Biology subjects

van Ede, F.

Publications and source records attributed to van Ede, F..

34 records · Page 2Linked to original sources

bioRxiv2023

Efficient spatial coding for covert selective attention

When holding information in mind, it is vital to keep individual representations separated and selectively accessible for behaviour. Space is known to serve as a foundational scaffold for mnemonic individuation, yet the format and flexibility of spatial scaffolding for working memory remain elusive. We hypothesised that information in working memory can be re-coded from its native format at encoding to organise and retain internal representations sparsely. To test this, we presented to-be-memorised visual objects at distinct directions and distances and leveraged gaze biases during mnemonic selection as an implicit read-out of spatial scaffolding for working memory. We report how the human brain abstracts away over incidental object distance when direction alone suffices as a scaffold, but incorporates distance when it aids mnemonic individuation. This unveils the principle of sparse spatial scaffolding for working memory, whereby the human brain flexibly resorts to the minimal spatial scaffold needed for the individuation of internal representations.

neuroscience↗

bioRxiv2023

Microsaccades track location-based object rehearsal in visual working memory

Besides controlling eye movements, the brains oculomotor system has been implicated in the control of covert spatial attention and the rehearsal of spatial information in working memory. We investigated whether the oculomotor system also contributes to rehearsing visual objects in working memory when object location is never asked about. To address this, we tracked the incidental use of locations for mnemonic rehearsal via directional biases in microsaccades while participants maintained two visual objects (coloured oriented gratings) in working memory. By varying the stimulus configuration (horizontal, diagonal, and vertical) at encoding, we could quantify whether microsaccades were more aligned with the configurational axis of the memory contents, as opposed to the orthogonal axis. Experiment 1 revealed that microsaccades continued to be biased along the axis of the memory content several seconds into the working-memory delay. In Experiment 2, we confirmed that this directional microsaccade bias was specific to memory demands, ruling out lingering effects from passive and attentive encoding of the same visual objects in the same configurations. Thus, by studying microsaccade directions, we uncover oculomotor-driven rehearsal of visual objects in working memory through their associated locations. SIGNIFICANCE STATEMENTHow humans rehearse information in working memory is a foundational question in psychology and neuroscience. To provide insight into the cognitive and neural bases of working-memory rehearsal, we turned to microsaccades - small eye-movements produced by the brains oculomotor system. We reveal how microsaccades track the locations of visual objects during memory rehearsal, even when object locations are never asked about. This brings three advances. From a psychology standpoint, it demonstrates how memory rehearsal automatically engages object locations. From a neuroscience standpoint, it demonstrates how such location-based rehearsal relies on brain circuitry that also controls our eyes. Finally, from a practical standpoint, it demonstrates how microsaccades can be utilised to track the properties of working-memory rehearsal across space and time.

neuroscience↗

bioRxiv2023

Flexible early prospection of potential behavior in working memory

For visual working memory to serve upcoming behavior, it is crucial that we prepare for the potential use of working-memory contents ahead of time. Recent studies have demonstrated how the prospection and planning for an upcoming manual action starts early after visual encoding, and occurs alongside visual retention. Here, we address whether such output planning in visual working memory flexibly adapts to different visual-motor mappings, and occurs even when an upcoming action will only potentially become relevant for behavior. Participants performed a visual-motor working memory task in which they remembered one or two visual items for later (potential) use. We tracked planning of upcoming behavior through contralateral attenuation of beta-band activity - a canonical motor-cortical EEG signature of manual-action planning. This revealed how action encoding and subsequent planning alongside visual working memory (1) reflects anticipated task demands rather than specific visual-motor mappings, (2) occurs even for actions that will only potentially become relevant for behavior, and (3) is associated with better performance for the encoded item, at the expense of performance to other working-memory content. This reveals how the potential prospective use of visual working memory content is flexibly planned early on, with consequences for later performance.

neuroscience↗

bioRxiv2023

Jointly looking to the past and the future in visual working memory

Working memory enables us to bridge past sensory information to upcoming future behaviour. Accordingly, by its very nature, working memory is concerned with two components: the past and the future. Yet, in conventional laboratory tasks, these two components are often conflated, such as when sensory information in working memory is encoded and tested at the same location. We developed a task in which we dissociated the past (encoded location) and future (to-be-tested location) attributes of visual contents in working memory. This enabled us to independently track the utilisation of past and future memory attributes through gaze, as observed during mnemonic selection. Our results reveal the joint consideration of past and future locations. This was prevalent even at the single-trial level of individual saccades that were jointly biased to the past and future. This uncovers the rich nature of working memory representations, whereby both past and future memory attributes are retained and can be accessed together when memory contents become relevant for behaviour.

neuroscience↗

bioRxiv2023

No trade-off between the use of space and time for working memory

Space and time can each act as scaffolds for the individuation and selection of visual objects in working memory. Here we ask whether there is a trade-off between the use of space and time for visual working memory: whether observers will rely less on space, when memoranda can additionally be individuated through time. We tracked the use of space through directional biases in microsaccades after attention was directed to memory contents that had been encoded simultaneously or sequentially to the left and right of fixation. We found that spatial gaze biases were preserved when participants could (Experiment 1) and even when they had to (Experiment 2) additionally rely on time for object individuation. Thus, space remains a profound organizing medium for working memory even when other organizing sources are available and utilised, with no evidence for a trade-off between the use of space and time. SIGNIFICANCE STATEMENTSpace and time provide two foundational dimensions that govern not only our sensations and actions, but also the organisation of internal representations in working memory. Space and time have each been shown to provide an automatic organising principle - or scaffold - for memory retention. We uniquely address whether there is a trade-off between the use of space and time for working memory. We show that the profound and automatic reliance on memorised space is preserved not only when time can, but even when time has to be used for individuation and selection of memory contents. This shows there is no trade-off between spatial and temporal codes available for memory organisation, advancing our understanding of the spatial-temporal architecture of mind.

neuroscience↗

bioRxiv2022

Microsaccades transiently lateralise EEG alpha activity

The lateralisation of 8-12 Hz alpha activity is a canonical signature of human spatial cognition that is typically studied under strict fixation requirements. Yet, even during attempted fixation, the brain produces small involuntary eye movements known as microsaccades. Here we report how spontaneous microsaccades - made in the absence of incentives to look elsewhere - can themselves drive transient lateralisation of EEG alpha power according to microsaccade direction. This transient lateralisation of posterior alpha power occurs similarly following start and return microsaccades and is driven by increased alpha power ipsilateral to microsaccade direction. This reveals new links between spontaneous microsaccades and human electrophysiological brain activity, and highlights how microsaccades are an important factor to consider in studies relating alpha activity to spatial cognition.

neuroscience↗

bioRxiv2022

Head-direction tracks internally directed selective attention in visual working memory

We shift our gaze even when we orient attention internally to visual representations in working memory. Here, we show the bodily orienting response associated with internal selective attention is widespread as it also includes the head. In three virtual reality (VR) experiments, participants remembered two visual items. After a working memory delay, a central colour cue indicated which item needed to be reproduced from memory. After the cue, head movements became biased in the direction of the memorised location of the cued memory item - despite there being no items to orient towards in the external environment. The heading-direction bias had a distinct temporal profile from the gaze bias. Our findings reveal that directing attention within the spatial layout of visual working memory bears a strong relation to the overt head orienting response we engage when directing attention to sensory information in the external environment. The heading-direction bias further demonstrates common neural circuitry is engaged during external and internal orienting of attention.

animal behavior and cognition↗

bioRxiv2022

A neural decision signal during internal sampling from working memory

How humans transform sensory information into decisions that steer purposeful behaviour is a central question in psychology and neuroscience that is traditionally investigated during the sampling of external sensations. The decision-making framework of gradual information sampling toward a decision has been proposed also to apply when sampling internal sensory evidence from memory. However, neural evidence for this proposal remains lacking. Here we report that sampling internal visual representations from working memory elicits a scalp-EEG potential associated with gradual evidence accumulation - the Central Parietal Positivity (CPP). Consistent with an evolving decision process, we show how this signal (i) builds up to, and scales with, the time participants require to reach a decision about the cued memory content and (ii) is amplified when having to select (decide) among multiple contents in working memory. These results bring the electrophysiology of decision making into the domain of working memory and suggest that variability in memory-guided behaviour may be driven (at least in part) by variations in the sampling of our inner mental contents.

neuroscience↗

bioRxiv2021

Planning the potential future during multi-item visual working memory

Working memory allows us to retain visual information to guide upcoming future behavior. In line with this future-oriented purpose of working memory, recent studies have shown that action planning occurs during encoding and retention of a single visual item, for which the upcoming action is certain. We asked whether and how this extends to multi-item visual working memory, when visual representations serve the potential future. Human participants performed a visual working memory task with a memory-load manipulation (one/two/four items), and a delayed orientation-reproduction report (of one item). We measured EEG to track 15-25 Hz beta activity in electrodes contralateral to the required response hand - a canonical marker of action planning. We show an attenuation of beta activity, not only in load one (with one certain future action), but also in load two (with two potential future actions), compared to load four (with low prospective-action certainty). Moreover, in load two, potential action planning occurs regardless whether both visual items afford similar or dissimilar manual responses; and it predicts the speed of ensuing memory-guided behavior. This shows that potential action planning occurs during multi-item visual working memory, and brings the perspective that working memory helps us prepare for the potential future.

neuroscience↗

bioRxiv2021

Functional but not obligatory link between microsaccades and neural modulation by covert spatial attention

Covert spatial attention is associated with spatially specific modulation of neural activity as well as with directional biases in fixational eye-movements known as microsaccades. Recently, this link has been suggested to be obligatory, such that modulation of neural activity by covert spatial attention occurs only when paired with microsaccades toward the attended location. Here we revisited this link between microsaccades and neural modulation by covert spatial attention in humans. We investigated spatial modulation of 8-12 Hz EEG alpha activity and microsaccades in a context with no incentive for overt gaze behaviour: when attention is directed internally within the spatial layout of visual working memory. In line with a common attentional origin, we show that spatial modulations of alpha activity and microsaccades co-vary: alpha lateralisation is stronger in trials with microsaccades toward compared to away from the memorised location of the to-be-attended item and occurs earlier in trials with earlier microsaccades toward this item. Critically, however, trials without attention-driven microsaccades nevertheless showed clear spatial modulation of alpha activity - comparable to the neural modulation observed in trials with attention-driven microsaccades. Thus, directional biases in microsaccades are correlated with neural signatures of covert spatial attention, but they are not a prerequisite for neural modulation by covert spatial attention to be manifest.

neuroscience↗

bioRxiv2021

Multiple and Dissociable Effects of Sensory History on Working-Memory Performance

AO_SCPLOWBSTRACTC_SCPLOWBehavioural reports of sensory information are biased by stimulus history. The nature and direction of such serial-dependence biases can differ between experimental settings - both attractive and repulsive biases towards previous stimuli have been observed. How and when these biases arise in the human brain remains largely unexplored. They could occur either via a change in sensory processing itself and/or during post-perceptual processes such as maintenance or decision-making. To address this, we analysed behavioural and magnetoencephalographic data from a working-memory task in which participants were sequentially presented with two randomly oriented gratings, one of which was cued for recall at the end of the trial. Behavioural responses showed evidence for two distinct biases: 1) a within-trial repulsive bias away from the previously encoded orientation on the same trial, and 2) a between-trial attractive bias towards the task-relevant orientation on the previous trial. Multivariate classification of stimulus orientation revealed that neural representations during stimulus encoding were biased away from the previous grating orientation, regardless of whether we considered the within- or between-trial prior orientation - despite opposite effects on behaviour. These results suggest that repulsive biases occur at the level of sensory processing and can be overridden at post-perceptual stages to result in attractive biases in behaviour.

neuroscience↗

bioRxiv2021

Reduced cortico-muscular beta coupling in Parkinsons disease predicts motor impairment

Long-range communication through the motor system is thought to be facilitated by phase coupling between neural activity in the 15-30 Hz beta range. During periods of sustained muscle contraction (grip), such coupling is manifest between motor cortex and the contralateral forearm muscles - measured as the cortico-muscular coherence (CMC). We examined alterations in CMC in individuals with Parkinsons disease (PD), while equating grip strength between individuals with PD (off their medication) and healthy control participants. We show a marked reduction in beta CMC in the PD group, even though the grip strength was comparable between the two groups. Moreover, the reduced CMC was related to motor symptoms, so that individuals with lower CMC also displayed worse motor symptoms. These findings highlight the CMC as a simple, effective, and clinically relevant neural marker of PD pathology, with the potential to aid monitoring of disease progression and the efficacy of novel treatments for PD.

neuroscience↗

bioRxiv2021

Transient beta activity and connectivity during sustained motor behaviour

Neural oscillations are thought to play a central role in orchestrating activity states between distant neural populations. In humans, long-range neural connectivity has been particularly well characterised for 13-30 Hz beta activity which becomes phase coupled between the motor cortex and the contralateral muscle during isometric contraction. Based on this and related observations, beta activity and connectivity have been linked to sustaining stable cognitive and motor states - or the status quo - in the brain. Recently, however, beta activity has been shown to be short-lived, as opposed to sustained - though so far this has been reported for regional beta activity in tasks without sustained motor demands. Here, we measured magnetoencephalography (MEG) and electromyography (EMG) in 18 human participants performing an isometric-contraction (gripping) task designed to yield sustained behavioural output. If cortico-muscular beta connectivity is directly responsible for sustaining a stable motor state, then beta activity should be (or become) sustained in this context. In contrast, we found that beta activity and connectivity with the downstream muscle were transient, even when participants engaged in sustained gripping. Moreover, we found that sustained motor requirements did not prolong beta-event duration in comparison to rest. These findings suggest that long-range neural synchronisation may entail short bursts of frequency-specific connectivity, even when task demands - and behaviour - are sustained. HighlightsO_LITrial-average 13-30 Hz beta activity and connectivity with the muscle appear sustained during stable motor behaviour C_LIO_LISingle-trial beta activity and connectivity are short-lived, even when motor behaviour is sustained C_LIO_LISustained task demands do not prolong beta-event duration in comparison to resting state C_LI

neuroscience↗

bioRxiv2020

Rhythmic modulation of visual perception by continuous rhythmic auditory stimulation

At any given moment our sensory systems receive multiple, often rhythmic, inputs from the environment. Processing of temporally structured events in one sensory modality can guide both behavioural and neural processing of events in other sensory modalities, but whether this occurs remains unclear. Here, we used human electroencephalography (EEG) to test the cross-modal influences of a continuous auditory frequency-modulated (FM) sound on visual perception and visual cortical activity. We report systematic fluctuations in perceptual discrimination of brief visual stimuli in line with the phase of the FM sound. We further show that this rhythmic modulation in visual perception is related to an accompanying rhythmic modulation of neural activity recorded over visual areas. Importantly, in our task, perceptual and neural visual modulations occurred without any abrupt and salient onsets in the energy of the auditory stimulation and without any rhythmic structure in the visual stimulus. As such, the results provide a critical validation for the existence and functional role of cross-modal entrainment and demonstrates its utility for organising the perception of multisensory stimulation in the natural environment. Significance StatementOur sensory environment is filled with rhythmic structures that are often multi-sensory in nature. Here we show that the alignment of neural activity to the phase of an auditory frequency-modulated sound has cross-modal consequences for vision: yielding systematic fluctuations in perceptual discrimination of brief visual stimuli that is mediated by accompanying rhythmic modulation of neural activity recorded over visual areas. These cross-modal effects on visual neural activity and perception occurred without any abrupt and salient onsets in the energy of the auditory stimulation and without any rhythmic structure in the visual stimulus. The current work shows that continuous auditory fluctuations in the natural environment can provide a pacing signal for neural activity and perception across the senses.

neuroscience↗

bioRxiv2020

Decoding visual colour from scalp electroencephalography measurements

Recent advances have made it possible to decode various aspects of visually presented stimuli from patterns of scalp EEG measurements. As of recently, such multivariate methods have been commonly used to decode visual-spatial features such as location, orientation, or spatial frequency. In the current study, we show that it is also possible to track visual colour processing by using Linear Discriminant Analysis on patterns of EEG activity. Building on other recent demonstrations, we show that colour decoding: (1) reflects sensory qualities (as opposed to, for example, verbal labelling) with a prominent contribution from posterior electrodes contralateral to the stimulus, (2) conforms to a parametric coding space, (3) is possible in multi-item displays, and (4) is comparable in magnitude to the decoding of visual stimulus orientation. Through subsampling our data, we also provide an estimate of the approximate number of trials and participants required for robust decoding. Finally, we show that while colour decoding can be sensitive to subtle differences in luminance, our colour decoding results are primarily driven by measured colour differences between stimuli. Colour decoding opens a relevant new dimension in which to track visual processing using scalp EEG measurements, while bypassing potential confounds associated with decoding approaches that focus on spatial features.

neuroscience↗

bioRxiv2019

Comparing the prioritisation of items and feature-dimensions in visual working memory

Selective attention can be directed not only to external sensory inputs, but also to internal sensory representations held within visual working memory (VWM). To date, this has been studied predominantly following retrospective cues directing attention to particular items, or their locations in memory. In addition to item-level attentional prioritisation, recent studies have shown that selectively attending to feature dimensions in VWM can also improve memory recall performance. However, no study to date has directly compared item-based and feature-based attention in VWM, nor their neural bases. Here, we compared the benefits of retrospective cues (retro-cues) that were directed either at a multi-feature item or at a feature-dimension that was shared between two spatially segregated items. Behavioural results revealed qualitatively similar attentional benefits in both recall accuracy and response time, but also showed that cueing benefits were larger following item cues. Concurrent EEG measurements further revealed a similar attenuation of posterior alpha oscillations following both item and feature retro-cues when compared to non-informative, neutral retro-cues. We argue that attention can act flexibly to prioritise the most relevant information - at either the item or the feature-level - to optimise ensuing memory-based task performance, and we discuss the implications of the observed commonalities and differences between item-level and feature-level prioritisation in VWM.

neuroscience↗