Although the nervous system is elegantly orchestrating movements, the underlying neural principles remain unknown. Since flexor- and extensor-muscles alternate during movements like walking, it is often assumed that the responsible neural circuitry is similarly alternating in opposition. Here, we present ensemble-recordings of neurons in the turtle lumbar spinal cord that indicate that, rather than alternation, the population is performing a “rotation” in neural space, i.e. the neural activity is cycling through all phases continuously during the rhythmic behavior. The radius of rotation correlates with the intended muscle force. Since existing models of spinal motor control offer inadequate explanation of this dynamics, we propose a new theory of neural generation of movement from which rotation and other unresolved issues, such as speed regulation, force control, and multi-functionalism, are conveniently explained.
Henrik Linden, Peter C. Petersen, Mikkel Vestergaard, Rune W Berg. “Movement is governed by rotational population dynamics in spinal motor networks”. bioRxiv, Submitted, September 2021. [pdf] [link]
Extracellular recordings in freely moving animals allow the monitoring of brain activity from populations of neurons at single-spike temporal resolution. While state-of-the-art electrophysiological recording devices have been developed in recent years (e.g., µLED and Neuropixels silicon probes), implantation methods for silicon probes in rats and mice have not advanced substantially for a decade. The surgery is complex, takes time to master, and involves handling expensive devices and valuable animal subjects. In addition, chronic silicon neural probes are practically single implant devices due to the current low success rate of probe recovery. To successfully recover silicon probes, improve upon the quality of electrophysiological recording, and make silicon probe recordings more accessible, we have designed a miniature, low cost, and recoverable microdrive system. The addition of a novel 3D-printed skull baseplate makes the surgery less invasive, faster, and simpler for both rats and mice. We provide detailed procedural instructions and print designs, allowing researchers to adapt and flexibly customize our designs to their experimental usage.
Mihály Vöröslakos, Hiroyuki Miyawaki, Sebastien Royer, Kamran Diba, Euisik Yoon, Peter C. Petersen* and György Buzsáki*. “3D-printed recoverable microdrive and base plate system for rodent electrophysiology”. *corresponding author, Bio-protocol, August 20, 2021. [pdf] [link] [website]