Biology subjects

Nestor, A.

Publications and source records attributed to Nestor, A..

9 recordsLinked to original sources

bioRxiv2026

Face ensembles reshape the neural other-race effect

The other-race effect (ORE), poorer recognition of other-race (OR) than same-race (SR) faces, is established for individual faces, but its neural expression during group viewing remains unclear. Twenty-two East Asian adults viewed East Asian and White faces in different formats: individually and in six-face ensembles during EEG recording. Behavioral testing confirmed an SR advantage. Decoding and generative reconstruction characterized neural discriminability, geometry, dynamics, sensor-level information, and recoverable content. Single SR faces were more discriminable, more dispersed in face space, and reconstructed more accurately. Ensembles preserved racial-composition information but reduced the cumulative SR-OR decoding difference and showed instead an early OR advantage. Reconstructions supported identification of individual faces and ensemble summaries, with an overall SR advantage but no reliable race-by-format interaction. Independent judgments revealed race- and format-dependent shifts in reconstructed age, valence, and arousal. These findings reveal a neural ORE whose expression depends on viewing context and representational measure.

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bioRxiv2025

Evidence for dimensional representations and anticipatory dynamics in facial expression perception

Expression recognition relies on the ability to distinguish subtle visual differences across a range of facial expressions. Here, we examine the neural representation of dynamic expressions as reflected by electroencephalography (EEG) data in human adults. We find that a wide range of expressions (i.e., 14 emotional and 10 conversational expressions) can be decoded from neural signals, and that their representational structure evinces the classic dimensions of valence and arousal. Critically, we recover, through EEG-based video reconstruction, dynamic representations whose content succeeds in capturing even fine differences across related expressions (e.g., happy-satiated versus schadenfreude). Further, time-resolved decoding reveals anticipatory dynamics that maximize accuracy before the occurrence of an apex expression in the visual stimulus. These results are validated against behavioral data, which yield static reconstructions consistent with their neural counterparts. Thus, our results shed light on the representational basis of expression recognition and serve to recover the dynamic content of visual experience.

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bioRxiv2025

Decoding the dynamics of cognitive control: Insights from reach movements and electroencephalography

The congruency sequence effect (CSE) refers to improved performance in conflict tasks, such as the Eriksen flanker task, when the congruency of the current trial matches that of the preceding one. Although widely attributed to dynamic adjustments in cognitive control, the neural mechanisms and temporal dynamics underlying this effect remain poorly understood. Here, we combined a release-and-press flanker task with EEG decoding to examine how trial congruency and response type shape behavior and brain activity in healthy adults. Behaviorally, the CSE emerged only when responses repeated, highlighting the dominant role of stimulus-response binding over abstract control mechanisms. Neural decoding mirrored the CSE: current-trial congruency was more reliably decoded on repeated-response trials following congruent versus incongruent trials. This neural CSE was stimulus-locked, occurred between 450-550ms post-stimulus onset, and was driven by theta-band activity. More broadly, congruency decoding was particularly robust over frontal channels while cross-temporal generalization indicated transient, sequential neural representations underlying control signals. Together, these findings demonstrate that both behavioral and neural signatures of the CSE are tightly constrained by response repetition and emerge within a narrow temporal window. By integrating reach-based measures with multivariate EEG analyses, this study provides a fine-grained account of when, where, and under what conditions control-related signals unfold after conflict.

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bioRxiv2024

Red means heavy: Action intentions reactivate representations of task-relevant cognitive cues

Recent research shows that the intention to act on an object alters its neural representation in ways as afforded by underlying sensorimotor processes. For example, the intention to grasp and pick up an object results in representations of the objects weight. But these representations become grasp-specific only immediately before object lift if weight information is relayed through object material. This feature triggers earlier representations regardless of intention probably because material-weight contingencies are overlearned. By contrast, recently learned weight cues should be recalled deliberately during grasp planning resulting in early grasp-specific representations. Here, we examined how action intentions affect the representation of newly acquired colour-weight contingencies. We recorded electroencephalography while human participants grasped or reached for objects that varied in shape and density as indicated by their colour. Multivariate analyses revealed a grasp-specific reactivation of colour during planning that was mirrored in beta band. This suggests that task-relevancy influences the representation of colour such that previously encoded colour-weight contingencies may be reactivated as required for grasping, mediated top-down via working memory. Grasp-specific representations of shape and colour were also present in theta band, perhaps reflecting attentional activity. These results provide novel insights into the interplay between cognition and motor planning processes. Significance StatementRecent research shows that the object feature weight, conveyed via highly overlearned material-weight contingencies, is more prominently represented within electrophysiological signals when people intend to grasp an object to lift it vs. reach for it. However, such differences occur late, immediately before object lift. Our study is the first to show that newly learned colour-weight contingencies yield early task-specific representations during action planning; we find that colour/weight representations, forming 140-210 ms after object onset, reactivate around 270 ms during grasp, but not reach planning, with the same pattern arising for beta band. These data suggest that the brain deliberately processes weight information depending on intention, arguably involving working memory representations. Our results highlight the interplay of cognition and motor planning.

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bioRxiv2024

Revealing the neural representations underlying other-race face perception

The other-race effect, a disadvantage at recognizing faces of other races than ones own, has received considerable attention, especially regarding its wide scope and underlying mechanisms. Here, we aim to elucidate its neural and representational basis by relating behavioral performance in East Asian and White individuals to neural decoding and image reconstruction relying on electroencephalography data. Our investigation uncovers a reliable neural counterpart of the other-race effect (i.e., a decoding disadvantage for other-race faces) along with its extended dynamics and prominence across individuals. Further, it retrieves, via neural-based image reconstruction, visual representations underlying other-race face perception and their intrinsic biases. Notably, our data-driven approach reveals that other-race faces are perceived not just as more typical but, also, as younger and more expressive. These findings, pointing to multiple visual biases surrounding the other-race effect, speak to the complexity of its neural mechanisms and its social implications.

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bioRxiv2023

Computation on demand: Action-specific representations of visual task features arise during distinct movement phases

It is commonly held that computations of goal-directed behaviour are governed by conjunctive neural representations of the task features. However, support for this view comes from paradigms with arbitrary combinations of task features and task affordances that require representations in working memory. Therefore, in the present study we used a task that is well-rehearsed with task features that afford minimal working memory representations to investigate the temporal evolution of feature representations and their potential integration in the brain. Specifically, we recorded electroencephalography data from human participants while they first viewed and then grasped objects or touched them with a knuckle. Objects had different shapes and were made of heavy or light materials with shape and weight being features relevant for grasping but not for knuckling. Using multivariate analysis, we found that representations of object shape were similar for grasping and knuckling. However, only for grasping did early shape representations reactivate at later phases of grasp planning, suggesting that sensorimotor control signals feed back to early visual cortex. Grasp-specific representations of material/weight only arose during grasp execution after object contact during the load phase. A trend for integrated representations of shape and material also became grasp-specific but only briefly during movement onset. These results argue against the view that goal-directed actions inevitably join all features of a task into a sustained and unified neural representation. Instead, our results suggest that the brain generates action-specific representations of relevant features as required for the different subcomponent of its action computations. Significance statementThe idea that all the features of a task are integrated into a joint representation or event file is widely supported but importantly based on paradigms with arbitrary stimulus-response combinations. Our study is the first to investigate grasping using electroencephalography to search for the neural basis of feature integration in such a daily-life task with overlearned stimulus-response mappings. Contrary to the notion of event files we find limited evidence for integrated representations. Instead, we find that task-relevant features form representations at specific phases of the action. Our results show that integrated representations do not occur universally for any kind of goal-directed behaviour but in a manner of computation on demand.

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bioRxiv2019

Image Reconstruction Reveals the Impact of Aging on Face Perception

Extensive work has demonstrated a decline in face recognition abilities associated with healthy aging. To date, however, there has been limited insight into the nature and the extent of aging-related alterations in internal face representations. Here, we sought to address these issues by using an image reconstruction approach that capitalizes on the structure of behavioral data to reveal the pictorial content of visual representations. To this end, healthy young and older adults provided similarity judgments with pairs of face images. Facial shape and surface features were subsequently derived from the structure of the data for each participant and combined into image reconstructions of facial appearance. Our findings revealed that image reconstruction was successful for every participant, irrespective of age. However, reconstruction accuracies of shape and surface information were lower for older individuals than young individuals. Specifically, facial features diagnostic for face perception, such as eye shape and skin tone, were reconstructed poorly in older adults relative to young adults. At the same time, we found that age-related effects only accounted for a relatively small proportion of individual variability in face representations. Thus, our results provide novel insight into age-related changes in visual perception, they account for the decline in facial recognition occurring with age and they demonstrate the utility of image reconstruction to uncovering internal representations across a variety of populations.

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bioRxiv2018

Multimodal evidence on shape and surface information in individual face processing

The significance of shape and surface information for face perception is well established, yet their relative contribution to recognition and their neural underpinnings await clarification. Here, we employ image reconstruction to retrieve, assess and visualize such information using behavioral, electroencephalography and functional magnetic resonance imaging data.\n\nOur results indicate that both shape and surface information can be successfully recovered from each modality but that the latter is better recovered than the former, consistent with its key role for face representations. Further, shape and surface information exhibit similar spatiotemporal profiles, rely on the extraction of specific visual features, such as eye shape or skin tone, and reveal a systematic representational structure, albeit with more cross-modal consistency for shape than surface.\n\nThus, the present results help elucidate the representational basis of individual face recognition while, methodologically, they showcase the utility of image reconstruction and clarify its reliance on diagnostic visual information.

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bioRxiv2017

Memory And Perception-based Facial Image Reconstruction

Visual memory for faces has been extensively researched, especially regarding the main factors that influence face memorability. However, what we remember exactly about a face, namely, the pictorial content of visual memory, remains largely unclear. The current work aims to elucidate this issue by reconstructing face images from both perceptual and memory-based behavioural data. Specifically, our work builds upon and further validates the hypothesis that visual memory and perception share a common representational basis underlying facial identity recognition. To this end, we derived facial features directly from perceptual data and then used such features for image reconstruction separately from perception and memory data. Successful levels of reconstruction were achieved in both cases for newly-learned faces as well as for familiar faces retrieved from long-term memory. Theoretically, this work provides insights into the content of memory-based representations while, practically, it opens the path to novel applications, such as computer-based sketch artists.

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