TABLE 1. Requirements of individual and multiple depth electrodes.

Electrode Configuration	Requirement
	Absolute	Relative
Individual electrode
	Avascular plane through brain	Reasonable entry point on scalp
	Accurately hit target	Less than 30° angle of traversing the skull
	Avoid deep sulci at the cortical surface	Over 3-mm safety margin to critical structures
		Maximize number of contacts in gray matter
Electrode arrangement
	Good 3D spatial sampling	Avoid redundant coverage
	Avoid electrode collision