125 Hz) (Kalatsky and Stryker, 2003). The square power of that was then assigned to that pixel. When applied to all pixels this generated a map on which the barrel was easily identified, and was further enhanced by using a 5 × 5 Gaussian filter. Mice were implanted with two monopolar surface electrodes

MK 8776 placed over the right barrel cortex and the cerebellum was used as reference. Electrodes made of stainless-steel wire isolated by polyester (diameter, 0.125 mm; FE245840; Goodfellow), were inserted between the skull and the dura then maintained by dental cement. Electroencephalographic (EEG) signals were amplified, filtered (1,000×, bandpass 0.1 Hz to 3 kHz; Model 3000; AM-Systems, Inc), and stored to hard disk (sampling rate: 1,240 Hz. NIDAQ-MX/BNC-2090[SE], National Instrument) using WinEDR software (Strathclyde Electrophysiology Software, Strathclyde

University). Mice were simultaneously filmed during the recording using a Logitech Carl Zeiss Tessar HD 1080p camera. Time frequency analysis was performed using sliding (87.5% overlap) fast Fourier transform after Hanning window using the Igor sonogram function. Mice were prepared as for “cranial window,” but instead of removing the skull, it was thinned enough to see the small blood vessels. Ultra low-temperature melting Agarose (USB) was applied on top of the skull and covered with a 1.2 cm cover glass (Fisherbrand). most We found ultra low-temperature melting Agarose crucial for success. The location of the barrel was identified with intrinsic-signal optical imaging. A 3 mm craniotomy was then made to encompass the PLX4032 cost identified barrel. Cell populations were labeled in superficial neocortical layers with the calcium indicator Oregon

Green BAPTA-1 (OGB-1, Invitrogen) mixed with Sulforhodamine-101 (Sigma) (Nimmerjahn et al., 2004) using the multicell bolus loading technique (Stosiek et al., 2003). Briefly, 50 μg of the membrane-permeant acetoxymethyl (AM) ester form of OGB-1 were dissolved in 4 μl DMSO/20% Pluronic F-127 (Invitrogen) and diluted 13 times with dye buffer (150 mM NaCl, 2.5 mM KCl, 10 mM HEPES [pH 7.4]) and with 1.5 μl Sulforhodamine (1 mM) to a final concentration of about 1 mM. The dye was delivered in depth of 250 microns through 4 MΩ glass pipettes over 1 min with a pressure of 10 PSI using a Picospritzer. After injections, the cranial window was sealed as described earlier. The mice were sedated and kept with 0.25%–0.4% Isoflurane. EEG recordings indicated that mice remained in a slow-wave EEG pattern for the entirety of the recording session. Video recording showed that whisker twitching was absent in the sedated mice over this period. Imaging was done in depth of 200–250 μm under the Dura using 4 Hz line scan (wavelength 870 nm) using a custom made 2-photon microscope with a 40× objective (Zeiss, 1.0 NA).