Biology subjects

Piazza, M.

Publications and source records attributed to Piazza, M..

13 recordsLinked to original sources

bioRxiv2026

The Brain Encodes Pure Logic Beyond Natural Language And At The Boundaries With Mathematics

You are not not reading this sentence. True, because you are. It's the law of double negation, a logical rule that states that a statement that is not not true is itself true. The development of pure logic - the study of the properties of formal systems, irrespective of their content - represents one of the most abstract intellectual achievements of human culture. Yet its neural correlates remain vastly unexplored. Is pure logic represented in a linguistic format like natural language, in an abstract symbolic format like other formal systems such as mathematics, or as a fully distinct domain of knowledge? To address this question, we monitored the brain activity of professional logicians and matched controls while they evaluated the truth of spoken statements of pure logic, and compared these activations to those elicited by language and mental arithmetic. We show that pure logic recruits left-lateralized brain circuits that are completely distinct from those involved in language processing. Those circuits only partially overlap with those involved in mathematics. These findings highlight an independent neural pathway for abstract thought and indicate that the brain's capacity to process structured rules of formal systems is implemented beyond language and at the boundaries with mathematics.

neuroscience↗

bioRxiv2026

Neural evidence for an abstract sense of number in humans at birth

One of the most astonishing abilities documented in human newborns is that they can abstract numerosity - the number of items in sets - across sensory modalities. Its underlying neural mechanisms remain unknown. Using high-density EEG and a frequency-tagging paradigm, we measured neural entrainment to periodically presented visual arrays that were either numerically congruent or incongruent with previously familiarized and concurrently presented auditory sequences in 21 newborns (0-3 days old). The amplitude of neural entrainment to the visual arrays provided a robust index of cross-modal numerical congruency: it was significantly reduced for numerically congruent relative to incongruent stimuli, consistent with a cross-modal numerosity repetition-suppression mechanism. These findings identify a candidate neural mechanism supporting newborns ability to encode numerosity in an abstract supramodal format, and reinforce the view that number constitutes a foundational dimension of human perception since birth.

neuroscience↗

bioRxiv2025

Numerosity Is Directly Sensed and Dynamically Transformed in the Human Brain: Evidence from MEG-MRI Fusion

Humans can estimate the number of objects in a scene within a fraction of a second, suggesting that numerosity is encoded rapidly and directly by the visual system. Yet how this encoding unfolds over time and interacts with other visual features remains unclear. Here, we combined magnetoencephalography (MEG) with time-resolved representational similarity analysis (RSA) and MEG-fMRI fusion to track how numerosity is represented in the brain over time. We also used multidimensional scaling (MDS) to visualize the evolving patterns of neural activity. Two main findings emerged. First, numerosity exhibited the hallmarks of a primary perceptual attribute: its neural signature appeared rapidly after stimulus onset, preceding the encoding of non-numeric features that could otherwise define number. Second, Visualization of the neural patterns using MDS suggested a temporal transformation in representational geometry, reflecting the engagement of two distinct coding schemes- an early, linear number line, consistent with a "summation code", dominating activity in occipital regions, and a later, curved number line, consistent with "numerosity-tuned code", emerging more strongly in associative areas along the dorsal stream. Together, these findings demonstrate that numerosity processing is encoded directly from the visual image and unfolds through a rapid hierarchical transformation, from a broad quantity signal to a finely tuned, number-specific code, linking perceptual encoding to higher-level numerical abstraction.

neuroscience↗

bioRxiv2025

A left-to-right bias in spatial numerical associations with dots and symbols

Number and space are intertwined in human and non-human cognition. A substantial body of research has shown that numerical magnitudes are mentally represented along a spatially oriented continuum, akin to a "mental number line". Some suggested that its directionality is determined by culture and context, an idea that was recently challenged by a study that showed that an implicit association between "left" and "small" emerges not only in literate adults, but also in unschooled indigenous adult populations and preschool Western children. This finding suggests that SNAs may originate from universal innate mechanisms rather than being solely a by-product of cultural learning. However, while the study reported a strong association between "left" and "decreasing" numerosity, there was only a very weak association between "right" and "increasing" numerosity. This asymmetry was not predicted and needs further investigation to be understood. Here, we investigated the number/space association in implicit tasks in educated Western adults in greater depth by using more variable and better-controlled stimuli compared to the ones used in the previous study, and also manipulating stimulus format, using both dot patterns and symbolic numbers. Fifty-one adult participants performed a numerical comparison task within a Go-No-Go paradigm on subsequent pairs of visual stimuli (with ratios spanning from 0.75 to 0.94) that could appear on the left or on the right of a fixation point and completed two different tasks: "press when more" and "press when less". Results revealed distinct response patterns depending on the symbolic/non-symbolic nature of the stimuli. When non-symbolic stimuli were used, a consistent association between small numerosities and the left side and large numerosities and the right side was observed. When symbolic stimuli were used, only an association between large numerosities and the right side was observed. These findings support the hypothesis that SNAs may reflect a biological predisposition associated with brain asymmetry and that task demands may interact with the underlying hemispheric specialisations.

neuroscience↗

bioRxiv2024

Heat Conduction Simulation of Chondrocyte-Embedded Agarose Gels Suggests Negligible Impact of Viscoelastic Dissipation on Temperature Change

Agarose is commonly used for 3D cell culture and to mimic the stiffness of the pericellular matrix of articular chondrocytes. Although it is known that both temperature and mechanical stimulation affect the metabolism of chondrocytes, little is known about the thermal properties of agarose hydrogels. Thermal properties of agarose are needed to analyze potential heat production by chondrocytes induced by various experimental stimuli (carbon source, cyclical compression, etc). Utilizing ASTM C177, a custom-built thermal conductivity measuring device was constructed and used to calculate the thermal conductivity of 4.5% low gelling temperature agarose hydrogels. Additionally, Differential Scanning Calorimetry was used to calculate the specific heat capacity of the agarose hydrogels. Testing of chondrocyte-embedded agarose hydrogels commonly occurs in Phosphate-Buffered Saline (PBS), and thermal analysis requires the free convection coefficient of PBS. This was calculated using a 2D heat conduction simulation within MATLAB in tandem with experimental data collected for known boundary and initial conditions. The specific heat capacity and thermal conductivity of 4.5% agarose hydrogels was calculated to be 2.85 J/g{degrees}C and 0.121 W/mK, respectively. The free convection coefficient of PBS was calculated to be 1000.1 W/m2K. The values of specific heat capacity and thermal conductivity for agarose are similar to the reported values for articular cartilage, which are 3.20 J/g{degrees}C and 0.21 W/mK (Moghadam, et al. 2014). This suggests that in addition to 4.5% agarose hydrogels mimicking the physiological stiffness of the cartilage PCM, they can also mimic the thermal properties of articular cartilage for in vitro studies.

bioengineering↗

bioRxiv2023

Neural codes for visual numerosity independent of other quantities are present both in the dorsal and in the ventral stream of the human brain

Visual numerosity, a feature of visual sets traditionally associated with the parietal cortex, has recently been suggested to be encoded in a broader range of cortical regions, including early visual and associative cortices of both streams. However, a clear picture of how numerosity information is represented alongside other non-numeric features across the cortex is still lacking. To address this, we conducted a whole-brain 3T fMRI study with thirty-one adult subjects (eighteen females) engaged in a numerosity estimation task involving visual sets varying in number, item size, total item area, total field area, and density, thus allowing us to perform a tight control of the stimulus properties. Using model-based semipartial correlation representational similarity analyses, we found that numerosity is represented independently of other visual properties already in early visual areas and amplified in both retinotopic and non-retinotopic associative areas along both the dorsal and ventral streams. Dimensionality reduction analyses of BOLD activity patterns revealed clearly distinct neural representational geometries of numerosity across brain regions: a one-dimensional representation of numerical rank in early visual and in associative retinotopic regions of the ventral stream, and a curved structure encoding rank-order together with distance to end-point in associative regions of both the dorsal and ventral stream. These findings indicate that numerosity is represented over and above other visual features broadly in the brain but with substantially different neural coding schemes across regions, and are discussed in light of two non necessarily exclusive interpretations.

neuroscience↗

bioRxiv2022

The neural signature of magnitude integration between time and numerosity

Magnitude dimensions such as time and numerosity are fundamental components of our visual experience, allowing us to understand the environment and interact with it. Different magnitudes are however not processed independently from each other, but show a relationship whereby the perception of one dimension depends on the others ("magnitude integration"). In this study, we use electroencephalography (EEG) to address whether such integration may arise from a shared brain processing stage where different dimensions are integrated together, or from independent parallel processes interfering with each other. In the experiment, participants judged either the average numerosity or duration of dynamic dot-array stimuli concurrently modulated in both dimensions. First, the behavioural results show a magnitude integration effect in both tasks, with duration affecting the judgement of numerosity and vice versa. The EEG results further show that both numerosity and duration significantly modulate event-related potentials at several distinct latencies. Crucially, however, we identified a significant interaction between numerosity and duration emerging in a specific latency window (360-460 ms) irrespective of the task performed by participants. In this latency window, the modulation of ERPs provided by the interfering magnitude dimension can be predicted by the strength of the behavioural bias. Our results thus support the idea of different magnitude dimensions converging onto a shared perceptual processing stage mediating their integration. Overall, our results demonstrate a clear electrophysiological signature of magnitude integration between numerosity and time, and provide new evidence for a shared representational system encompassing different magnitude dimensions.

neuroscience↗

bioRxiv2020

Multiple spatial codes for navigating 2-D semantic spaces

When mammals navigate in the physical environment, specific neurons such as grid-cells, head-direction cells, and place-cells activate to represent the navigable surface, the faced direction of movement, and the specific location the animal is visiting. Here we test the hypothesis that these codes are also activated when humans navigate abstract language-based representational spaces. Human participants learnt the meaning of novel words as arbitrary signs referring to specific artificial audiovisual objects varying in size and sound. Next, they were presented with sequences of words and asked to process them semantically while we recorded the activity of their brain using fMRI. Processing words in sequence was conceivable as movements in the semantic space, thus enabling us to systematically search for the different types of neuronal coding schemes known to represent space during navigation. By applying a combination of representational similarity and fMRI-adaptation analyses, we found evidence of i) a grid-like code in the right postero-medial entorhinal cortex, representing the general bidimensional layout of the novel semantic space; ii) a head-direction-like code in parietal cortex and striatum, representing the faced direction of movements between concepts; and iii) a place-like code in medial prefrontal, orbitofrontal, and mid cingulate cortices, representing the Euclidean distance between concepts. We also found evidence that the brain represents 1-dimensional distances between word meanings along individual sensory dimensions: implied size was encoded in secondary visual areas, and implied sound in Heschls gyrus/Insula. These results reveal that mentally navigating between 2D word meanings is supported by a network of brain regions hosting a variety of spatial codes, partially overlapping with those recruited for navigation in physical space.

neuroscience↗

bioRxiv2020

Excessive visual crowding effects in developmental dyscalculia

Visual crowding refers to the inability to identify objects when surrounded by other similar items. Crowding-like mechanisms are thought to play a key role in numerical perception by determining the sensory mechanisms through which ensembles are perceived. Enhanced visual crowding might hence prevent the normal development of a system involved in segregating and perceiving discrete numbers of items and ultimately the acquisition of more abstract numerical skills. Here, we investigated whether excessive crowding occurs in developmental dyscalculia (DD), a neurodevelopmental disorder characterized by difficulty in learning the most basic numerical and arithmetical concepts, and whether it is found independently of associated major reading and attentional difficulties. We measured spatial crowding in two groups of adult individuals with DD and control subjects. In separate experiments, participants were asked to discriminate the orientation of a Gabor patch either in isolation or under spatial crowding. Orientation discrimination thresholds were comparable across groups when stimuli were shown in isolation, yet they were much higher for the DD group with respect to the control group when the target was crowded by closely neighbouring flanking gratings. The difficulty in discriminating orientation (as reflected by the combination of accuracy and reaction times) in the DD compared to the control group persisted over several larger target flanker distances. Finally, we found that the degree of such spatial crowding correlated with impairments in mathematical abilities even when controlling for visual attention and reading skills. These results suggest that excessive crowding effects might be a characteristic of DD, independent of other associated neurodevelopmental disorders. Bullet pointsO_LIPeople with DD have difficulty learning about numbers and arithmetics. C_LIO_LIPerception of non-symbolic number seems to be modulated by visual crowding. C_LIO_LICan stronger than normal crowding effects contribute to the origin of DD? C_LIO_LIWe measured crowding with orientation discrimination tasks using Gabor gratings. C_LIO_LIAbnormal crowding characterizes DD independently of other developmental deficits. C_LI

neuroscience↗

bioRxiv2019

Attentional amplification of neural codes for number independent of other quantities along the dorsal visual stream

Humans and other animals base important decisions on estimates of number, and intraparietal cortex is thought to provide a crucial substrate of this ability. However, it remains debated whether an independent neuronal processing mechanism underlies this 'number sense', or whether number is instead judged indirectly on the basis of other quantitative features. We performed high-resolution 7 Tesla fMRI while adult human volunteers attended either to the numerosity or to an orthogonal dimension (average item size) of visual dot arrays. Numerosity explained a significant amount of variance in activation patterns, above and beyond non-numerical dimensions. Its representation was progressively enhanced along the dorsal visual pathway and was selectively amplified by attention when task relevant. These results reveal a dedicated extraction mechanism for numerosity that operates independently of other quantitative dimensions of the stimuli, and suggest that later stages along the dorsal stream are most important for the explicit manipulation of numerical quantity.

neuroscience↗

bioRxiv2018

A cortical route for face-like pattern processing in human newborns

Humans are endowed with an exceptional ability for detecting faces, a competence that in adults is supported by a set of face-specific cortical patches. Human newborns already shortly after birth preferentially orient to faces even when they are presented in the form of highly schematic geometrical patterns, over perceptually equivalent non-face-like stimuli. The neural substrates underlying this early preference are still largely unexplored. Is the adult face-specific cortical circuit already active at birth, or does its specialization develop slowly as a function of experience and/or maturation? We measured EEG responses in 1-4 days old awake, attentive human newborns to schematic face-like patterns and non-face-like control stimuli, visually presented with a slow oscillatory \"peekaboo\" dynamics (0.8 Hz) in a frequency-tagging design. Despite the limited duration of newborns attention, reliable frequency-tagged responses could be estimated for each stimulus from the peak of the EEG power spectrum at the stimulation frequency. Upright face-like stimuli elicited a significantly stronger frequency-tagged response than inverted face-like controls in a large set of electrodes. Source reconstruction of the underlying cortical activity revealed the recruitment of a partially right-lateralized network comprising lateral occipito-temporal and medial parietal areas largely overlapping with the adult face-processing circuit. This result suggests that the cortical route specialized in face processing is already functional at birth.\n\nSignificance statementNewborns show a remarkable ability to detect faces even minutes after birth, an ecologically fundamental skill that is instrumental for interacting with their conspecifics. What are the neural bases of this expertise? Using EEG and a slow oscillatory visual stimulation, we identified a reliable response specific to face-like patterns in newborns, which underlying cortical sources largely overlap with the adult face-specific cortical circuit. This suggests that the development of face perception in infants might rely on an early cortical route specialized in face processing already shortly after birth.

neuroscience↗

bioRxiv2018

Asymmetrical interference between number and item size perception provide evidence for a domain specific impairment in dyscalculia

Dyscalculia, a specific learning disability that impacts arithmetical skills, has previously been associated to a deficit in the precision of the system that estimates the approximate number of objects in visual scenes (the so called number sense system). However, because in tasks involving numerosity comparisons dyscalculics judgements appears disproportionally affected by continuous quantitative dimensions (such as the size of the items), an alternative view linked dyscalculia to a domain-general difficulty in inhibiting task-irrelevant responses.\n\nTo arbitrate between these views, we evaluated the degree of reciprocal interference between numerical and non-numerical quantitative dimensions in adult dyscalculics and matched controls. We used a novel stimulus set orthogonally varying in mean item size and numerosity, putting particular attention into matching both features perceptual discriminability. Participants compared those stimuli based on each of the two dimensions. While control subjects showed no significant size interference when judging numerosity, dyscalculics numerosity judgments were strongly biased by the unattended size dimension. Importantly however, both groups showed the same degree of interference from number when judging mean size. Moreover, only the ability to discard the irrelevant size information when comparing numerosity (but not the reverse) significantly predicted calculation ability across subjects.\n\nOverall, our results show that numerosity discrimination is less prone to interference than discrimination of another quantitative feature (mean item size) when the perceptual discriminability of these features is matched, as here in control subjects. By quantifying, for the first time, dyscalculic subjects degree of interference on another orthogonal dimension of the same stimuli, we are able to exclude a domain-general inhibition deficit as explanation for their poor / biased numerical judgement. We suggest that enhanced reliance on non-numerical cues during numerosity discrimination can represent a strategy to cope with a less precise number sense.

neuroscience↗

bioRxiv2017

Discriminability of numerosity-evoked fMRI activity patterns in human intra-parietal cortex reflects behavioral numerical acuity

Areas of the primate intraparietal cortex have been identified as an important substrate of numerical cognition. In human fMRI studies, activity patterns in these and other areas have allowed researchers to read out the numerosity a subject is viewing, but the relation of such decodable information with behavioral numerical proficiency remains unknown.\n\nHere, we estimated the precision of behavioral numerosity discrimination (internal Weber fraction) in twelve adult subjects based on psychophysical testing in a delayed numerosity comparison task outside the scanner. FMRI data were then recorded during a similar task, to obtain the accuracy with which the same sample numerosities could be read out from evoked brain activity patterns, as a measure of the precision of the neuronal representation. Sample numerosities were decodable in both early visual and intra-parietal cortex with approximately equal accuracy on average. In parietal cortex, smaller numerosities were better discriminated than larger numerosities of the same ratio, paralleling smaller behavioral Weber fractions for smaller numerosities. Furthermore, in parietal but not early visual cortex, fMRI decoding performance was correlated with behavioral number discrimination acuity across subjects (subjects with a more precise behavioral Weber fraction measured prior to scanning showed greater discriminability of fMRI activity patterns in intraparietal cortex, and more specifically, the right LIP region).\n\nThese results suggest a crucial role for intra-parietal cortex in supporting a numerical representation which is explicitly read out for numerical decisions and behavior.

neuroscience↗