WASHINGTON, June 27— Research on monkeys at the center of a long animal rights dispute has shown that the brains of adult primates may recover from injury much more fully than previously believed, scientists said today.

The researchers said dormant brain areas in the monkeys had reorganized themselves to attain new functions to a degree 10 times greater than had been thought possible.

The findings, by scientists at the National Institute of Mental Health and Vanderbilt University, indicated that one day it might be possible to manipulate this compensating mechanism with drugs or surgery to help people with brain or nerve injury recover some lost functions. Animal rights advocates seeking to stop the experiments had said they would not produce useful data. 'Beginning to Learn'

Dr. Tim P. Pons of the mental health institute, the head researcher in the study, said it had long been thought that shortly after birth, the nervous systems of higher animals became "hard-wired" in their functions and lost their ability to grow and make new connections.

"We're beginning to learn that the system is not hard-wired functionally and parts of the brain that lose their primary function do not remain unresponsive or fall fallow," Dr. Pons said. "Things are not fixed with no chance of change."

The results of the study were immediately challenged by animal rights advocates who had attempted to stop the experiments, which were conducted last year when the monkeys were killed. The animals' Federal custodians, the National Institutes of Health, said they had been in ill health. 'A Pointless Experiment'

"This was a pointless experiment, and we learned nothing we didn't know," said Dr. Neal D. Barnard, president of the Physicians Committee for Responsible Medicine, a group that promotes alternatives to animal research. "We don't see anything here that will help disabled people or lead toward a treatment."

The monkeys have been the subject of extensive court battles between the Government and advocates of animal rights since 1981, when the animals were seized at the Silver Spring, Md., laboratory of a health institutes contractor. The seizure of the monkeys came when a technician, Alex Pacheco, who would go on to found People for the Ethical Treatment of Animals, a national animal rights group, accused managers of the laboratory of inflicting unnecessary cruelty on the animals and not giving them adequate care.

The director of the laboratory at the time, Dr. Edward Taub, was convicted on state animal cruelty charges, but the verdict was later overturned. Dr. Taub, now at the University of Alabama, is listed as an author of the latest study, which is being published in Friday's issue of the journal Science.

Many of the animals involved in the case had nerves to various limbs severed one or two years before they were seized. The severing of nerves was for studies aimed at eventually aiding human victims of brain and spinal cord injuries.

The animals, 16 crab-eating macaques and one rhesus monkey, did not belong to the health institutes, but the agency assumed custody of them not long after they were seized. In 1986, the 15 animals surviving then were shipped to the Delta Regional Primate Research Center in Covington, La., a unit of Tulane University. Four of these animals, who had not been disabled, were later transferred to the San Diego Zoo. Two monkeys, including the uninjured rhesus monkey that was used as a control, survive.

The Silver Spring monkey case became a pivotal one to the animal rights movement. Publicity it generated was instrumental in passage of a revision of the Animal Welfare Act in 1985, which toughened standards for animal care in research. A Decade in Courts

Animal rights advocates spent a decade in state and Federal courts seeking custody of the remaining animals, an action that the health institutes resisted. The Government won court permission to put five animals to death last year and to conduct experiments on their brains at the same time.

In the years since the animals first became research subjects, other research has indicated that areas of the brain cut off from their normal activity might assume new functions, a phenomenon called neuroplasticity. Researchers have found that when the brain loses sensory input from a part of the body, there is tendency for nerve impulses from neighboring parts to encroach on the dormant area.

But this earlier work indicated only a small amount of movement of nerve impulses into the unused area, or about 1 to 2 millimeters. Dr. Pons said his study indicated the reorganized area getting new signals extended from 10 to 14 millimeters, or 0.39 inch to 0.55 inch.

In the study, scientists placed the monkeys into deep coma with drugs, opened their skulls and placed microelectrodes capable of detecting the faint electrical signals of brain activity into portions of the cortex that would normally feel sensations from disabled arms.

Points on the face and trunk of each animal were then stimulated, and the electrodes registered electrical impulses from the stimulation of the face, but not of the trunk.

Dr. Pons said this showed that a portion of the brain that normally processes information for the arm, for instance, can just as easily process information for the face.