Biology subjects

Abraham, I.

Publications and source records attributed to Abraham, I..

4 recordsLinked to original sources

bioRxiv2026

Multi-site MRI analysis of morphometric differences in brain regions in the presence of hearing loss and tinnitus across the adult lifespan

The impact of age and hearing loss on the brain has garnered significant attention, as both factors have been implicated in the development of cognitive impairment or dementia. In this study, we investigated the impact of hearing loss and tinnitus on gray matter in the brain, while accounting for age. We used a comprehensive secondary analysis of structural MRI data obtained from multiple research sites (256 unique individuals) using voxel-based and surface-based morphology. After harmonization of this multi-site brain data, our research replicated the previously reported finding of age-related decline in total cortical volume, but there was no significant effect of either hearing loss or tinnitus on total cortical volume. When a region of interest analysis was conducted, the hippocampus emerged as the only brain region that showed a direct impact of hearing loss, after accounting for variance associated with age. This effect on hippocampal volume was evident in our sample from age 52 years onwards; when adjusted for hearing loss, the decline began at age 56 years. For the presence of tinnitus, ventral posterior cingulate gyrus showed main effects with respect to cortical volume and surface area while medial occipito-temporal gyrus and operculum of the inferior frontal gyrus showed significant main effects only with surface area. Post-hoc analysis revealed that posterior cingulate gyrus showed significantly higher volume and larger surface area in individuals with tinnitus compared to those without tinnitus. Similarly medial occipito-temporal gyrus surface area was increased whereas surface area of the inferior frontal opercular gyrus was reduced in those with tinnitus when compared to those without tinnitus. Notably, while past studies have reported that the presence of tinnitus appeared to moderate some of these effects in certain participant groups, our results suggest a more complex relationship between sensory degradation, chronic tinnitus, and brain structure in individuals across the adult lifespan. HighlightsO_LIHearing loss and tinnitus can exacerbate regional brain atrophy in the adult lifespan. C_LIO_LIHigh-frequency hearing loss affects auditory cortex gray matter volume to a larger degree in older age. C_LIO_LIHearing loss may accelerate decline in hippocampal volume by about 4 years. C_LIO_LIChronic subjective tinnitus is associated with a larger volume of cingulate cortex, increased surface area in cingulate cortex and the lingual gyrus, and decreased surface area of frontal operculum compared to controls. C_LIO_LITinnitus-related effects on regional brain atrophy are not modified by the degree of hearing deficits. C_LI

neuroscience↗

bioRxiv2021

Slow Cortical Waves via Cyclicity

Fine-grained understanding of dynamics in cortical networks is crucial in unpacking brain function. Here, we introduce a novel analytical method to characterize the dynamic interaction between distant brain regions, and apply it to data from the Human Connectome Project. Resting-state fMRI results in time series recordings of the activity of different brain regions, which are aperiodic and lacking a base frequency. Cyclicity Analysis, a novel technique robust with respect to time-reparametrizations, is effective in recovering temporal ordering of such time series along a circular trajectory without assuming any time-scale. Our analysis detected slow cortical waves of activity propagating across the brain with consistent lead-lag relationships between specific brain regions. We also observed short bursts of task-modulated strong temporal ordering that dominate overall lead-lag relationships between pairs of regions in the brain. Our results suggest the possible role played by slow waves of information transmission between brain regions that underlie emergent cognitive function.

neuroscience↗

bioRxiv2020

Live cell imaging of single neurotrophin receptor molecules on human neuron in Alzheimer's disease

The changes in the receptor dynamics such as the surface movement of the receptor molecules on the plasma membrane are essential to receptor function. However, whether the receptor dynamics are affected by disease conditions is unknown. Neurotrophin receptors such as TrkA and p75NTR play a critical role in neuronal survival and their functions are highly affected in Alzheimers disease (AD). Using live-cell single-molecule imaging of neurotrophin receptors we examined the surface trafficking of TrKA and p75NTR molecules on human induced pluripotent stem cells (hiPSCs) derived live neurons from presenilin 1 (PSEN1) mutant AD patients and healthy subjects. Here we report that surface trafficking of p75NTR molecules on neurites is faster than that of TrkA molecules in healthy controls. The surface dynamics of TrkA molecules were elevated in AD patients compared to healthy individuals. In contrast, the surface movement of p75NTR was significantly smaller in AD patients compared to healthy individuals. Interestingly, amyloid beta1-42 (A{beta}1-42) administration increased the surface trafficking of both TrkA and p75NTR in healthy hiPSCs neurons. These findings provides the first evidence that the surface diffusion of TrkA and p75NTR molecules are altered in patients suffering from AD. Our data also suggest that A{beta}1-42 may responsible for the alteration of the surface movements of TrkA but not for p75NTR. One Sentence SummaryThe surface movements of neurotrophin receptors such as TrkA and p75NTR are altered in neurons derived from patients suffering from familial Alzheimers disease.

neuroscience↗

bioRxiv2019

WHISKiT Physics: A three-dimensional mechanical model of the rat vibrissal array

Rodents tactually explore the environment using ~62 whiskers (vibrissae), regularly arranged in arrays on both sides of the face. The rat vibrissal system is one of the most commonly used models to study how the brain encodes and processes somatosensory information. To date, however, researchers have been unable to quantify the mechanosensory input at the base of each whisker, because the field lacks accurate models of three-dimensional whisker dynamics. To close this gap, we developed WHISKiT Physics, a simulation framework that incorporates realistic morphology of the full rat whisker array to predict time-varying mechanical signals for all whiskers. The dynamics of single whiskers were optimized based on experimental data, and then validated against free tip oscillations and the dynamic response to collision. The model is then extrapolated to include all whiskers in the array, taking into account each whiskers individual geometry. Simulations of first mode resonances across the array approximately match previous experimental results and fall well within the range expected from biological variability. Finally, we use WHISKiT Physics to simulate mechanical signals across the array during three distinct behavioral conditions: passive whisker stimulation, active whisking against two pegs, and active whisking in a natural environment. The results demonstrate that the simulation system can be used to predict input signals during a variety of behaviors, something that would be difficult or impossible in the biological animal. In all behavioral conditions, interactions between array morphology and individual whisker geometry shape the tactile input to the whisker system.

neuroscience↗