Fig. 1.

Convection-enhanced delivery and bulk-loading of calcium-sensitive dye. (a) Schematic diagram of convection-enhanced delivery of calcium-sensitive dye. The calcium-sensitive dye is injected into the cortex via the electrode. The dye is driven by the pressure and propagates in spherical space. A large volume of calcium dye is injected into the cortex and a large area of the cortex is stained (up to 6 mm). Examples of (b) the older multiple injection technique for bulk-loading and (c) convection-enhanced delivery (CED) technique stained brain. The images were taken $\sim 300\mu \text{m}$ below the surface. Note that the CED technique provides smooth loading to a broad area that slowly decreases with distance from the injection site.