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Synthetic brain rhythms | Scientists used optogenetic stimulation to induce slow brain rhythms in vivo

August 21, 2018: Researchers from the Bernstein Center Freiburg and the Massachusetts Institute of Technology used an innovative optogenetic stimulation paradigm to evoke synthetic brain rhythms in vivo. In contrast to conventional optogenetic stimulations protocols that rely on light pulses, this protocol employed continuously modulating light intensities to mimic normal brain rhythms using a new implant. These findings have recently been published in Journal of Neural Engineering, and open up possibilities to cell-specifically dissect the neuronal circuits underlying pathological and physiological slow brain oscillations.

Synthetic brain rhythms | Scientists used optogenetic stimulation to induce slow brain rhythms in vivo

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Rhythmic changes of activity in large groups of neurons are a prominent feature of the brain. These brain rhythms are involved in sensory processing, spatial navigation and memory formation but can also indicate pathological brain states like Parkinson's disease or epilepsy. The mechanisms underlying these oscillations, in particular the contribution of individual neuron populations, are not yet fully understood. Modifying theses rhythms by targeting specific neuron populations will help to develop a mechanistic understanding of brain rhythms – and how to interfere with them.

With the invention of optogenetics, it became feasible to activate or deactivate genetically modified nerve cells in living systems by light. This is commonly done by light pulses. Antje Kilias, PhD student at the Bernstein Center Freiburg, the Cluster of Excellence BrainLinks – BrainTools and the Dept. of Microsystems Engineering, University of Freiburg, and her colleagues Andres Canales and Ulrich Froriep from the Massachusetts Institute for Technology have now developed a stimulation protocol that is based on using constantly modulating light intensities. The oscillating light input mimics the fluctuating currents that could underlie slow brain rhythms.

To realize this they developed a new fiber probe that permits to send light into the brain tissue as well as to simultaneously record the electrical neuronal response to the stimulation. “The ability to interfere with brain rhythms in a cell and frequency specific manner could support the improvement of stimulation strategies against pathological neuronal oscillations or help to elucidate the fundamental mechanisms of neuronal oscillations,” Antje Kilias concludes.

Figure Capture
Multi-functional flexible fiber-probes combine optical stimulation and electrical recording features in a single miniaturized device (tow row). We employed these devices to apply sinusoidal light stimulation (blue trace) to light-sensitive hippocampal neurons and record from the stimulated neuron population. We reliably evoked hippocampal network rhythms (red trace) by this stimulation paradigm.

Original publication
Kilias, A.*, Canales, A.*, Froriep, U.*, Park, S., Egert, U., Anikeeva, P. (2018) Optogenetic entrainment of neural oscillations with hybrid fiber probes. Journal of Neural Engineering

Contact
Bernstein Center Freiburg
University of Freiburg
Hansastr. 9a
79104 Freiburg
and 

University of Freiburg

Biomicrotechnology, Dept. of Microsystems Engineering
Faculty of Engineering
Georges-Köhler-Allee 102
79110 Freiburg

Antje Kilias
Tel.: +49 (0)761 203 7523
E-mail: kilias@bcf.uni-freiburg.de

Prof. Dr. Ulrich Egert
Tel.: +49 (0)761 203-7524
E-mail: egert@imtek.uni-freiburg.de
 

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