Strokes and other damage to the central nervous system often lead to paralysis. Constrained-induced movement therapy or CIMT can help patients regain the use of paralyzed limbs.

Victims of strokes or other damage to the central nervous system (CNS) often suffer paralysis of certain body parts. An important form of treatment for such cases is constrained-induced movement therapy. The method was developed by Edward Taub. He believed that stroke patients often stop using the affected limbs because they are discouraged by the difficulty they encounter. This “learned non-use”, he argued, leads to further deterioration.  

In order to stop this process, CIMT or “Taub’s therapy”, as it is also called, forces the patient to use the affected limb. This is brought about by restraining the unaffected limb for an extended period of time. During this time, the affected limb is used and exercised intensively. The repetitive exercises induce the development of new neural pathways in the brain, and the patients learn to use the paralyzed limb again.  

CIMT is widely used and medically acclaimed in Germany, but its origins are almost never discussed publicly. In fact, however, the method is based on animal research. Taub performed his experiments on macaque moneys. His Silver Spring monkeys became the most famous lab animals in history.  

The animals came to public attention as a result of a bitter, ten-year battle between scientists and PETA (People for the Ethical Treatment of Animals). The conflict is centered around the fact that Taub’s work involved experimental deafferentation of the animals. This means that the sensory ganglia in the spinal cord, through which we receive information about the state of our limbs, are completely segregated from the motor nerves. A monkey whose limbs have been deafferented will not feel them, and it will not be able to sense where they are in space.  

Taub’s reasoning was that a monkey will not use the deafferented arm if it can rely on its good arm instead. If both arms are deafferented, however, it will be forced to use them. This might seem paradoxical, but the hypothesis was confirmed by the experiments. Taub even deafferented the entire spinal cord, so the monkey received no sensory input from any of its limbs, but the animal was still able to use them if forced to do so by electric stimulation or hunger.  

Edward Taub was sued by PETA. Many people have seen a photograph of the Silver Spring monkeys in which it looks like the animals are being crucified. Few know, however, that there is quite a bit of evidence that these photographs were staged by antivivisectionists working as caretakers at the institute (see the review by Nobel laureate David Hubel in Annual Reviews in Neuroscience 1991, 14:1-8: DOI: 10.1146/annurev.ne.14.030191.000245). Police temporarily housed the monkeys in the basement of a house belonging to a PETA member. The animals were then reported stolen, but turned up again when it became clear that Taub could not be prosecuted without the monkeys as evidence. Ultimately the monkeys were transferred to a National Institutes of Health (NIH) facility.  

Many years later the court allowed a group of researchers at the NIH to conduct a terminal experiment on one of the monkeys that had become ill. Under anesthesia, electrodes were placed in its brain, and hundreds of recordings were taken. In Laboratory Primate Newsletter, scientists reported 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.” But the changes went beyond the cortex; the structure of the thalamus had reorganized itself as well, apparently as a result of progressive nerve degeneration caused by the deafferentation.  

Based in part on this work, Edward Taub went on to develop novel physical therapy techniques. Thanks to his methods, thousands of patients with damage to the central nervous system have learned to use their paralyzed limbs once more. The American Stroke Association calls Taub’s therapy “at the forefront of a revolution” in the treatment of stroke patients.