Biology subjects

Vignaud, A.

Publications and source records attributed to Vignaud, A..

4 recordsLinked to original sources

bioRxiv2023

Human brain representations of internally generated outcomes of approximate calculation revealed by ultra-high-field brain imaging

Much of human cultures advanced technology owes its existence to the ability to mentally manipulate quantities. Neuroscience has described the brain regions overall recruited by numerical tasks and the neuronal codes representing individual quantities during perceptual tasks. Nevertheless, it remains unknown how quantity representations are combined or transformed during mental computations and how specific quantities are coded in the brain when generated as the result of internal computations rather than evoked by a stimulus. Here, we imaged the brains of adult human subjects at 7 Tesla during an approximate calculation task designed to disentangle in- and outputs of the computation from the operation itself. While physically presented sample numerosities were distinguished in activity patterns along the dorsal visual pathway and within frontal and occipito-temporal regions, a representation of the internally generated result was most prominently detected in higher order regions such as angular gyrus and lateral prefrontal cortex. Behavioral precision in the task was related to cross-decoding performance between sample and result representations in medial IPS regions. This suggests the transformation of sample into result may be carried out within dorsal stream sensory-motor integration regions, and resulting outputs maintained for task purposes in higher-level regions in a format possibly detached from sensory-evoked inputs.

neuroscience↗

bioRxiv2020

Glycine receptor subunit-β -deficiency in a mouse model of spasticity results in attenuated physical performance, growth and muscle strength

Spasticity is the most common neurological disorder associated with increased muscle contraction causing impaired movement and gait. The aim of this study was to characterize physical performance and skeletal muscle function and phenotype of mice with a hereditary spastic mutation (B6.Cg-Glrbspa/J). Motor function, gait and physical activity of juvenile and adult spastic mice and the morphological, histological and mechanical characteristics of their soleus (SO) and gastrocnemius medialis (GM) muscles were compared with their wild-type (WT) littermates. Spastic mice showed attenuated growth, impaired motor function and low physical activity. Gait of spastic mice was characterized by a typical hopping pattern. Spastic mice showed lower muscle forces, which were related to the smaller physiological cross-sectional area of spastic muscles. The muscle-tendon complex length-force relationship of adult GM was shifted towards shorter lengths, which was explained by attenuated longitudinal tibia growth. Spastic GM was more fatigue resistant than WT GM. This was largely explained by a higher mitochondrial content in muscle fibers and relatively higher percentage of slow type muscle fibers. Muscles of juvenile spastic mice showed similar differences compared to WT juvenile mice, but these were less pronounced than between adult mice. This study shows that in spastic mice, disturbed motor function and gait is likely the result hyperactivity of skeletal muscle and impaired skeletal muscle growth, which progress with age.

physiology↗

bioRxiv2019

Mapping numerical perception and operations in relation to functional and anatomical landmarks of human parietal cortex

Human functional imaging has identified the middle part of the intraparietal sulcus (IPS) as an important brain substrate for different types of numerical tasks. This area is often equated with the macaque ventral intraparietal area (VIP) where neuronal selectivity for non-symbolic numbers is found. However, the low spatial resolution and whole-brain averaging analysis performed in most fMRI studies limit the extent to which an exact correspondence of activation in different numerical tasks with specific sub-regions of the IPS can be established. Here we disentangled the functional neuroanatomy of numerical perception and operations (comparison and calculation) by acquiring high-resolution 7T fMRI data in a group of human adults, and relating the activations in different numerical contrasts to anatomical and functional landmarks on the cortical surface. Our results reveal a functional heterogeneity within human intraparietal cortex where the visual field map representations in superior/medial parts of IPS and superior parietal gyrus are involved predominantly in numerosity perception, whereas numerical operations predominantly recruit lateral/inferior parts of IPS. Since calculation and comparison-related activity fell mainly outside the field map representations considered the functional equivalent of the monkey VIP/LIP complex, the areas most activated during such numerical operations in humans are likely different from VIP.

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↗