*3.3. BrainGate*

The technology which has thus far shown itself to be of the most practical use in this area is the microelectrode array known as the Utah Array, more popularly (and commercially) referred to nowadays as the BrainGate.

The array consists of 100 spikes which are 1.5 mm long and taper to a tip diameter of less than 90 microns. The spikes, essentially silicon shafts, are arranged in a 10 by 10 array on a 4 mm × 4 mm substructure and each has a platinum electrode on its tip. The electrodes are linked to platinum wires and in this way the array can be employed bi-directionally to both directly monitor neural activity and also to apply stimulating currents.

A number of trials have been carried out that did not use humans as test subjects, these involving chickens or rats. However it is human studies only that we are more interested in here and these are limited to two groups of studies at the moment. In these experiments the array has been fired into either the human brain or nervous system. In the first set of these experiments to be considered, the array has been employed in a purely recording role for therapeutic results.

Electrical activity from a few neurons monitored by the array electrodes, positioned in the motor cortex, has been decoded into a signal that enabled a severely paralysed individual to position a cursor on a computer screen using neural signals for control in combination with visual feedback. The same technique was later deployed to allow the individual recipient, who was paralysed, to operate a robot arm even to the extent of learning to feed themselves in a rudimentary fashion by maintaining sufficient control over the robot arm [24,25].

The same implant was employed to enable a paralysed individual to regain some control over his own arm [26]. In this case signals from the individual's motor cortex were employed to bring about stimulation of hand/wrist muscles via a cuff worn around the person's arm. The effect of this was a sort of bi-pass of the non-functioning nervous system. As a result the individual recipient could make isolated finger movements and perform six different wrist and hand motions.

Initially fMRI scans were taken of the recipient's brain while he tried to copy videos of hand movements. This identified an exact area of the motor cortex dealing with the movements exhibited. Surgery was then performed to implant the array to detect the pattern of electrical activity arising when the recipient thought about moving his hand. These patterns were then sent to a computer which translated the signals into electrical messages, which were in turn transmitted to a flexible sleeve that wrapped around the forearm and stimulated the muscles.

### *3.4. Case 3 Conclusions*

We have seen in this section how brain/nervous system to technology connections can be employed to overcome problems such as depression or paralysis. However they have been included here as much to show just how the functioning of the human brain can be altered by the employment of electronic signals. OK here we have considered injection of those signals into specific regions for therapeutic purposes, but obviously other regions and other purposes could be chosen.
