Biology subjects

Choi, Y. M.

Publications and source records attributed to Choi, Y. M..

4 recordsLinked to original sources

bioRxiv2026

Listening shapes seeing: Sustained auditory spatial attention enhances early visual-cortical processing

How does the auditory system implement spatial selection without a dedicated cortical map for space? One hypothesis holds that auditory spatial attention draws on a supra-modal network including the parietal-occipital cortex; an alternative implicates subcortical structures (e.g., superior colliculus) with no direct recruitment of visual cortex. To adjudicate between these accounts, we used a dichotic listening paradigm and tested whether sustained auditory spatial attention produces the behavioral and neural signatures of visual spatial attention, which would only be expected if auditory attention engages the same cortical mechanisms. Participants listened to two digit streams, spoken by male and female voices, played from left and right speakers. They were instructed to attend to either the left stream, the right stream, or a specific voice gender. A behavioral experiment (N=24) showed higher discrimination accuracy for visual stimuli appearing intermittently at the auditorily attended relative to unattended location. Furthermore, participants gaze was reliably biased towards the attended location. In a second experiment (N=14), we used electrophysiological recordings of frequency-tagged visual evoked potentials to more directly assess early visual processing, and found enhanced visual-cortical responses for stimuli matching the location of the attended auditory stream. In addition, occipital alpha power (8-11 Hz) was reduced over the hemisphere contralateral to the attended sound stream. Together, these effects mirror the hallmarks of visual-spatial attention, suggesting that auditory spatial attention co-opts the architecture of the visual cortex to implement spatial selection, thereby directly enhancing visual processing. Significance statementHuman can effortlessly direct spatial attention to a sounds location in the external world. Yet the auditory system has no dedicated spatial map in the brain, raising a fundamental question: how does auditory spatial attention arise? We show that sustained attention to a sound based on its location produces well-known signatures of visual spatial attention: enhanced visual-perceptual sensitivity, larger early visual-cortical responses, and modulation of occipital alpha-band activity and oculomotor behavior. This converging behavioral and neural evidence demonstrates that auditory spatial attention actively engages and reshapes early visual processing, pointing to a supra-modal attention system shared across the senses.

neuroscience↗

bioRxiv2026

Dithionite quenching of NBD-labeled lipids reveals artificial lipid droplet purity and neutral lipid surface accessibility

Artificial lipid droplets (aLDs) provide a controllable platform for studying lipid biochemistry, but their use is limited by contamination with other membrane structures and the lack of quantitative methods to assess sample purity. Here, we establish dithionite quenching of NBD-labeled lipids as a simple approach to evaluate aLD purity. The approach relies on dithionites ability to selectively quench NBD fluorophores exposed in the phospholipid monolayer of aLDs and in the outer leaflet of liposome bilayers, but not those protected within the inner leaflet of liposome bilayers. Consistent with liposome contamination, bulk aLD preparations exhibit incomplete quenching, which can be separated by sucrose gradient centrifugation into liposome-like and droplet-enriched populations based on quenching behavior. Guided by this assay, sonication conditions were optimized to increase aLD purity and reduce liposome contamination. A biotin-streptavidin immobilization strategy further enabled stable imaging of individual aLDs. Finally, we applied dithionite quenching to probe the accessibility of neutral lipids within aLDs. This revealed hydrophobicity-dependent quenching kinetics of neutral lipids, with less hydrophobic diacylglycerols showing greater surface exposure within aLDs than more hydrophobic triacylglycerols and cholesterol esters. Taken together, these establish dithionite quenching of NBD-labeled lipids as a simple quantitative method for assessing aLD purity and demonstrate its utility for studying lipid accessibility.

biochemistry↗

bioRxiv2025

Post-Saccadic Disruption of Semantic Category Information in Naturalistic Scenes

During natural vision, people make saccades to efficiently sample visual information from complex scenes. However, a substantial body of evidence has shown impaired visual information processing around the time of a saccade. It remains unclear how saccades affect the processing of high-level visual attributes - such as semantic category information-which are essential for navigating dynamic environments and supporting complex behavioral goals. Here, we investigated whether/how the processing of semantic category information in naturalistic scenes is altered immediately after a saccade. Through both human behavioral and neuroimaging studies, we compared semantic category judgments (Experiments 1A and 1B) and neural representations (Experiment 2) for scene images presented at different time points following saccadic eye movements. In the behavioral experiments, we found a robust reduction in scene categorization accuracy when the scene image was presented within 50 ms after saccade completion. In the neuroimaging experiment, we examined neural correlates of semantic category information in the visual system using fMRI multivoxel pattern analysis (MVPA). We found that scene category representations embedded in the neural activity patterns of the parahippocampal place area (PPA) were degraded for images presented with a short (0-100 ms) compared to a long post-saccadic delay (400-600 ms), despite no corresponding reduction in overall activation levels. Together, these findings reveal that post-saccadic disruption extends beyond basic visual features to high-level visual attributes of naturalistic scenes, highlighting a limitation of visual information processing in the short post-saccadic period before executing the next saccade.

neuroscience↗

bioRxiv2021

The middle lipin (M-Lip) domain is a new dimeric protein fold that binds membranes

Phospholipid synthesis and fat storage as triglycerides is regulated by lipin phosphatidic acid phosphatases (PAPs), whose enzymatic PAP function requires association with cellular membranes. Using hydrogen deuterium exchange mass spectrometry, we find mouse lipin 1 binds membranes through an N-terminal amphipathic helix and a middle lipin (M-Lip) domain that is conserved in mammalian and mammalian-like lipins. Crystal structures of the M-Lip domain reveal a previously unrecognized and novel protein fold that dimerizes. The isolated M-Lip domain binds membranes both in vitro and in cells through conserved basic and hydrophobic residues. Deletion of the M-Lip domain in full-length lipin 1 influences PAP activity, membrane binding, subcellular localization, oligomerization, and adipocyte differentiation, but does not affect transcriptional co-activation. This establishes the M-Lip domain as a new dimeric protein fold that binds membranes and is critical for full functionality of mammalian lipins.

biochemistry↗