Biology subjects

Zanon, M.

Publications and source records attributed to Zanon, M..

12 recordsLinked to original sources

bioRxiv2026

How sensory load shapes the neural processing and perception of visual durations

The sensory content and temporal structure of stimuli have been shown to consistently bias duration perception. Temporal intervals filled with continuous sensory input ("filled intervals"), are often perceived as lasting longer than intervals marked only by their onset and offset ("empty intervals"). Despite this robust behavioral finding, it remains unclear whether filled and empty intervals rely on similar or distinct neural mechanisms and, more generally, how sensory format shapes the neural processing of millisecond time. To address this question, we asked twenty-one healthy participants to reproduce visual durations across different stimulus configurations while high-density scalp EEG was recorded. Behavioral results revealed differences in performance across stimulus configurations. Event-related potentials (ERPs) recorded at occipito-parietal and fronto-central electrodes between 0.1 and 0.4 s after duration offset were modulated in amplitude by both stimulus duration and format. These modulations scaled with the sensory load of the stimulus and its duration, suggesting a common underlying mechanism. A Representational Similarity Analysis (RSA) of the ERP data showed that perceived time was represented more strongly than physical time particularly at occipito-parietal electrodes, but only within the 0.2-0.3 s post-offset window, where stimulus format exerted a pronounced effect on the ERP signal. These findings highlight the role of sensory processing in shaping duration perception and its neural coding, and reveal an early neural signature of perceived time in occipito-parietal electrodes. 1 Significance statementOur perception of subsecond durations is distorted by the sensory content of stimuli. Here, we investigated how stimulus configuration shapes the neural correlates of visual duration perception. Specifically, we asked whether temporal intervals filled with continuous sensory input are processed differently from those lacking such content. We found that, between 0.2 and 0.3 s after interval offset, ERP amplitudes were modulated by stimulus content, and in this same temporal window the EEG signal reflected the perceptual bias. These findings support the view that duration processing and perception are deeply rooted in sensory processing.

neuroscience↗

bioRxiv2026

Space-number association in zebrafish

Spatial-numerical associations reflect the tendency to map small numerosities to the left and larger numerosities to the right. Although widely documented in humans and some non-human species, its presence in teleost fish has remained unclear. Here, we investigated whether zebrafish exhibit a spatial-numerical association by presenting fish with a left-right numerical discrimination task in a controlled behavioral assay. Zebrafish showed a reliable leftward preference when selecting smaller numerosities and a rightward preference when selecting larger ones, indicating a systematic coupling between numerical magnitude and spatial direction. These results provide the first evidence of a number-space association in zebrafish and demonstrate that number-space mapping extends to a basal vertebrate lineage. This establishes zebrafish as a tractable model for probing the neurobiological foundations of number-space associations. HighlightsO_LIZebrafish map numerical magnitudes onto left-right spatial positions. C_LIO_LISpatial biases are more robust for small numerosities but still present for larger ones. C_LIO_LIContinuous physical controls disproportionately affect the strength of spatial mapping for large sets. C_LI

animal behavior and cognition↗

bioRxiv2026

Evolution of visual time throughout goal driven action learning

Timing is intimately woven into human cognition and behaviour, underscoring peoples ability of comprehending speech, playing instruments and competing in sports. Converging evidence suggests that our perceptual experience of time is grounded in our ability to control actions: time processing leverages motor control neural machinery, and perceived time is significantly distorted in proximity of action. However, the dynamic interplay between timing and action systems remains unexplored, particularly in goal-directed contexts where action control is gradually refined through practice. Through combined behavioural, neural and modelling approaches, we investigate how time processing gradually evolves as participants gain experience in goal-driven manual reaching actions, varying in terms of action-plan specificity. Participants judged brief visual durations while preparing hand movements aimed at visual targets displayed on a monitor. Subjective time expanded in the foreperiod preceding action onset, and this effect increased over trials, mirroring gradual improvements in action readiness as motor plans became more rapidly and efficiently deployed. Representation Similarity Analysis, integrating electroencephalographic and behavioural data, reveals that actions shape timing through independent mechanisms: planning specific behaviours shapes how duration information is written into timekeeping neural circuits as stimuli unfold (encoding). Parallely, more general aspects of motor engagement and anticipation shape how duration information is read-out from timing circuits following stimulus presentation (decoding). These findings highlight a dynamic, learning-driven coupling between perceptual time and motor control, where subjective time is recalibrated as goal-directed action preparation is optimized, shaped through independent time encoding and decoding mechanisms. Significance statementDespite lacking dedicated sensory and neural systems for duration, humans reveal a highly developed sense of time, for instance when noticing subtle tempo changes in music. We show that perceptual understanding of time is linked to the ability of learning and fine-tuning action: our internal metric of time shifts as action preparation processes are gradually refined, affecting how quickly behaviours are planned and executed. This interaction is mediated by independent neural processes affecting the encoding (online monitoring) and decoding (offline readout) of duration. These findings shift our understanding of timing, from a passive sensory readout to one that is actively constructed and finetuned through action learning, and provide a mechanistic account of neural processes linking action preparation to time processing

neuroscience↗

bioRxiv2025

Predisposed and learned preferences for multipoint visual statistics in visually naïve newly hatched chicks

Significance statementWe show that visually naive chicks spontaneously prefer specific multipoint correlation patterns, mirroring preferences seen in humans and rats, and reflecting the most informative structures in natural scenes. This provides evidence that efficient coding mechanisms may be innately driven by evolutionary predispositions. Notably, early visual experience through imprinting can alter these preferences, highlighting a role for learning in shaping visual processing. Recent studies have revealed that human and non-human animals (rats) can detect luminance distribution and correlations between pixels in an image (ranging from 2-point to 4-point). This sensitivity is believed to stem from optimization processes in the visual system that operate through efficient coding mechanisms to extract the most informative image statistics from the environment. However, it is yet to be determined whether this optimization is evolutionarily given by inborn mechanisms or shaped by visual experience. Here we report that newly-hatched visually naive domestic chicks spontaneously prefer to approach luminance, 2-point and 4-point correlation patterns (respectively, horizontal lines and rectangular patterns), while showing no preference for 3-point correlation over white noise controls. This parallels the ranking observed in adult humans and rats, thus suggesting that evolutionarily given biological predispositions largely drive efficient coding of natural images. We also found that learning by exposure to visual stimuli, as occurs naturally during visual imprinting, induced a preference for white noise over point correlation patterns in chicks exposed to 3- and 4-point patterns. We hypothesize that this behavior could reflect chicks preference for stimuli of lower statistical complexity.

animal behavior and cognition↗

bioRxiv2024

Neural Basis of Number Sense in Larval Zebrafish

Number sense, the ability to discriminate discrete quantity, is widespread across animals, yet how this capacity develops remains unknown. Using two-photon light-sheet imaging, we recorded whole-brain activity at single-cell resolution in larval zebrafish (Danio rerio) exposed to controlled visual numerosity stimuli. We discovered that number-selective neurons emerge in a striking developmental sequence: cells tuned to numerosity 1 are already present at 3 days post-fertilization (dpf), and neurons selective for 2, 3, and higher quantities appear in increasing abundance later, at 5 and 7 dpf, accompanied by a relative reduction in 1-tuned cells. The proportion of number-selective cells, summed over all tested numerosities, relative to all identified neurons in the brain, was found to decrease over time. We further showed that a machine-learning decoder based on the activity of the number-selective neurons can predict the number stimulus seen by the animals with accuracies at better than twice chance level. These results reveal how neuronal circuits develop structured numerical codes and provide a framework for studying the emergence of cognitive primitives at cellular resolution.

neuroscience↗

bioRxiv2024

Innate face detectors in the nidopallium of young domestic chicks

Soon after birth, naive animals and newborn babies show spontaneous attraction towards faces and face-like stimuli with three dark features representing eyes and a mouth/beak. While neurons selectively responding to faces have been found in the inferotemporal cortex of adult primates, face-selective domains in the brains of young monkeys seem to develop only later in life after exposure to faces. This has fueled a debate on the role of experience in the development of face-detector mechanisms, since face preferences are well documented in naive animals, such as domestic chicks reared without exposure to faces. Here we demonstrate that neurons in a cortex-homologue area of one-week-old face-naive domestic chicks selectively respond to a face-like configuration. Our single-cell recordings show that these face detectors do not respond to alternative configurations or isolated facial features. Moreover, the population activity of face-selective neurons accurately encoded the face-like stimulus as a unique category. Thus, our findings show that face detectors are present in the brains of very young animals without pre-existing experience.

animal behavior and cognition↗

bioRxiv2023

A Kaspar Hauser experiment for innateness of numerical cognition

Whether non-symbolic encoding of quantity is predisposed at birth with dedicated hard-wired neural circuits is debated. Here we presented newly-hatched visually naive chicks with stimuli (flashing dots) of either identical or different numerousness (with a ratio 1:3) with their continuous physical appearance (size, contour length, density, convex hull) randomly changing. Chicks spontaneously tell apart the stimuli on the basis of the number of elements. Upon presentation of either fixed or changing numerousness chicks also showed different expression of early gene c-fos in the visual Wulst, the hippocampal formation, the intermediate medial mesopallium, and the caudal part of the nidopallium caudolaterale. The results support the hypothesis that the ability to discriminate quantities does not require any specific instructive experience. Evidence for innateness of non-symbolic numerical cognition have implications for both neurobiology and philosophy of mathematics.

neuroscience↗

bioRxiv2022

All-optical manipulation of the Drosophila olfactory system.

Thanks to its well-known neuroanatomy, limited brain size, complex behaviour, and extensive genetic methods, Drosophila has become an indispensable model in neuroscience. A vast number of studies have focused on its olfactory system and the processing of odour information. Optogenetics is one of the recently developed genetic tools that significantly advance this field of research, allowing to replace odour stimuli by direct neuronal activation with light. This becomes a universal all-optical toolkit when spatially selective optogenetic activation is combined with calcium imaging to read out neuronal responses. Initial experiments showed a successful implementation to study the olfactory system in fish and mice, but the olfactory system of Drosophila has been so far precluded from an application. To fill this gap, we present here optogenetic tools to selectively stimulate functional units in the Drosophila olfactory system, combined with two-photon calcium imaging to read out the activity patterns elicited by these stimuli at different levels of the brain. This method allows to study the spatial and temporal features of the information flow and reveals the functional connectivity in the olfactory network.

neuroscience↗

bioRxiv2022

Number neurons in the nidopallium of young domestic chicks

Numerical cognition is ubiquitous in the animal kingdom. Domestic chicks are a widely used developmental model for studying numerical cognition. Soon after hatching, chicks can perform sophisticated numerical tasks. Nevertheless, the neural basis of their numerical abilities has remained unknown. Here, we describe for the first time number neurons in the caudal nidopallium (functionally equivalent to the mammalian prefrontal cortex) of young domestic chicks. Number neurons that we found in young chicks showed remarkable similarities to those in the prefrontal cortex and caudal nidopallium of adult animals. Thus, our results suggest that numerosity perception based on the labeled-line code provided by number neurons might be an inborn feature of the vertebrate brain. SignificanceNumerosity, i.e. the number of items in a set, is a significant aspect in the perception of the environment. Behavioural and in silico experiments suggest that number sense belongs to a core knowledge system and can be present already at birth. However, neurons sensitive to the number of visual items have been so far described only in the brain of adult animals. Therefore, it remained unknown to what extent their selectivity would depend on visual learning and experience. We found number neurons in the caudal nidopallium (a higher associative area with functional similarities to the mammalian prefrontal cortex) of very young, numerically naive domestic chicks. This result suggests that numerosity perception is possibly an inborn feature of the vertebrate brain.

neuroscience↗

bioRxiv2021

Archerfish number discrimination

Debates have arisen as to whether non-human animals actually can learn astract non-symbolic numerousness or whether they always rely on some continuous physical aspect of the stimuli covarying with number. Here we investigated archerfish (Toxotes jaculatrix) non-symbolic numerical discrimination with accurate control for co-varying continuous physical stimulus attributes. Archerfish were trained to select one of two groups of black dots (Exp. 1: 3 vs. 6 elements; Exp. 2: 2 vs. 3 elements); these were controlled for several combinations of physical variables (elements size, overall area, overall perimeter, density and sparsity), ensuring that only numerical information was available. Generalization tests with novel numerical comparisons (2 vs. 3, 5 vs. 8 and 6 vs. 9 in Exp. 1; 3 vs. 4, 3 vs. 6 in Exp. 2) revealed choice for the largest or smallest numerical group according to the relative number that was rewarded at training. None of the continuous physical variables, including spatial frequency, were affecting archerfish performance. Results provide evidence of the spontaneous use of abstract relative numerical information in archerfish for both small and large numbers.

animal behavior and cognition↗

bioRxiv2021

Towards a standardization of non-symbolic numerical experiments: GeNEsIS, a flexible and user-friendly tool to generate controlled stimuli

Several studies have suggested that vertebrate and invertebrate species may possess a number sense, i.e. an ability to process in a non-symbolic and non-verbal way the numerousness of a set of items. However, this hypothesis has been challenged by the presence of other non-numerical continuous physical variables, that vary along with numerosity (e.g. any change in the number of visual physical elements in a set naturally involves a related change in visual features such as area, density, contour length and convex hull of the stimulus). It is therefore necessary to control and manipulate the continuous physical information when investigating the ability of humans and other animals to perceive numerousness. During decades of research, different methods have been implemented in order to address this issue, which has implications for experiments replicability and inter-species comparisons, since no general standardized procedure is currently being used. Here we present the "Generation of Numerical Elements Images Software" (GeNEsIS) for the creation of non-symbolic numerical arrays in a standardized and user-friendly environment. The main aim of this tool would be to provide researchers in the field of numerical cognition with a manageable and precise instrument to produce visual numerical arrays controlled for all the continuous variables; additionally, we implemented the possibility to actively guide stimuli presentation during habituation/dishabituation and dual-choice comparison tasks used in human and comparative research.

animal behavior and cognition↗

bioRxiv2018

Bodily sensations in social scenarios: Where in the body?

Bodily states are fundamental to emotions emergence and are believed to constitute the first step in the chain of events that culminate in emotional awareness. Recent works have given fresh support to this view by showing that distinct topographical maps can be derived to describe how basic and more complex emotions are represented in the body. However, it is still unclear whether these bodily maps can also extend to emotions experienced specifically within social interactions and how these representations relate to basic emotions. To address this issue, we used the emBODY tool to obtain high-resolution bodily maps that represent the body activation and deactivation experienced by healthy participants in social scenarios depicting establishment or loss of social bonds. We show that clear patterns of activation/deactivation across the body emerge depending on the valence and on the characteristics of the single social scenarios, but also a common activation of head, chest and limbs across scenarios. Furthermore, we showed that maps related to complex social scenarios are strongly correlated with bodily states experienced in basic emotions, suggesting that the patterns of body activation/deactivation found for social scenarios might represent a combination of different basic emotions these experiences elicit. Our data tackle conscious emotional experiences and show for the first time how painful social events are felt on the body, providing findings that complement verbal reports and neuroimaging data on social rejection. Furthermore, they show that bodily feelings related to complex social scenarios, despite referring to unified independent emotional states, are also related to bodily correlates of basic emotions.

neuroscience↗