Biology subjects

Jabeen, T.

Publications and source records attributed to Jabeen, T..

3 recordsLinked to original sources

bioRxiv2026

Infant cortical tracking of speech shows emerging spatial release from masking in the first year of life

Natural listening environments are filled with competing sounds. One mechanism that helps overcome this challenge is spatial release from masking (SRM), whereby spatial separation between a target signal and interfering sounds improves perception of the target. SRM has been observed in a wide range of species including songbirds, crocodilians, ferrets, and human adults, suggesting an evolutionarily conserved strategy for listening in noise. However, an important question remains: Is an infants developing brain able to tap into the same mechanism to cope with the noisy world? To address this question, we recorded electroencephalography (EEG) from 7- and 11-month-old infants (N = 53) and adults (N = 20) as they listened to natural speech in quiet, collocated noise, and spatially segregated noise. Our results revealed that both infants and adults showed robust cortical tracking of speech across quiet and noisy listening conditions. For adults, spatial separation between the target speaker and distracting talkers led to enhanced cortical tracking of the target speech, consistent with SRM. Infants also showed SRM, with stronger tracking in segregated than collocated noise, although the effect was confined to a frontal-central region rather than broadly distributed across the scalp as in adults. These findings provide the first neurophysiological evidence that, although still immature, the developing brain can benefit from spatial cues in the first year of life. Together, these results add new insight into how the infant brain solves a fundamental perceptual problem - identifying a relevant voice in a noisy environment - using a mechanism that is evolutionarily grounded.

neuroscience↗

bioRxiv2021

Variable autoinhibition among deafness-associated variants of Diaphanous 1 (DIAPH1)

One of the earliest mapped human deafness genes, DIAPH1, encodes the formin DIAPH1. To date, at least three distinct mutations in the C-terminal domains and two additional mutations in the N-terminal region are associated with autosomal dominant hearing loss. The underlying molecular mechanisms are not known, and the role of formins in the inner ear is not well understood. In this study we use biochemical assays to test the hypotheses that autoinhibition and/or actin assembly activities are disrupted by DFNA1 mutations. Our results indicate that C-terminal mutant forms of DIAPH1 are functional in vitro and promote actin filament assembly. Similarly, N-terminal mutants are well-folded and have quaternary structures and thermal stabilities similar to the WT protein. The strength of the autoinhibitory interactions varies widely among mutants, with the ttaa, A265S and I530S mutations having an affinity similar to WT and the 1213x and {Delta}ag mutations completely abolishing autoinhibition. These data indicate that, in some cases, hearing loss may be linked to reduced inhibition of actin assembly.

biochemistry↗

bioRxiv2020

Active outer hair cell motility can suppress vibrations in the organ of Corti

High sensitivity and selectivity of hearing require active cochlea. The cochlear sensory epithelium, the organ of Corti, vibrates due to external and internal excitations. The external stimulation is acoustic pressures mediated by the scala fluids, while the internal excitation is generated by a type of sensory receptor cells (the outer hair cells) in response to the acoustical vibrations. The outer hair cells are cellular actuators that are responsible for cochlear amplification. The organ of Corti is highly structured for transmitting vibrations originating from acoustic pressure and active outer hair cell force to the inner hair cells that synapse on afferent nerves. Understanding how the organ of Corti vibrates due to acoustic pressure and outer hair cell force is critical for explaining cochlear function. In this study, excised cochlear turns were freshly isolated from young gerbils. The organ of Corti in the excised cochlea was subjected to mechanical and electrical stimulation that are analogous to acoustical and cellular stimulation in the natural cochlea. Organ of Corti vibrations including those of individual outer hair cells were measured using optical coherence tomography. Respective vibration patterns due to mechanical and electrical stimulation were characterized. Interactions between the two vibration patterns were investigated by applying the two forms of stimulation simultaneously. Our results show that the interactions could be either constructive or destructive, which implies that the outer hair cells can either amplify or suppress vibrations in the organ of Corti. We discuss a potential consequence of the two interaction modes for cochlear frequency tuning. Statement of SignificanceThe function of the mammalian cochlea is characterized by sharp tuning and high-level of amplification. Both tuning and amplification are achieved mechanically through the action of cellular actuators in the sensory epithelium. According to widely accepted theory, cochlear tuning is achieved by selectively amplifying acoustic vibrations. This study presents a set of data suggesting that the cochlear actuators can both amplify and suppress vibrations to enhance cochlear tuning. Presented results will explain why the actuator cells in the cochlea spend energy in the locations where there is no need for amplification.

neuroscience↗