Plasticity in the Athletic Brain

Animation of an MRI
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Athletes are known to be quicker, stronger, more agile and more accurate when compared to non-athletes. There is something different happening in the brains of these athletes. Plastic changes are occurring in their brains, where the neuronal circuits in their brains are either being rewired or enforced. Plasticity has replaced the view that our brains are static, but our brains are changing throughout our entire life [1]. Plasticity has already been shown in many studies with piano players, where the more they practiced playing the piano, the more their brains (motor cortex) had changed [2]. This same concept can be applied to athletes as well, but on a broader spectrum as many athletes use many parts of their body at once, so multiple areas as well as other changes may be occurring.

1.1 Non-Invasive Neuroimaging Techniques

Non-invasive neuroimaging techniques are used to measure the brain activity in humans, as well as many animals. These techniques are used to look at the cognitive and motor processing in the brains of athletes [3]. EEG, fMRI and TMS are 3 techniques that are vital to studying the changes in the brain.

1.1a EEG

Using electroencephalography (EEG), is one way to measure functional brain activity. Synaptic currents generate the signal and it produces a very high temporal resolution (order of milliseconds) [3]. In one study, they used an EEG to show that expert tennis players when compared to novice ones, showed changes in different brain regions. By using an EEG, you can show that elite players show more neural efficiency when compared to novice players [4].

TMS stimulation
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TMS stimulation over the motor cortex in an elite athlete (Jensen et al., 2005)

1.1b fMRI

Functional magnetic resonance imaging (fMRI) measures blood oxygenation level dependent (BOLD), and it measures the hemoglobin activity in the brain. It indirectly measures neuronal activity while it directly measures the de-oxygenation state of the brain [3]. This is another technique that can be used to measure changes happening in the brains of athletes.

1.1c TMS

By using transcranial magnetic stimulation (TMS), you can activate the brain by using a magnetic field over the scalp of an individual. You can activate or inhibit different parts of the brain by using TMS [3].
In one study, they used TMS to show that there were differences in the motor maps of elite tennis players between their playing hand and non-playing hand [3]. TMS shows us that different muscles have a unique response to different types of training. It shows us how the central nervous system adapts after different types of training to different muscles.

2.1 Different brain regions which show plastic changes

Many brain regions experience plastic changes as an athlete is training or playing. In elite athletes, the brain regions which showed the greatest increase in connection density were areas related to sensorimotor, attentional, and default systems. A study was done with elite gymnasts showing that there were distinct differences in ten brain regions when compared to controls: left precentral gyrus, left postcentral gyrus, right anterior angulate gyrus, temporal lobes, right superior temporal gyrus, left temporal pole, superior temporal gyrus, and right middle temporal gyrus. All of these regions showed a higher regional efficiency in the brain [5]. There are anatomical and physiological changes in the primary motor cortex which correspond to acquiring a new skill. When there is a change at the cortical level, there is also a change seen in the how the spinal nerve circuits transmit their signal [6].

2.1a Connectivity changes within different regions of the brain

Brain regions that show plastic changes
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Changes in different brain regions in elite gymnasts (Wang et al., 2013)

There are many brain regions which show plastic changes, and these changes are attributable to changes within the connectivity within the brain. There may be activation of some of these connections which are deemed relevant to the training that is occurring, but there may also be deactivation to some irrelevant connections [3].
In elite tennis players, cortical motor maps in their playing hand are different than their non-playing hand. This suggests an increase in activation in connections in the motor maps of their playing hand and deactivation of connections in their non-playing hand as it is not relevant to them [4]. Certain muscles must get activated at a certain time for a particular movement to happen, so the nervous system accounts for this by changing connections within the brain [1].
Many brain regions seem to be more efficient and this may be due to shorter connections between different networks in the brain. This process must still make sure that the proper muscles are activated in the right order at the right time [1].

2.1b Imagery and mirror neurons in the brains of athletes

When an athlete visualizes their sport being performed, there is an increase in the activity of their mirror neurons. This is specific to their sport, as shown in a study with ballet dancer, their mirror neurons were more activated only when watching ballet as opposed to other dance routines [3]. Another study with tennis players showed that there was increased corticospinal activity when watching a tennis swing when, but not when watching a golf swing [3]. As well, in expert high jumpers, their motor areas are activated in the pre motor cortex and cerebellum when visualizing a high jump. They also show that there are many equivalent changes seen in the brain when watching the sport or performing it [7].

Grey matter density
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Increases in grey matter density in the brains of athletes compared to non-athletes (Gaoxia et al., 2009)

2.2 White matter and grey matter changes in plasticity

While playing different sports, there are white and grey matter changes in the brain. A study involving diving players showed that they had an increase of grey matter in the thalamus and left precentral gyrus. The thalamus is shown to be associated with motor skills, as when there is a lesion, there are disturbances in performing those motor skills. The left precentral gyrus is shown to be important in execution of certain movements and motor planning [8]. In badminton players, there was an increase in grey in the cerebellum (specifically the right anterior and posterior lobes), so the cerebellum had therefore enlarged [9]. This then shows that the athlete is executing more advanced motor skills. The enlarged cerebellum may also show that the athlete has better hand-eye coordination.
As well, a study with world class gymnasts showed that these athletes experienced changes in their white matter. This was shown to be helpful in developing the gymnasts’ specific motor skills. An increase in white matter translates to an increase in myelination. This also showed that there was an increase in the fractional anisotropy in the cerebrospinal tract of the champions when compared to controls. The axis of diffusion was more restrictive, possibly meaning a faster signal [5].

3.1 Motor skill training produces plastic changes in the brain

While performing a motor skill, it causes plastic changes to occur in the brain. If an athlete is working on their speed or accuracy, then there will be changes in the primary motor cortex [4]. The primary motor cortex plays a role when someone is trying to acquire a new skill [6].
The changes happening in the brains of elite athletes are very specific to the skill that they are practicing. In expert golfers, there seems to be more activity in the superiorparietal cortex, lateral dorsal premotor cortex, and the occipital lobes. If someone who is not an expert at golf who is practicing golf, they will show activation all over the brain [4]. This shows that expert golf players are able to filter out what information is no important to their training, while novice players are unable to do this. Another example of this is with elite volleyball players, where only the motor maps for the hand muscles they use while playing are increased in the primary motor cortex [4].

Skill Acquisition
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The time it takes to learn a specific motor skill (Yarrow et al., 2009)

3.2 Strength training produces plastic changes in the brain

Strength training also leads to changes in the brain. There were changes in the spinal cord, where its functional properties had changed [10]. There were also changes in the representation of the muscles (expansion of them) that were being strengthened [6]. This expansion is more correlated to how the muscle is used in the training, not just the muscle itself [1]. These changes in the brain lead to increase muscle strength and muscle coordination [6]. Each muscle responds differently to the training that it receives [10].

3.3 Repeated training leads to longer lasting brain changes

By executing motor skills during daily training, you can find plastic changes in the brain where there are reinforced networks [3]. This is done through extensive repeated training over many days and weeks. In the motor cortex, there is an increase in the neuronal firing rate as well as an increase in the number of synapses [3]. As a player continues to practice, there is less of an effort required to perform the skill. A player’s MEP max (motor evoked potential) is increased when there is daily training [6]. In the brain, the volume of the primary cortex is enlarged with more training [4]. There is also an increase in the motor cortical excitability of the muscle that is undergoing repeated training [6]. It also does not matter what type of training occurs (motor skill or strength training), there will be increased corticospinal activity when there is repeated training. If a player keeps repeating a task over and over, they will essentially become better at that certain task. The long lasting changes in the brain are more pronounced if the task is more engaging, and therefore more difficult to perfect [1].

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5. Wang, B., Fan, Y., Lu, M., Li, S., & Song, Z. (2013). Brain anatomical networks in world class gymnasts: A dti tractography study. Neuroimage, 65, 476-87.
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7. Olsson, C., Jonsson, B., Larsson, A., & Nyberg, L. (2008). Motor representations and practice affect brain systems underlying imagery: an fmri study of internal imagery in novice and active high jumpers. Open Neuroimaging Journal, 2, 5-13.
8. Gaoxia, W., Jing, L., & Youfa, L. (2009). Brain structure in diving players on MR imaging studied with voxel-based morphometry. Progress in Natural Science,19(10), 1397-1402.
9. Di, X., Zhu, S., Jin, H., Wang, P., & Yi, Z. (2012). Altered resting brain function and structure in professional badminton players. Brain Connectivity, 2(4), 225-33.
10. Kidgell, D., & Pearce, A. (2011). What has transcranial magnetic stimulation taught us about neural adaptations to strength training. J Strength Cond Res, 25(11), 3208-17.

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