Physics Department, Bucharest University

SYMNET - Atlas of clinical effects evoked by intracranial high-frequency electrical stimulation

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The SYMNET atlas contains threshold and activation maps for eliciting clinical effects evoked by high-frequency electrical stimulation in 41 patients with drug-resistant epilepsy. The patients are investigated at Bucharest Emergency University Hospital, while data processing is performed by Physics Department at Bucharest University. The methodology for performing alternating polarity stimulation and analyzing the responses is described in Barborica et al., Hum Brain Mapp 2022 (https://doi.org/10.1002/hbm.25749). This project is funded through Romanian UEFISCDI grant PN-III-P4-ID-PCE-2020-0935.

The stimulation current threshold map for all 972 stimulations is shown below. The HCP-MMP parcellation (Glasser et al., Nature 2016, https://balsa.wustl.edu/study/show/RVVG) has been used.

Stimulated sites evoking clinical effects are marked in green, whereas the sites not evoking a clinical effect with a maximum current of 3 mA are marked as open circles.

The areas activated by electrical stimulation are shown in the figure below:

The magnitude of the intracranial EEG responses evoked by electrical stimulation is averaged for all n=18227 non-epileptogenic SEEG contact pairs in each HCPMMP1 parcel and represented as a colormap.

Clinical effects are categorized according to Fisher et al., Epilepsia, 2017 (https://doi.org/10.1111/epi.13670), as shown in the table below. The thresholds and activation maps for each evoked clinical effect are summarized in the table below.

Level 1

Level 2

Level 3

Cognitive