Biology Reference
In-Depth Information
1. GENERAL INTRODUCTION
Loss of function of denervated areas due to nerve injury or loss of a
limb severely affects the ability to perform activities of daily living (ADL)
and can significantly reduce quality of life of people who suffer from these
conditions. Therefore, development of new approaches to partially mimic
or restore the lost functions is an active field of research. If the connection
between the central nervous system (CNS) and the target organ is no longer
available but the muscles responsible for the lost action are still preserved,
several systems with functional electrical stimulation (FES) have been devel-
oped and implanted to artificially stimulate the remaining organs or nerves,
thus achieving the functions that could be carried out before the lesion. After
limb loss due to amputation or congenital, the use of artificial prostheses is
intended to substitute the missing parts of the body and recover its previous
normal roles. The use of cosmetic prostheses can help to cope with the psy-
chological distress produced by the missing body part improving patient's
own image and self-assurance. However, with such prostheses, no restora-
tion of sensorimotor lost functions is achieved. Thus, an ideal prosthesis
would be that which (1) looks and feels familiar for the patient as happens
with the aesthetic prostheses, (2) is thought controlled by the own patient,
(3) allows for multiple degrees of freedom to resemble as much as possible
the movements of the lost limb, and (4) provides the subject with sensory
information from sensors located in the prosthesis. In order to be able to pro-
vide a natural-like control of the prosthesis, an interface is needed between
the peripheral nervous system (PNS) and the machine. Thus, an electrode
placed in the severed proximal nerves might selectively record motor effer-
ent commands from the brain and transform these impulses into electrical
signals that activate the motors of the prosthesis. Under the best circum-
stances, the electrode should also be able to translate the signals of the sensors
in the device into electrical inputs and properly transform this information
into sensory feedback ( Micera & Navarro, 2009 ). Thus, nerve electrodes
should bidirectionally and selectively interface different specific motor
and sensory pathways with the best possible long-term biocompatibility.
The main goal of this chapter is to review the current electrodes and strat-
egies available for the development of advanced nerve-machine interface
systems.
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