Effects of brain stimulation can be conditioned

Brain activity can be stimulated with transcranial magnetic stimulation.
Photo Credit: © RUB, Marquard

What worked with Pavlov's dog also works with an artificially induced change in nerve cell activity.

Researchers at the Ruhr University Bochum have succeeded in a special form of classic conditioning. In a group of 75 people, they showed that effects of transcranial magnetic stimulation, or TMS for short, can only be triggered by hearing a sound. Prof. Dr. Burkhard Pleger from the neurology of the Bergmannsheil University Hospital describes the results together with doctoral students Stefan Ewers and Timo Dreier as well as other colleagues in the journal Scientific Reports.

Magnetic stimulation causes the thumb muscle to contract

For the TMS, a magnetic coil is placed from the outside over a specific part of the brain. The strong magnetic field stimulates the underlying nerve cells to act. If you stimulate a certain area of the motor cortex in this way, the index finger or the thumb moves, for example. The Bochum team used the so-called paired pulse TMS stimulation for its work. Two TMS stimuli followed each other every twelve milliseconds, which leads to a stronger contraction of a muscle on the thumb than a TMS individual stimulation. In the conditioning phase, the researchers always combined these paired pulses TMS with a tone that the participants were presented via headphones parallel to the TMS stimulus.

Bochum research team: Burkhard Pleger (left) and Timo Dreier
Photo Credit: © RUB, Marquard

Muscle contraction is reinforced by conditioned tone

In the test phase, the participants no longer received a TMS double stimulation, but only a single TMS pulse - either paired with the conditioned tone or with a tone that the participants had not heard before. At the same time, the researchers again measured the strength of muscle contraction on the thumb. This was significantly stronger when the conditioned tone sounded compared to the tone that the test subjects had not heard during conditioning.

Conditioning could be useful for therapeutic applications

"Our basic research proves that classic conditioning does not only work with conscious behavior patterns," concludes Burkhard Pleger. “Hirn activity manipulated from the outside by brain stimulation can also be conditioned. "This is interesting because the TMS can also be used therapeutically, for example to improve mobility in people with Parkinson's disease or to treat depression. “The effects of the TMS are basically only of a temporary duration. They disappear if the stimulation is not continued. If these effects could be maintained by conditioned tones, the therapy could be significantly simplified,” Pleger describes a possible benefit of the work.

Funding: The work was funded by the Medical Faculty of the Ruhr University Bochum as part of the FoRUM program (F943R-2019).

Published in journal: Scientific Reports

Source/Credit: Ruhr University Bochum

Reference Number: ns042423_01

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