Discovering the brain by light.

We aim to create a set of genetic tools where permanent opsin expression (ChR or NpHR) is precisely limited to the population of neurons that express immediate early gene c-fos during a specific temporal window of behavioral training. Since the c-fos gene is only expressed in neurons that form experience-dependent ensemble, this approach will result in specific labeling of a small subset of cells that create memory trace for the learned behavior. To this end we employ two alternative inducible gene expression systems: Tet Expression System and Cre-Lox System. In both cases, the temporal window for opsin induction is controlled pharmacologically, by doxycycline or tamoxifen, respectively. Both systems will be used for creating lines of transgenic animals.