Sinusoidal stimulation on afferent fibers modulates the firing pattern of downstream neurons in rat hippocampus

Abstract

Electrical stimulation in the brain is an emerging therapy for treating a wide range of neurological disorders. Although electrical pulses are commonly used in the clinic, other electrical waveforms such as sinusoidal-waves have been investigated to improve the therapeutic efficacy, to reduce the risk of tissue damage induced by stimulation, and to decrease the consumption of electrical energy. However, the effects of sinusoidal stimulation on neuronal activity are still unclear. In the present study, we investigated the neuronal responses to the stimulation of 50-Hz sinusoidal-waves applied on the afferent fibers of the neurons in the hippocampal CA1 region of Sprague-Dawley rat in vivo. Results show that the stimulation increased the firing rate of both pyramidal neurons and interneurons in the downstream region of stimulation. Also, the stimulation eliminated the original theta rhythms (2-5 Hz) in the singleunit activity of the two types of neurons and entrained these neurons to fire at the stimulation rhythm. These results provide new clues for the mechanisms of brain stimulation to suppress the pathological rhythms in the neuronal activity, and for the application of sinusoidal waveforms in brain stimulation therapy.

Dynamics of neuronal firing modulated by high-frequency electrical pulse stimulations at axons in rat hippocampus

“…The initial 30 s periods of 2 min HFS were not used to analyze unit spikes due to the interference of the stimulationevoked PS [27,30]. The firing rhythms of both types of neurons were examined using the following spectrum of auto-correlograms for binary sequences representing the spike firing of individual neurons [26,33,34]. Firstly, the auto-correlogram of each binary sequence was calculated and normalized by its mean value to eliminate the impact of firing rate.…”