Numerical Simulation Study of Firing Threshold of STN Neuron Stimulated by Focused Ultrasound

Electroencephalography (EEG) is one of the functional brain imaging techniques to effectively measure neuronal activity, but its low spatial resolution makes it difficult to localize evoked excitatory neurons or areas of abnormal firing. Multimodal imaging techniques are expected to combine the high spatial resolution (mm level) of focused ultrasound (FUS) with the high temporal resolution (ms level) of EEG. The technique must be performed under the premise that ultrasound stimulation does not affect neuronal firing, and there is an urgent need to determine the threshold of this ultrasound stimulation parameter.

In this paper, the subthalamic nucleus neuronal firing model and the bilayer sonophore model are combined to numerically simulate the neuronal firing rhythm under the conditions of different stimulation parameters. The correlation and frequency differences of neuronal firing rhythms with and without ultrasound stimulation were compared and used as an index to evaluate the degree of change, and the final range of effective threshold parameters for ultrasound stimulation of neurons but not inducing neuronal firing was obtained.

The results showed that the correlation of neuronal firing rhythms in both conditions with and without stimulation decreased and the frequency difference increased with increasing ultrasound parameters such as duty cycle, intensity, center frequency and pulse repetition frequency.

An effective range of stimulation threshold parameters can be obtained based on the correlation coefficients and frequency difference matrices under different parameter combinations.

The threshold can further promote the safe and effective application of FUS for multimodal electrophysiological imaging.