Biology subjects

Shim, W. M.

Publications and source records attributed to Shim, W. M..

3 recordsLinked to original sources

bioRxiv2025

Neural Gain Modulation Propagates from Posterior to Anterior Brain Regions to Optimize Orientation Perception in Chronic Astigmatism

While visual impairments commonly occur daily, many individuals fail to recognize these distortions. Yet, the brains role in adapting to distorted sensory inputs remains largely unknown. In this study, we focused on how the brain recalibrates physical orientation-specific blur after chronic exposure to astigmatism. By reconstructing the population orientation tuning response from electroencephalogram activity patterns and estimating neural gain modulation using an optics-based computational model (data from 42 participants, including 15 females), we found enhanced neural gain for underrepresented orientations and reduced gain for overrepresented ones, especially in individuals with long-term astigmatism. The strength of the gain modulation correlated with the optimization of orientation perception in these participants. Furthermore, this push-pull neural gain modulation dynamically propagated from the posterior brain regions to others, and the strength of the propagation correlated with the degree of perceptual optimization. In contrast, short-term exposure resulted in transient and short-lived neural optimization, characterized by a relatively stronger anterior-to-posterior transference pattern. These results show how feature-specific information is modified across the entire brain in response to systematic visual distortion, revealing duration-dependent strategies the brain employs to handle sensory impairments.

neuroscience↗

bioRxiv2025

Motion-corrected eye tracking (MoCET) improves gaze accuracy during visual fMRI experiments

Human eye movements are essential for understanding cognition, yet achieving high-precision eye tracking in fMRI remains challenging. Even slight head shifts from the initial calibration position can introduce drift in eye tracking data, leading to substantial gaze inaccuracies. To address this, we introduce Motion-Corrected Eye Tracking (MoCET), a novel approach that corrects drift using head motion parameters derived from the preprocessing of fMRI data. MoCET requires no additional hardware and can be applied retrospectively to existing datasets. We show that it outperforms traditional detrending methods with respect to accuracy of gaze estimation and offers higher spatial and temporal precision compared to MR-based eye tracking approaches. By overcoming a key limitation in integrating eye tracking with fMRI, MoCET facilitates investigations of naturalistic vision and cognition in fMRI research.

neuroscience↗

bioRxiv2022

Large-scale neural dynamics in a shared low-dimensional state space reflect cognitive and attentional dynamics

Cognition and attention arise from the adaptive coordination of neural systems in response to external and internal demands. The low-dimensional latent subspace that underlies large-scale neural dynamics and the relationships of these dynamics to cognitive and attentional states, however, are unknown. We conducted functional magnetic resonance imaging as human participants performed attention tasks, watched comedy sitcom episodes and an educational documentary, and rested. Whole-brain dynamics traversed a common set of latent states that spanned canonical gradients of functional brain organization, with global synchrony among functional networks modulating state transitions. Neural state dynamics were synchronized across people during engaging movie watching and aligned to narrative event structures. Neural state dynamics reflected attention fluctuations such that different states indicated engaged attention in task and naturalistic contexts whereas a common state indicated attention lapses in both contexts. Together, these results demonstrate that traversals along large-scale gradients of human brain organization reflect cognitive and attentional dynamics.

neuroscience↗