Biology subjects

Tyagi, C.

Publications and source records attributed to Tyagi, C..

4 recordsLinked to original sources

bioRxiv2026

Postnatal maturation of putamen microstructure accompanies topographic white matter connectivity and altered circuits in autism

The putamen is a major hub of the basal ganglia that emerges early in gestation. However, whether its mature organization is established before birth or emerges postnatally remains unknown. Using cross-sectional and longitudinal quantitative MRI (R1 and R2*, related to tissue density and iron, respectively) and diffusion MRI, we characterized the development of putamen's microstructure and its white matter connectivity with cortex from birth to 12 months and compared their trajectories with those in adults. Despite its prenatal emergence, the putamen undergoes substantial postnatal development. R1 increases from birth to 12 months, producing a prominent anterior-posterior gradient, whereas R2* increases primarily between age one and adulthood, producing a medial-lateral gradient. Cortico-putamen white matter connectivity is diffuse in infants but becomes topographic in adults, with anterior putamen linked to frontal cortex and posterior putamen to sensorimotor cortex. In autism spectrum disorder, this organization is largely preserved and accompanied by increased anterior putamen-prefrontal connectivity. Our findings reveal distinct spatial developmental trajectories of putamen microstructure and cortical connectivity providing a developmental framework for understanding the organization of the putamen in infancy, which has implications for assessing neurodevelopmental disorders of the basal ganglia.

neuroscience↗

bioRxiv2026

Multiphasic myelination and dendritic growth modulate qMRI signals in human visual cortex.

How does myelin develop in human visual cortex? By combining immunohistochemistry with in vivo and postmortem magnetic resonance imaging of longitudinal relaxation rate (R1), which increases with myelin content, we find that myelin and R1 increase across development but follow distinct trajectories. Immunohistochemistry reveals two phases of myelination: an infant phase of limited oligodendrogenesis, with myelin restricted to deep cortical layers, followed by widespread myelination across all layers during childhood. Cortical R1 also increases across development and correlates with myelin by childhood. However, in infancy, R1 increases outpace myelin growth and instead tracks dendritic arborization, indicating that the microstructural drivers of R1 change across development. We hypothesize that deep layer myelination in infancy contributes to early visual function whereas later myelination of superficial layers enables prolonged cortical plasticity and learning of complex visual behaviors.

neuroscience↗

bioRxiv2025

Hierarchical microstructural tissue growth of the gray and white matter of human visual cortex during the first year of life

Development of gray and white matter tissue microstructure is critical for the emergence of sensory and cognitive functions. However, it is unknown how microstructural tissue properties of the human visual system develop in the first year of human life. Here, we use tissue relaxation rate (R1) obtained using quantitative MRI to measure the longitudinal development of gray and white matter in brain areas spanning three visual processing streams: dorsal, lateral, and ventral, during the first year of life. R1 in gray and white matter of all visual regions in the three processing streams increases postnatally, indicating microstructural tissue growth. R1 increases faster between 0-6 months than 6-12 months, and faster in white matter than gray matter, with white matter R1 surpassing that of gray matter after two months of age. Strikingly, this microstructural growth is hierarchical: across all streams, early visual areas are more mature at birth than higher-level areas but develop more slowly postnatally than higher-level areas. The exception is TO1 (MT) which is similar to V1: it is microstructurally more mature at birth and develops slower than neighboring areas. Overall, our findings provide the first comprehensive measurement of microstructural tissue growth in infancy across three visual processing streams and propose a new hypothesis that functional development of the visual cortex may be coupled with microstructural development and follows a similar hierarchical trajectory.

neuroscience↗

bioRxiv2024

White matter connections of human ventral temporal cortex are organized by cytoarchitecture, eccentricity, and category-selectivity from birth

Category-selective regions in ventral temporal cortex (VTC) have a consistent anatomical organization, which is hypothesized to be scaffolded by white matter connections. However, it is unknown how white matter connections are organized from birth. Here, we scanned newborn to 6-month-old infants and adults to determine the organization of the white matter connections of VTC. We find that white matter connections are organized by cytoarchitecture, eccentricity, and category from birth. Connectivity profiles of functional regions in the same cytoarchitectonic area are similar from birth and develop in parallel, with decreases in endpoint connectivity to lateral occipital, and parietal, and somatosensory cortex, and increases to lateral prefrontal cortex. Additionally, connections between VTC and early visual cortex are organized topographically by eccentricity bands and predict eccentricity biases in VTC. These data show that there are both innate organizing principles of white matter connections of VTC, and the capacity for white matter connections to change over development.

neuroscience↗