g., Ray and Maunsell, 2010, Siegel and König, 2003 and Vinck et al., 2010), and can also be modulated by cognitive functions, such as attention (Fries et al., 2001) and memory (Pesaran et al., 2002). It remains to be investigated whether extracellular findings on synchronization could be accounted for by Vm synchrony among a large population

of local neurons. An intriguing possibility is that Vm synchrony not only exists but is even more versatile in the awake brain and is fundamental to many cognitive functions, including perception. Anesthesia was induced in adult female cats aged 4–6 months with ketamine hydrochloride (30 mg/kg i.m.) and acepromazine maleate (0.3 mg/kg i.m.), and was maintained by intravenous infusion of sodium thiopental (20 mg/kg initial; 1–2 mg/kg/hr selleck screening library maintenance) or a mixture of propofol and sufentanil (5–10 mg/kg/hr + 0.75–1.5 μg/kg/hr, i.v.). After initial surgery, paralytic

(vecuronium bromide, 1.5 mg/kg initial dose, 0.2 mg/kg/hr maintaining rate) was administered and the animal was artificially ventilated through a tracheal cannula (end-tidal CO2: 3.6%–4.0%). To improve recording stability, the thoracic vertebrae were suspended and a bilateral pneumothoracotomy was performed. Body temperature was feedback controlled with a heating lamp at 38°C. Depth of the anesthesia was assessed by EEG pattern and heart rate stability. All vital parameters PI3K Inhibitor Library solubility dmso (heart rate, EEG, CO2 ratio, and temperature) were continuously monitored and recorded. All procedures were approved by the Northwestern University Animal Care and Use Committee. The pupils were dilated with 1% atropine and the nictitating membranes retracted with 2.5% isothipendyl phenylephrine hydrochloride. Contact lenses were inserted and corrective lenses were placed to focus the retina on a computer monitor (ViewSonic, Walnut, CA) 50 cm distant from the eyes. Sinusoid drifting gratings were generated on the monitor using the Psychophysics toolbox (Brainard, 1997 and Pelli, 1997) running under Matlab (MathWorks, Natick, MA).

The monitor refresh rate and mean luminance were 100 Hz and 20 cd/m2. Gratings were usually less than 4 degrees in radius and were large enough to cover the receptive fields of both cells in a recorded pair. Stimuli were presented monocularly, although binocular stimulation did not change the basic findings on Vm synchrony. For studying orientation dependence of synchrony, the stimulus spatial frequency was chosen to lie between the optimal spatial frequencies of two cells in a pair. In each trial, a blank period (0.25–1 s) preceded and followed visual stimulation (1.5–4 s). One or two blocks of blank stimulation were presented for each set of stimuli. Stimuli in a set were presented in random order and the set was repetitively presented for 5–20 times.