NFL teams now have new, stricter instructions for when players should be allowed to return to games or practices after head injuries, guidelines that go into effect this week.

In the latest step by the league to address a hot-button issue, commissioner Roger Goodell sent a memo to the 32 clubs yesterday saying a player who gets a concussion should not return to action on the same day if he shows certain signs or symptoms.

Those include an inability to remember assignments or plays, a gap in memory, persistent dizziness, and persistent headaches.

The old standard, established in 2007, said a player should not be allowed to return to the same game if he lost consciousness.

Yesterday's memo also says players "are to be encouraged to be candid with team medical staffs and fully disclose any signs or symptoms that may be associated with a concussion."

Nearly one-fifth of 160 NFL players surveyed by The Associated Press from Nov. 2 to 15 replied that they have hidden or played down the effects of a concussion.

The league said its concussion committee, team doctors, outside medical experts and the NFL Players Association developed the new standards.

NFLPA assistant executive director George Atallah said the union is "encouraged by this new policy." He added that the NFLPA "will continue to examine these issues independently to recommend the best possible policies and procedures."

BEARS

Chicago placed linebacker Pisa Tinoisamoa on injured reserve yesterday because of ligament damage on his right knee, formally ending his season.

Tinoisamoa, a University of Hawai'i alum, tore the posterior cruciate ligament during the opener at Green Bay, an injury that ultimately ended his season. He was inactive for the next three games, and started against Atlanta on Oct. 18 before getting carted off the field during that game.

BROWNS

Cleveland Browns running back Jamal Lewis has been placed on injured reserve with post-concussion symptoms, prematurely ending his NFL career.

Lewis, who announced last month that he planned to retire after this season, sustained an unspecified head injury in Sunday's loss at Cincinnati.

Lewis rushed for 10,607 career yards, ranking him 21st on the NFL's all-time list.