neuroimaging-guided-tmseeg-for-real-time-cortical-network-mapping

Neuroimaging-Guided TMS&#8211;EEG for Real-Time Cortical Network Mapping

The cerebral cortex is organized into structurally and functionally segregated networks, enabling the human brain to process information highly ...

Aalto University School of Science

The corpus callosum (CC) is the largest fiber tract in the human brain, allowing interhemispheric communication by connecting homologous areas of the two cerebral hemispheres. In adults, CC size shows a robust allometric relationship with brain size, with larger brains having larger callosa, but smaller brains having larger callosa relative to brain size. Such an allometric relationship has been shown in both males and females, with no significant difference between the sexes. But there is some evidence that there are alterations in these allometric relationships during development. However, it is currently not known whether there is sexual dimorphism in these allometric relationships from birth, or if it only develops later. We study this in neonate data. Our results indicate that there are already sex differences in these allometric relationships in neonates: male neonates show the adult-like allometric relationship between CC size and brain size; however female neonates show a significantly more positive allometry between CC size and brain size than either male neonates or female adults. The underlying cause of this sexual dimorphism is unclear; but the existence of this sexual dimorphism in neonates suggests that sex-differences in lateralization have prenatal origins.

Allometry in the corpus callosum in neonates: Sexual dimorphism.

Modulating brain networks in space and time: Multi-locus transcranial magnetic stimulation.

Neuromodulation is based on the principle that brain stimulation produces plastic changes in cerebral circuitry. Given the intersubject structural and functional variability, neuromodulation has a personalized effect in the brain. Moreover, because of cerebral dominance and interhemispheric functional and structural differences in the same individual, the characterization of specific brain circuitries involved is currently not feasible. This notion is extremely important for neuromodulation treatments applied in neuropsychiatry. Specifically, the efficacy of the neuromodulation treatments is critically dependent on the anatomical precision of the brain target and the circuitry which has been affected by the TMS intervention. Furthermore, for a complete understanding of how the brain behaves under stimulation, the characterization of its neurophysiological response is necessary as well. This goal can be achieved with TMS-EEG guided by current multimodal neuroimaging techniques in real time, namely MRI-based anatomical segmentation and diffusion MRI-based tractographic analysis.

Optimization of TMS target engagement: current state and future perspectives.

The accurate processing of neonatal and infant brain MRI data is crucial for developmental neuroscience but presents unique challenges that child and adult data do not. Tissue segmentation and image coregistration accuracy can be improved by optimizing template images and related segmentation procedures. Here, we describe the construction of the FinnBrain Neonate (FBN-125) template, a multi-contrast template with T1- and T2-weighted, as well as diffusion tensor imaging-derived fractional anisotropy and mean diffusivity images. The template is symmetric, aligned to the Talairach-like MNI-152 template, and has high spatial resolution (0.5 mm³). Additionally, we provide atlas labels, constructed from manual segmentations, for cortical grey matter, white matter, cerebrospinal fluid, brainstem, cerebellum as well as the bilateral hippocampi, amygdalae, caudate nuclei, putamina, globi pallidi, and thalami. This multi-contrast template and labelled atlases aim to advance developmental neuroscience by achieving reliable means for spatial normalization and measures of neonate brain structure via automated computational methods. We also provide standard volumetric and surface co-registration files to enable investigators to transform their statistical maps to the adult MNI space, improving the consistency and comparability of neonatal studies or the use of adult MNI space atlases in neonatal neuroimaging.

The FinnBrain multimodal neonatal template and atlas collection.

In transcranial magnetic stimulation (TMS), a pulse of current driven through a coil on the scalp induces an electric field on the cortex, eliciting neuronal activation. Multi-locus TMS (mTMS) uses multiple coils to generate various electric field patterns, enabling electronic control of stimulation location and orientation. However, changing the stimulation target with mTMS can take up to a few seconds when the driving voltages are adjusted for each coil.

Article	Year
Allometry in the corpus callosum in neonates: Sexual dimorphism. Human brain mapping\| PubMed ID: 35722945	2022
Modulating brain networks in space and time: Multi-locus transcranial magnetic stimulation. Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology\| PubMed ID: 38184469	2024
Optimization of TMS target engagement: current state and future perspectives. Frontiers in neuroscience\| PubMed ID: 39944889	2025
The FinnBrain multimodal neonatal template and atlas collection. Communications biology\| PubMed ID: 40217092	2025
Multi-locus transcranial magnetic stimulation with pulse-width modulation. Brain stimulation\| PubMed ID: 40239740	2025

Elena Ukharova

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