Controlling brain thunderstorms

With the help of Helsinki University infrastructure funding, the Cognitive Brain Research Unit CBRU has acquired a transcranial magnetic stimulation (TMS) device. Being neither invasive nor painful, TMS breaks new ground for brain navigation and research.

Controlling brain thunderstorms

Our brain contains about 100 billion neurons that continuously communicate through electrical impulses - the basis for all perception and cognition. By means of quickly changing, strong magnetic fields, transcranial magnetic stimulation, or TMS, can affect these processes. The magnetic fields generate electricity, which may either stimulate or inhibit brain areas.

The Finnish Nexstim NBS4, a new TMS system with superior navigation accuracy, provides an exact mapping of a patient's brain before brain surgery. It may also be used therapeutically, for instance, in the treatment of depression or acoustic hallucinations.

"However, this device is not only the world's best system for clinical practice, it also takes brain research to a new level", states postdoctoral researcher Alina Leminen. Nextim NBS4 in the Cognitive Brain Research Unit at Siltavuorenpenger is the only one of this new type of TMS equipment in Nordic countries that solely serves research purposes. Inhibiting certain areas of the brain, for instance, helps researchers conclude which areas are responsible for what task. Take, for example, speech processing, one of the key research fields of HU’s CBRU. Researcher Leminen has been a participant herself:

“When my posterior temporal area was inhibited, I was shown a picture of a doll, but I involuntarily named it a teddy bear. This is how we learned which brain area was responsible for ascribing the meaning to an object.”

Alina Leminen holds a postdoctoral research position in a Finnish Academy research project until December 2013. The project aims at using naturalistic linguistic and visual stimuli in brain research. Research methods such as EEG, MEG, eye-tracking and TMS are combined in order to get a broader picture of cognitive processing.

“When testing the functional significance of a cortical area, we not only need to know where or when it happens, we need to consider both dimensions at the same time”, stresses Leminen.

TMS generates large magnetic fields in the brain; the field maximum might be as strong as in an MRI. Even when stimulating only one millimetre of the brain’s surface, tens of thousands of neurons are affected at the same time.

“This makes TMS much more complex than it may appear initially. It requires highly professional personnel to apply it in diagnosis and especially in therapy”, laboratory engineer Miika Leminen cautions. For instance, in order to obtain consistent responses to a stimulus, the coil must be adjusted very accurately in many dimensions, such as location and angle.

Cognitive Brain Research Unit CBRU »»

Research Database TUHAT: Alina Leminen »»

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Text: Claudia Gorr
Photo: Veikko Somerpuro
University of Helsinki, digital communications

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