Threshold for Tonic Motor Effects from Random Waveform in a Rat Experimental Model of Frontal Cortex Stimulation

Abstract

Background: Brain stimulation is utilized to treat a variety of neurological disorders. Clinical brain stimulation technologies currently utilize charge-balanced pulse stimulation. The brain may better respond to other stimulation waveforms. This study was designed to evaluate the motor threshold of the brain to stimulation with various waveforms.

Methods: Three stimulation waveforms were utilized on rats with surgically implanted brain electrodes: pulses, square waves, and random waveform. The peak-to-peak stimulation voltage was increased in a step-wise manner until motor signs were elicited.

Results: The random waveform had the highest motor threshold with brain stimulation compared to the other waveforms. Random waveform stimulation reached maximum voltage without motor side effects while stimulating through both 1 and 8 electrodes. In contrast, the stimulation thresholds for motor side effects of the other two waveforms were on average less than half of the maximum voltage and lower for stimulation through 8 electrodes than stimulation through 1 electrode (p < 0.0005).

Conclusion: The random waveform was better tolerated than the other waveforms and may allow for the use of higher stimulation voltage without side effects.

Keywords: Brain cortex; Random waveform; Stimulation.