Seite - 68 - in Cyborg Mind - What Brain–Computer and Mind–Cyberspace Interfaces Mean for Cyberneuroethics

68 • Cyborg Mind Brain Electrode-Chips One neuronal interface system that may enable a feedback loop in a single device is a square microchip containing a number of very small hair-thin electrodes that can both read the state of certain neurons and also stimulate them (i.e. they are bidirectional devices).84 These electrode-microchips can be implanted on the surface of the brain of an individual, through surgery, enabling the electrical activity from hundreds of neurons to be recorded from the relevant brain areas. This activity can then be translated into meaningful signals and sent to an appliance. Such brain interfaces have already been considered in clinical trials with the aim of restoring some functionality for a limited group of severely motor- impaired individuals85 whose thought signals are read in order to translate them into an application. The pins of the electrode may look very slim to the human eye, but rela- tive to the scale of neurons in the brain, they are massive. Consequently, each electrode can monitor the average activity of many hundreds of neurons, which is far beyond the more intricate level of activity in which the brain operates. Electrodes in Capillaries One major restriction of electrode-chips is that they only monitor the effect of large groups of neurons. This has led to a group of researchers in the United States to propose an alternative approach using the brain’s extremely comprehensive network of blood vessels with capillaries that supply oxygen and nutrients to the brain’s neurons. Because this reaches throughout the tissue and comes into close contact with most neurones, the scientists believe that it may be possible to feed probes through these capil- laries to reach the most difficult-to-access parts of the brain with minimal disturbance. In laboratory experiments in vitro, this proposal was examined using very small platinum electrodes that were successfully inserted into capillaries, which supplies oxygen through the blood, to neurons in the spinal cord. 86 Researchers now hope to further miniaturise the probe to make it steerable by employing electrically stimulated shape changes so that these very small wire-probes can be placed into the desired blood vessels and create the first true steerable nano-endoscope. It would be an enormous technical feat if such electrodes in capillaries proved to be successful. But it is difficult to determine how they can move beyond the research stage in the near future. Indeed, in order to make con- nections with all the neurons in the brain, it would be necessary for billions This open access edition has been made available under a CC-BY-NC-ND 4.0 license thanks to the support of Knowledge Unlatched. Not for resale.