FIG. 2.

Controlled Cortical impact diagram. Test animals are held in a stereotactic frame using ear bars and an incisor bar. A double-acting pneumatic piston drives an impactor tip into the test animal's intact dura overlying the brain or, less commonly, onto the intact skull. The piston can be precisely moved to control the depth of impact and the velocity is determined by controlling the pressure applied to the piston. There is an electromagnetically driven alternative to a pneumatically actuated piston (not pictured).