SUMMARY Corticotropin-releasing factor (CRF) that is released from the paraventricular nucleus (PVN) of the hypothalamus is essential for mediating stress response by activating the hypothalamic-pituitary-adrenal (HPA) axis. CRF-releasing PVN neurons receive inputs from multiple brain regions that convey stressful events, but their neuronal dynamics on the timescale of behavior remain unknown. Here, our recordings of PVN CRF neuronal activity in freely behaving mice revealed that CRF neurons are activated immediately by a range of aversive stimuli. By contrast, CRF neuronal activity starts to drop within a second of exposure to appetitive stimuli. Optogenetic activation or inhibition of PVN CRF neurons was sufficient to induce a conditioned place aversion (CPA) or preference (CPP), respectively. Furthermore, CPA or CPP induced by natural stimuli was significantly decreased by manipulating PVN CRF neuronal activity. Together, these findings suggest that the rapid, biphasic responses of PVN CRF neurons encode the positive and negative valences of stimuli.

Transcranial focused ultrasound stimulation (tFUS) is an effective noninvasive treatment modality for brain disorders with high clinical potential. However, the therapeutic effects of ultrasound neuromodulation are not widely explored due to limitations in preclinical systems. The current preclinical studies are head-fixed, anesthesia-dependent, and acute, limiting clinical translatability. Here, this work reports a general-purpose ultrasound neuromodulation system for chronic, closed-loop preclinical studies in freely behaving rodents. This work uses microelectromechanical systems (MEMS) technology to design and fabricate a small and lightweight transducer capable of artifact-free stimulation and simultaneous neural recording. Using the general-purpose system, it can be observed that state-dependent ultrasound neuromodulation of the prefrontal cortex increases rapid eye movement (REM) sleep and protects spatial working memory to REM sleep deprivation. The system will allow explorative studies in brain disease therapeutics and neuromodulation using ultrasound stimulation for widespread clinical adoption.

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