Biology subjects

Rapp, B.

Publications and source records attributed to Rapp, B..

3 recordsLinked to original sources

bioRxiv2025

Longitudinal changes in functional connectivity networks in the first year following stroke

The functional organization of the brain consists of multiple subsystems, or modules, with dense functional communication within modules (i.e., visual, attention) and relatively sparse but vital communications between them. The two hemispheres also have strong functional communications, which presumably supports hemispheric lateralization and specialization. Subsequent to stroke, the functional organization undergoes neuroplastic changes over time. However, empirical longitudinal studies of human subjects are lacking. Here we analyzed three large-scale, whole-brain resting-state functional MRI connectivity measures: modularity, hemispheric symmetry (based on system segregation), and homotopic connectivity in a group of 17 participants at 1-month, 3-months, and 12-months after a single left-hemisphere stroke. These measures were also compared to a group of 13 age-matched healthy controls. The three measures exhibited different trajectories of change: (1) modularity steadily decreased across the 12-month period and became statistically inferior to control values at 12 months, indicating a less modular organization; (2) hemispheric symmetry values were abnormally low at 1-month and then increased significantly in the first 6 months, leveling off at levels not significantly below control levels by 12 months, suggesting that the two hemispheres diverged initially after the unilateral damage, but improved over time; and (3) homotopic connectivity exhibited a U-shaped function with a significant decrease from 1-6 months and then an increase from 6-12 months, to levels that were not significantly different from controls. The results revealed a complex picture of the dynamic changes the brain undergoes as it responds to abrupt onset damage.

neuroscience↗

bioRxiv2024

Perinatal liver inflammation is associated with persistent elevation of CXCL10 and its canonical receptor CXCR3 on common myeloid progenitors

Biliary atresia (BA) is a leading cause of liver failure in infants. Despite effective surgical drainage, patients with BA exhibit attenuated immune responses to childhood vaccines, suggesting there are long-lasting alterations to immune function. The perinatal liver is home to hematopoietic stem and progenitor cells (HSPCs) and serves as the epicenter for rapidly progressive and significantly morbid inflammatory diseases like BA. We have previously established the role of neonatal myeloid progenitors in the pathogenesis of perinatal liver inflammation (PLI) and hypothesize that PLI leads to long-term changes to HSPCs in mice that recovered from PLI. To test this hypothesis, we compared the changes that occur to HSPCs and mature myeloid populations in the bone marrow of adult mice during homeostasis and during PLI. Our results demonstrate that HSPCs from animals that recover from PLI ("PLI-recovered") undergo long-term expansion with a reduced proliferative capacity. Notably, PLI leads to persistent activation of common myeloid progenitors through the involvement of CXCL10 and its canonical receptor, CXCR3. Our data suggests that the CXCR3-CXCL10 axis may mediate the changes in HSPCs that lead to altered immune function observed in BA, providing support for a targetable pathway to mitigate the detrimental long-term immune effects observed in patients with BA.

immunology↗

bioRxiv2022

Neural signatures of reading-related orthographic processing in braille

Blind readers use a tactile reading systems consisting of raised dot arrays: braille/. How does the human brain implement reading by touch? The current study looked for signatures of reading-specific orthographic processes in braille, separate from low-level somatosensory responses and semantic retrieval. Of specific interest were responses in posterior parietal cortices (PPC), because of their role in high-level tactile perception. Congenitally blind, proficient braille readers read real words and pseudowords by touch while undergoing fMRI. We leveraged the system of contractions in English braille, where one or more braille cells can represent combinations of English print letters (e.g., "ing" , "one" ), making it possible to separate physical and uncontracted letter-length. All words in the study consisted of 4 braille cells, but their corresponding Roman spellings varied from 4 to 7 letters (e.g., "con-c-er-t" . contracted: 4 cells; uncontracted: 7 letters). We found that the bilateral supramarginal gyrus (SMG) in the PPC increased its activity as the uncontracted word length increased. By contrast, in the hand region of primary somatosensory cortex (S1), activity increased as a function of a low-level somatosensory feature: dot-number per word. The PPC also showed greater response to pseudowords than real words and distinguished between real and pseudowords in multi-voxel-pattern analysis. Parieto-occipital, early visual and ventral occipito-temporal, as well as prefrontal cortices also showed sensitivity to the real-vs-pseudoword distinction. We conclude that PPC is involved in sublexical orthographic processing for braille, possibly due to brailles tactile modality. Significance statementBlind readers use tactile reading systems of raised dot arrays: braille. To identify signatures of orthographic processing for reading by touch, and dissociate it from tactile and linguistic process, we leveraged the system of contractions in English braille, where one or more braille characters represents combinations of English print letters. Blind proficient braille readers read real words and pseudowords during fMRI scans. While all words consisted of 4 braille characters, the uncontracted spelling ranged from 4-7 letters. Activity in bilateral-posterior-parietal cortices, just posterior to primary-somatosensory cortex, increased with uncontracted word length, independent of tactile complexity (number of raised dots per word). By contrast, primary-somatosensory activity increased with tactile complexity. The posterior-parietal cortices contribute to tactile reading.

neuroscience↗