Learning behind movement studied

A brain chemical called GABA is the reason why “some people dance like Fred Astaire – while others have the natural rhythm of Ann Widdecombe”, the Daily Mail has reported.

The news is based on a study involving 12 healthy young adults who had their brains stimulated with electrodes to alter levels of GABA, one of the main chemicals regulating the transmission of electrical impulses in the brain. The subjects’ brain activity and reaction speed were then tested while they learned a task involving pressing buttons in response to visual cues, with the researchers looking at how performance related to normal and altered GABA levels.

Though of scientific interest, this experimental scenario was carried out in very few people and has only limited direct implications. The study only assessed each individual’s ability in one test of time reaction, and the results cannot be applied to other types of movement, including dance. The findings would also require replication in much larger numbers of people, with different tests of movement, before GABA could be considered to be responsible for our capacity to learn movement.

Where did the story come from?

The study was carried out by researchers from the Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), at the University of Oxford, and was funded by the Wellcome Trust and the National Institute for Health Research Biomedical Research Centre, Oxford. The study was published in the peer-reviewed scientific journal Current Biology.

What kind of research was this?

This was a laboratory study that aimed to investigate the role a brain chemical called GABA plays in the learning of movement. GABA (γ-aminobutyric acid) is one of the main chemicals involved in regulating the transmission of electrical impulses through the nervous system, and also has a direct effect upon muscle tone. Its main overall effect is in muscle relaxation. The researchers theorised that variation between people in the responsiveness of their GABA system could influence their capacity to learn new movements, and they wanted to test the theory.

The news has greatly oversimplified this scientific laboratory study, which used artificial methods to alter levels of GABA and assess how this affected learned finger movements. The study had nothing to do with dancing. The study, though enhancing our understanding of nervous activity and chemical transmission, does not provide a complete explanation of GABA’s role in learning movement.

What did the research involve?

The research involved a technique known as transcranial direct current stimulation (tDCS), which is known to decrease GABA, thus increasing nerve transmission and enhancing short-term learning. tDCS is performed by running a small current across two electrodes, one placed over the right side of the head and one over the left. The authors say that they used tDCS because of time constraints, as prolonged periods performing complex visual-motor tasks are required to alter GABA levels naturally, and their study could not allow for this. They anticipated that individuals with lower levels of GABA due to tDCS would demonstrate less activity in motor areas of the brain when learning new movements, and also demonstrate less behavioural evidence of learning.

The researchers recruited 12 healthy young adults (average age 23) who took part in three testing sessions on different days. In the first two sessions, 10 minutes of tDCS were delivered to the brain with the activity of brain chemicals measured before and after using a scanning technique known as magnetic resonance spectroscopy (MRS). In particular, the researchers were interested in activity in the areas of the brain controlling hand movements and vision. The researchers assessed brain metabolic activity and obtained a 15-minute spectrum of GABA activity prior to stimulation and in the 20 minutes immediately after stimulation.

Session three did not involve tDCS. Participants performed a task of visually-cued reaction time while brain images were taken. The task involved participants trying to learn a pattern of button pressing on a small keypad using just four fingers. While performing the tasks functional magnetic resonance imaging (fMRI) was taken. fMRI is a special type of MRI brain scan that allows measurement of activity of the nervous system. It does this through observing changes in blood flow. Transcranial stimulation was then repeated to reduce the GABA in participants' brains by applying a small current, as in session one. The participants were asked to repeat the sequencing task while their brain activity was reassessed using fMRI.

What were the basic results?

In session three the researchers noted variation in motor learning ability across the 12 individuals, although, generally, as the number sequences got harder, reaction times decreased in all participants. MRS showed a correlation between mean reaction time during the sequencing tests and the baseline levels of GABA (GABA levels before tDCS was performed), with those with higher GABA levels having slower reaction times.

As expected, GABA release decreased following tDCS, but the degree of decrease varied and correlated with the person’s reaction times and their level of brain nervous activity (people with better reaction times showed greater decrease in GABA levels).

How did the researchers interpret the results?

The authors conclude that the responsiveness of the GABA system in the individual could have an effect upon the short-term ability of a person to learn new movements.

Conclusion

This research is of scientific interest, and demonstrates the responsiveness of chemical transmitters in the central nervous system when undergoing direct stimulation. It also examines how this relates to a person’s capacity to learn a new motor activity.

However, this experimental scenario in 12 people has limited direct implications. The study only assessed each individual’s ability in one test of time reaction, and the results cannot be applied to all other areas of movement, such as dance. Also, it is not possible to attribute the effect to GABA alone, as other chemical transmitters could be involved. As the authors acknowledge, it may be that their measure of GABA is a surrogate marker for other chemical changes that are taking place and having a direct effect. The findings would require replication in much larger numbers of people, with different tests of movement, before the theory that GABA is responsible for our capacity to learn movement could be confirmed.