SACRAMENTO  (AP) — Democratic lawmakers on key policy committees said Wednesday that they want to limit California's practice of keeping hundreds of inmates in solitary confinement for years, sometimes decades, as a way of controlling violent prison gangs.

They held the first in a planned series of hearings in response to an inmate hunger strike this summer that at one point involved more than 30,000 of the 133,000 inmates in state prisons.

The inmates were protesting conditions for gang leaders held in isolation at Pelican Bay and three other prisons.

More than 4,000 inmates are currently in the isolation units. Nearly 1,000 have been there for more than five years. Of those, nearly 200 have spent more than 10 years in the unit, and more than 100 have been there at least 15 years. Eighty-four gang leaders have been in isolation for at least two decades, and 23 have served more than a quarter-century in the units.

They spend as many as 22 hours of each day alone in tiny cells, are fed through slots in the doors, exercise in fenced enclosures and are confined in cages the size of telephone booths while they receive treatment outside the units.

"There's just so many comparisons to a zoo," said Assemblyman Tom Ammiano of San Francisco. "We've got to do something about that."

He and fellow Democrat Sen. Loni Hancock of Berkeley said they will seek to make unspecified changes to state policy or law to restrict their use. They head the Assembly and Senate public safety committees and convened the four-hour hearing.

Prison officials emphasized that they already have changed the rules to limit use of the isolation units and let gang members earn their way out through good behavior. Of 528 gang leaders reviewed through last month, 343 were cleared to return to the general prison population.

Gang leaders' social contact has been restricted because prison officials and federal prosecutors allege that they have often been able to run violent street gangs from behind prison walls despite officials' best efforts.

The lawmakers and advocates acknowledged that some inmates merit solitary confinement for public safety reasons, but said the isolation should be brief and should not preclude indirect social contact like letters and phone calls.

"To be in a sterile hell where it's not only that you are shut off from other people, you are shut off from bird song, a blade of grass — that's profoundly dehumanizing. You don't recover from that," said Margaret Winter, associate director of the National Prison Project of the American Civil Liberties Union.

Assemblywoman Nancy Skinner, D-Berkeley, said California should follow other states like Illinois, Maine and Mississippi that have limited their use of isolation units.