der Stigchel, S.

Publications and source records attributed to Van der Stigchel, S..

At least 19 recordsLinked to original sources

bioRxiv2026

Covert attentional tracking with invisible phase tagging

Attention forms a fundamental component of visual processing. The locus and spread of covert attention reveals how specific locations or features in the environment are preferentially processed, however, tracking this process in a time-resolved fashion is not easy. Rapid Invisible Frequency Tagging (RIFT) is a recent advance in localizing covert attention. This technique uses stimuli that flicker at unique frequencies to invisibly "tag" areas of the visual field. The frequency-specific response elicited offers a measure of visual processing (and covert attention) over time. However, the narrow frequency band compatible with RIFT restricts the number of distinct frequency tags that can be simultaneously used. This limitation can be addressed by using oscillatory phase as an additional tagging feature. Here, we conducted a RIFT-EEG experiment (n=24) with 8 unique tags based on both frequency and phase modulation. We show that modulations in visual processing can be measured at several tagged locations with identical frequency but different phases. This also allowed for the use of combined phase- and frequency- modulated RIFT to quantify the distribution of attention across the visual field. By integrating phase-modulation into invisible frequency tagging studies of attention, we bring the field a step closer towards fine-resolution attentional tracking continuously over time and space, allowing novel insights across various domains of visual cognition.

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bioRxiv2026

Visual Attention doesnt Travel, it Teleports

Attention forms a key, yet elusive component of visual processing. We shift attention constantly across the visual field to enhance processing of relevant locations or stimuli in service of goal-directed behavior. Here, we investigate a fundamental property of attentional shifts: when covertly shifting from one location to another, does visual attention "travel" (enhance processing at intermediate locations) or "teleport" (not interact with intermediate locations)? While most shifts of information or movement "travel" (e.g., eye and body movements, neuronal signalling), for attentional shifts such intermediate processing enhancement might not be necessary, nor functional. To answer this question while tackling the difficulty of tracking covert attentional dynamics, we conducted an EEG-eyetracking experiment (n=24) paired with Rapid Invisible Frequency Tagging (RIFT). This let us track attentional enhancement during covert attentional shifts with high temporal and spatial precision. We successfully registered covert shifts, but found no evidence for any attentional modulation in-between the start and end-point of an attentional shift. Additional insilico modelling of attentional shifts confirmed that our method was sensitive enough to pick up on these modulations had they been present. Our results support a "teleporting" model of attention, suggesting that attention is implemented in a fundamentally different manner compared to overt visual behaviours such as eye movements.

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bioRxiv2026

Luminance-corrected Pupillometry for Reliable Effort-tracking in Dynamic Environments

Pupillometry provides an objective way to index effort across domains. However, pupil size is strongly affected by luminance changes, which can obscure effort-related effects, and limit its use in most applied scenarios with dynamic visual input. We here introduce and validate a method to overcome this problem. To this end, participants performed an auditory n-back task of differing difficulty while viewing either constant visual input or dynamic driving movie clips. Effort was assessed physiologically (pupil size), behaviorally (accuracy), and subjectively (NASA-TLX). Accuracy, questionnaire scores, and pupil size were analyzed at the session level, while pupillometry additionally provided continuous time-resolved information. As expected, pupillometry tracked differences in effort, but its discriminability was substantially reduced under dynamic visual input. Correcting for the effects of overall luminance and moment-to-moment luminance changes using a dynamic, explainable, and open-source modeling procedure (Open-DPSM) considerably improved effort discriminability on both aggregate and time-resolved levels. At the aggregate level, luminance-corrected pupillometry slightly outperformed accuracy and NASA-TLX. Combining all three measures yielded the highest classification performance (AUC = 0.98), supporting the view that effort is multifaceted and best captured multimodally. These findings establish a practical basis for fine-grained physiological tracking of effort and arousal in both fundamental and applied research using complex, dynamic stimuli. A tutorial section guides researchers in applying luminance correction to their own pupillometric data in dynamic viewing environments using the here validated approach.

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bioRxiv2026

Attentional selection is a neuroeconomic decision

Sensorimotor decisions require balancing extrinsic rewards against intrinsic action costs. How these signals are integrated during rapid eye-movement choices remains unclear. We show that human saccade selection follows cost-benefit computations consistent with neuroeconomic decision-making. Across two experiments, participants maximized rewards and minimized effort-costs. Reward titration revealed that more effortful saccades required higher monetary rewards to be chosen equally often. While effort-costs affected choices linearly, small reward differences shifted choices more than equally-sized larger ones. Furthermore, effort-cost (but not reward) differences regulated decision engagement: Deliberation was extended only when cost differences were large. Together, costs and rewards play dissociable roles in saccade selection, positioning eye movements as a tractable model system for economic decision-making.

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bioRxiv2025

Independent Markers of Attentional Shifts

Visuospatial attention has been extensively studied using a wide variety of markers in the brain and in behaviour. We can broadly classify these markers into two distinct groups: reactive measures, where the presence and strength of attentional biases is inferred from the reaction to a probe stimulus, and proactive measures, which track attentional biases without (or before) the presentation of a probe stimulus. A difference in either type of measure (between two experimental conditions) is typically interpreted to reflect a difference in attentional resources. However, it is not a given that these various reactive and proactive measures of attention all read out the same construct; they may very well tap into independent processes. Here, we measure some of these proactive and reactive signatures of attending a location (changes in cortical excitability as measured by RIFT, alpha lateralization, gaze bias, probe-evoked ERPs, and behavioral reports) in an EEG-eyetracking task (n=23). Though all these metrics indeed correlate with our attentional manipulation, we show that they are not direct correlates of each other, and that of all the proactive measures only the gaze bias predicts subsequent behavioral responses. This demonstrates that existing markers of attention cannot be used interchangeably, and likely capture independent subprocesses of attention.

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bioRxiv2025

Tracking attention using RIFT with a consumer-monitor setup

Rapid Invisible Frequency Tagging (RIFT) is a recent technique that extends the traditional frequency tagging approach by modulating the luminance of distinct locations on a screen at frequencies beyond the threshold of perception ([≥]60Hz). Retrieving the corresponding frequencies from M/EEG recordings provides a time-resolved and location-specific measure of early visual processing, without the confounding effect of introducing visible stimuli. This method is most frequently harnessed as a tracker of covert attention in experimental paradigms across various disciplines in cognitive neuroscience. However, almost all existing RIFT work so far has made use of expensive display hardware limited in its accessibility. Recent work has shown that a RIFT response elicited by a 480Hz refresh-rate consumer monitor can be retrieved from the EEG, but it is not yet clear whether such a setup can be utilized to track the locus of attention. Here, using a spatial cueing paradigm (n=24) while simultaneously tagging two locations (60.0Hz and 65.5Hz), we show that covert attention can be reliably measured with RIFT on a 360Hz refresh rate consumer monitor. We hope that this study will facilitate the widespread application of using consumer-grade high refresh-rate gaming monitors with RIFT for future scientific and applied research.

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bioRxiv2025

Anticipated Relevance Prepares Visual Processing for Efficient Memory-Guided Selection

Finding an object typically involves using working memory to select relevant visual information at the right time. Using EEG, we investigated how predictable changes in stimulus relevance influence top-down visual selection. Participants memorized an oriented grating, followed by a cue indicating which of two sequentially presented probes was relevant for a memory-match/-mismatch judgment. Consistent with earlier work, relevant probes evoked stronger univariate responses than irrelevant probes. Furthermore, responses to (memory-matching and memory-mismatching) probes were more distinct when they were relevant compared to irrelevant. Crucially, using rapid invisible frequency tagging (RIFT), we found that visual responses to the (empty) probe location were enhanced even before the presentation of relevant (compared to irrelevant) probes. Predictable changes in stimulus relevance, therefore, induce both pro-active and re-active changes in visual processing. We conclude that anticipating the (ir)relevance of upcoming visual events enables the visual system to prepare for efficient memory-guided visual selection.

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bioRxiv2025

Visual working memory precision is under voluntary control

Visual working memory allows us to guide behavior based on recently seen information. Most research builds on the assumption that people always try to store visual information as precisely as possible, regardless of what the upcoming action requires. In everyday life, however, different (memory-guided) actions demand different levels of precision. Here we asked whether people flexibly adjust how deeply they encode, how much effort they put in maintaining visual information based on the task demands. Across three experiments participants memorized up to four colors, while we manipulated the required precision for a delayed report to be considered correct. We found that when required precision was higher, reports became slower and (in some cases) more precise. Crucially, we found that higher precision demands led to (1) stronger pupil constriction during encoding, indicating deeper encoding, and (2) larger pupil dilation during maintenance, indicating greater cognitive effort. Moreover, this adaptive increase in maintenance effort occurred not only when precision demands were known before encoding (Experiments 1 and 2), but even when they were revealed only after encoding (Experiment 3). Thus, the maintenance of visual information can be flexibly tuned in response to changing task demands. Yet, this flexibility had limitations: with increasing precision requirements, participants increased effort even when it no longer improved performance. Together, these findings show that visual working memory is not a passive store that is always maximally loaded. Instead, how visual information is encoded, maintained, and used is tuned to the demands of upcoming behavior.

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bioRxiv2025

Population-Level Activity Dissociates Preparatory Overt from Covert Attention

The neural signatures of preparing overt eye movements and directing covert spatial attention overlap as they recruit the same brain areas. Yet, these neural signatures are dissociable at the single-cell level: Specific cells within visuo-oculomotor areas are exclusively involved in motor preparation or covert attention. Nevertheless, it has been proposed that many cells in visuo-oculomotor areas are involved in both motor preparation and covert attention, and consequently their neural signatures should functionally overlap to a large degree. Here, we directly tested this proposal: we combined human (both sexes) EEG with sensitive decoding techniques to investigate whether the neural signatures of preparatory overt and covert attention are dissociable across large-scale neuronal populations. We found that neural decoding reliably discerned whether overt or covert attention was shifted well before saccade initiation. Further, inverted encoding modeling revealed earlier and sharper spatially-tuned activity in preparatory overt than in covert attention. We then asked whether preparatory overt attention achieved sharper spatially-tuned activity by using more-of-the-same covert attention, or by recruiting additional spatially selective neural processing. Cross-decoding results demonstrated that preparatory overt attention recruited at least one additional, frontal process. This additional spatially selective process emerged early and likely reflects motor preparation or predictive remapping. To summarize, we found that the neural signatures of overt and covert attention overlap, yet diverge rapidly, in part because overt attention employs an additional spatially selective neural process. Extending beyond a dissociation on the single-cell level, our findings demonstrate that population-level neural activity dissociates preparatory overt from covert attention. Significance statementThe world provides much more visual input than the brain can process simultaneously. Spatial visual attention allows for the selective processing of only the most important parts of this input. Spatial attention shifts either overtly (with an eye movement) or covertly (without an accompanying eye movement). The neural signatures underlying these types of spatial attention have long thought to overlap to a large degree. This strong overlap was thought to only break down at the level of single neurons. In our EEG study, we instead demonstrate that large populations of neurons dissociate overt from covert attention. Our results show that the neural signatures of overt and covert attention differ on a much broader scale than previously thought.

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bioRxiv2025

Decoding auditory working memory load from EEG alpha oscillations

Working memory (WM) enables temporary retention of task-relevant information for imminent use. Increases in visual WM load are accompanied by elevated contralateral delay activity (CDA), and EEG alpha-band power. While most WM research focuses on the visual domain, it remains unknown whether similar EEG responses also reflect WM load in the auditory domain. Using EEG, we set out to establish such neural markers of auditory WM load. Participants memorized the pitches of 1 to 4 pure tones presented to one ear, with 1 to 4 identical distractor tones presented to the other ear. Behaviorally, auditory WM capacity plateaued between set-sizes two and three. Unlike for visual WM, auditory WM load was not reflected in lateralized EEG responses. This shows that the CDA is a vision-specific rather than domain-general neural marker of WM load. Applying multivariate pattern analyses on the delay activity revealed that auditory WM load is reflected in patterns of alpha-band oscillations. Surprisingly, a temporal generalization analysis revealed that the alpha patterns reflecting specific load conditions changed throughout the maintenance period (despite load being inherently constant), revealing dynamic coding of auditory WM load.

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bioRxiv2024

Gaze biases can reflect task-specific spatial memorization strategies

Previous work has suggested that small directional eye movements not only reveal the focus of external spatial attention towards visible stimuli, but also accompany shifts of internal attention to stimuli in visual working memory (VWM)(van Ede et al., 2019). When the orientations of two bars are memorized and a subsequent retro-cue indicates which orientation needs to be reported, participants gaze is systematically biased towards the former location of the cued item (Figure 1AB). This finding was interpreted as evidence that the oculomotor system indexes internal attention; that is, attention directed at the location of stimuli that are no longer presented but are maintained in VWM. Importantly, as the location of the bars is presumably not relevant to the memory report, the authors concluded that orientation features in VWM are automatically associated with locations, suggesting that VWM is inherently spatially organized. This conclusion depends on the key assumption that participants indeed memorize and subsequently attend orientation features. Here we re-analyse Experiment 1 by van Ede et al. (2019) and demonstrate that this assumption does not hold. Instead of memorizing orientation features, participants deployed an alternative spatial strategy by memorizing bar endpoints. Although we do not call into question the conclusion that internal attention is inherently spatially organized, our results do imply that directional gaze biases might also reflect attention directed at task-relevant stimulus endpoints, rather than internal attention directed at memorized orientations. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=161 SRC="FIGDIR/small/610231v2_fig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@940e51org.highwire.dtl.DTLVardef@37ec3dorg.highwire.dtl.DTLVardef@176b186org.highwire.dtl.DTLVardef@180e8a7_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 1.C_FLOATNO Gaze density maps from Experiment 1 by van Ede et al. (2019) (N = 23, trials included = 20.864, 400 to 1000 ms). AB. Original reported effect of cued item location on gaze bias. Calculated by subtracting cued-item-left and cued-item-right gaze density maps. Rectangles indicate used stimulus positions and orientation ranges (min: 20{degrees}, mean: 45{degrees}, max: 70{degrees}; min: 110{degrees}, mean: 135{degrees}, max: 160{degrees}) of bar stimuli. C. Normalized Gaze bias vectors per condition (red dotted lines), horizontal vectors (dotted black lines) and average vectors pointing towards most foveal bar endpoints (solid black lines). Gaze bias vector endpoints were calculated from the centre of mass of each condition, ignoring negative values. Circular t-tests revealed that individual gaze bias vector angles (red dotted lines) were significantly different from horizontal vectors (dotted black lines) but not significantly different from endpoint vectors (solid black lines). FI. Vertical gaze bias revealed by separating trials based on bar orientations. Red dotted lines depict group average gaze bias vectors. F. Both bar endpoints "upwards" (left: 20{degrees} to 70{degrees} right: 110{degrees} to 160{degrees}) minus both bars endpoints "downwards" (left: 110{degrees} to 160{degrees}, right: 20{degrees} to 70{degrees}). I. Both "downwards" minus both "upwards". DEGH. Individual gaze density maps for each attention (left versus right) and bar endpoint direction (upwards versus downwards) separately. Solid black Lines show average vector pointing towards closest 45{degrees}/135{degrees} bar endpoint (i.e., average optimal gaze location for solving the memory task through memory maintenance of a spatial location). Red dotted lines depict group average gaze bias vectors (calculated from the centre of mass of each condition, ignoring negative values). C_FIG

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bioRxiv2024

Dissociating External and Internal Attentional Selection

Visual Working Memory (VWM) stores visual information for upcoming actions. Just as attention can shift externally towards relevant objects in the visual environment, attention can shift internally towards (i.e., prioritize) VWM content that is relevant for upcoming tasks. Internal and external attentional selection share a number of key neural and functional characteristics, which include their spatial organization: recent work has shown that spatial attention is directed towards the previous location of a prioritized memory item, similar to how a perceived stimulus is prioritized. Attending stimuli that are physically present is useful, as it enhances processing of the relevant visual input. When prioritizing items in memory, however, attending the prior stimulus location cannot serve this purpose, as there is no visual input to enhance. Here, we address this apparent contradiction which highlights the gaps in our understanding of the mechanisms underlying external and internal visual attention. In two EEG experiments, we compare location-specific sensory enhancement during the attentional selection of external (perceived) as compared to internal (memorized) stimuli. During both internal and external selection we observed a lateralization of alpha oscillations and gaze position bias toward the previous locations of prioritized items, confirming earlier findings that suggested an inherent spatial organization within VWM. Critically, using Rapid Invisible Frequency Tagging (RIFT), we show that sensory enhancement at the attended location is only observed during external attentional selection of (perceived) stimuli. No such location-specific sensory enhancement was observed during attentional selection of items in VWM. Furthermore, we found no clear relationship across trials between alpha lateralization and sensory enhancement (measured through RIFT) during external attention, suggesting that these two metrics indeed reflect distinct cognitive mechanisms. In sum, using a novel combination of EEG and RIFT, we demonstrate a fundamental distinction between the neural mechanisms underlying the selection of perceived and memorized objects. Both types of selection operate within a spatial reference frame, but only external selection modulates early sensory processing. Our findings suggest that the visual system is not vestigially recruiting existing mechanisms of external attention for prioritization in VWM, but is instead using space as an organizational principle to store and select items in VWM.

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bioRxiv2024

Effort Drives Saccade Selection

What determines where to move the eyes? We recently showed that pupil size, a well-established marker of effort, also reflects the effort associated with making a saccade (saccade costs). Here we demonstrate saccade costs to critically drive saccade selection: when choosing between any two saccade directions, the least costly direction was consistently preferred. Strikingly, this principle even held during search in natural scenes in two additional experiments. When increasing cognitive demand experimentally through an auditory counting task, participants made fewer saccades and especially cut costly directions. This suggests that the eye-movement system and other cognitive operations consume similar resources that are flexibly allocated among each other as cognitive demand changes. Together, we argue that eye-movement behavior is tuned to adaptively minimize saccade-inherent effort.

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bioRxiv2024

Sensory Input Matching Visual Working Memory Guides Internal Prioritization

Adaptive behavior necessitates the prioritization of the most relevant information in the environment (external) and in memory (internal). Internal prioritization is known to guide the selection of external sensory input, but the reverse may also be possible: Does the environment guide the prioritization of memorized material? Here we addressed whether reappearing sensory input can facilitate the prioritization of other non-reappearing memorized items held in visual working memory (VWM). Participants (total n = 96) memorized three orientations. Crucially some, but not all, items maintained in VWM were made available again in the environment. These reappearing items never had to be reproduced later. Experiment 1 showed that the reappearance of all but one memory item benefited accuracy and speed to the same extent as a spatial retro cue. This shows that reappearing items allow for the dynamic prioritization of another non-reappearing memorized item. What aspects of the reappearing sensory input drive this effect? Experiments 2-4 demonstrated that prioritization was facilitated most if reappearing items matched VWM content in terms of both location and orientation. Sensory input fully matching VWM is possibly processed more efficiently and/or protects against interference, ultimately leading to stronger prioritization of other memory content. We propose that the link between sensory processing and VWM is bidirectional: internal representations guide the processing of sensory input, which in turn facilitates the prioritization of other VWM content to subserve adaptive behavior. All data and analysis scripts are available here: https://osf.io/qzvkc/.

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bioRxiv2024

Rapid Invisible Frequency Tagging (RIFT) in a novel setup with EEG

Steady-State Visual Evoked Potentials (SSVEPs) provide a report-free and continuous measure of neural processing. Recent progress in display technology has allowed for the tagging of multiple stimuli simultaneously at >60Hz frequencies - high enough to evade perceptibility, while still evoking an oscillatory neural response. Known as Rapid Invisible Frequency Tagging (RIFT), this technique has currently only been used in combination with Magnetoencephalography (MEG), which is less accessible compared to Electroencephalography (EEG). Although responses to LEDs flickering at similar frequencies have been shown in EEG, it is currently unclear whether RIFT, using a more conventional stimulus display, can sufficiently evoke a response in EEG, and therefore whether it is worth adding the RIFT-EEG pairing to the cognitive neuroscientists toolkit. Here, we successfully implement the first RIFT-EEG setup. We show that the oscillatory input is measurable in the EEG trace, what its topographical spread is, a rough range of applicable frequencies, and that this response is comparable to that evoked in MEG.

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bioRxiv2023

SSVEPs reveal dynamic (re-)allocation of spatial attention during maintenance and utilization of visual working memory

Visual Working Memory (VWM) allows us to temporarily store goal-relevant information to guide future behavior. Prior work has established that VWM and spatial attention are intrinsically connected - even if location is irrelevant for responses: behavioral and neural correlates of attention show spatial biases, specific to the location at which memory items were encoded. This suggests that VWM is spatially organized and that maintaining information might rely on the allocation of spatial attention towards the location of memory items. Importantly, attention often needs to be dynamically redistributed between several locations, e.g. in preparation for an upcoming probe. Very little is known about how attentional resources are distributed between multiple locations during a VWM task and even less about the dynamic changes governing such attentional shifts over time. This is largely due to the inability to use behavioral outcomes to reveal fast dynamic changes within trials. We here demonstrate EEG Steady-State Visual Evoked Potentials (SSVEPs) to successfully track the dynamic allocation of spatial attention during a VWM task. Participants were presented with to-be-memorized gratings and distractors at two distinct locations. During maintenance and retrieval, each location was tagged with a disk flickering at either 10 or 13 Hz. This allowed us to dynamically track attention allocated to memory and distractor items via their coupling with space by quantifying the amplitude and coherence of SSVEP responses in the EEG signal to flickering stimuli at the former memory and distractor locations. SSVEP responses at memory locations did not differ from distractor locations during early parts of the maintenance window. However, shortly before probe comparison, we observed a decrease in SSVEP coherence over distractor locations indicative of a reallocation of spatial attentional resources. Reaction times were shorter when preceded by stronger decreases in SSVEP coherence at distractor locations, reflecting the reallocation of attention from the distractor location to the memory location or towards the distinct upcoming probe location. Broader Significance We demonstrate that SSVEPs can inform about dynamic processes in VWM, even if location does not have to be reported by participants. This finding not only supports the notion of a spatially organized VWM, but also reveals that SSVEPs betray a dynamic prioritization process of working memory items and locations over time that is directly predictive of memory performance.

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bioRxiv2022

A matter of availability: Neural representations of task-relevant stimulus features are sharper when stimuli are memorized rather than perceived.

Our visual environment is relatively stable over time and an optimized visual system ought to capitalize on this by not devoting any representational resources to objects that are still present. Subjective experience, however, suggests that externally available (i.e., perceived) information is more strongly represented in neural signals than memorized information. To distinguish between these possibilities, we use EEG multivariate pattern analysis to quantify the strength of representation of task-relevant features (color or spatial frequency) in anticipation of a change-detection task. Perceptual availability was manipulated between experimental blocks by either keeping the stimulus on the screen during a two second delay period (perception) or removing it shortly after its initial presentation for the same time period (memory). We find that task-relevant (i.e., attended) memorized features are more strongly represented than irrelevant features. More importantly, we find significantly weaker representations for available (perceived and attended) features than for unavailable (memorized and attended) features. Contrary to what subjective experience suggests, our findings demonstrate that vividly perceived and attended stimuli elicit weaker neural representations (in terms of detectable multivariate information) than stimuli maintained in visual working memory. We hypothesize that an efficient visual system spends little of its limited resources on the internal representation of information that is externally available anyway.

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bioRxiv2020

Exploring the interaction between the pupillary light response after exogenous attentional cueing and detection performance

Pupil size changes under different light conditions. Whereas this pupillary light response (PLR) has long been regarded to be influenced by luminance only, recent studies indicated the PLR is also modulated by cognitive factors such as the allocation of spatial attention. This attentional modulation of the PLR has previously been hypothesized to facilitate detection and discrimination of visual information. Here, we replicated the finding that the pupil dilates when a cue is presented at the dark side of a screen and constricts when the cue is presented at the bright side, even when the eyes are fixated at the center. Furthermore, we investigated whether this modulation of the PLR, evoked by exogenous shifts of covert attention, facilitates perception operationalized as detection performance for threshold stimuli. Results showed that a larger pupil was indeed related to increased detection performance, although this effect was restricted to conditions in which both cue and target appeared on a dark surface. Our findings are in line with the notion that pupil dilations improve detectability, whereas pupil constrictions enhance discriminability of small stimuli.

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