Operant conditioning of spinal reflexes: from basic science to clinical therapy

Abstract

New appreciation of the adaptive capabilities of the nervous system, recent recognition that most spinal cord injuries are incomplete, and progress in enabling regeneration are generating growing interest in novel rehabilitation therapies. Here we review the 35-year evolution of one promising new approach, operant conditioning of spinal reflexes. This work began in the late 1970’s as basic science; its purpose was to develop and exploit a uniquely accessible model for studying the acquisition and maintenance of a simple behavior in the mammalian central nervous system (CNS). The model was developed first in monkeys and then in rats, mice, and humans. Studies with it showed that the ostensibly simple behavior (i.e., a larger or smaller reflex) rests on a complex hierarchy of brain and spinal cord plasticity; and current investigations are delineating this plasticity and its interactions with the plasticity that supports other behaviors. In the last decade, the possible therapeutic uses of reflex conditioning have come under study, first in rats and then in humans. The initial results are very exciting, and they are spurring further studies. At the same time, the original basic science purpose and the new clinical purpose are enabling and illuminating each other in unexpected ways. The long course and current state of this work illustrate the practical importance of basic research and the valuable synergy that can develop between basic science questions and clinical needs.

A decision underlies phototaxis in an insect

“…They are commonly thought to be less flexible and more automatic, but with the advantage of either being especially efficient, fast, or with only a low cognitive demand. However, recent research has shown that many of these behaviours are either more complex than initially imagined [16][17][18][19] or liable to exploitation [20]. Moreover, several studies have shown that the state of the animal modulates how sensory structures process identical stimuli [21 -26] and many of these modulations are caused by aminergic actions & 2016 The Authors.…”

Electrocorticographic activity over sensorimotor cortex and motor function in awake behaving rats

“…This task-dependent adaptation was clearly differentiated from a long-term change in H-reflex size, which developed gradually over many more sessions. Change in presynaptic inhibition is the most likely mechanism of this task-dependent adaptation, and available evidence from both humans and animals suggests that the SMC is responsible (Segal 1997;Thompson and Wolpaw 2014;Wolpaw and Chen 2009). If further studies find that task-dependent adaptations in H-reflex size do reflect changes in the SMC state, it will be clear that the immediate role of the SMC in motor function goes beyond its well-known direct activation of spinal motoneurons.…”

“…We are seeking to define the SMC activation patterns responsible for short-term and long-term control of the H-reflex pathway. Understanding this interaction could lead to new techniques for inducing, guiding, and evaluating recovery after injury and could provide new insight into the acquisition and maintenance of motor skills (Thompson et al 2013; Thompson and Wolpaw 2014;Wolpaw 2010).…”

“…The motoneuron excitation produced by the H-reflex pathway contributes to locomotion and to other important behaviors; despite its apparent simplicity, the pathway adapts to the requirements of these different behaviors in the short term (e.g., standing or walking or running) and in the long term (e.g., during development and skill acquisition), and it changes in response to trauma and disease (Capaday 1997;Capaday and Stein 1986; Thompson and Wolpaw 2014;Wolpaw 2006Wolpaw , 2010Wolpaw and Tennissen 2001).…”

The effect of voluntary modulation of the sensory-motor rhythm during different mental tasks on H reflex

“…Again, although SMR and theta are neighbouring frequency bands, theta band power decreased while SMR power increased. It is believed that the sensory-motor cortex presents the major supraspinal site for modulation of the H reflex (Wolpaw 2007, Thompson andWolpaw 2014). However the effect of the self-induced modulation of SMR on the H reflex has not been sufficiently explored.…”