Biology subjects

Kiran, S.

Publications and source records attributed to Kiran, S..

8 recordsLinked to original sources

bioRxiv2026

Communication as a Two-Person Neural Process: fNIRS Hyperscanning in Adults with and without Post-Stroke Aphasia

Communication is inherently interactive, yet most neuroimaging studies examine individuals in isolation. Here, we used functional near-infrared spectroscopy (fNIRS) hyperscanning to investigate interbrain synchrony (IBS) during naturalistic communication. In Study 1, 13 healthy familiar dyads completed Joint Singing, Joint Reading, and Picture Guessing tasks. IBS was quantified using wavelet transform coherence across bilateral frontal and temporoparietal regions. Joint Singing produced higher IBS than the other tasks in several regions, including the dorsolateral prefrontal cortex and temporoparietal junction, and selected effects were greater in true than pseudo-dyads. In Study 2, we applied the same paradigm to five individuals with chronic post-stroke aphasia interacting with trained speech-language pathologists. IBS could be estimated in all dyads after lesion-informed channel exclusion, although regional coverage varied with lesion location. These findings demonstrate that fNIRS hyperscanning can capture task-dependent interpersonal neural coupling during spoken interaction and can be extended to communication involving individuals with aphasia. This approach provides a foundation for studying how neural coordination between communication partners relates to functional communication and partner-supported interaction.

neuroscience↗

bioRxiv2026

Network measures from the REWIRED simulation framework enhance prediction of post-stroke aphasia severity

Predicting post-stroke aphasia severity remains challenging, in part because language outcomes reflect not only focal cortical damage but also widespread disruption of structural and functional networks. Computational models of large-scale cortical dynamics offer a principled way to infer these network-level consequences from patient-specific lesions. Here, we present and evaluate REWIRED, a lesion-informed cortical dynamics framework designed to simulate individualized alterations in large-scale brain network organization after stroke. We first evaluated whether simulation-derived functional connectivity captured patient-specific variation in empirical functional connectivity beyond lesion burden and structural disconnection alone. We then developed a multiscale feature set combining lesion volume, lesion distribution patterns, probabilistic disconnectome metrics, and simulation-derived measures of functional connectivity and effective information flow (EIF). Finally, using a nested support vector regression (SVR) framework in a separate dataset, we tested whether simulation-derived features improve prediction of chronic aphasia severity, measured by the Western Aphasia Battery - Revised Aphasia Quotient (WAB-AQ), beyond lesion-distribution and structural-connectivity predictors. Simulation-derived functional connectivity significantly predicted empirical functional connectivity beyond local lesion burden and structural disconnection alone. With respect to WAB-AQ prediction, lesion-based (Set 1) and disconnectome-based (Set 2a) features alone yielded modest accuracy. Adding simulation-derived features (Set 2b) produced substantial gains, and the full feature set (Set 3) achieved the best performance (RMSE = 14.5; r = 0.83), reaching accuracy that is competitive with recent multimodal neuroimaging approaches, despite relying solely on lesion-distribution inputs. EIF measures were consistently selected as top predictors, indicating that disruptions in interregional communication patterns carry behaviorally relevant information not captured by structural features alone. These results support REWIRED as a framework for linking structural injury to distributed network dysfunction and behavioral outcomes. By integrating lesion information with large-scale cortical dynamics modeling, REWIRED provides a foundation for future individualized modeling of recovery and rehabilitation.

neuroscience↗

bioRxiv2026

Genomic Footprints of Bottlenecks, Isolation, and Inbreeding: A Case Study of Two Vulture Cohorts in India

Genomic erosion as a manifestation of small effective population size (Ne) and consanguinity subverts long-term perpetuation of threatened species by compromising their adaptive potential; however, the integration of genomics remains limited in applied conservation efforts to guide priorities. This study combines non-invasive sampling, double-digest Restriction site-associated DNA sequencing (ddRAD), and population-genomic analyses to assess genetic health in two vulture assemblages-mixed wild enclosure and captive breeding cohorts. Both the geographical locations exhibit signs of populations in distress: low genetic diversity and abundant intermediate-length runs of homozygosity (RoH), consistent with long-term reduced Ne plus recent demographic isolation. Our demographic model runs favoured ancient migration (AM) topology characterised by an ephemeral window of gene flow, taken over by a prolonged population separation period. The mutation quantification results from approximately 59,000 outgroup-polarised SNPs reveal higher additive burden and more homozygous-derived sites in BKN. However, this was later traced to low-impact and non-coding variants rather than a surge in the loss-of-function (LoF) alleles. The data support a genomic profile that carries an elevated risk from polygenic/aggregate deleterious burden in BKN despite a scarcity of high-impact mutations. By highlighting the disconnect between genetic resilience and demographic recovery, our results accentuate the need to incorporate genomics-informed inbreeding and monitoring programs, while also focusing on reducing anthropogenic mortality with genetic augmentation.

genomics↗

bioRxiv2025

Evidence for an Integrated Bilingual Language System from Discourse Tasks in Aphasia

BackgroundThe extent to which bilingual individuals represent and process their two languages within a shared or partially distinct neural architecture remains a topic of ongoing debate. While both parallel and divergent patterns of impairment have been reported in bilingual aphasia, such findings likely reflect a spectrum of representational overlap influenced by dominance, proficiency, and task demands. Critically, few studies have examined how breakdown manifests across multiple levels of linguistic structure using ecologically valid, discourse-based tasks. AimsThis study investigates whether Spanish-English bilinguals with aphasia exhibit parallel or dissociable patterns of impairment across their two languages, focusing on naturalistic narrative production and fine-grained analysis of error types and code-switching. Methods & ProceduresThirteen bilingual individuals with aphasia following acquired brain injury produced story retellings in both languages. Speech samples were transcribed and coded for phonological, morphological, syntactic, and semantic errors, and for the word type at which they occurred. Code-switches were also identified and categorized. Analyses included generalized linear modeling and unsupervised clustering. Outcomes & ResultsWhile participants made more errors in their non-dominant language, the structure and distribution of errors were highly similar across languages. Clustering algorithms revealed that impairments were parallel across languages and did not group by language dominance. Code-switching occurred more frequently from the non-dominant to the dominant language, consistent with activation-based lexical selection. ConclusionsFindings support an integrated bilingual language system that spans multiple levels of linguistic representation, modulated by language dominance. Naturalistic discourse tasks allow for richer characterization of bilingual language breakdown and may better inform both theoretical models and clinical management of bilingual aphasia.

neuroscience↗

bioRxiv2024

Inclusivity in fNIRS Studies: Quantifying the Impact of Hair and Skin Characteristics on Signal Quality with Practical Recommendations for Improvement

Functional Near-Infrared Spectroscopy (fNIRS) holds transformative potential for research and clinical applications in neuroscience due to its non-invasive nature and adaptability to real-world settings. However, despite its promise, fNIRS signal quality is sensitive to individual differences in biophysical factors such as hair and skin characteristics, which can significantly impact the absorption and scattering of near-infrared light. If not properly addressed, these factors risk biasing fNIRS research by disproportionately affecting signal quality across diverse populations. Our results quantify the impact of various hair properties, skin pigmentation as well as head size, sex and age on signal quality, providing quantitative guidance for future hardware advances and methodological standards to help overcome these critical barriers to inclusivity in fNIRS studies. We provide actionable guidelines for fNIRS researchers, including a suggested metadata table and recommendations for cap and optode configurations, hair management techniques, and strategies to optimize data collection across varied participants. This research paves the way for the development of more inclusive fNIRS technologies, fostering broader applicability and improved interpretability of neuroimaging data in diverse populations.

neuroscience↗

bioRxiv2024

The language network ages well: Preserved selectivity, lateralization, and within-network functional synchronization in older brains

Healthy aging is associated with structural and functional brain changes. However, cognitive abilities vary in how they change with age: whereas executive functions, like working memory, show age-related decline, aspects of linguistic processing remain relatively preserved. The heterogeneity of the cognitive-behavioral landscape in aging predicts differences among brain networks in whether and how they should change with age. To evaluate this prediction, we used individual-subject fMRI analyses (precision fMRI) to examine the language-selective network and--for control purposes--the Multiple Demand (MD) network, which supports executive functions, in older adults (n=64) relative to young controls (n=483). In line with past claims, relative to young adults, the MD network of older adults shows weaker, less spatially extensive, and more topographically variable activations during an executive function task and reduced within-network functional connectivity. However, in stark contrast to the MD network, we find remarkable preservation of the language network in older adults. Their language network responds during language comprehension as strongly and selectively as in younger adults, and shows a similar degree of left-hemispheric lateralization and within-network functional connectivity. Our findings suggest that the language network remains young-like--at least on standard measures of function and connectivity--and align with behavioral preservation of language comprehension in healthy aging.

neuroscience↗

bioRxiv2023

Pars opercularis underlies efferent predictions and successful auditory feedback processing in speech: Evidence from left-hemisphere stroke

Hearing ones own speech allows for acoustic self-monitoring in real time. Left-hemisphere motor planning regions are thought to give rise to efferent predictions that can be compared to true feedback in sensory cortices, resulting in neural suppression commensurate with the degree of overlap between predicted and actual sensations. Sensory prediction errors thus serve as a possible mechanism of detection of deviant speech sounds, which can then feed back into corrective action, allowing for online control of speech acoustics. The goal of this study was to assess the integrity of this detection-correction circuit in persons with aphasia (PWA) whose left-hemisphere lesions may limit their ability to control variability in speech output. We recorded magnetoencephalography (MEG) while 15 PWA and age-matched controls spoke monosyllabic words and listened to playback of their utterances. From this, we measured speaking-induced suppression of the M100 neural response and related it to lesion profiles and speech behavior. Both speaking-induced suppression and cortical sensitivity to deviance were preserved at the group level in PWA. PWA with more spared tissue in pars opercularis had greater left-hemisphere neural suppression and greater behavioral correction of acoustically deviant pronunciations, whereas sparing of superior temporal gyrus was not related to neural suppression or acoustic behavior. In turn, PWA who made greater corrections had fewer overt speech errors in the MEG task. Thus, the motor planning regions that generate the efferent prediction are integral to performing corrections when that prediction is violated.

neuroscience↗

bioRxiv2019

ATAC-seq identifies thousands of extrachromosomal circular DNA in cancers and cell lines

Extrachromosomal circular DNAs (eccDNAs) lack centromeres and are not passed equally into daughter cells and thus provide a source of cell-cell heterogeneity in normal and tumor cells. Previously we and other groups purified circular DNA and linearized them by rolling circle amplification for paired end high throughput sequencing to identify eccDNA in cells and tissues. We hypothesized that many eccDNA will have more open chromatin and so will be susceptible to linearization and sequencing by tagmentation. Indeed, we find that ATAC-seq on cell lines and cancers, without any enrichment of circular DNA, identifies thousands of eccDNAs. The identified eccDNAs in cell lines were validated by inverse PCR on DNA that survives exonuclease digestion of linear DNA and by metaphase FISH. We demonstrate that ATAC-seq data generated in Lower Grade Gliomas (LGG) and Glioblastomas (GBM) identify eccDNAs, including one containing the well-known EGFR gene amplicon from chr7. Many of the eccDNAs are identified even before amplification of the locus is detected by genotyping arrays. Thus, standard ATAC-seq is a sensitive method to detect segments of DNA that are present as eccDNA in a subset of the tumor cells, ready to be further amplified under appropriate selection, as during therapy.

genomics↗