Seite - 55 - in Cyborg Mind - What Brain–Computer and Mind–Cyberspace Interfaces Mean for Cyberneuroethics

Neuronal Interface Systems • 55 recording of neuronal activity across the entire brain with relatively high spatial resolution (range of millimetres) and moderate temporal resolution (range of seconds).34 However, caution should be shown when interpreting the statistical prob- ability of results obtained from fMRI, especially in cognitive examinations, since a significant amount of fMRI research on emotion, personality and social cognition may be using unreliable procedures.35 Electroencephalogram (EEG) and Magnetoencephalography (MEG) Ever since the German psychiatrist Hans Berger (1873–1941) invented the electroencephalography (EEG) in 1924 by attaching multiple electrodes to the outside scalp of a head, a form of direct communication between the brain and an external device has become possible. A similar procedure called magnetoencephalography (MEG), in which sensors replace the electrodes on the head to record naturally occurring magnetic fields produced by electrical currents in the brain, was then developed. In this regard, measurements are now usually collected by placing up to one hundred electrodes or sensors on the person’s head using a wet gel to improve contact with the skin.36 These are sometimes attached individually or built into a cap. EEG detects the very small synchronised electrical activity of many hun- dreds of thousands of neurons, whereas MEG detects the very small changes in magnetic fields associated with the electrical activity of these large groups of neurons. These results enable the production of a ‘map’ of human brain activity second by second associated with thought processes directly and noninvasively. However, the spatial resolution of EEG and MEG is limited because of the difficulty in measuring electrical or magnetic signals deep within the brain and the intrinsic complexity of trying to correspond signals on the scalp with activity in specific brain areas. But EEG can still be used, for example, to detect general patterns of electrical activity resulting from thought processes or the brain waves that occur during sleep. When a person is asleep, his or her brain goes through a number of cycles of activity. Initially he or she will be in a light sleep and the surface electrodes will record small amplitude high frequency waves. As a person moves into a deeper phase of sleep, the waves increase in amplitude and decrease in frequency. It is then possible to see specific patterns associated with dreaming. Indeed, when individuals wake up from a deep sleep, their brainwave fre- quencies will increase through the different specific stages of brainwave activ- ity. During the waking cycle, it is possible for individuals to stay in the mixed state of activity for 5–15 minutes, whereby their brain is running through a 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.