Figure 6.

Learning-related spine loss is specific to principal barrel column E1, receiving the majority of CS whisker signals. A, Location of imaging sites for the E1 and E2 barrels with respect to the barrel field in three test mice (rows). Left, Two-photon imaging fields of view used to count spines framed by white boxes. YFP-labeled dendrites appear green and vessels labeled by intravenous bolus injection of Texas red are red. Scale bar, 50 μm. Center, Same but lower magnification. Scale bar, 100 μm. Right, Surface picture and circumference of intrinsic imaging signal obtained with stimulation of E1 (red) and E2 (orange) whisker. Sites of E1 and E2 barrel column are labeled in the second mouse—in the other cases, correspondence is equivalent. B, Two-photon images of dendritic spines in E1 and E2. In E1, but not in E2, spine loss is observed during training. The green arrowhead indicates spine formation, red arrowheads indicate spine elimination. Scale bar, 10 μm. C, Relative reduction of spine counts found in E1 (red) versus E2 (orange) and B1 columns (blue) in the three animals. Light-colored lines replot data of all test and control mice as a reference (same as in Fig. 4C). Spine loss occurs in barrel column E1, but is absent in the adjacent column, E2, and the more distant column, B1. Inset: Schematic depicting the three investigated barrels E1 (red), E2 (orange), and B1 (blue) within the barrel field.