Biology subjects

Busch, N. A.

Publications and source records attributed to Busch, N. A..

17 recordsLinked to original sources

bioRxiv2026

Spatial attention and lateralized pre-stimulus alpha shape iconic memory via inhibition

The earliest stage of visual memory is often characterized as pre-attentive, yet recent work suggests that spatial attention and pre-stimulus alpha oscillations both shape iconic memory at its onset. Whether these influences reflect a common inhibitory mechanism or contribute independently is unknown. We combined an endogenous spatial pre-cue (valid, invalid, neutral) with an analysis of pre-stimulus alpha power in a partial-report paradigm, at target-to-post-cue onset asynchronies (SOAs) of 0, 120, and 1240 ms, while recording EEG from 45 participants. Behaviorally, perceptual sensitivity (d') showed a cost-dominated signature: invalid cues impaired performance relative to both neutral and valid cues at the 0 and 120 ms SOAs, with no benefit of valid over neutral cues. The pre-stimulus EEG mirrored this asymmetry: at 120 ms, stronger alpha power ipsilateral to the target predicted higher d', whereas contralateral alpha had no effect at any SOA, indicating suppression of the irrelevant hemifield rather than facilitation of the target. This ipsilateral effect was additive with cue validity rather than interactive, and it persisted in neutral trials without any directional cue. Iconic memory is thus continuously biased by the inhibitory state of early visual cortex, to which endogenous attention and spontaneous excitability fluctuations contribute through separable channels. Significance StatementWhether the earliest stage of visual memory depends on attention has long been debated. We show that the same asymmetry with which spatial attention shapes iconic memory--misdirecting attention impairs memory, but correctly directing it yields no benefit--also appears in EEG alpha power. Stronger prestimulus alpha power over the hemisphere ipsilateral to the target improves memory, while activity over the target-processing hemisphere does not. This alpha effect occurs even without any spatial cue, showing that it does not depend on deliberate attention. Because the cue-driven and spontaneous alpha effects add together rather than interact, they reflect two separable routes to the same outcome: suppression of irrelevant input. Early visual memory is thus continuously gated by the inhibitory state of visual cortex.

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bioRxiv2026

Encoding and Retrieval in Parallel: ERP Correlates of Continuous Recognition Memory for Natural Scenes

Human long-term memory for visual scenes is remarkably robust, yet the neural mechanisms supporting memory encoding and retrieval remain poorly understood when both processes must operate at the same time. For instance, this might happen when we encounter a familiar place while simultaneously forming new memories of this encounter. We investigated electrophysiological correlates of visual recognition memory using a continuous recognition task (CRT), in which participants judged a continuous stream of scene photographs as previously seen or new, such that encoding and retrieval occurred in parallel on every trial. To make recognition particularly demanding, stimuli were drawn from only four scene categories. Thirty-one participants performed the task while EEG was recorded, and we analyzed canonical ERP markers of retrieval (mid-frontal FN400, 300-550 ms; late parietal effect, LPE, 550-800 ms) and encoding (subsequent memory effect, SME) as a function of stimulus repetition and lag between consecutive presentations. FN400 showed robust old/new effects for both repetitions, whereas LPE differences emerged only at the second repetition. While FN400 amplitude was insensitive to lag, LPE amplitude decreased systematically with increasing lag, mirroring the behavioral pattern of declining accuracy and slower responses. A significant SME emerged selectively for images subsequently recognized on both repetitions, indicating that the SME in continuous recognition is specific for the most robustly encoded items and reflects the strength of encoding. Together, these findings show that canonical ERP markers of recognition memory are preserved even when encoding and retrieval operate concurrently, but their expression depends on how often and how recently an item has previously been encoded - parameters that can be flexibly manipulated within the CRT. This demonstrates that the CRT is sensitive to fine-grained temporal dynamics of memory formation and retrieval that could be missed under standard single-repetition designs.

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bioRxiv2026

Scene memorability reflects representational distinctiveness within visual categories

Some images are consistently remembered better than others, suggesting that memorability reflects intrinsic image properties. We tested whether within-category distinctiveness underlies this effect. Across three experiments (N = 477), participants categorized indoor scenes previously rated for subjective typicality and then completed recognition memory tests. Typical scenes were categorized faster and more accurately, but were remembered worse and showed a more liberal response bias than atypical scenes. These opposing effects were robust across categories. To link subjective typicality to visual representations, we quantified image distinctiveness using a convolutional neural network (CNN). Across layers, CNN-derived distinctiveness closely tracked human typicality judgments and predicted both categorization speed and memorability, with strongest effects in higher, semantic layers. Critically, the memory advantage for atypical scenes persisted even when most images were atypical, ruling out rarity within the experimental context. Together, the results show that intrinsic scene memorability reflects an images position within a category-specific representational space.

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bioRxiv2026

Effects of spatial attention on iconic memory are primarily driven by costs rather than benefits

The role of spatial attention in iconic memory - an early interface between visual perception and short-term memory - remains poorly understood. Across two experiments run in 2025, we investigated how endogenous spatial attention modulates iconic memory using a partial-report paradigm. In both exper-iments, pre-cues manipulated the allocation of spatial attention before stimulus onset. Stimulus arrays were then briefly presented to one hemifield and followed by a post-cue that probed iconic memory at varying delays after stimulus offset. In Experiment 1 (N = 47), valid attentional cues improved perfor-mance at short delays. Performance was modeled with an exponential decay function to dissociate effects on initial stimulus availability at short SOAs, the rate of iconic decay, and later transfer to working mem-ory. This analysis indicated that valid pre-cues increased initial stimulus availability relative to invalid pre-cues. In Experiment 2 (N = 66), a neutral pre-cue condition was added, and post-cues were pre-sented at three delays (0, 120, and 1240 ms). This revealed that performance differences were driven by attentional costs at invalidly cued locations, with no detectable benefits at validly cued locations relative to neutral cues. Together, these results show that spatial attention modulates the earliest measurable phase of iconic memory by shaping the initial sensory trace. The cost-dominated pattern suggests that attention primarily suppresses information at unattended locations rather than enhancing representa-tions at attended locations. This finding challenges the view of iconic memory as a pre-attentive sensory store and indicates that attentional selection operates earlier than previously assumed. Significance StatementThe influence of attention on iconic memory - a high-capacity, ultra-brief sensory store - remains highly debated. We demonstrate that endogenous spatial attention modulates iconic memory at its earliest measurable stage. Critically, this modulation reflects an attentional cost at unattended locations rather than a benefit at attended locations, suggesting that spatial attention acts through inhibitory suppression of irrelevant sensory input. These findings challenge models proposing that early sensory representation is categorically attention-free and establish a suppressive role for attention in shaping visual short-term memory at its earliest stage.

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bioRxiv2025

Pre-stimulus pupil-linked arousal enhances initial stimulus availability and accelerates decay in iconic memory.

Pupil diameter reflects not only reflexive responses to light but also spontaneous fluctuations in arousal. Such pre-stimulus fluctuations may shape visual performance, yet it remains unclear whether they only affect perceptual sensitivity or decision processes in near-threshold tasks, or instead influence the temporal availability of sensory information even for highly visible stimuli. We tested whether pupil-linked arousal modulates iconic memory, a high-capacity but short-lived visual store bridging sensory encoding and short-term memory. Based on a model in which a brief stimulus evokes an internal response decaying over a few hundred milliseconds, we hypothesized that increased arousal enhances performance either by amplifying the initial response or by slowing its decay. Thirty-seven participants viewed brief displays of six oriented stimuli, followed by a cue after a variable stimulus-cue onset asynchrony indicating which item to report. Pre-stimulus pupil diameter was continuously recorded, and behavioral data were fitted with an exponential decay function estimating initial stimulus availability, decay rate, and asymptotic performance. Larger pre-stimulus pupil dilation was associated with higher initial stimulus availability but faster decay of the iconic trace, while information transferred into short-term memory and confidence ratings remained unaffected. These findings demonstrate that spontaneous fluctuations in arousal shape the temporal dynamics of sensory persistence. Elevated arousal boosts the initial strength of visual representations but shortens their duration, suggesting that arousal adaptively prioritizes rapid updating of visual input over prolonged stability. Significance StatementHow does arousal shape the earliest stages of visual memory? By leveraging a criterion-free partialreport task that emphasizes the temporal availability of sensory information, we show that spontaneous pre-stimulus pupil dilation - an index of arousal - selectively boosts the initial availability of iconic memory while accelerating its decay. This dual effect suggests that arousal tunes the temporal dynamics of sensory persistence, potentially prioritizing rapid updating of incoming information. These findings advance the understanding of how state-dependent fluctuations in arousal shape early perception in a context that minimizes decision-bias confounds.

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bioRxiv2025

Theta-rhythmic attentional exploration of space

Attention facilitates stimulus processing by selecting specific locations (spatial attention) or features (feature-based attention). It can be sustained on a given location or feature, or re-oriented between locations or between features, enabling attentional exploration. Sustained attention was associated with alpha (8-12Hz1-4) oscillations. More recently, authors suggested that exploratory attention was instead related to theta (4-7Hz; for review5-7). To date, there is no systematic evaluation of attentional exploration across stimulus dimensions (space, features) in relation to theta oscillations. Using attentional cueing and electroencephalography (EEG) in humans, we assessed exploration of stimulus dimension during the (1) precue-to-stimulus (first attentional orienting) and (2) post-stimulus (during stimulus processing) trial periods. In the precue-to-stimulus period, we classified the cued dimension (attending to a location/feature) from EEG topographies to assess the neural dynamics of sustained and exploratory attentional orienting. Temporal generalization matrices showed oscillatory patterns of classification accuracies across time. When attention was sustained on a cued location but explored the feature dimension as the target feature was unknown, only the alpha frequency was observed. When attention was sustained on a cued feature but explored locations, both alpha and theta frequencies were observed. Focusing on post-stimulus theta oscillations revealed increased theta power in invalid trials (attention reorients from the precued distractor location/feature to the target -exploration) relative to valid trials in both feature-based and spatial attention conditions. Post-stimulus theta oscillations further predicted behavioral performance. Together, our results show that while alpha oscillations are associated with sustained attention regardless of the attended dimension, theta oscillations are specifically related to spatial exploration.

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bioRxiv2024

Spontaneous alpha-band lateralization extends persistence of visual information in iconic memory by modulating cortical excitability.

Pre-stimulus alpha oscillations in the visual cortex modulate neuronal excitability, influencing sensory processing and decision-making. While this relationship has been demonstrated mostly in detection tasks with low-visibility stimuli, interpretations of such effects can be ambiguous due to biases, making it difficult to clearly distinguish between perception-related and decision-related effects. In this study, we investigated how spontaneous fluctuations in pre-stimulus alpha power affect iconic memory, a high-capacity, ultra-short visual memory store. Data from 49 healthy adults (34 female and 15 male) was analyzed. We employed a partial report task, where a brief display of six stimuli was followed by a report cue indicating the target stimulus. In this paradigm, accuracy at short stimulus-cue onset asynchronies (SOAs) is typically high, reflecting the initial availability of sensory information, but it rapidly declines at intermediate SOAs due to the decay of the iconic memory trace, stabilizing at a low asymptote at long SOAs, representing the limited capacity of short-term memory. Crucially, performance in this task is constrained by the temporal persistence of sensory information, not by low visibility or response bias. We found that strong pre-stimulus alpha power enhanced performance by amplifying initial stimulus availability without affecting the speed of iconic decay. This effect was driven predominantly by stronger pre-stimulus alpha power in the hemisphere ipsilateral to the to-be-reported target, likely suppressing neuronal excitability of neurons coding irrelevant stimuli. Our findings underscore the role of alpha oscillations in modulating neuronal excitability and visual perception, independent of decision-making strategies implicated in prior studies.

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bioRxiv2023

Contralateral delay activity and alpha lateralization reflect retinotopic and screen-centered reference frames in visual memory

The visual system represents objects in a lateralized manner, with contralateral cortical hemispheres responsible for left and right visual hemifields. This organization extends to visual short-term memory (VSTM), as evidenced by electrophysiological indices of VSTM maintenance: contralateral delay activity (CDA) and alpha-band lateralization. However, it remains unclear if VSTM represents object locations in gaze-centered (retinotopic) or screen-centered (spatiotopic) coordinates, especially after eye movements. In two experiments, participants encoded the colors of target objects and made a lateral saccade during the maintenance interval, thereby shifting the objects location on the retina. A non-lateralized probe stimulus was then presented at the new fixation for a change detection task. The CDA maintained lateralization towards the targets original retinotopic location, unaffected by subsequent saccades, and did not invert polarity even when a saccade brought that location into the opposite hemifield. We also found conventional alpha lateralization towards the targets location before a saccade. After a saccade, however, alpha was lateralized towards the screen center regardless of the targets original location, even in a control condition without any memory requirements. This suggest that post-saccadic alpha-band lateralization reflects attentional processes unrelated to memory, while pre- and post-saccade CDA reflect VSTM maintenance in a retinotopic reference frame.

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bioRxiv2022

Alpha-band lateralization and microsaccades elicited by exogenous cues do not track attentional orienting

We explore the world by constantly shifting our focus of attention towards salient stimuli, and then disengaging from them in search of new ones. The alpha rhythm (8-13 Hz) has been suggested as a pivotal neural substrate of these attentional shifts, due to its local synchronization and desynchronization that suppresses irrelevant cortical areas and facilitates relevant areas, a phenomenon called alpha lateralization. Whether alpha lateralization tracks the focus of attention from orienting toward a salient stimulus to disengaging from it is still an open question. In this study, we addressed this question by leveraging the well-established phenomenon of Inhibition of Return (IOR), consisting of an initial facilitation in response times (RTs) for target stimuli appearing at an exogenously cued location, followed by a suppression of that location. Our behavioral data showed a typical IOR effect with both early facilitation and subsequent inhibition. By contrast, alpha was lateralized only in the cued direction, but never re-lateralized in a manner compatible with the behavioral inhibition effect. Importantly, also the initial lateralization towards the cue ocurred too late to account for the behavioral facilitation effect. Furthermore, we analyzed the interaction between alpha lateralization and microsaccades: at the same time when alpha was lateralized towards the cued location, microsaccades were mostly oriented away from the cued location. Crucially, the two phenomena showed a significant positive correlation. These results indicate that alpha lateralization reflects primarily the processing of salient stimuli, challenging the view that alpha lateralization is directly involved in exogenous attentional orienting per se. We discuss the relevance of the present findings for an oculomotor account of alpha lateralization as a modulator of cortical excitability in preparation of a saccade.

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bioRxiv2021

Pupillometry and electroencephalography in the digit span task

This dataset consists of raw 64-channel EEG, cardiovascular (electrocardiography and photoplethysmography), and pupillometry data from 86 human participants recorded during 4 minutes of eyes-closed resting and during performance of a classic working memory task - digit span task with serial recall. The participants either memorized or just listened to sequences of 5, 9, or 13 digits presented auditorily every 2 seconds. The dataset can be used for (1) developing algorithms for cognitive load discrimination and detection of cognitive overload; (2) studying neural (event-related potentials and brain oscillations) and peripheral (electrocardiography, photoplethysmography, and pupillometry) physiological signals during encoding and maintenance of each sequentially presented memory item; (3) correlating cognitive load and individual differences in working memory to neural and peripheral physiology, and studying the relationship between the physiological signals; (4) integration of the physiological findings with the vast knowledge coming from behavioral studies of verbal working memory in simple span paradigms. The data are shared in Brain Imaging Data Structure (BIDS) format and freely available on OpenNeuro (https://openneuro.org/datasets/ds003838).

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bioRxiv2021

Spontaneous alpha-band oscillations bias subjective contrast perception

Perceptual decisions depend both on the features of the incoming stimulus and on the ongoing brain activity at the moment the stimulus is received. Specifically, trial-to-trial fluctuations in cortical excitability have been linked to fluctuations in the amplitude of pre-stimulus alpha oscillations ({approx}8-13 Hz), which are in turn are associated with fluctuations in subjects tendency to report the detection of a stimulus. It is currently unknown whether alpha oscillations bias post-perceptual decision making, or even bias subjective perception itself. To answer this question, we used a contrast discrimination task in which subjects reported which of two gratings - one in each hemifield - was perceived as having a stronger contrast. Our EEG analysis showed that subjective contrast was reduced for the stimulus in the hemifield represented in the hemisphere with relatively stronger pre-stimulus alpha amplitude, reflecting reduced cortical excitability. Furthermore, the strength of this spontaneous hemispheric lateralization was strongly correlated with the magnitude of individual subjects biases, suggesting that the spontaneous patterns of alpha lateralization play a role in explaining the intersubject variability in contrast perception. These results indicate that spontaneous fluctuations in cortical excitability, indicted by patterns of pre-stimulus alpha amplitude, affect perceptual decisions by altering the phenomenological perception of the visual world. Significance StatementOur moment to moment perception of the world is shaped by the features of the environment surrounding us, as much as by the constantly evolving states that characterize our brain activity. Previous research showed how the ongoing electrical activity of the brain can influence whether a stimulus has accessed conscious perception. However, evidence is currently missing on whether these electrical brain states can be associated to the subjective experience of a sensory input. Here we show that local changes in patterns of electrical brain activity preceding visual stimulation can bias our phenomenological perception. Importantly, we show that the strength of these variations can help explaining the great inter-individual variability in how we perceive the visual environment surrounding us.

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bioRxiv2021

Respiration aligns perception with neural excitability

Recent studies from the field of interoception have highlighted the link between bodily and neural rhythms during action, perception, and cognition. The mechanisms underlying functional body-brain coupling, however, are poorly understood, as are the ways in which they modulate behaviour. We acquired respiration and human magnetoencephalography (MEG) data from a near-threshold spatial detection task to investigate the trivariate relationship between respiration, neural excitability, and performance. Respiration was found to significantly modulate perceptual sensitivity as well as posterior alpha power (8 - 13 Hz), a well-established proxy of cortical excitability. In turn, alpha suppression prior to detected vs undetected targets underscored the behavioural benefits of heightened excitability. Notably, respiration-locked excitability changes were maximised at a respiration phase lag of around - 30{degrees} and thus temporally preceded performance changes. In line with interoceptive inference accounts, these results suggest that respiration actively aligns sampling of sensory information with transient cycles of heightened excitability to facilitate performance.

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bioRxiv2020

Theta rhythmic attentional enhancement of alpha rhythmic perceptual sampling

Accumulating evidence suggests that visual perception operates in an oscillatory fashion at an alpha frequency (around 10 Hz). Moreover, visual attention also seems to operate rhythmically, albeit at a theta frequency (around 5 Hz). Both rhythms are often associated to "perceptual snapshots" taken at the favorable phases of these rhythms. However, less is known about the unfavorable phases: do they constitute "blind gaps," requiring the observer to guess, or is information sampled with reduced precision insufficient for the task demands? As simple detection or discrimination tasks cannot distinguish these options, we applied a continuous report task by asking for the exact orientation of a Landolt rings gap to estimate separate model parameters for precision and the amount of guessing. We embedded this task in a well-established psychophysical protocol by densely sampling such reports across 20 cue-target stimulus onset asynchronies in a Posner-like cueing paradigm manipulating involuntary spatial attention. Testing the resulting time courses of the guessing and precision parameters for rhythmicities using a fast Fourier transform, we found an alpha rhythm (9.6 Hz) in the precision parameter and a theta rhythm (4.8 Hz) in the guess rate for invalidly cued trials. These results indicate that the perceptual alpha rhythm reflects fluctuations in spatial resolution, while the attentional theta rhythm provides periodic enhancement of this resolution. We propose a tentative model for this interplay and argue that both rhythms result in an environmental sampling characterized by fluctuating spatial resolution, speaking against a strict succession of blind gaps and perceptual snapshots.

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bioRxiv2019

Exploitation of local and global information in predictive processing

While prediction errors have been established to instigate learning through model adaptation, recent studies have stressed the role of model-compliant events in predictive processing. Specifically, so-called checkpoints have been suggested to be sampled for model evaluation, particularly in uncertain contexts.\n\nUsing electroencephalography (EEG), the present study aimed to investigate the interplay of such global information and local adjustment cues prompting on-line adjustments of expectations. Within a stream of single digits, participants were to detect ordered sequences (i.e., 3-4-5-6-7) that had a regular length of five digits and were occasionally extended to seven digits. Across experimental blocks, these extensions were either rare (low irreducible uncertainty) or frequent (high uncertainty) and could be unexpected or indicated by incidental colour cues.\n\nExploitation of local cue information was reflected in significant decoding of cues vs non-informative analogues using multivariate pattern classification. Modulation of checkpoint processing as a function of global uncertainty was likewise reflected in significant decoding of high vs low uncertainty checkpoints. In line with previous results, both analyses comprised the P3b time frame as an index of excess model-compliant information sampled from probabilistic events.\n\nAccounting for cue information, an N400 component was revealed as the correlate of locally unexpected (vs expected) outcomes, reflecting effortful integration of incongruous information. Finally, we compared the fit of a global model (disregarding local adjustments) and a local model (including local adjustments) using representational similarity analysis (RSA). RSA revealed a better fit for the global model, underscoring the precedence of global reference frames in hierarchical predictive processing.

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bioRxiv2018

Multiple mechanisms link prestimulus neural oscillations to sensory responses

Spontaneous fluctuations of neural activity may explain why sensory responses vary across repeated presentation of the same physical stimulus. To test this hypothesis, we recorded electroencephalography in humans during stimulation with identical visual stimuli and analyzed how prestimulus neural oscillations modulate different stages of sensory processing reflected by distinct components of the event-related potential (ERP). We found that strong prestimulus alpha- and beta-band power resulted in a suppression of early ERP components (C1 and N150) and in an amplification of late components (after 0.4 s). Whereas functional inhibition of sensory processing underlies the reduction of early ERP responses, we found that the modulation of non-zero-mean oscillations (baseline shift) accounted for the amplification of late responses. Distinguishing between these two mechanisms is crucial for the understanding of how internal brain states modulate the processing of incoming sensory information.

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bioRxiv2018

Attention explores space periodically at the theta frequency

Voluntary attention is at the core of cognitive functions. Attention can be sustained at a location, or reoriented in space to allow processing at other locations, critical in an ever-changing environment. Numerous studies have investigated attentional orienting in time and space but little is known about the spatio-temporal dynamics of attentional reorienting. Here, we explicitly manipulated attentional reorienting using a cueing procedure in a 2-AFC orientation discrimination task. At various delays during the task, we interrogated attentional deployment by flashing two probe stimuli. Then, solving a second-degree equation to estimate the report probability at each probe location, we demonstrated that attention reorients periodically at ~4 Hz (theta) between the two stimulus locations. We further observed that each stimulus location is sampled at ~11 Hz (alpha). Finally, we support our mathematical approach using simulations and show that this method is sufficiently powered making it a valuable tool for studying the spatio-temporal dynamics of attention.

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bioRxiv2017

Moment-to-moment fluctuations in neuronal excitability bias subjective perception rather than decision-making

Perceiving an external stimulus not only depends on the physical features of the stimulus, but also fundamentally on the current state of neuronal excitability, indexed by the power of ongoing alpha oscillations. Recent studies suggest that heightened excitability does not improve perceptual acuity, but biases observers to report the presence of a stimulus regardless of its physical presence. It is unknown whether this bias is due to changes in observers subjective perceptual experience (perceptual bias) or their perception-independent decision-making strategy (decision bias). We tested these alternative interpretations in an EEG experiment in which human participants performed two-interval forced choice (2IFC) detection and discrimination. According to signal detection theory, perceptual bias only affects 2IFC detection, but not discrimination, while interval decision bias should be task-independent. We found that detection was optimal in trials in which excitability before the stimulus-present interval exceeded that before the stimulus-absent interval, consistent with an effect of excitability on perceptual bias. By contrast, discrimination accuracy was unaffected by excitability fluctuations between intervals, ruling out an effect on interval decision bias. We conclude that the current state of neuronal excitability biases the perceptual experience itself, rather than the decision process.

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