In a study published in the Neuroelectronics Journal, researchers from Laval University, the University of Bordeaux, and the CERVO Brain Research Centre introduced a safe and reliable wireless power transfer system for electrophysiological recording in freely moving laboratory mice. The design approach prioritized a lightweight and compact receiver coil, minimizing interference with the animals' natural behavior. The findings indicate that the system's design effectively balances power transfer efficiency and operational practicality, providing a robust platform for real-time neuronal activity monitoring, validated through continuous in-vivo recordings.
Electrophysiological recording and neural stimulation in freely moving laboratory mice offer significant potential for advancing neuroscience research, enabling the study of neural activities and brain functions in natural surroundings. Using wireless technologies and miniaturized devices, researchers can monitor and manipulate the electrical activity of neurons in real time while the animals engage in complex behaviors. However, the autonomy of a wireless system is often limited to a few minutes or a few hours due to size and weight constraints. To address this, a wireless link for continuous power transmission is essential to run practical experiments. Working with mice is challenging due to their small size and limited volume available, necessitating the use of very small and light electronics. It is also crucial to maintain the Specific Absorption Rate (SAR) within safe limits to prevent heating and temperature rises that could interfere with physiological conditions and measurements.
This study developed an inductive wireless power transfer (WPT) system embedded within the homecage to power small bioinstruments such as an electrophysiology recording headstage equipped with a lightweight power receiver coil attached to the head of a laboratory mouse. The system includes a power amplifier injecting current into a primary coil, which produces magnetic flux. On the receiver side, the flux is induced into the receiver coil, providing current for a headstage and enabling continuous brain activity monitoring in freely moving mice. This eliminates the need for wires or tethered power sources, allowing mice to move naturally while recording their neural activity in real time.
By optimizing the power transfer link, the system achieves high efficiency without bulky equipment. The lightweight, compact design ensures the animals can move freely during experiments. The system operates at a frequency that transfers power efficiently while meeting safety standards, avoiding risks of overheating or tissue damage, even during extended use. This approach allows scientists to conduct longer, more complex experiments and observe behaviors that were previously difficult to study with traditional tethered systems. The wireless system enables continuous monitoring of brain activity in real time, offering exciting possibilities for more extensive and long-term neuroscience studies.
In an in-vivo experiment, the system successfully powered a device that recorded neural signals while the mouse moved freely within its cage. This marks a significant step forward for neuroscience, as it allows for real-time tracking of brain activity in a natural environment, offering more accurate insights into how the brain works during everyday behavior.
This advancement could pave the way for new treatments for brain disorders, as well as innovations in brain-machine interfaces and other neural technologies. It also opens up new possibilities for studying how the brain controls behavior in real-world settings, with potential applications in learning, memory research, and developing better therapies for neurological conditions.
This paper was published in Neuroelectronics Journal. Hayati H, Bilodeau G, Brochoire L, Gagnon-Turcotte G, Fossat P, De Koninck Y, and Gosselin B. Optimized multi-coil wireless power transfer for experimental neuroscience settings with live animals: a robust design methodology. Neuroelectronics 2024(1):0001.
