Ideal current dipoles are appropriate source representations for simulating neurons for intracranial recordings

Area of Science:

• Neuroscience
• Biophysics
• Medical Imaging

Background:

• Stereo-EEG (sEEG) is crucial for understanding brain activity.
• Accurate neural source modeling is essential for interpreting sEEG data.
• Dipoles are a simplified model for neural electrical activity.

Purpose of the Study:

• To evaluate the suitability of dipoles as simplified neural source models for sEEG.
• To assess the accuracy of dipole models across different spatial scales and distances relevant to sEEG.
• To quantify the impact of dipole approximation on sEEG source localization accuracy.

Main Methods:

• Compared voltage distributions from single dipoles, realistic neuron models, and cortical regions.
• Analyzed model accuracy at varying spatial scales and electrode-to-neuron distances.
• Quantified source localization errors using standardized low-resolution electrotomography (sLORETA).

Main Results:

• Dipole models showed high correlation (>0.9) with pyramidal neuron models at distances >1 mm.
• Voltage errors were <100 µV for small cortical regions (∼0.1 cm²).
• Larger cortical regions (>5 cm²) introduced >50 µV errors within 1.5 cm, necessitating multiple dipoles.
• sEEG source localization errors were <5 mm when using dipoles for realistic neural sources.

Conclusions:

• Single dipoles effectively model single neurons and small active cortical regions in sEEG.
• Multiple dipoles are required for accurate representation of large active cortical areas.
• Dipole models are computationally efficient and valid for sEEG source localization.