Introduction to “The Behavior-Analytic Origins of Constraint-Induced Movement Therapy: An Example of Behavioral Neurorehabilitation”

In a study by Zhao et al. (2005), the neurological function of rats was assessed prior to and for several weeks after experimentally induced cortical stroke using several behavioral tests. In one test, rats were free to explore a clear plastic enclosure where they frequently reared up and leaned against the walls. Which forepaw they used (left or right, or both) when they did so was counted. In another test, rats were cradled in the researcher's hand and their vibrissae (whiskers) were gently brushed against the edge of a table. If the right-side vibrissae were so stimulated, rats reliably placed their right paw on the table; left-paw placement occurred in response to left vibrissae stimulation. The experimental stroke caused severe damage to the left cortex and disrupted the use of the right forelimb: the percentage of rears in which rats used their right paws to brace themselves fell from a normal level of about 50% to less than 25%, and the probability of paw placement after vibrissae stimulation fell from 1 to about .1.

Recovery of limb function differed markedly in these two tasks. In the vibrissae-paw placement task, clear recovery was observed as the reflex was tested repeatedly over time, so that by 8 weeks after stroke the probability of paw placement elicited by vibrissae stimulation returned to about .9. Little to no recovery was seen in the open field test; rats rarely braced themselves with their affected forepaws when they reared. Thus, behavioral recovery depended on the demands placed on the rats; in the vibrissae-paw placement task, the reflex was repeatedly tested in a context in which the rats could not escape the testing, and recovery occurred. In the open field test there was no such demand; rats were free to allow their affected limb to hang as they reared and braced themselves with their unaffected limb, and no recovery was observed. This experiment suggests that the behavioral effects of stroke damage may be overcome, but recovery requires repeated, consistent, effective experience.

This observation is confirmed again and again in the groundbreaking work of Edward Taub and his colleagues, described in the following article (Taub, 2012). Based on extensive experimentation with animal models of peripheral nerve injury, Taub and colleagues have created an approach to overcoming movement and verbal behavior disorders in patients who have suffered strokes that is a model for behavior analysts who are interested in helping people with brain disease and injury. Central to the method, called constraint-induced movement therapy (CIMT), is the concept of learned nonuse; according to this concept, the initial disruption of movement caused by stroke creates a situation in which attempts to use the limb are either ineffective (extinction) or, by upsetting or breaking objects or causing pain or embarrassment, are punished. Use of the unaffected limb instead of the affected one is reinforced, further reducing the likelihood that behavior with the affected limb will be attempted. The eventual level of disability is greater than what can be attributed to the brain injury alone (i.e., nonuse is learned).

By constraining use of the unaffected limb and using extensive shaping and other behavioral tools to gradually improve movement in the affected limb, patients relearn to use the limb in daily life situations, thereby greatly enhancing their quality of life. The fundamentals of the method have proven beneficial for overcoming some of the verbal behavior disorders caused by stroke (e.g., aphasia) and have also been applied to other brain diseases and injuries. Theoretically the most important implication stems from the neuroscience research showing large and reliable brain changes (i.e., neuroplasticity) in response to brain injury and treatment of its behavioral effects. The cortical region involved in motion of the affected limb is expanded by CIMT, which may allow permanent recovery of limb function. Ultimately the work has created an understanding of stroke damage as a highly neuroplastic situation in which the repeated application of contingencies of reinforcement for movement and verbal behavior lead to behavioral and brain changes in a thoroughly interactive system. The interactions of brain and behavior in this clinical scenario should be intriguing to behavior analysts.

In his address at the 30th annual western regional conference of the California Association for Behavior Analysis, Schlinger (2012) noted that the success of behavior analysis in dealing with persons with autism has led to a state of affairs in which a large proportion of behavior-analytic resources (in practice, training, and research) are now devoted to this single problem. He suggested that our field would be strengthened if efforts were distributed across a wider range of human problems. In this context, Taub's work is not only a demonstration of the power of behavior analysis against the devastating behavioral consequences of brain damage due to stroke. It is also an invitation to behavior analysts to continue to explore opportunities to make a difference in the lives of persons with nervous system disorders, such as traumatic brain injury, multiple sclerosis, muscular dystrophy, childhood genetic disorders, Alzheimer's disease, Parkinson's disease, infectious diseases, chronic pain, epilepsy, and even brain tumors. Each of these can have behavioral effects that the application of behavioral interventions may be able to prevent or overcome or slow or ease. We are pleased that Taub has shared this review of his work with the readers of The Behavior Analyst. We hope students of behavior analysis read his paper with an appreciation of the consistent and effective application of behavioral principles to help people who have had strokes, and with an eye toward continuing the expansion of both basic and applied behavior analysis to all neurobehavioral disorders.