Neural recordings have been utilized for controlling brain–machine
interfaces, such as artificial arms, since the late 1960s . Neural
recording devices play a central role in paralysis prosthetics, stroke,
Parkinson’s disease, prosthetics for blindness, and experimental
neuroscience systems. Several attempts have been conducted in recent years
to implement large-scale multi-electrode neural recording , .
Experiments have been conducted on a variety of species ranging from rats
 and monkeys  to humans .
Figure 33.1 shows how a brain–machine interface (BMI) can help several
patients. Figure 33.1(a) shows conceptually how BMIs can help patients who
suffer from damaged arm muscles, preventing the signal from reaching the
brain, or those who have artificial limbs . Vivid examples of recent
efforts in using BMIs to help paralyzed patients include the thought control
of a wheelchair , as seen in Figure 33.1(b), and thought control of a
robotic arm by a patient suffering from paralysis for 15 years , as shown
in Figure 33.1(c). However, better quality of life could be imparted to
these patients if a fully implantable wireless solution was available.
Figure 33.2 shows an illustrative picture of a brain implant system. The
implant’s power is wirelessly harvested to allow battery-free operation.
Wireless transmission is necessary to allow for non-invasive operation.