Biology subjects

Gilboa, A.

Publications and source records attributed to Gilboa, A..

3 recordsLinked to original sources

bioRxiv2025

Theta-mediated conceptual reinstatement in vmPFC precedes perceptual reinstatement in ventral visual cortex during memory recall

When recalling past episodes, different features of an experience, such as conceptual meaning and perceptual detail, are reconstructed and reinstated across distributed cortical regions. However, current models of human memory remain unclear how these feature-specific reinstatements unfold over time, and whether they interact hierarchically during memory retrieval. Using magnetoencephalography (MEG) and time-resolved encoding-retrieval cross-phase classification analysis, we compared the time course of conceptual and perceptual reinstatement during cued visual recall. Conceptual information decoding in the ventromedial prefrontal cortex (vmPFC) preceded perceptual information decoding in the ventral visual cortex (VVC), and the two were expressed in distinct frequency bands: theta (4-8 Hz) for conceptual and gamma (30-40 Hz) for perceptual information. Cross-correlation and spectral Granger causality analyses revealed that during reinstatement conceptual information in vmPFC predicted and directed perceptual information in VVC, with theta-band information flow predominantly from vmPFC to VVC. In addition, bottom-up connectivity from VVC to vmPFC was expressed in the alpha band. These findings suggest that memory retrieval proceeds from abstract conceptual reconstruction to the reinstatement of perceptual details, mediated by theta oscillatory communication between prefrontal and sensory areas. We propose a hierarchical interactive model in which vmPFC initiates conceptual activation through theta-band top-down signals, while VVC provides alpha-band feedback for evaluating reconstructed perceptual details.

neuroscience↗

bioRxiv2022

Sensitivity of diffusion-tensor and correlated diffusion imaging to white-matter microstructural abnormalities: application in COVID-19

There has been growing attention on the effect of COVID-19 on white-matter microstructure, especially among those that self-isolated after being infected. There is also immense scientific interest and potential clinical utility to evaluate the sensitivity of single-shell diffusion MRI methods for detecting such effects. In this work, the sensitivities of three single-shell-compatible diffusion MRI modeling methods are compared for detecting the effect of COVID-19, including diffusion-tensor imaging, diffusion-tensor decomposition of orthogonal moments and correlated diffusion imaging. Imaging was performed on self-isolated patients at baseline and 3-month follow-up, along with age- and sex-matched controls. We demonstrate through simulations and experimental data that correlated diffusion imaging is associated with far greater sensitivity, being the only one of the three single-shell methods to demonstrate COVID-19-related brain effects. Results suggest less restricted diffusion in the frontal lobe in COVID-19 patients, but also more restricted diffusion in the cerebellar white matter, in agreement with several existing studies highlighting the vulnerability of the cerebellum to COVID-19 infection. These results, taken together with the simulation results, suggest that a significant proportion of COVID-19 related white-matter microstructural pathology manifests as a change in water diffusivity. Interestingly, different b-values also confer different sensitivities to the effects. No significant difference was observed in patients at the 3-month follow-up, likely due to the limited size of the follow-up cohort. To summarize, correlated diffusion imaging is shown to be a sensitive single-shell diffusion analysis approach that allows us to uncover opposing patterns of diffusion changes in the frontal and cerebellar regions of COVID-19 patients, suggesting the two regions react differently to viral infection.

biophysics↗

bioRxiv2019

Precuneus stimulation alters the neural dynamics of autobiographical memory retrieval

Autobiographical memory (AM) unfolds over time, but little is known about the dynamics of its retrieval. Space-based models of memory implicate the hippocampus, retrosplenial cortex, and precuneus in early memory computations. Here we used inhibitory continuous theta burst stimulation (cTBS) to determine the causal role of the precuneus in the temporal dynamics of AM retrieval. Compared to vertex, precuneus stimulation altered evoked neural activity during early memory construction, as early as 400 ms after cue presentation, as well as during later memory elaboration. We further identified a parietal late positive component during memory elaboration, the amplitude of which was associated with spatial perspective during recollection. Precuneus stimulation disrupted this association, suggesting that this region plays a crucial role in the neural representation of spatial perspective during AM. These findings help clarify the neural correlates of early memory retrieval and demonstrate a causal role for the precuneus in the temporal dynamics of AM retrieval.

neuroscience↗