Our ability to balance can vary based on factors such as age, attention and fatigue. Failing to maintain balance can lead to falls and injuries, especially when multi-tasking.
One complex balancing exercise is slacklining. Research shows that slackline training improves postural stability and balance, making it a valuable exercise for sports training and clinical settings. Also, practicing complex balancing tasks can help prevent falls in older individuals.
Dual-tasking (DT) often involves cognitive-motor interference (CMI), where performance in one or both tasks is reduced. This shows that the brain can only handle so much at once and focuses more on keeping the body balanced and safe.
EEG is a common method for assessing CMI. The P3 component of event-related potentials (ERPs) is linked to cognitive resource allocation and processing speed. Studies have shown that P3 amplitudes decrease and latencies increase during DT compared to single-tasking (ST).
Most CMI research has been conducted in controlled laboratory settings. But, recent advances in mobile EEG technology allow for the study of natural movements in real-world conditions. Let’s take a look at this setup!
(A) Participant is walking a slackline in the park. (B) Experimental procedure.All the recordings were done outside, in a city park. Researchers used mbt’s EEG system to record data on a mobile phone, which was also used for presenting auditory stimuli.
Next to EEG, they also recorded motion data – gyroscope data from the EEG amp itself + accelerometer data from the phone. All is synched using LSL protocol, on one phone (located in the pocket!)
In the beginning, 18 participants stood still on the ground while recording a baseline period. After that, they performed 3 different conditions.
What were these conditions? Scientists wanted to compare standing on a slackline and on ground, while doing an auditory task. Then, they also included a condition of just slacklining, without any extra tasks. These conditions were repeated 6 times, each lasting 2 minutes.
For the auditory task, the study used an oddball paradigm. Participants hear 2 different tones in a random fashion, where one of the tones is a target one. They had to count appearances of target tones only. Target occurs with 15% probability, and non-target (distractor) tones is 85%.
A closer look at the equipment: Smarting amp and cap are placed on the head and are wirelessly sending data to the mobile phone. To play the oddball task, the study used Neurobs Presentation app + a pair of wired earphones.P300 component shows no significant difference in Standing vs. Slackline
The study looked into ERP responses at the posterior-central scalp area – Pz electrode. Based on resulting topographies, researchers found that this area showed P300 component maxima. This also aligns with previous studies.
Showing P3 component for both standing and slacklining conditions. We can clearly see a difference in the brain’s response between target (deviant) and standard sound in both cases. On the left side of both plots, we can see the topography showing P3 activity on all electrode sites.The study found a significant effect of stimulus type on P3 amplitude. But, contrary to their hypothesis, type of movement (stand vs. slackline) didn’t affect P3 amplitudes or latencies. We can see the boxplots representing these conclusions below:
(A) P3 latency between 2 movement conditions. Same participants are connected with the grey line. In the picture, we can see that the difference is “ns” = not significant. (B) Same plot is shown for amplitude differences between conditions. The difference was also ”ns”. However, we can also see the amplitude distribution for the standard sound, next to deviant. We can see it reached statistical difference.A relatively short task duration could be the cause too. But balancing on a slackline longer than 2 mins would be challenging even for more experienced participants. As a result, the shorter task run has probably led to a lower cognitive load then expected.
Correlation between Skill and P3 morphology
Correlation between skill and P3 (A) Latency and (B) Amplitude. A Spearman’s correlation test found no significant correlation in (B), but found significant correlation in (A); rho = -0.513, p = 0.029.Individual differences in motor skills influenced the results. They suggest that individuals with higher motor skills experienced the task effort as moderate, while others experienced a higher task load. Thus, researchers concluded that motor skill differences significantly influence the strength of P3 dual-tasking effects.
Movement during different conditions and it’s correlation with skill level
There was significant difference in postural sway between standing and slacklining. What’s interesting is comparing slacklining (ST) and slacklining + oddball task (DT). The study found more acceleration in ST condition compared to DT.
They noted that expert athletes often perform better under DT conditions, which might be seen in the experienced slackliners here. Participants might have prioritized their posture during DT to avoid falls, supporting the posture-first hypothesis. This hypothesis states that resources are allocated to motor tasks to ensure physical integrity during DT.
The study also found there was no significant correlation between movement data and skill level.
Another metric to look into is participant’s performance. The short task duration in this study might have positively influenced accuracies. Participants achieved over 95% accuracy in both conditions!
As with previous metrics, lower task load through the stationary scenario and short runs may explain these results.
In summary, the study shows that it’s possible to use mobile EEG to measure brain activity during balancing tasks. Also, that both cognitive and motor activities might use the same mental resources, which are often thought to be just cognitive.
You can find the original paper linked here.
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