For details, see Supplemental Experimental Procedures. C57/Bl6 as well as Thy1-ChR2 transgenic mice aged between postnatal day 20 (P20) and P40 were anesthetized by isoflurane (Abbott) at concentrations between 0.8% and 1.5% in pure O2. From then on, the animals were kept at a constant depth of anesthesia, characterized by a loss of reflexes (tail pinch, eye lid) and respiration rates of 80–100 breaths HKI272 per minute. A small craniotomy was made above the respective cortical or thalamic area; for details, see Supplemental Experimental Procedures. The coordinates of the craniotomy were as follows: for primary visual cortex

(V1) (from bregma): AP −3.8 mm, ML 2 mm (relative to midline); frontal cortex: AP 3 mm, ML 1 mm, dLGN: AP −2 mm, ML 2 mm; and VPM: AP −1.75, ML 1.2. The injection solution containing OGB-1 was prepared as described in Garaschuk et al. (2006a) and Stosiek et al. (2003). We filled 5 μl of the dye-containing solution into a patch pipette and inserted 300 μm for all cortical stainings, 2.5 mm for dLGN, and 3.5 mm for VPM. Approximately 1–2 μl of the staining solution were injected into the brain. About 30 min after dye application,

the fiber selleck products tip was inserted into the stained region with a micromanipulator to the depth, providing maximal fluorescence intensity, typically at 100 μm below the cortical surface. For thalamic recordings, the optical fiber was inserted according to the DV coordinates used for staining, and insertion

was halted a minimum of 100 μm above staining depth to avoid lesion of stained area. All recordings were obtained in conditions in which the cortex and thalamus were in a continuously oscillatory state, producing regularly recurring slow oscillation-associated Ca2+ waves. For visual stimulation, light flashes with durations of 50 ms were delivered to both eyes of the mouse by two white LEDs (SLSNNWH812TS, Samsung) with a light power of 0.12 mW each. A light-dense cone was used to confine visual stimulation light to the eyes. Optogenetic stimulation was conducted at varying Terminal deoxynucleotidyl transferase laser power levels ranging between 1 and 10 mW. Light power at the tip of the fiber was linearly dependent on the output laser power, ranging between 7.3 mW/mm2 and 73 mW/mm2. Pulse duration and power levels were controlled by custom-written software in LabView and applied via a PCI 6731 (National Instruments) AD/DA converter. Time marks at the start of each stimulus were recorded together with the continuous fluorescence waveform for offline analysis. For the analysis of typically activated neurons in the Thy-1 transgenic animals, see Supplemental Experimental Procedures. For recordings of the epidural electrocorticogram, two silver wires (0.25 mm diameter; insulated except the nodular ends) were implanted epidurally.