Optimal Energy Delivery by a Brain Pacemaker for Cerebellar Control of After-Discharge

In recent years, electrical stimulation of the cerebellum has been used successfully to control epileptic seizure activity in man. This paper deals with the minimization of the energy transferred from a brain pacemaker to the cerebellum. Reducing this energy may reduce considerably the damage done to the brain tissue, and will probably prolong the life of an implanted power source used to energize such a pacer. Using an electrical model for stainless steel electrodes imbedded in brain tissue, it is shown theoretically that an exponentially increasing stimulating pulse can reduce the energy for inhibition of after-discharge activity by at least 30 percent compared to the corresponding quantity obtained for a rectangular waveform. Preliminary in vivo tests of this theory have been conducted in cats. Electrically induced after-discharge activity was obtained by stimulating the sensorymotor cortex. Three different waveshapes (rectangular, triangular, and exponentially increasing) were applied to the cerebellum, and the minimum energy required to inhibit the elicited after-discharge was found for various pulsewidths, repetition rates, and train lengths. The preliminary data indicate that nonrectangular waveforms require less energy than the rectangular waveshape to achieve threshold inhibition of after-discharge activity.