Equipment for optogenetic Experiments
Thomas RECORDING offers a newly developed optical fiber technique (Thomas Optical Fiber™) for Photostimulation assisted Identification of Neuronal Populations (PINP).
Understanding the circuit level functional organization of the brain will play an important role in basic and clinical neuroscience. An important limitation of extracellular recording is that it provides little information about the identity of the neurons generating the spike trains, and therefore provides limited insight into the function of different neuronal populations. To overcome this limitation the PINP technique was developed and first described by Lima et al. .
Thomas RECORDING now offers a technical solution for PINP. Our optical glass fibers, called “Thomas Optical Fibers™” have an outer diameter of 120µm and a conical tip shape so that tissue penetration is easy to realize. Beside the optical fibers we offer also constant current controlled light sources with continuous and reproducible adjustment of constant amounts of light. Light sources with different colors are available (e.g. white, green , blue, red). The Thomas Optical Fibers™ are available ready for use with Thomas microdrive systems and also adaptable to other microdrive applications. Using Thomas microdrive systems has the advantage, that Thomas Optical Fibers™ and Thomas recording microelectrodes can be placed very close together (80-120µm spacing).
 Lima S.Q., Hromádka T., Znamenskiy P., Zador A.M.
PINP: A new method of tagging neuronal populations for identification during in vivo electrophysiological recording
PLos ONE, July 2009, Vol 4, Issue 7
Our single core optical glass fiber has an outer diameter of 120µm and is available with different tip shapes, ready for use in neurophysiological experiments together with extracellular recording electrodes. Especially the combination of our optical fiber and our quartz glass insulated platinum tungsten microelectrodes in our Multielectrode microdrive systems (e.g. Eckhorn Matrix, Mini Matrix, etc.) allow a very precise control of optical fiber and microelectrodes in the micrometer range. With our microdrives we are able to drive for example a single optical fiber together with recording microelectrodes (see figure 1) to different depths of the brain. Cortical as well as deep brain optical stimulation experiments are possible in different species (e.g. mice, rats, primates). The minimum electrode spacing that we can realize is 80µm!
Figure 1: One optical fiber and 6 recording microelectrodes loaded to a 7 electrode Eckhorn Matrix. The electrode spacing is 305µm, we used a concentric arrangement with the optical fiber in the center position and the 6 recording electrode arranged around the center fiber.
Beside the optical fiber for our manipulators we offer also fibers for use in other Microdrive systems (e.g. manual manipulators). See details in the chapter Optical fibers
Optrodes and Optetrodes
With our microdrives it is possible to drive single core microelectrodes, tetrodes (4 metal cores) or heptodes (7 metal cores) to different depths of the brain with high axial (accuracy 1µm) and lateral precision (accuracy 80µm). For use with other manipulator systems we offer ready for use optrodes and optetrodes. This is a combination of our quartz glass insulates single and 4 core microelectrodes with one of our optical fibers.
Figure 2: Thomas optrode, a combination of a Thomas quartz glass insulated platinum/tungsten microelectrode (OD=80µm) with a Thomas optical fiber (OD=120µm). The optical fiber is shown with reduced light intensity!
For those who just want to use an optical fiber in combination with a separate recording electrode we offer our optical fibers as a separate solution.
Figure 3: Thomas optical fiber (conical tip shape, A, pulled & ground) strengthened with a glass pipette
LED Light Source
For our optical fibers we offer an LED light source that avoids additional optical fibers and fiber connections with light loss between the light source and the final glass fiber. We have designed a single optical fiber connection to our LED light source. The light source is placed close to your recording setup on a special designed and customizable holder.
Figure 4: High brightness LED light source (blue). Other colors are available
LED Light Source Control Unit
Our LED light source control unit (see figure 5) provides tunable DC constant current for the high power LED light source.
Figure 5: LED light source control unit
This control unit drives LED currents up to 700mA and is controlled manually or via personal computer interface.