Miniature ultrasound ring array transducers for transcranial ultrasound neuromodulation of freely-moving small animals.

BACKGROUND: Current transcranial ultrasound stimulation for small animal in vivo experiment is limited to acute stimulation under anesthesia in stereotaxic fixation due to bulky and heavy curved transducers.

METHODS: We developed a miniaturized ultrasound ring array transducer which is capable of invoking motor responses through neuromodulation of freely-moving awake mice.

RESULTS: The developed transducer is a 32-element, 183-kHz ring array with a weight of 0.035 g (with PCB: 0.73 g), a diameter of 8.1 mm, a focal length of 2.3 mm, and lateral resolution of 2.75 mm. By developing an affixation scheme suitable for freely-moving animals, the transducer was successfully coupled to the mouse brain and induced motor responses in both affixed and awake states.

CONCLUSION: Ultrasound neuromodulation of a freely-moving animal is now possible using the developed lightweight and compact system to conduct a versatile set of in vivo experiments.