Volume Conduction & Spherical Head Models

Solve a radial dipole in a three-shell spherical head, compare a homogeneous conductor, and quantify skull-induced spatial spread.

Chapter 7
EEG
Legendre expansion
volume conduction

Peak scalp

4.58 µV

Peak / homogeneous

0.342

Half-peak arc diameter

5.65 cm

100→120 order residual

0.000000000

Scalp potential vs source angle

Three shellsHomogeneous sphere

Upper-scalp potential

−4.579 to +4.579 µV · blue − / red +

Skull-induced spatial spread

Layered normalizedHomogeneous normalized

Model scope

Exact concentric, isotropic 3-shell boundary model for a radial dipole only: brain/skull/scalp radii 80/85/90 mm, brain and scalp 0.33 S/m, insulating surface. Top view is an orthographic projection of the upper scalp, with source at the pole; not an anatomical 10–20 cap.

Preparing the simulation…

Conceptual bridges & related modules

Nernst & Goldman Membrane Potentials
prerequisite · Chapter 7
Move from cellular electrogenesis to measurable extracellular fields.
Lead Fields, Reciprocity & Sensitivity
prerequisite · Chapter 7
Compare layered radial conduction with differential infinite-medium lead sensitivity.
MEG vs EEG: The Sarvas Dipole Model
physical contrast · Chapter 7
Contrast skull-dependent electric conduction with spherical magnetic-field symmetry.
Imaging Modality Physics Simulator
physical contrast · Chapter 9 · Sections 4–6; Chapter 8 bridge
Compare tomographic image formation with quasi-static volume conduction; neither inversion is noise-free.