Effects of local pressure on cortical electrical activity and cortical vessels in the dog

✓ Suppression of the cortical electrical activity and resistance of cortical vessels to collapse were investigated under various pressures applied locally by an inflatable balloon over the cerebral cortex of dogs. The locally applied pressure and the transmitted general intracranial pressure were measured by a special pressure switch. To produce a 50% suppression of the electrical activity required an average of 45.4 mm Hg local pressure; for 100% suppression, an average of 164 mm Hg. Thus, suppression of the cortical electrical activity is proportional to the pressure applied. In separate experiments with transparent cranial windows, collapse of the cortical veins was produced by an average local pressure of 48.5 mm Hg and collapse of the cortical arteries by an average of 188 mm Hg. It is concluded that the cortical electrical activity is suppressed as a result of changes in local blood flow which are in turn a result of local compression and tissue distortion.