Zapping the brain with a weak magnetic pulse can wipe out unwanted neural connections, in mice at least.

The discovery could lead to treatment for conditions associated with abnormal neural circuitry, such as schizophrenia.

In transcranial magnetic stimulation (TMS), a magnetic coil induces electric currents in the brain that can strengthen or suppress neural connections. This technique has been shown to improve symptoms in people with brain disorders such as autism and depression.

Now, Jennifer Rodger from the University of Western Australia in Crawley and colleagues have found that stimulating the brain at intensities lower than would make a neuron fire can remove unwanted neural connections in mice.

Rodger used low-intensity, pulsed magnetic field stimulation (PMF) on the rodents’ superior colliculus (SC), which is involved in motion detection. In these mice, 90 per cent of the axons in the SC had extended into the wrong areas, making it difficult for the rodents to follow moving objects in their line of sight.

After treatment, tissue analysis showed that only 45 per cent of the abnormal axons were still there. “The axons that weren’t in the right place were wiped out,” says Rodger. After treatment the mice were also better at tracking objects.

Ref.: Jennifer Rodger et al., Transcranial pulsed magnetic field stimulation facilitates reorganization of abnormal neural circuits and corrects behavioral deficits without disrupting normal connectivity, The FASEB Journal, 2012 [DOI: 10.1096/fj.11-194878]