Effects of Short-Term Training on Sensory and Motor Function in Severed Nerves of Long-Term Human Amputees

Abstract

Much has been studied and written about plastic changes in the CNS of humans triggered by events such as limb amputation. However, little is known about the extent to which the original pathways retain residual function after peripheral amputation. Our earlier, acute study on long-term amputees indicated that central pathways associated with amputated peripheral nerves retain at least some sensory and motor function. The purpose of the present study was to determine if these functional connections would be strengthened or improved with experience and training over several days time. To do this, electrodes were implanted within fascicles of severed nerves of long-term human amputees to evaluate the changes in electrically evoked sensations and volitional motor neuron activity associated with attempted phantom limb movements. Nerve stimulation consistently resulted in discrete, unitary, graded sensations of touch/pressure and joint-position sense. There was no significant change in the values of stimulation parameters required to produce these sensations over time. Similarly, while the amputees were able to improve volitional control of motor neuron activity, the rate and pattern of change was similar to that seen with practice in normal individuals on motor tasks. We conclude that the central plasticity seen after amputation is most likely primarily due to unmasking, rather than replacement, of existing synaptic connections. These results also have implications for neural control of prosthetic limbs.

Decoding Information From Neural Signals Recorded Using Intraneural Electrodes: Toward the Development of a Neurocontrolled Hand Prosthesis

“…In order to achieve an effective solution, one of the most important requisites is the development of an intuitive interface between the natural and the artificial systems, allowing the user to interact with the artificial system in a simple and natural manner. In recent years, several attempts have been carried out [1][2][3][4][5][6] to restore this natural link by developing different Hybrid Bionic Systems (HBSs, [5][6]). Among HBSs, active hand prostheses represent an interesting example of the need for natural interfaces between biological and artificial devices.…”

“…Among them, Longitudinal intra-fascicular electrodes (LIFEs), intraneural electrodes inserted longitudinally into the nerve tissue [24], are potentially very interesting due to their selectivity and relatively low level of invasiveness. In fact, a recent study showed that the principle of bidirectional control of artificial devices [1][2] was possible in short-term clinical trials with amputees. In particular, it was shown that the subjects were able to control a one-degree of freedom prosthesis by processing efferent neural signals and to receive robust and reliable sensory feedback by stimulating the afferent nerves.…”

Neural interfaces for somatosensory feedback

“…Sensation was perceived on the phantom, but was generally diffuse sensation, unstable, and the quality of the sensation was generally described as paresthesia. Nerve stimulation for somatosensory restoration was then largely ignored until 2005 when a series of articles was published describing the acute trials with the LIFE electrodes placed in the median nerve [120,123,124]. There were localized sensory percepts with perceptual intensity proportional to stimulation frequency and a spread of sensory area with increased stimulation intensity.…”

A Novel Application of Virtual Reality for Pain Control: Virtual Reality-Mirror Visual Feedback Therapy

“…These LIFEs also seem to be able to provoke sensory feedback. In a preliminary study on amputees conducted by Horch et al, they reported that stimulating different afferent nerves using LIFEs could provide sensory feedback [37].…”