The Federal Reserve on Thursday banned individual stock purchases by top officials who work at the central bank and placed limits on other activities. The new rules come several weeks after reports of active trading by high-level Fed policymakers triggered calls for an ethics investigation. Now, the fed will implement rules limiting the types of financial securities that top Fed officials can own, including the aforementioned ban on individual stock purchases or holding individual bonds. Any transactions require advance notice from the official, and it stipulates that investments have to be held for at least one year. Officials will have to give 5 days’ notice in advance of buying or selling any securities that are allowed, according to a news release announcing the rules. They also can’t purchase funds during periods of “heightened financial market stress,” the release said. “These tough new rules raise the bar high in order to assure the …