Spinal cord rehabilitation has progressed enormously since World War II, and persons with spinal cord injuries now have long life expectancies. Research has recently concentrated on improvement of the quality of life, and on neural mechanisms of recovery. This article will explore some aspects of both of these areas. In the ®rst section, the potential applications of sensory substitution systems for such functions as sex sensation and sensation from feet and from robotic hands will be examined. In the second section, the potential role of nonsynaptic di usion neurotransmission (NDN) in neural reorganization after spinal cord injury will be considered. This article includes portions of previous publications and reports.Keywords: incomplete SCI; neurotransmission; plasticity; robotic hand; sex sensation; rehabilitation
Sensory substitutionBackground For the brain to correctly interpret information from devices, it is not necessary that it be presented in the same form as in natural sensory information systems. We do not SEE with the eyes; 1 the visual image does not go beyond the retina, where it is turned into patterns of pulses along nerves. Those individual pulses are not di erent from the pulses from the big toe. It is the brain which recreates the image from the patterns of pulses. We have previously demonstrated that the brain is able to recreate`visual' images that originate in an arti®cial receptor (a TV camera), which are transduced into a tactile display (the TVSS system), and carried to the brain via tactile nerve pathways. 1 Thus, it is only necessary to present the information from a device in a form of energy that can be mediated by the receptors at the man-machine interface, and for the brain, through a motor system (eg a head-mounted camera under the motor control of the neck muscles, for blind persons), to know the origin of the information. We have previously developed tactile vision substitution systems (TVSS) to deliver visual information to the brain via arrays of stimulators in contact with the skin of one of several parts of the body (abdomen, back, thigh, ®nger-tip). Optical images picked up by a TV camera are transduced into a form of energy (vibratory or direct electrical stimulation) that can be mediated by the skin receptors. The visual information reaches the perceptual levels for analysis and interpretation via somatosensory pathways and structures.After su cient training with the TVSS, our blind subjects reported experiencing the images in space, instead of on the skin. They learned to make perceptual judgments using visual means of analysis, such as perspective, parallax, looming and zooming, and depth judgments. Our studies with the TVSS have been extensively described. 1 ± 10 After training, our blind subjects using the TVSS system did not feel anything on the skin on which the interface was placed; rather they perceived it out in three dimensional space if they controlled the camera movement. Although the TVSS systems have only had between 100 and 1032 point arrays, the low res...