Causing an Effect
Computers
Computer systems are often used as effectors for brain-computer-interface or BCI applications because usually individuals that require such systems are severely paralyzed and so are not candidates (at the state of current technology) for robotic prostheses. Computer interfaces give paralyzed individuals the ability to communicate, access to entertainment, and sometimes control of their environment. Most BCI systems translate brain activity into the control of a computer cursor. Software packages like EZKeys, Words+, or Lancaster implement simplified computer interfaces in which objects on a screen can be selected by cursor hovering. Commonly a BCI interface will provide easy push-button access to e-mail, a word processor, the internet, and possibly other computer controlled modules like the air conditioning in a room, or a stereo. Below is a video of a Braingate patient using a neurally controlled cursor to navigate a simple computer interface:
Braingate participant demonstrating computer (cursor) interface.
In this technological age there is very little that a computer cannot do when attached to the right kinds of specialized equipment. This property of the computer as an effector opens many possibilities for people who are completely disabled—the only limiting factor is the amount control afforded by the signal transduction hardware and software. [15]
Robotics
Robotics are often used to build prostheses for amputees, but in other forms may also be used to assist the severely disabled. Robotic prosthetics usually use server motors to generate movements dictated by interpreted biopotentials. In the past, robotic prostheses were heavy, large, and had few degrees of freedom around each joint. Today, as computers become smaller, robotic prosthetics (especially robotic arms) are becoming more agile and practical. Though not controlled by human biopotential, the Luke Arm invented by Dean Kamen demonstrates the current state of the art in robotic prosthetics and offers insight into the possible future of robotic effectors for human-computer interfaces. [3]
"Luke Arm" Demonstration
Robots in other forms may be able to assist the severely disabled. Most notably, researchers working on the Braingate project have demonstrated that a Braingate participant can steer a robotic wheelchair based on neural signals alone. Other devices like robotic vacuum cleaners or the like may also assist the wheelchair-bound.
Functional Electrical Stimulation
Functional Electrical Stimulation or FES is the artificial stimulation of muscles through electrical pulses. Using FES as an effector for interpreted intention is a future goal for human-computer-interfacing technology as no current systems are capable of providing the control necessary to allow a paralyzed person to walk or stand unassisted. However, FES has proven to be a valid method for restoring muscle movement in patients who can control an electrical pulse generator with their hands. In fact, ParaStep is a clinically available FES systems that gained FDA approval in the 1990’s and may be used by paraplegics to walk with the aid of a walker. [15]
Functional Electrical Stimulation Demonstration