A 28-year-old employe of the Great Oaks Center for the mentally disabled in Silver Spring has been charged with second-degree rape in an attack on a 38-year-old Great Oaks resident, according to Prince George's County police.

Police said that Patrick Joseph Obryhim of 7 Deep Run Pkwy., Elkridge, was arrested and charged at 5:30 a.m. yesterday. Bond was set at $100,000.

The identity of the woman, who police say has the mental functions of a 6-year-old, was not released.

Officials from the Maryland Department of Mental Health and Hygiene verified that Obryhim is employed by the center but refused to provide any more details.

The rape of the 38-year-old follows a possible sexual assault earlier in the week of a severely retarded 26-year-old deaf woman. That woman apparently strayed from the center about 9 p.m. Monday and was found two hours later, about a mile from the center.

Police said evidence suggested she had been raped, but they have been unable to question her because of her disabilities.

In 1984, a severely retarded woman became pregnant after she was raped while under care at Great Oaks. In a case that received national attention, the Supreme Court ruled that she could have an abortion.

Built in 1971 as a model facility, Great Oaks is the state's second largest institution for the retarded, with 425 residents.

In 1980, it was the subject of an investigation by the state's attorney office after complaints filed by parents of the residents.

Last year, two employes were charged with beating residents, including one case in which a staff member hit a resident on the head with an aerosol can.

Also last year, after an employe union asked for an investigation of the facility, two top administrators were removed from their jobs after a state review found what was called "a significant management problem."