The man on the street is more likely to use pharmaceutical enhancement at some point in his life than any of the methods discussed in this section. Nevertheless, nonpharmaceutical methods for altering brain function have evolved rapidly over the past decade. It seems likely that they will become more widely used for the treatment of neurological and psychiatric disorders and, eventually, for the enhancement of normal healthy brains. Three lines of research are paving the way for nonpharmacologic brain enhancement. The first is brain stimulation, either by implanted devices or transcranial magnetic stimulators.

Transcranial magnetic stimulation (TMS) involves stimulation of small areas of the brain by magnetic fields generated outside the head. In recent years it has moved from lab to clinic as a means of treating depression. It is also being explored with healthy subjects as a means to alter mood and or boost creativity, although its efficacy for these purposes has not been well established. Direct current stimulation (DCS) is another method of stimulating cortex noninvasively, using low currents, typically generated by a 9 volt battery, and has been shown to enhance specific cognitive abilities in normal volunteers.

Invasive methods of brain stimulation with implanted electrodes are currently last-resort treatments for Parkinson’s disease, epilepsy, depression and obsessive-compulsive disorder. However, at a time when few new pharmacological treatments for neuropsychiatric disorders are visible on the horizon, the early successes of deep brain stimulation (DBS) have attracted great interest on the part of physicians. Because it is capable of improving mood and cognitive function in at least some cases, they may eventually gain wider use for those purposes. The invasiveness of DBS limits its conceivable uses to patients with serious illnesses.

The second line of research on nonpharmacologic brain enhancement involves surgery to remove or disconnect specific structures within the brain. The history of "frontal lobotomy" was rife with bad science (the functions of prefrontal cortex and its connections to other brain areas were poorly understood) and bad clinical ethics (inadequate or nonexistent informed consent). Modern psychosurgery operates in the shadow of this tragic history, and is currently practiced as a last resort. However, with more precisely targeted lesions and more thorough evaluations of outcome, the state of the art can be expected to improve and may become an option for more patients.

The third line of research is on brain-machine interfaces (BMIs). Here the goals are primarily to enable information from the world to be transduced into neural activity and to enable neural activity to be transduced into information that is externally useful for communication or robotic control. Some BMIs are already in clinical use. The most common BMI is the cochlear implant, which transduces sound waves into electrical patterns that can be sensed by auditory neurons in order to restore hearing in some deaf individuals. Systems that take information in the opposite direction, from brain to world, have been used clinically with paralyzed patients. These systems typically use features of the patient’s EEG, recorded noninvasively from electrodes on the scalp, to convey simple commands, although some humans have participated in research trials with neural implants.

The full potential of BMIs has only begun to be explored, primarily in research with nonhuman subjects. Memory augmentation, as well as perceptual and motor prostheses, is under study. In addition to the formidable technical challenges of interfacing silicon with sufficient numbers of neurons with sufficient precision and reliability, fundamental scientific problems remain. For example, to "converse" with the brain we must speak its "language." One of the goals of BMI research is to better understand the neural coding of information.

Research on electronic brain enhancement conjures up frightening scenarios involving mind control and new breeds of cyborg. The dominant role of the American military in funding the most cutting edge research in this area does little to allay these worries. In the short term, however, the ethical concerns here are similar to those raised by the pharmacological enhancements discussed elsewhere on this site: safety, social effects, and philosophical conundrums involving personhood. Of course, the irreversible nature of some of the non-pharmacological interventions exacerbates these problems.

In the long term, humanity may indeed find itself transformed by the incorporation of new technology into our nervous systems. An intriguing (and reassuring) perspective on this transformation is offered by Andy Clark, who suggests that we are already cyborgs of a kind, and no worse for it.

Martha J. Farah