Layer 2/3 neurons exhibit strong tuning for stimulus orientation, whereas layer 4 neurons are tuned only weakly.A, Orientation tuning for 61 layer 2/3 recording sites, with preferred orientation normalized to 0. Individual sites are shown in gray, with the average tuning curve shown inblack. B, Orientation tuning for 35 layer 4 recordings (gray) and average tuning curve (black), normalized as in A.C, Histogram of OSI values for layers 2/3 (black) and 4 (white). Values >0.7 are considered to be tuned for orientation.