To map spatial RF, a set of bright and dark squares within an 11 × 11 grid (grid size 3°–5°) or a set of bright and dark bars (3°–3.5°) at optimal and orthogonal orientations were flashed individually (duration = 200 ms, interstimulus interval = 240 ms) in a pseudorandom sequence. For 2D mapping CDK inhibitor of spike RFs, each location was stimulated for ≥5 times; for 1D mapping of membrane potential and synaptic RFs, each location was stimulated for 10 times. The same number of On and

Off stimuli were applied. The On and Off subfields were derived from responses to the onset of bright and dark stimuli, respectively. To measure orientation tuning, two types of oriented stimuli were used: drifting sinusoidal gratings (2 Hz, 0.04 cycle/°, contrast 40%) or drifting bars (4° width, 60° length, 50°/s speed, contrast 40%) of 12 directions (30° step). For drifting sinusoidal gratings, stationary

grating of one orientation was first presented on the full screen for 1.8 s before it drifted for 1.5 s. The grating stopped drifting for 500 ms before another grating pattern appeared. Drifting bars were moved across the screen with an interstimulus interval of 1.5 s. The 12 patterns were presented selleck screening library in a random sequence, and were repeated for 5–10 times. Orientation preference tested with sinusoidal gratings was similar to that tested with single bars (Figure S2A; also see Niell and Stryker,

2008). Spikes were sorted offline after loose-patch recordings. Spikes evoked by flashing stimuli were counted within a 70–270 ms time window after the onset of the stimulus. Spikes evoked by drifting gratings were counted within a 70–2,000 ms window after the start of drifting. The baseline firing rate was subtracted from stimulus-evoked spike rates. Responses with peak firing rates Phosphoprotein phosphatase exceeding three standard deviation of the baseline activity were considered as significant. The averaged firing rates were used to plot RF maps, which were smoothed with bilinear interpolation. In current-clamp recordings with the K+ gluconate-based intrapipette solution, subthreshold Vm responses were analyzed after removing spikes with an 8 ms median filter (Carandini and Ferster, 2000). Simple cells were identified by overlap index (OI) of spike response <0.3 or OI of membrane potential response <0.71 according to previous criteria (Liu et al., 2009 and Liu et al., 2010). In voltage-clamp recordings, excitatory and inhibitory synaptic conductances were derived according to the following equation (Wehr and Zador, 2003, Tan et al., 2004, Liu et al., 2007 and Wu et al., 2008). I(t)=Gr(V(t)−Er)+Ge(t)(V(t)−Ee)+Gi(t)(V(t)−Ei).I(t)=Gr(V(t)−Er)+Ge(t)(V(t)−Ee)+Gi(t)(V(t)−Ei).