Current between the ears…

 "Current between the ears" 

In the weekend edition of a major Dutch newspaper (called the Volkskrant), the science section immediately got my attention. "Current between the ears". Since most people seem to have a brain between their ears, this article might be telling us about neural stimulation.

And so it did! It describes a technique called ‘Transcranial Direct Current Stimulation’ (tDCS). Two external electrodes are placed on the head of the subject. By sending a DC current in the order of 1mA through these electrodes the brain functionality can be influenced.

At the positive electrode, the tissue potential is slightly elevated. This means that the threshold for neurons to become activated is decreased and therefore the part of the brain close to the positive electrode becomes more active. The opposite holds for the negative electrode: this part becomes less active.

In this way it is possible to either stimulate or suppress particular neural functions. It can for example be used to temporarily increase the memory ability of the brain. Or to suppress mechanisms that lead to addiction. Or to help depression patients by suppressing the part that is associated with bad feelings.

The big advantage of this technology is obviously that is is non-invasive. That must however also be a disadvantage. To support 1mA currents, the electrode must be quite big in order not to exceed their charge injection limitations. This means that the spatial resolution of this method must be quite poor: a relatively large area is affected using this method. 

Nevertheless the article shows some interesting results, both obtained by the department of Developmental Psychology of the UvA and by research groups throughout the world. Once again it shows the fascinating world that opens up as soon as we apply (electrical) technology to the most complex organ we have: our brain.

Marijn van Dongen 

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