Silver Spring Monkeys - Final Experiments and Euthanasia

Final Experiments and Euthanasia

The NIH had said in 1987 that no further invasive research would be conducted on the monkeys, but in fact further experiments were performed on them in 1990. NIH presented the experiments in the lawsuit for custody of the animals in 1989. It proposed to perform deep surgical anesthesia during all procedures followed by euthanasia. After euthanasia, tissue examination would continue. The court allowed a group of researchers from the NIH to conduct a terminal experiment on January 14, 1990 on one of the monkeys who had become ill. Under anesthesia, electrodes were placed in his brain and hundreds of recordings taken. The Laboratory Primate Newsletter said it revealed an "unprecedented degree of reorganization of the sensory cortex. An 8–10-millimeter-wide area that would normally receive input from the hand was found to have completely filled in with input from the face." Brainmapping studies were conducted on the remaining monkeys on July 6, 1990, three days after PETA's application for custody was rejected. The monkeys were subsequently euthanized. During these experiments, scientists discovered an unpredicted change in thalamus structure apparently caused by progressive nerve degeneration through the dorsal root ganglia (which were severed) and the dorsal columns all the way to the thalamus (a second order synaptic target).