For Cmn photolysis, an LED with emission of 385 nm (≥190 mW; Prizmatix) was installed at the microscope to deliver light through the objective. Light power that reached the samples was measured to be 8 mW/cm2. Electrophysiological chemicals were purchased from Sigma-Aldrich or Tocris Bioscience. Data are expressed as mean ± SEM, and statistical significances (p < 0.05) were determined by Student’s t test. All measurements were made at ∼33°C. We thank Dr. Michael Hausser for

helpful discussions. I.C. was supported by a Marie Curie fellowship from the European Commission within the Seventh Framework Programme. D.K. and D.D.M.O. are supported by the National Institutes of Health (R01NS31558 and R01MH086147). L.W. acknowledges support from The Salk Epacadostat in vitro Innovation Grant, the California Institute for Regenerative Medicine (RN1-00577-1), and the National Institutes of Health (1DP2OD004744-01 and P30CA014195). “
“The recently developed capacity to optically image neural activity at cellular resolution in behaving animals has the potential to find more transform the study of neural circuits underlying behavior. Two-photon laser-scanning microscopy (TPM) (Denk et al., 1990), in

combination with genetically encoded calcium indicators, has been used to image the activity of hundreds of simultaneously recorded individual neurons in behaving animals. The recordings are unbiased in the sense that the entirety of the neuronal population within the field of view is imaged and recorded from. Vascular landmarks and the stable relative positioning of neuronal somata allow the same neurons to be recorded on successive days, which is difficult to verify with microelectrode recording. Using cellular-resolution

functional imaging, choice-specific sequences of neural activity have recently been measured during a two-alternative forced choice navigation task (Harvey et al., 2012); also, the plasticity of the neural representation of sensory stimuli and movement has been studied over the course of learning (Huber however et al., 2012). In mammals, cellular resolution functional imaging during behavior has been primarily applied to mice. However, rats are the most widely studied species in behavioral research and in neurophysiology (Aitman et al., 2008 and Dwinell, 2010) and can be efficiently trained in tasks that require cognitive abilities, such as working memory. Recent developments in rat genetics have led to the ability to engineer the rat genome with unprecedented efficiency (Geurts et al., 2009, Huang et al., 2011 and Tesson et al., 2011) and to the production of genetically modified rat strains for basic neuroscience research (Witten et al., 2011), as well as new genetic models of human neurological disorders such as schizophrenia and autism (Dolgin, 2010).