Biology subjects

Quek, G. L.

Publications and source records attributed to Quek, G. L..

17 recordsLinked to original sources

bioRxiv2026

Enhanced neural encoding of individual exemplars in the Super-Recogniser brain is specific to faces

Super-Recognisers are known for their exceptional ability to encode and remember faces. Recent work has found robust neural codes for face identity in brain activity. Here we test whether the enhanced individuation of face identity in super-recogniser neural codes extends to exemplars from non-face categories. We recorded 64-channel electroencephalography (EEG) as 22 Super-Recognisers and 20 typical recognisers viewed rapid, randomised sequences of faces, dogs, houses, and cars (10 different images of 10 different exemplars per category). Using a neural decoding approach, we found that Super-Recognisers neural responses contained stronger and more temporally sustained information discriminating individual face identities. Moreover, Super-Recognisers displayed increased inter-individual consistency in the organisation of their face-identity representations, suggesting a more stable and/or canonical representational structure in individuals with superior face recognition abilities. Crucially, there was no evidence to suggest that these encoding advantages generalised to non-face categories: neural discrimination of individual dogs, cars, and houses was comparable across groups, and group-differences in inter-subject consistency were evident only for faces. Together, these findings suggest that enhanced perceptual encoding underlying exceptional face recognition is highly category-specific, supporting the view that expertise in this group reflects specialised mechanisms for processing facial identity rather than broadly enhanced visual discrimination capacities.

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bioRxiv2026

Robust neural face identity codes in the Super-Recogniser brain

Super-Recognisers show exceptional ability in face recognition, providing a natural model of how perceptual systems optimise for individuating visually similar stimuli in variable viewing conditions. However, the neural representations supporting this extreme perceptual expertise are unknown. Here, we tested whether Super-Recognisers (n = 23) differed from typical recognisers (n = 21) in the dimensional organisation of neural face identity coding. We recorded 64-channel electroencephalography while participants viewed random and rapidly-presented sequences containing 10 naturally varying images of 40 unfamiliar identities. Using time-resolved representational similarity analysis we measured the geometry of identity representations, their consistency across observers, and how clearly they specified face identity. Although neural expression of identity information was robust in both groups, we found three key differences between Super-Recognisers and typical recognisers. First, the geometry of face identity representations differed between groups. Second, Super-Recognisers showed greater inter-individual consistency in representational geometry. Third, Super-Recognisers neural signals discriminated between face identities more strongly than those of typical recognisers. Differences in the coding of broader face categories (sex, age, ethnicity) were notably weaker, suggesting that the observed group differences reflected fine-scale differences in identity coding rather than global reshaping of representational geometry. Strikingly, all three differences emerged within a common mid-latency interval ([~]300-500ms), implicating higher-stages of face processing associated with representations that are sensitive to face familiarity and link between perceptual and semantic domains. Together, these findings indicate that individual differences in face recognition ability reflect higher-level differences in neural identity coding, rather than enhanced early sensory processing. Significance statementSuper-Recognisers have an exceptional ability to recognise unfamiliar faces, yet the neural basis of this advantage has remained unclear. We find brain activity expresses the identity of unfamiliar faces more strongly and consistently in Super-Recognisers than typical recognisers. These advantages were specific to individual identity and could not be explained by enhanced encoding of broader facial categories such as sex, age, or ethnicity. Critically, group differences emerged during a mid-latency stage of processing ([~]300-500 ms) associated with higher-level representations that support stable identity coding across variable images. The findings suggest that exceptional face recognition arises from more robust neural representations of individual identity rather than enhanced early visual processing, providing new insight into the neural basis of perceptual expertise.

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bioRxiv2026

A multibrain advantage for cooperative human behaviour

Collaboration is a cornerstone of human behaviour, enabling individuals to achieve complex goals that transcend individual capabilities. While previous research has largely focused on the alignment of neural representations across brains during social interactions, real-world cooperation frequently involves complementary roles, where success depends on integrating distinct yet interdependent representations. Here, we combined electroencephalography (EEG) hyperscanning and multivariate pattern analysis (MVPA) methods to investigate neural representations in pairs of participants as they jointly performed a speeded two-dimensional visual matching task with asymmetric controls to encourage task division (i.e., attending to different stimulus features). Our results provide direct neural evidence of the emergence of selective information encoding within individual brains and complementary information encoding across brains during successful cooperation. Specifically, optimally divided task dimensions give rise to a late (> 485 ms) multibrain advantage, wherein the combined neural signals of the two participants carry more target-related information than that of either brain individually. Notably, the magnitude of these information-processing modulations within and across brains robustly predicted pairs collective task performance. These findings have broader implications for future research on collaboration, highlighting the need to move beyond representational alignment to harness diverse human as well as machine capabilities across our societies to unlock collective potential.

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bioRxiv2025

Disentangling objects' contextual associations from perceptual and conceptual attributes using time-resolved neural decoding

Humans effortlessly relate what they see to what they know, drawing on existing knowledge of objects perceptual, conceptual, and contextual attributes while searching for and recognising objects. While prior studies have investigated the temporal dynamics of perceptual and conceptual object properties in the neural signal, it remains unclear whether and when contextual associations are uniquely represented. In this study, we used representational similarity analysis on electroencephalography (EEG) data to explore how the brain processes the perceptual, conceptual, and contextual dimensions of object knowledge over time. Using human similarity judgments of 190 naturalistic object concepts presented as either as images or words, we constructed separate behavioural models of objects perceptual, conceptual, and contextual properties. We correlated these models with neural patterns from two EEG datasets, one publicly available and one newly collected, both recorded while participants passively viewed the same object stimuli. Across both datasets, we found that perceptual features dominated the early EEG response to object images, while conceptual features emerged later. Contextual associations were also reflected in neural patterns, but their explanatory power largely overlapped with that of conceptual models, suggesting limited unique representation of objects contextual attributes under passive viewing conditions. These results highlight the brains integration of perceptual and conceptual information when processing visual objects. By combining high temporal resolution EEG with behaviourally derived models, this study advances our understanding of how distinct dimensions of object knowledge are encoded in the human brain.

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bioRxiv2025

The neural processes of illusory occlusion in object recognition

Fast and accurate object recognition is crucial for effective behaviour in dynamic visual environments. In some cases, the visual system must overcome ambiguity in visual input during object recognition, such as when an object is partially hidden behind another. Recurrent processing between higher- and lower-order areas is thought to play a role in resolving such ambiguity, enabling the filling in of missing visual information. Here we examined this claim using a novel paradigm in which partial object images appear occluded by an illusory Kanizsa figure, perception of which also depends on recurrent processing by the grouping of Pacmen inducers. If both recognising the partial object and perceiving the illusory shape depend on recurrent processing, object recognition should vary as a function of the presence of illusory shape. Across two behavioural experiments and a separate EEG decoding study, we found no evidence for an interaction between illusion perception and object recognition, and different neural time courses for the illusory figures alone compared to those of the partial objects, which were decoded earlier. Ultimately, our study highlights the robustness of the visual system to solve the identity of the ambiguous object, independently from the processing of different ambiguities occurring at the same time, providing new insights into the mechanisms of recurrence in the early and late stages of information processing and its application to ambiguous object recognition.

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bioRxiv2025

Neural decoding of competitive decision-making in Rock-Paper-Scissors using EEG hyperscanning

Social interactions are fundamental to daily life, yet social neuroscience research has often studied individuals brains in isolation. Hyperscanning, the simultaneous recording of neural data from multiple participants, enables real-time investigation of social processes by examining multiple brains while they interact. Previous hyperscanning research has largely focused on cooperative tasks, with fewer studies examining competitive contexts. Here, we obtained electroencephalography (EEG) hyperscanning data from 62 participants (31 pairs) who played a computerised version of the Rock-Paper-Scissors game, a classic paradigm for studying competitive decision-making. Although the optimal strategy is to be unpredictable and thus act randomly, participants exhibited behavioural biases, deviating from this ideal. Using multivariate decoding methods to measure neural representations within the two players brains in interaction, we found information about decisions made by participants during gameplay, revealing certain strategies. Notably, losers uniquely represented information about prior trials, suggesting this may impair optimal performance. These results reveal how competitive decision-making is shaped by cognitive biases and previous outcomes, highlighting the difficulty of achieving randomness in strategic contexts. This work advances our understanding of decision-making and cognitive dynamics in competitive interactions.

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bioRxiv2025

Unlocking information alignment between interacting brains with EEG hyperscanning

Social interactions shape our perception of the world, influencing how we interpret incoming information. Alignment between interacting individuals sensory and cognitive processes is key to successful cooperation and communication, but the neural processes underlying this alignment remain unknown. Here, we leveraged Representational Similarity Analysis (RSA) on electroencephalography (EEG) hyperscanning techniques to investigate information alignment in 24 pairs of participants who performed a categorisation task together based on agreed upon rules. Significant interbrain information alignment emerged within 45 ms of stimulus presentation and persisted for hundreds of milliseconds. Early alignment (45-180 ms) occurred in both real and randomly matched pseudo-pairs, reflecting shared sensory responses. Importantly, alignment after 200 ms strengthened with practice and was unique to real pairs, driven by shared representations associated with, and extending beyond, the categorisation rules they formed. Together, these findings highlight distinct processes underpinning interbrain information alignment during social interactions, that can be effectively captured and disentangled with Interbrain RSA.

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bioRxiv2024

Mapping object space dimensions: new insights from temporal dynamics

How is object information organized in high-level visual cortex? Recently, a comprehensive model of object space in macaques was proposed, defined by the orthogonal axes of animacy and aspect ratio (Bao et al., 2020). However, when using stimuli that dissociated category, animacy, and aspect ratio in humans, no tuning of aspect ratio was observed in fMRI data (Yargholi & Op de Beeck, 2023). This difference could be a result of different stimuli, the limited temporal resolution of fMRI, or information available about the presented stimuli. Here, we asked if and when information about aspect ratio, animacy, and category is available over time. We collected whole-brain electroencephalography (EEG) data while participants (N = 20) viewed the stimulus set used by Yargholi & Op de Beeck (2023). To mask object details and increase reliance on shape information, we also presented silhouette versions of the stimuli. Stimuli were presented in 5Hz streams using rapid serial visual presentation, with intact and silhouette stimuli sets were shown in separate streams. Using standard multivariate decoding pipelines and representational similarity analysis, we found that aspect ratio, category, and animacy were represented during visual object processing. The dominant dimension was modulated by stimulus type, demonstrating that the observable dimensions of object space depend on the nature of the stimuli presented. Taken together, these findings demonstrate that aspect ratio is represented during object processing, however earlier and more transiently than categorical dimensions, such as animacy. By focusing on underlying temporal dynamics, our results provide clear new insights into the contradicting findings reported in previous work and reveal a more nuanced understanding of how object space evolves over time.

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bioRxiv2024

Rapid visual engagement in neural processing of detailed touch interactions

Touch perception is an inherently multisensory process in which vision plays an essential role. However, our understanding of how vision encodes sensory and emotional-affective aspects of observed touch, and the timing of these processes, is still limited. Here we address this gap by investigating the neural dynamics of visual touch observation by analysing electroencephalographic (EEG) data from participants viewing detailed hand interactions from the Validated Touch-Video Database. We examined how the brain encodes basic body cues such as hand orientation and viewing perspective, in addition to sensory aspects, including the type of touch (e.g., stroking vs. pressing; hand vs. object touch) and the object involved (e.g., knife, brush), as well as emotional-affective dimensions. Using multivariate decoding, information about body cues was present within 60 ms, with sensory and emotional details, including valence, arousal, and pain present around 130 ms, demonstrating efficient early visual processing. Threat was most clearly identified by approximately 265 ms, similarly involving visual regions, suggesting that such evaluations require slightly extended neural engagement. Our findings reveal that bottom-up, automatic visual processing is integral to complex tactile assessments, important for rapidly extracting both the personal relevance and the sensory and emotional dimensions of touch.

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bioRxiv2023

Visual periodicity reveals distinct attentional signatures for face and non-face categories

Observers can selectively deploy attention to regions of space, moments in time, specific visual features, individual objects, and even specific high-level categories - for example, when keeping an eye out for dogs while jogging. Here we exploited visual periodicity to examine how category-based attention differentially modulates selective neural processing of face and non-face categories. We combined electroencephalography (EEG) with a novel frequency-tagging paradigm capable of capturing selective neural responses for multiple visual categories contained within the same rapid image stream (faces/birds in Exp 1; houses/birds in Exp 2). We found that the pattern of attentional enhancement and suppression for face-selective processing is unique compared to other object categories: Where attending to non-face objects strongly enhances their selective neural signals during a later stage of processing (300-500ms), attentional enhancement of face-selective processing is both earlier and comparatively more modest. Moreover, only the selective neural response for faces appears to be actively suppressed by attending towards an alternate visual category. These results underscore the special status that faces hold within the human visual system, and highlight the utility of visual periodicity as a powerful tool for indexing selective neural processing of multiple visual categories contained within the same image sequence.

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bioRxiv2023

Better together: Objects in familiar constellations evoke high-level representations of real-world size

High-level vision is frequently studied at the level of either individual objects or whole scenes. An intermediate level of visual organisation that has received less attention is the "object constellation" - a familiar configuration of contextually-associated objects (e.g., plate + spoon). Recent behavioural studies have shown that information from multiple objects can be integrated to support observers high-level understanding of a "scene" and its constituent objects. Here we used EEG in human participants (both sexes) to test when the visual system integrates information across objects to support recognition, using representations of objects real-world size as a proxy for recognition. We briefly presented masked object constellations consisting of object silhouettes of either large (e.g., chair + table) or small (e.g., plate + spoon) real-world size, while independently varying retinal size. As a control, observers also viewed each silhouette in isolation. If object context facilitates object recognition, real-world size should be inferred more effectively when the objects appear in their contextually-associated pairs than in isolation, leading to the emergence of real-world size information in multivariate EEG patterns. Representational similarity analysis revealed that neural activity patterns captured information about the real-world size of object constellations from [~]200 ms after stimulus onset. This representation was stronger for, and specific to, object pairs as compared to single objects, and remained significant after regressing out visual similarity models derived from computational models. These results provide evidence for inter-object facilitation of visual processing, leading to a qualitatively different high-level representation of object pairs than single objects. Significance StatementThis study used electroencephalography decoding to reveal the neural timecourse of inter-object facilitation present for contextually-associated groups of objects (e.g., chair + table). Although ubiquitous in daily life, the object constellation level of representation has rarely been examined compared to isolated objects or entire scenes. By shedding new light on facilitatory interactions between objects, arising before 200ms of visual processing, our results provide insight into the continuum along which objects and scenes exist. At the same time, this work advances the current understanding of the neural basis of real-world size, using strict visual controls to show that inferred information about objects spatial scale in the real world emerges around 200 ms after stimulus onset.

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bioRxiv2020

Visual mismatch responses index surprise signalling but not expectation suppression

The ability to distinguish between commonplace and unusual sensory events is critical for efficient learning and adaptive behaviour. This has been investigated using oddball designs in which sequences of often-appearing (i.e. expected) stimuli are interspersed with rare (i.e. surprising) deviants. Resulting differences in electrophysiological responses following surprising compared to expected stimuli are known as visual mismatch responses (VMRs). VMRs are thought to index co-occurring contributions of stimulus repetition effects, expectation suppression (that occurs when ones expectations are fulfilled), and expectation violation (i.e. surprise) responses; however, these different effects have been conflated in existing oddball designs. To better isolate and quantify effects of expectation suppression and surprise, we adapted an oddball design based on Fast Periodic Visual Stimulation (FPVS) that controls for stimulus repetition effects. We recorded electroencephalography (EEG) while participants (N=48) viewed stimulation sequences in which a single face identity was periodically presented at 6 Hz. Critically, one of two different face identities (termed oddballs) appeared as every 7th image throughout the sequence. The presentation probabilities of each oddball image within a sequence varied between 10-90%, such that participants could form expectations about which oddball face identity was more likely to appear within each sequence. We also included expectation neutral 50% probability sequences, whereby consistently biased expectations would not be formed for either oddball face identity. We found that VMRs indexed surprise responses, and effects of expectation suppression were absent. That is, ERPs were more negative-going at occipitoparietal electrodes for surprising compared to neutral oddballs, but did not differ between expected and neutral oddballs. Surprising oddball-evoked ERPs were also highly similar across the 10-40% appearance probability conditions. Our findings indicate that VMRs which are not accounted for by repetition effects are best described as an all-or-none surprise response, rather than a minimisation of prediction error responses associated with expectation suppression. Highlights- We used a recently-developed oddball design that controls for repetition effects - We found effects of surprise but not expectation suppression on ERPs - Surprise responses did not vary by stimulus appearance probability

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bioRxiv2020

Critical information thresholds underlying concurrent face recognition functions

Humans rapidly and automatically recognise faces on multiple different levels, yet little is known about how the brain achieves these manifold categorisations concurrently. We bring a new perspective to this emerging issue by probing the relative informational dependencies of two of the most important aspects of human face processing: categorisation of the stimulus as a face (generic face recognition) and categorisation of its familiarity (familiar face recognition). Recording electrophysiological responses to a large set of natural images progressively increasing in image duration (Expt. 1) or spatial frequency content (Expt. 2), we contrasted critical sensory thresholds for these recognition functions as driven by the same face encounters. Across both manipulations, individual observer thresholds were consistently lower for distinguishing faces from other objects than for distinguishing familiar from unfamiliar faces. Moreover, familiar face recognition displayed marked inter-individual variability compared to generic face recognition, with no systematic relationship evident between the two thresholds. Scalp activation was also more strongly right-lateralised at the generic face recognition threshold than at the familiar face recognition threshold. These results suggest that high-level recognition of a face as a face arises based on minimal sensory input (i.e., very brief exposures/coarse resolutions), predominantly in right hemisphere regions. In contrast, the amount of additional sensory evidence required to access face familiarity is highly idiosyncratic and recruits wider neural networks. These findings underscore the neurofunctional distinctions between these two recognition functions, and constitute an important step forward in understanding how the human brain recognises various dimensions of a face in parallel. Significance StatementThe relational dynamics between different aspects of face recognition are not yet well understood. We report relative informational dependencies for two concurrent, ecologically relevant face recognition functions: distinguishing faces from objects, and recognising people we know. Our electrophysiological data show that for a given face encounter, the human brain requires less sensory input to categorise that stimulus as a face than to recognise whether the face is familiar. Moreover, where sensory thresholds for distinguishing faces from objects are remarkably consistent across observers, they vary widely for familiar face recognition. These findings shed new light on the multifaceted nature of human face recognition by painting a more comprehensive picture of the concurrent evidence accumulation processes initiated by seeing a face.

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bioRxiv2020

Contextual and spatial associations between objects interactively modulate visual processing

Much of what we know about object recognition arises from the study of isolated objects. In the real world, however, we commonly encounter groups of contextually-associated objects (e.g., teacup, saucer), often in stereotypical spatial configurations (e.g., teacup above saucer). Here we used EEG to test whether identity-based associations between objects (e.g., teacup-saucer vs. teacup-stapler) are encoded jointly with their typical relative positioning (e.g., teacup above saucer vs. below saucer). Observers viewed a 2.5Hz image stream of contextually-associated object pairs intermixed with non-associated pairs as every fourth image. The differential response to non-associated pairs (measurable at 0.625Hz in 28/37 participants), served as an index of contextual integration, reflecting the association of object identities in each pair. Over right occipitotemporal sites, this signal was larger for typically-positioned object streams, indicating that spatial configuration facilitated the extraction of the objects contextual association. This high-level influence of spatial configuration on object identity integration arose [~]320ms post stimulus onset, with lower-level perceptual grouping (shared with inverted displays) present at [~]130ms. These results demonstrate that contextual and spatial associations between objects interactively influence object processing. We interpret these findings as reflecting the high-level perceptual grouping of objects that frequently co-occur in highly stereotyped relative positions.

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bioRxiv2019

Yellow strawberries and red bananas: The influence of object-colour knowledge on emerging object representations in the brain

The ability to rapidly and accurately recognise complex objects is a crucial function of the human visual system. To recognise an object, we need to bind incoming visual features such as colour and form together into cohesive neural representations and integrate these with our pre-existing knowledge about the world. For some objects, typical colour is a central feature for recognition; for example, a banana is typically yellow. Here, we applied multivariate pattern analysis on time-resolved neuroimaging (magnetoencephalography) data to examine how object-colour knowledge affects emerging object representations over time. Our results from 20 participants (11 female) show that the typicality of object-colour combinations influences object representations, although not at the initial stages of object and colour processing. We find evidence that colour decoding peaks later for atypical object-colour combinations in comparison to typical object-colour combinations, illustrating the interplay between processing incoming object features and stored object-knowledge. Taken together, these results provide new insights into the integration of incoming visual information with existing conceptual object knowledge. Significance StatementTo recognise objects, we have to be able to bind object features such as colour and shape into one coherent representation and compare it to stored object knowledge. The magnetoencephalography data presented here provide novel insights about the integration of incoming visual information with our knowledge about the world. Using colour as a model to understand the interaction between seeing and knowing, we show that there is a unique pattern of brain activity for congruently coloured objects (e.g., a yellow banana) relative to incongruently coloured objects (e.g., a red banana). This effect of object-colour knowledge only occurs after single object features are processed, demonstrating that conceptual knowledge is accessed relatively late in the visual processing hierarchy.

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bioRxiv2018

Immediate stimulus repetition abolishes stimulus expectation and surprise effects in fast periodic visual oddball designs

Oddball designs are widely used to investigate the sensitivity of the visual system to statistical regularities in sensory environments. However, the underlying mechanisms that give rise to visual mismatch responses remain unknown. Much research has focused on identifying separable, additive effects of stimulus repetition and stimulus appearance probability (expectation/surprise) but findings from non-oddball designs indicate that these effects also interact. We adapted the fast periodic visual stimulation (FPVS) unfamiliar face identity oddball design (Liu-Shuang et al., 2014) to test for both additive and interactive effects of stimulus repetition and stimulus expectation. In two experiments, a given face identity was presented at a 6 Hz periodic rate; a different identity face (the oddball) appeared as every 7th image in the sequence (i.e., at 0.857 Hz). Electroencephalographic (EEG) activity was recorded during these stimulation sequences. In Experiment 1, we tested for surprise responses evoked by unexpected face image repetitions by replacing 10% of the commonly-presented oddball faces with exact repetitions of the base rate face identity image. In Experiment 2, immediately repeated or unrepeated face identity oddballs were presented in high and low presentation probability contexts (i.e., expected or surprising), allowing assessment of expectation effects on responses to both repeated and unrepeated stimuli. Across both experiments objective (i.e., frequency-locked) visual mismatch responses driven by stimulus expectation were only found for oddball faces of a different identity to base rate faces (i.e., unrepeated identity oddballs). Our results show that immediate stimulus repetition (i.e., repetition suppression) can reduce or abolish expectation effects as indexed by EEG responses in visual oddball designs.\n\nHighlights- We studied visual mismatch responses with a fast periodic oddball design\n- Our design cleanly separates immediate stimulus repetition and expectation effects\n- Stimulus expectation effects were only present for unrepeated stimuli\n- Immediate stimulus repetition reduced EEG expectation effects

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bioRxiv2017

Category-Selective Human Brain Processes Elicited In Fast Periodic Visual Stimulation Streams Are Immune To Temporal Predictability

Recording direct neural activity when periodically inserting exemplars of a particular category in a rapid visual stream of other objects offers an objective and efficient way to quantify perceptual categorization and characterize its spatiotemporal dynamics. However, since periodicity entails predictability, perceptual categorization processes identified within this framework may be partly generated or modulated by temporal expectations. Here we present a stringent test of the hypothesis that temporal predictability generates or modulates category-selective neural processes. In Experiment 1, we compare neurophysiological responses to periodic and nonperiodic (i.e., unpredictable) variable face stimuli in a fast (12 Hz) visual stream of nonface objects. In Experiment 2, we assess potential responses to rare (10%) omissions of periodic face events (i.e., violations of periodicity) in the same fast visual stream. Overall, our observations indicate that long duration category(face)-selective processes elicited in a fast periodic stream of visual objects are immune to temporal predictability. These observations do not support a predictive coding framework interpretation of category-change detection in the human brain and have important implications for understanding human perceptual categorization in a rapidly changing (i.e., dynamic) visual scene.

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