Image: Red trajectories show grasp movements after stroke, while green trajectories show rehabilitation (Photo courtesy of Tabea Kraus/ ETH).
A new study shows how optogenetics and machine learning can be used to analyze changes in motor skills, aiding stroke patient recovery.
Developed at the Swiss Federal Institute of Technology (ETH; Zurich, Switzerland), the University of Heidelberg (Germany), and other institutions, the new therapeutic approach is based on using optogenetics to activate corticospinal circuitry. The optogenetic stimulation, in conjunction with intense, scheduled rehabilitation can lead to the restoration of lost movement patterns (rather than induced compensatory actions), as revealed by a computer vision-based automatic behavior analysis in a stroke model study in rats.
The rat movements were recorded with a video camera and automatically analyzed to monitor the rehabilitation process to adjust the optogenetic stimulation. The results revealed that optogenetically activated corticospinal neurons promote axonal sprouting from the intact to the denervated cervical hemi-cord. Conversely, silencing subsets of corticospinal neurons in the recovered animals resulted in mistargeting of restored grasping function, identifying reestablishment of specific, anatomically localized cortical microcircuits. The study was published on October 30, 2017, in Nature Communications.
“Using our automatic evaluation of the movement processes, we were able to demonstrate a full recovery,” said senior author Professor Björn Ommer, PhD, of the Heidelberg University Interdisciplinary Center for Scientific Computing (IWR). “The new computer vision technique is able to quantify even the slightest changes in motor functions. By recording and analyzing the movements, we can objectively assess whether there was true restoration of the original function or merely compensation.”
“Neurorehabilitation is the only treatment option for the majority of stroke victims. Many approaches in basic science and in the clinic aim to trigger regeneration processes post-stroke by stimulating healthy brain regions of indeterminate size,” said lead author neuroscientist Anna-Sophia Wahl, MD, PhD, of ETH. “These results provide a conceptual framework to improve established clinical techniques such as transcranial magnetic or transcranial direct current stimulation in stroke patients.”
Optogenetics is a biological technique which involves the use of light to control cells in living tissue that have been genetically modified to express light-sensitive ion channels. For neuromodulation, it is used to control and monitor the activities of individual neurons in living tissue. Key reagents in optogenetics include light-sensitive proteins, such as channelrhodopsin, halorhodopsin, and archaerhodopsin, while optical recording of neuronal activities can be made with the help of optogenetic sensors for calcium (GCaMP), vesicular release (synapto-pHluorin), Neurotransmitter (GluSnFRs), or membrane voltage.
Swiss Federal Institute of Technology
University of Heidelberg