Projects

Optogenetics, one of the most innovative neuroscientific methods developed in the past decade, provides theuniqueopportunity tocontrol neural activity by optical stimuli of specific types of neurons in well-defined brain regions. Aside from molecular tools transferred into the cell membrane using for example viral transfection, miniaturized micro-optical tools, i.e. so-called optrodes, are the technical interfaces to interfere with genetically modified brain tissue. Viral transfection of nerve cells in brain tissue results in generation of light sensitive ion channels that can be activated or inhibited with these optrodes. InWOLDORweaimfor replacing conventionally applied optical glass fibers allowing more natural behavior of test animals. New, more sophisticated miniaturized, implantable optogenetic instruments will be developed that comprise laser diode (LD) chips combined with polymeric waveguides and light-emitting diodes (LED) enabling the layer and position specific illumination of brain tissue, respectively. By integrating both recording electrodes and light sources we will be able tosimultaneouslymanipulateandrecordbrainactivity allowingtoanalyzebrainfunction and dysfunction as well as to provide a tool suitable for a closed-loop interaction. A broad range of implantable micro-optical tools using silicon and polymers was developed and validated, i.e. polyimide and silicone rubber as substrate materials for penetrating as well as flexible surface tools for intracortical and epicortical in vivo optogenetic experiments, respectively. Among others, we successfully characterized silicon-based optrodes with integrated LDs and recording electrodes realized in a wide variety of probe designs for application specific experiments of our neuroscientific partners. We further established innovative process technologies needed for hermetically sealed micro-packages of LD and LED chips to be integrated in planar electrode arrays. The technical developments are supplemented by an intense material characterization of waveguide materials addressing their long-term stability in wet environments. Our highly miniaturized and compact optrodes will be further developed and validated in the project extension period and ultimately used as optogenetic instruments in in vivo applications with freely behaving animals.