Modelling electrical stimulation of the human cerebral cortex

Electrical stimulation mapping is usually done on epilepsy surgery candidates in order to localize motor, sensory, and cognitive functions, thus avoiding excision of crucial cerebral tissue. However, no a priori information is available on the current density distributions generated by direct cortical electrical stimulation. We, therefore, simulated electrical stimulation of the human cerebral cortex using an anatomically accurate three dimensional Finite Element Model built from MRI scans. We found that: a) Each current density distribution is unique, and is highly dependent on the location of the stimulating electrode pair; b) The anatomical location of the electrode pair determines the amount of current being shunted by the CSF layer underneath the electrode pair; c) The temporary lesion created by the passage of electrical current is highly focused and is located in a very small region under the stimulating electrodes; and d) The field distributions in conjunction with the cognitive deficits obtained from electrical stimulation provide us with a unique method to study the functional organization of the human cerebral cortex.