TECHNOLOGY

A Magnetic BoostActivating certain neurons may alleviate depression

Up to 40 percent of people with depression do not respond to anti-depressant medication. For these patients, hope may come in the form of transcranial magnetic stim-ulation, or TMS, a technique that acti-vates neurons by sending pulses of magnetic energy into the brain.

Although researchers have been studying the effects of TMS on depression for more than 10 years, it has been largely viewed as an experi-mental procedure because of con-cerns about safety issues, such as seizures. Now psychiatrists at the Uni-versity of Pennsylvania report suc-cessful results from the largest-ever trial of TMS, countering many critics’ doubts. The team tested about 300 patients with major depression who had failed to respond to medication and found that those who received about 40 minutes of TMS daily for four weeks experienced signifi cant symp-tomatic improvement. No major side effects were reported, although the technique is not recommended for anyone with a history of seizures.

TMS delivers its neuron-activating magnetic fi eld via small metallic coils attached to the scalp, which investi-

gators can position to target specifi c brain areas. In this study, the team tar geted a region of the prefrontal cor-tex previously shown to be less active in depressed subjects. BecauseTMS is both noninvasive and precise in aim, the technique readily lends itself to unusual research, from triggering ordinary people’s inner mathematical savant to studying the root of religious experience (in its incarnation as the “God helmet” [see “Searching for God in the Brain,” by David Biello; SciAmMind, October/November 2007]).

Although TMS is already available to patients in Australia and Canada, stricter regulations mean it could be several months to years before patients in the U.S. have access to the therapy, says John O’Reardon, lead author of the new study. He and other experts believe that eventually TMS will also help patients with schizophrenia, bipolar disorder and Tourette’s syndrome. —Erica Westly

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SPEECH

Wait, Don’t Tell Me … The brain region responsible for that word on the tip of your tongue

We all know the maddening experience of not being able to think of a certain word that is un-doubtedly in our repertoire. Now researchers have discovered an association between a specifi c region in the neural language system and these tip-of-the-tongue (TOT) experiences, which are a normal part of aging. Deborah Burke of Pomona College and her team found that TOT moments became more frequent as gray matter density in the left insula declined. This area of the brain has been impli-cated in sound processing and production. The fi ndings support a mod-el proposed by Burke and her colleagues, which predicts that when we do not often use a word the connections among all its various represen-tations in the brain become weak. “Words aren’t stored as a unit,” Burke says. “Instead you have the sound information connected to semantic information, connected to grammatical information, and so on. But the sounds are much more vulnerable to decay over time than other kinds of information, and that leads to the TOT experience.” —Nicole Branan

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