Page - 51 - in Cyborg Mind - What Brain–Computer and Mind–Cyberspace Interfaces Mean for Cyberneuroethics

Neuronal Interface Systems • 51 Research on invasive output neuronal interface systems is now increasingly being considered to provide new functionality to certain disabled persons. In this regard, one of the first experiments took place in the year 2000 whereby a number of electrodes were implanted into the brain of an individual who had suffered a stroke, resulting in paralysis. This enabled the patient to learn to move a cursor on a computer screen by thinking about various hand movements.20 By and large, the best resolutions obtained from brain signals with humans involve the implantation, through surgery, of very small electrodes directly into the brain of an individual at a depth of about 1.5–3 mm. This enables the recording of signals from very small groups of neurons giving the greatest level of control.21 But since functions in the brain are not usually associated with a single group of neurons, it is often necessary to consider a more gen- eral picture of the brain using a number of electrodes.22 However, it should be noted that such invasive neuronal interfaces are prone to scar-tissue build- up, which may cause the signals to become weaker, or even non-existent, as the body reacts over time to the foreign device in the brain. Partially Invasive Output Neuronal Interface Systems Some neuronal interface systems are less invasive and can analyse brain sig- nals on the surface of the brain but inside the skull. In this case, because there is no forced penetration of the brain, less damage is inflicted to the cerebral cortex.23 But in these partially invasive systems, the electrodes are still posi- tioned through surgery with the associated risk of infection. Recordings through partially invasive systems may provide a better spatial resolution than those recorded on the scalp and may enable greater stability than recordings taking place inside the brain. However, their resolution usu- ally remains inferior to more invasive neuronal interfaces and, so far, only limited investigations have been undertaken on humans.24 Noninvasive Output Neuronal Interface Systems Noninvasive output neuronal interface systems usually analyse brain activity through the use of neuroimaging, including the application of electrodes on the surface of the head rather than through direct implantation inside the skull. This makes surgery unnecessary and avoids the associated risks of neuronal damage and infection. In this way, a kind of image of what is happening in the brain is examined. Clinical applications for human disor- ders are progressing only slowly. These include neuronal interfaces used to analyse movement intentions for patients who are paralysed.25 They can also be considered for patients who are not able to express themselves, such as 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.