The Progressive Era. During the period known as the Progressive Era (1890s to about 1920) the U.S. government became increasingly activist in both domestic and foreign policy.
One possible link between brain freeze and other headaches is local changes in brain blood flow. If further research confirms all these types of headaches are caused by blood flow changes, new drugs that block widening of the blood vessels - called vasodilation - could improve treatment for sufferers.
Some yawns may result from blood stagnation in the brain. One of the causes of cerebral infarction is a blockage in the brain blood vessels. When this occurs, the flow of blood gets blocked, resulting in the death of tissues in the brain due to decreased amount of oxygen.