For years, scientists and physicians have been trying to tap into the
brain to investigate and manipulate the neurons that make up its intricate
circuitry. Such studies have sought, for example, to understand how thoughts
are formed, to find ways to relieve intractable depression, and to block the
neurodegeneration of such conditions as Alzheimer and Huntington diseases.
One technique, transcranial magnetic stimulation (TMS), has been used
by many scientists to turn on and off particular parts of the brain in research
efforts. The technique has also been investigated as a possible therapeutic
alternative to electroconvulsive therapy (ECT) for depression. But TMS, which
was developed in the 1980s, has been slow to catch on as a viable therapy
for psychiatric and neurological conditions because its effects have been
small, variable, and short-term.