Circuit-specific sonogenetics modulates specific behaviours in mice

Abstract

Controlling specific neural activities through physical intervention is an effective tool to gain great insight into brain functions and treatments for brain diseases. In the past few decades, many techniques have been developed, such as deep brain stimulation (DBS), transcranial direct current stimulation (tDCS), transcranial magnetic stimulation (TMS), focus ultrasound stimulation (FUS), chemogenetics and optogenetics. However, these methods are either invasive, lack of cell-type selectivity, or have low spatial resolution. Low intensity ultrasound is an emerging and promising modality for brain stimulation. Although it has properties of non-invasiveness and enhanced spatial focus, the lack of cell-type selectively is still a crucial concern. In recent years, studies showed that mechanosensitive ion channels were capable of sensitizing cells to ultrasound stimulation in vitro. Preliminary in vivo studies indicated that these channels could be activated by acoustic stimuli in mouse brain, which were mainly confirmed by c-Fos staining (a marker of neural activity). However, its rigorous characterization of the treatment and demonstration of robust behavioral effects remains to be elucidated. It is important to connect brain activity with behavioral effects with feasible intervention approaches that alter the dynamic of neural pathway, which might open a door to explore how brain neural activities control corresponding behavior. Here, we demonstrate a sonogenetic approach which utilizes a mechanosensitive ion channel (MscL-G22S) to implement transcranial ultrasonic activation of well-defined neural circuits in forebrain and midbrain. Plane ultrasonic wave with approximately 5 mm diameter beam width was generated by our setup, which selectively activated MscL-expression regions of 1.5 mm diameter but not surrounding areas. Combining low intensity ultrasound stimulation and fiber photometry technique, we monitored the real time effects of sonogenetic stimulation on calcium dynamic of specific brain regions in vivo. MscL-expressing neurons of mice barrel cortex or dorsal striatum could be activated by low intensity ultrasound stimulation, generating robust and synchronized calcium responses, whereas EYFP-expressing (control group) mice showed no or smaller response to the same stimulation condition. Furthermore, we found that transcranial MscL-mediated ultrasound stimulation enabled the evocation of whisker-barrel cortex pathway, resulting in stronger whisker deflection in head-restrained, awake mice. In addition, spatially and selectively activating neurons of the dorsal striatum enhanced motor function in freely behaving mice. Moreover, using this method, we successfully evoked endogenous dopamine release in nucleus accumbens (NAc) through modulating the mesolimbic pathway in mice. Finally, we specifically targeted dopaminergic neurons in the ventral tegmental area (VTA) with our strategy and modulated appetitive conditioning. Together, we conclude that our sonogenetic method can manipulate neural activities of specific cell types and alter animals' behavior, which provides genetically and spatially targetable, and temporal precise activation of brain pathways without fiber implantation. Modulating animal's behavior with this approach may help to enrich our understanding of cell pathophysiology and almost certainly lead to development of novel treatment for neuropsychiatric and non-neural diseases.