Biology subjects

Valter, Y.

Publications and source records attributed to Valter, Y..

3 recordsLinked to original sources

bioRxiv2026

Neuronavigation-free and MRI-free Localization of Deep Brain Targets

Emerging non-invasive brain stimulation modalities, including transcranial focused ultrasound and transcranial interferential stimulation, offer the promise of safely and non-invasively modulating deep brain structures. Accurate targeting of these regions typically involves subject-specific MRI, limiting widespread deployment. Here, we introduce an MRI-free, neuronavigation-free method for localizing deep brain targets using only three simple scalp measurements. These measures define an affine transformation that maps the MNI152 standard head model to an individuals head geometry. We evaluated our approach on 50 healthy adults, comparing our model{square}predicted coordinates against ground-truth coordinates obtained via MRI-based nonlinear normalization. Across ten deep brain targets, our method achieved a mean localization error of 3.82 mm demonstrating a more accessible and cost-efficient alternative than MRI- or neuronavigation-based approaches.

neuroscience↗

bioRxiv2026

Morphological bias of the MNI152 brain

The MNI152 template is widely treated as a representative average brain in neuroimaging, computational modeling, and neuromodulation research, yet its fidelity to true population morphology has not been systematically evaluated. In this study, we compared the MNI152 template to 430 individual MRI scans from a publicly available dataset spanning Asian, Black, and White participants. We additionally generated an alternative template using ANTsPy to assess whether a modern diffeomorphic approach yields a more anatomically representative average. We conducted affine registrations and deformation-based morphometry to detect and quantify gross morphological differences as well as local voxel-level deformations. Across all racial groups, the MNI152 template required consistent global contraction, and its Jacobian fields revealed spatially heterogeneous deformations, indicating systematic mismatches in both size and shape. In contrast, the ANTsPy template showed mean scaling and deformation values near 1.0, reflecting closer correspondence to real human anatomy. These findings demonstrate that the MNI152 template does not accurately represent the morphology of the studied population and that linear registration alone cannot correct its inherent biases. Reliance on MNI152 may therefore introduce unintended distortions in applications requiring anatomically realistic head models. More robust, unbiased template-generation pipelines, and potentially demographic-specific templates, may be necessary for improved accuracy.

neuroscience↗

bioRxiv2025

MRI-free Virtual Neuronavigation for TMS

Methods to determine coil position are paramount in TMS. Existing approaches are limited to scalp heuristics or depend on some combination of neuronavigation hardware, average brain templates, as well as subject MRI and/or evoked responses. We developed head-model guided TMS virtual neuronavigation without subject MRI, specialized hardware, or evoked responses. The MRI-free virtual neuronavigation involves three scalp measurements which are then used to generate an individualized head model by applying ellipsoid-based affine transformations to the MNI standard head model. Virtual neuronavigation is then performed on this individualized head model for any brain target. The coil position is then provided to the operator in simple geodesic measurements. We simulated this process on MRI data of fifteen subjects showing a mean error of 2.75 mm, outperforming the accuracy of scalp heuristic targeting approaches.

bioengineering↗