A new type of brain stimulation device for combating difficult-to-treat cases of major depressive disorder is likely to break into the large American market soon. Its maker, Jerusalem-based Brainsway, plans to apply to the U.S. Food and Drug Administration for permission to market the device this month. The move follows initial results from a large-scale trial of the system, in which 30.4 percent of treated patients went into remission and 36.7 percent showed significant improvement. Research into device-based treatments for psychiatric problems has grown rapidly, and if the FDA gives its go-ahead, Brainsway’s system will become the fourth device-based therapy to go on the market since 2005.

Deep transcranial magnetic stimulation (TMS), as its name suggests, uses magnetic fields to stimulate activity in structures deep in the brain. The patient wears a helmet in which powerful, specially designed electromagnets have been carefully positioned. When a pulse of electricity flows through the magnets’ coils, the resulting magnetic field induces current to flow through a portion of the brain.

There are subtle differences between deep TMS and repetitive transcranial magnetic stimulation (rTMS), a brain stimulation tool widely used in research and also marketed as a treatment for depression. The electromagnetic elements in deep TMS are designed to produce a magnetic field that reaches its greatest strength deep within the brain. Ordinarily, magnetic fields fall away quickly inside the brain, but the orientation and structure of the coils in deep TMS lessens that effect. “The concept was to reduce the rate of reduction of the magnetic field as a function of distance,” says Abraham Zangen, coinventor of the technology. In contrast, rTMS typically uses a single coil that produces a tightly focused field just a few centimeters below the brain’s surface.

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In an unlikely marriage of quantum physics and neuroscience, tiny particles called quantum dots have been used to control brain cells for the first time.

Having such control over the brain could one day provide a non-invasive treatment for conditions such as Alzheimer’s disease, depression and epilepsy. In the nearer term, quantum dots could be used to treat blindness by reactivating damaged retinal cells.

“Many brain disorders are caused by imbalanced neural activity,” says Lih Lin at the University of Washington, Seattle. “Manipulation of specific neurons could permit the restoration of normal activity levels.”

Methods to stimulate the brain artificially already exist, though each has its drawbacks. Deep brain stimulation is used in Parkinson’s disease to trigger brain cell activity and prevent the abnormal signalling that causes debilitating tremors, but placing the electrodes required is highly invasive. Transcranial magnetic stimulation can stimulate brain cells from

outside the head, but is not highly targeted and so affects large areas of the brain at once. Researchers in optogenetics can control genetically modified brain cells using light but because of these modifications, the technique is not yet deemed safe to use in humans.

Lin’s team has now come up with an alternative using quantum dots – light-sensitive, semiconducting particles just a few nanometres in diameter.

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