An Exploration of the Electrocorticogram Signatures Evoked by Ultrasound Thalamus Stimulation Under Isoflurane Anesthesia in Rats.

Abstract

The transcranial ultrasound stimulation (TUS) on the thalamus can indirectly induce cortical response. Studies have shown that general anesthetic induced unconsciousness is related to interruption of thalamocortical connectivity. However, the neural mechanism of how anesthesia levels influence cortical responses during ultrasound thalamus stimulation has never been explored yet. And it remains unknown what cortical responses signatures are evoked by ultrasound thalamus stimulation under different anesthesia levels. We recorded multichannel electrocorticogram (ECoG) evoked by ultrasound thalamus stimulation of rats at various isoflurane concentrations (i.e., 0.5%, 1.0%, 1.5%, and 2.0% (v/v)). We analyzed ECoG signatures in temporal, spatial, and frequency domains by using the ultrasound-evoked potentials (UEPs), omega complexity (OC), and phase amplitude coupling (PAC), respectively. The pattern of UEPs was influenced by the anesthesia level, and the response amplitude of UEPs increased with the increase in anesthesia level (0.5% vs. 1.0% and 1.5% (v/v), p < 0.05). Also, the OC of stimulated ECoG decreased with the increase in anesthesia level (at the 1.0%, 1.5% and 2.0% (v/v), p < 0.05). The TUS promoted the coupling between the amplitude and the phase (at the 1.5% and 2.0% (v/v), p < 0.05), and the modulation index of PAC was anesthesia level-dependent. The cortical response induced by ultrasound thalamus stimulation is related to the anesthesia level. TUS on the thalamus combined with ECoG (TUS-ECoG) may be a potential non-invasive neuromodulation approach for understanding consciousness. This work supplied further implications on the neuromodulatory mechanisms and evaluative applications of TUS under general anesthesia.