Page - 65 - in Cyborg Mind - What Brain–Computer and Mind–Cyberspace Interfaces Mean for Cyberneuroethics

Neuronal Interface Systems • 65 scalp with transcranial direct current stimulation (TDCS) and transcranial alternating current stimulation (TACS). The principle of electromagnetic stimulation underlying TBS is that elec- trical currents can be created to selectively activate certain parts of the brain, producing particular outcomes by affecting large volumes of neurons. They are generally considered in research since TMS and TDCS can be used to both suppress as well as stimulate neuronal activity. They are thus particu- larly useful when combined with purely observational neuroimaging tech- niques, since the procedures can examine whether the activity of neurons in a specific brain area is necessary or causal for a certain brain function.64 TBS can also be used to understand the functioning of the brain by tracking net- works and pathways. The ability to modify brain activity raises the question whether TBS pro- cedures may, in addition, be able to deliberately change brain functions and, as a consequence, modify thoughts or behaviour. Interestingly, some of these procedures are already being used in clinical settings, such as in trying to address drug-resistant depression or treat other psychiatric and learning disorders, though the exact mechanisms of their therapeutic effects are still being researched.65 But already 10,000 adults have undergone such stimula- tion, which seems to be safe in the short term.66 Transcranial Magnetic Stimulation (TMS) Transcranial magnetic stimulation (TMS) has been used by scientists since the mid 1980s, especially in studies examining motor control. The procedure involves placing a coil of wire (enclosed in plastic) near the scalp over the brain area to be stimulated and then delivering a pulse of large current last- ing less than one millisecond. This produces a magnetic field, creating weak electrical currents inside the brain through electromagnetic induction. As a result, the thousands or millions of neurons in the area below the coil are briefly stimulated, in a nonspecific fashion, to a depth of approximately 3.5 cm into the skull, thereby affecting cognition or motor function. As such, TMS may be used as a diagnostic tool as well as in research, where it is employed, for example, to examine how the pulses alter the amount of time it takes for a person to recognise a face, add numbers or complete sentences.67, In 2008, the U.S. Food and Drug Administration approved TMS to treat migraine and refractory depression in adults,68 and there are no known long- term effects, though there is a very small risk of initiating an epileptic seizure during stimulation.69 The procedure is also increasingly being considered to address a number of psychiatric and neurological disorders such as mania, obsessive-compulsive disorders, schizophrenia and Parkinson’s disease.70 At 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.