About

Tilak Ratnanather is an Associate Research Professor of Biomedical Engineering at Johns Hopkins University. His research focuses on the analysis of brain structures such as the hippocampus, cingulate gyrus, planum temporale, superior temporal gyrus, and the auditory and prefrontal cortexes. These structures are implicated in neuropsychiatric and neurodevelopmental disorders including schizophrenia, Alzheimer's disease, epilepsy, major depression, and speech and language processing. His interests also extend to the physiological fluid mechanics of the cochlear outer hair cell, the study of nonlinear partial differential equations in computational anatomy and bioacoustics, and continuing education through online courses in applied mathematics.

Selected publications

• Accessibility in Academic Conferences: Barriers, Solutions, and a Framework for Inclusive Participation

  2026-03-22

  articleOpen access

  Scientific conferences play a central role in knowledge exchange, networking, and career progression, yet they remain variably accessible to researchers with disabilities. Barriers can arise across the full conference lifecycle, including abstract submission, registration, travel, venue navigation, participation in sessions, networking opportunities, and peri-event engagement. To better understand these challenges, we conducted a scoping review of empirical and qualitative literature examining accessibility and inclusion at academic conferences and scientific meetings. Across 4,695 screened records published between 2010 and 2026, only eight studies met inclusion criteria, highlighting a striking scarcity of conference-specific research on disability and accessibility. Despite this limited evidence base, the identified barriers were consistent and clustered across structural, technological, attitudinal, financial, and logistical domains. Common challenges included inaccessible venues and digital platforms, inflexible scheduling, additional financial burdens, and ableist assumptions that shift responsibility for accommodations onto individuals. The literature also identified feasible solutions, including hybrid participation models, proactive accessibility governance, inclusive communication practices, and flexible program design. However, implementation remains uneven and is often treated as optional rather than integral to conference design. Drawing on the review findings and sector-led perspectives, we propose a staged framework for improving accessibility in academic events, including governance mechanisms, digital access standards, and inclusive physical and programmatic design. Our findings suggest that accessibility barriers at conferences are systemic rather than incidental, and that embedding accessibility into conference planning can enhance participation, learning, and collaboration for a wide range of attendees. Addressing these barriers is essential not only for equity but also for advancing a more inclusive and innovative scientific community.

  PublisherDOI

• Tous pour un, un pour tous (All for one, one for all): Accessible neuroimaging and research dissemination via speech to text apps

  Aperture Neuro · 2026-03-17

  articleOpen accessSenior author

  Accessibility is a vital aspect of diversity and inclusivity within clinical and research environments. For professionals in neuroimaging – neuroscientists, radiographers, radiologists and neurologists – hearing accessibility is particularly crucial, both during magnetic resonance imaging (MRI) procedures and in academic settings such as conferences. This commentary highlights the significance of hearing accessibility in neuroimaging, and demonstrates recent advancements aimed at improving auditory inclusion in MRI environments and scientific conferences. Although originally developed for the Organisation for Human Brain Mapping (OHBM) community, the recommendations presented here are broadly applicable and intended to enhance hearing accessibility across the wider neuroimaging field.

  PublisherOA PDFDOI

• Rostral Associations of MRI Atrophy of the Amygdala and Entorhinal Cortex Across the AD Spectrum

  medRxiv · 2026-01-30

  articleOpen access

  Abstract This paper examines associations of atrophy in the amygdala, entorhinal cortex and hippocampus based on magnetic resonance imaging (MRI) and Positron Emission Tomography (PET) scans from two independent cohorts: Alzheimer’s Disease Neuroimaging Initiative (ADNI) and Biomarkers of Cognitive Decline Among Normal Individuals (BIOCARD) study. The amygdala and entorhinal cortex (ERC) are shown to change earlier in the disease than the hippocampus based on atrophy of laminar thickness of the ERC and amygdala volumes. Over four hundred laminar reconstructions showed that ERC volume loss is linked to cortical thinning, as a more specific measure historically linked to the layer specific pattern of tau pathology deposition. Additionally, high field atlasing with delineations of amygdala subregions shows predominant volume loss in medial subregions including basomedial, basolateral, and corticocentromedial compared with the lateral subregion. In the context of earlier work linking MRI-based atrophy with hyperphospho-rylated tau deposition in the ERC and amygdala, the atrophy rate marker is shown to be strongly associated with tau deposition as measured by tau positron emission tomography imaging and co-localization of the atrophy marker to the spatial distribution of tau deposition. Highlights Structural MRI analyses across ADNI and BIOCARD cohorts reveal significantly greater early atrophy in amygdala and entorhinal cortex (ERC), marking them as sensitive indicators of preclinical Alzheimer’s disease. ERC volume loss is shown to correspond to cortical laminar thinning by surface-based diffeomorphic reconstructions, confirming MRI volume atrophy as a biologically valid marker of early neuronal degeneration. Predominant atrophy in medial amygdala subregions (basomedial, basolateral, corticocentromedial) are identified compared to the lateral amygdala using high-field (11T) atlases, mirroring known histopathological tau distribution. MRI volume atrophy correlates with tau burden measured by tau PET imaging, demonstrating region-specific correspondence between structural atrophy and molecular pathology.

  PublisherDOI

• Abstract TP254: Hydration Status and Regional Brain Volumetrics in a Population of Hospitalized Stroke Patients

  Stroke · 2026-01-29

  article

  Background: Measuring hydration status after stroke is especially important due to alterations in cerebral perfusion, though to date is reliant on crude bedside observations of the patient or indirect laboratory markers (e.g. blood urea nitrogen (BUN)/creatinine ratios). We hypothesized that regional brain volumetrics could differ based on hydration status at the time pf presentation with stroke. In this study, we sought to use methods of computational anatomy to quantify whether or not there are differences in brain region shape in underhydrated versus at the time of acute stroke. Methods: Clinical data was obtained from sequential stroke patients admitted to the Johns Hopkins Comprehensive Stroke Center. We used blood urea nitrogen: creatinine ratio (BUN/creatinine ratio) >15 to indicate a state of relative dehydration at the time of hospital arrival. Once the list of brain volumes was connected to each patient, each patient’s data was then normalized for intracranial volume (ICV). The dehydrated and hydrated volumes per each brain area underwent the Kolmogorov–Smirnov test, which checked the likelihood that two sets were drawn from the same distribution. To correct for multiple hypothesis testing, the Benjamini–Hochberg procedure was applied to the resulting p-values to control the false discovery rate. For any p-values less than 0.05, the sets were considered statistically likely to come from different distributions. The analysis was done on volumes partitioned at level 3 and level 5 granularity. Results: At level 5 granularity, significant volumetric differences were observed in 14.92% of brain regions with 99% confidence. At level 3 granularity, differences were identified in 11.11% of regions with 95% confidence. In both analyses, the body of the corpus callosum and the lateral ventricles exhibited significant shrinkage in dehydrated patients. Additional shrinkage was observed in the frontal lobe, parietal lobe, and central sulci. Conversely, the medulla demonstrated an increase in volume in the dehydrated group at both granularities. Conclusions: The corpus callosum and lateral ventricles may demonstrate vulnerability to hydration status in this cohort of patients. These regions may serve as potential biomarkers for hydration status in acutely ill stroke patients. Future work will be needed to determine how these volume differences relate to functional outcomes and recovery.

  PublisherDOI

• Reduced Vestibular Function is Associated With Cortical Surface Shape Changes in the Frontal Cortex

  Human Brain Mapping · 2025-07-01 · 1 citations

  articleOpen access

  Aging-associated decline in peripheral vestibular function is linked to deficits in behaviors and cognitive abilities that are known to rely on the sensorimotor and frontal cortices, but the precise neural pathways are unknown. To fill this knowledge gap, this cross-sectional study investigates the relationship between age-related variation in vestibular function and surface shape alterations of the frontal and sensorimotor cortices, considering age, intracranial volume, and sex. Data from 117 older adults (aged 60+) from the Baltimore Longitudinal Study of Aging, who underwent end-organ-specific vestibular tests (cVEMP for the saccule, oVEMP for the utricle, and vHIT for the horizontal canal) and T1-weighted MRI scans on the same visit, were analyzed. We examined a subset of 10 frontal and sensorimotor brain structures in the broader, distributed vestibular network: the middle-superior part of the prefrontal cortex (SFG_PFC), frontal pole (SFG_pole), and posterior pars of the superior frontal gyrus (SFG), the dorsal prefrontal cortex and posterior pars of middle frontal gyrus (MFG_DPFC, MFG), the pars opercularis, pars triangularis, and pars orbitalis of the inferior frontal gyrus, as well as the precentral gyrus and postcentral gyrus (PoCG) of the sensorimotor cortex. For each region of interest (ROI), shape descriptors were estimated as local compressions and expansions of the population average ROI surface using Large Deformation Diffeomorphic Metric Mapping (LDDMM) surface registration. Shape descriptors were linearly regressed onto standardized vestibular variables, age, intracranial volume, sex, and in follow-up analyses, multisensory function (hearing, vision, proprioception). We found that lower utricular function was linked with surface compression in the left MFG and expansion in the bilateral SFG_pole and left SFG. Reduced canal function was associated with surface compression in the right SFG_PFC and SFG_pole and left SFG. Both reduced saccular and utricular function correlated with surface compression in the posterior medial part of the left MFG. Our findings illuminate the complexity of the relationship between vestibular end-organ function and the focal morphology in aging in areas of the frontal and sensorimotor cortices relevant to executive ability, motor planning, and self-motion perception. An improved understanding of these pathways could help in developing interventions to enhance the quality of life in aging and populations with cognitive impairment.

  PublisherOA PDFDOI

• Susceptibility MRI Helps Predict Mild Cognitive Impairment Onset and Cognitive Decline in Cognitively Unimpaired Older Adults

  Radiology · 2025-09-01 · 7 citations

  articleOpen access

  Tissue magnetic susceptibility elevations measured at MRI in the entorhinal cortex and putamen were significant predictors of onset of mild cognitive impairment and cognitive decline in cognitively unimpaired older adults, especially those with amyloid neuropathologic abnormalities.

  PublisherOA PDFDOI

• Altered hippocampal shape morphology in schizophrenia and at-risk mental state

  Psychiatry Research Neuroimaging · 2025-12-31

  articleOpen access
  PublisherOA PDFDOI

• Library of realistic 4D digital beating heart models based on patient CT data

  Medical Physics · 2025-07-01 · 1 citations

  articleOpen access

  BACKGROUND: The prevalence of cardiovascular disease (CVD) has risen alongside new medical imaging technologies designed for its diagnosis and treatment. Computational phantoms play a crucial role in imaging research, supporting applications ranging from basic simulation studies to larger-scale virtual imaging trials (VITs). PURPOSE: In this work, we develop a population of detailed, anatomically variable 4D beating heart models for medical imaging research. METHODS: 32 sets of 4D CT data from the PROspective Multicenter Imaging Study for Evaluation of Chest Pain (PROMISE) national clinical trial served as the basis for the cardiac library. Each dataset was electrocardiogram-gated, containing 10 lower-resolution frames over the cardiac cycle and one high-resolution frame at mid-diastole. The 4D data for each patient was segmented using the AI-based Automatic Segmentation (AS) Cardio tool from Synopsys Simpleware. The segmented high-resolution frame was used to define the initial instance of the heart, each structure defined as a polygon mesh. The multi-channel Large Deformation Diffeomorphic Metric Mapping (MC-LDDMM) image registration algorithm was then used to calculate the frame-to-frame motion of the heart from the low-resolution segmentations. The motion was applied to the cardiac model, creating a time-changing mesh model. Cubic spline curves were fit to the time-changing vertex locations, creating a 4D continuous model from which any number of time points can be generated. An example heart model was imported into a whole-body XCAT computational phantom and imaged with the DukeSim CT simulator for demonstration. RESULTS: Compared to reference values, the image-based cardiac models mimic the twisting, contracting motion of the heart for anatomically variable subjects. When combined with DukeSim, realistic virtual cardiac imaging data can be produced. CONCLUSIONS: 4D beating heart models were successfully created combining AI-based segmentation and image registration. The library of realistic cardiac models can be a vital tool for 4D cardiac imaging studies.

  PublisherOA PDFDOI

• The Inner Ear and Aging Brain: A Cross-Sectional Study of Vestibular Function and Morphometric Variations in the Entorhinal and Trans-Entorhinal Cortex

  Journal of the Association for Research in Otolaryngology · 2025-02-24 · 1 citations

  articleOpen access

  PURPOSE: While the vestibular system is crucial for balance, posture, and stable vision, emerging evidence connects vestibular loss in older adults to spatial cognitive deficits. However, the specific neural pathways remain unclear. This study examines morphometric changes in the entorhinal cortex (ERC) and trans-entorhinal cortex (TEC), key regions in the vestibular spatial cognitive network, with vestibular function. METHODS: This cross-sectional study used T1-weighted MRI images and vestibular physiological data from 103 Baltimore Longitudinal Study of Aging participants (74 males and 29 females). Vestibular function was assessed through the cervical vestibular-evoked myogenic potential (cVEMP), ocular VEMP (oVEMP), and video head-impulse test (vHIT), examining both categorical presence/absence of responses and continuous measures (cVEMP amplitude, oVEMP amplitude, and VOR gain). Morphometric changes in the ERC and TEC were analyzed by examining surface expansions and contractions relative to average shapes. RESULTS: Reduced saccular function correlated with surface expansion in the left ERC's pro-rhinal, right ERC's intermediate caudal and superior regions, and right TEC's sulcal region. The decreased utricular function was associated with surface contraction in the left lateral TEC, left ERC's anterior sulcal and trans-entorhinal regions, and surface expansion in the lateral region of the left ERC. Reduced canal function showed surface contraction in the right ERC's pro-rhinal and lateral regions and the right TEC's posterior sulcal and trans-entorhinal regions. CONCLUSION: These findings highlight the intricate link between vestibular function and ERC/TEC morphology, emphasizing their role in spatial and cognitive abilities. Future research will assess if structural changes due to vestibular loss contribute to cognitive deficits in aging and Alzheimer's disease.

  PublisherOA PDFDOI

• Associations Between Vestibular Function and White Matter Microstructure in Healthy Older Adults

  medRxiv · 2025-09-07

  preprintOpen access

  The relationship between vestibular function and white matter (WM) integrity is poorly understood, despite increasing evidence linking vestibular sensory decline and motor and cognitive deficits in older adults. This study examined associations between vestibular function and the microstructural integrity of 19 WM pathways in 394 cognitively healthy participants aged 60+ from the Baltimore Longitudinal Study of Aging who had regional WM microstructure assessed by diffusion tensor imaging metrics: fractional anisotropy and mean diffusivity. The vestibular functions of the saccule, utricle, and horizontal semi-circular canal were assessed using the cVEMP and oVEMP tests and the vHIT, respectively. Multiple linear regression of WM metrics onto vestibular function, adjusted for age, sex, intracranial volume, and scanner type, was used to examine the association between WM and vestibular function. We found that higher canal function was associated with higher integrity in the external capsule, the cingulum projection to the hippocampus, the inferior fronto-occipital fasciculus, and the genu of the corpus callosum, but lower integrity in the limbs of the internal capsule, sagittal stratum, posterior thalamic radiation, the cingulum projection to the cingulate gyrus, and fornix. Utricular function was associated with higher integrity in the anterior limb of the internal capsule and the fornix but lower integrity in the retrolenticular limb of the internal capsule. Saccular function was not associated with WM microstructure. This study demonstrates for the first time potential associations between vestibular end-organ function and WM microstructure in healthy, older adults, with horizontal canal function exhibiting diffuse associations with multi-sensorimotor tracts, whereas utricular function shows more focal associations. Because these findings are concomitant with lower age-related WM integrity, they suggest that better vestibular function may confer resilience in certain pathways while potentially accelerating age-related degeneration in others. Longitudinal studies will be needed to robustly identify WM neuroimaging markers of aging-associated vestibular loss over time.

  PublisherOA PDFDOI

Awards & honors

• 2023 Diversity Recognition Award from the Johns Hopkins Dive…