Animation provided by courtesy of a first author Rob Zink.
This research measures outdoor EEG to investigate how physical activity and cognitive distraction affect cognition. The experiment setup was in an outdoor setting, where participants were cycling. To perform such a study, the researchers used a wireless EEG device SMARTING.
The study focused on the P300 ERP component, associated with attentional processes. The research team reported that the complex outdoor setting modulates the P300 amplitude due to increased cognitive demand.
Understanding the Challenge
Typically, EEG studies were conducted in controlled environments to reduce external influences. Such settings do not adequately represent real-life situations that comes with its challenges.
Unconstrained setups can introduce new variable, such as body movement and increased muscle activity. These can lead to the movement artifacts that influence the data and so the results.
Previous studies already reported the decrease in P300 responses during outdoor tasks. involving walking compared to stationary indoor conditions. Some researchers speculate that the decrease in P300 amplitude in outdoor settings is the purely consequence of increased artifacts.
The researchers in this work challenged such a hypothesis. They analysed both, sensory (N100) and cognitive (P300) components of an ERP waveform. With such approach, they showed that the P300 amplitude was reduced due to increased cognitive demands, rather than due to movement artifacts.
Experiment Design and Outdoor EEG Equipment
15 healthy participants performed a three-tone auditory oddball task. The participants’ task was to silently count the target tones and ignore the two other tones. Eight subjects attended the lower (600 Hz) tone, and the others attended the high (1200 Hz) tone. The subjects’ attention to a certain tone should elicit a distinguishable P300, as compared to the non-attended tones.
The researchers covered the following three conditions: stationary (still), biking in a fixed position (pedal), and biking in an outdoor setting (move).
The participants in the study wore an acquisition PC tablet in the backpack. They ran the experiment in OpenVibe that recorded the outdoor EEG data and presented the auditory stimuli.
The outdoor EEG experiment conditions: Still, Pedal on a static bicycle and moveKey Findings
Two ERP components that were under investigation were the P300 and the N100 ERP.
While the P300 responses were above chance in all conditions, they were notably reduced during outdoor biking. N100 component did not differ between the three conditions. That was not surprising, as N100 is related to purely sensory auditory input.
Grand average ERPs to Target, Deviant and standard stimuli in the study. Far left is a still condition; pedal condition is in the middle; and the move condition is on the rightThis is in line with the authors hypothesis. The P300 was not reduced due to the increase in artifacts in the biking condition. If the artifacts were accountable for P300 reduction, the same would apply to the N100 amplitude.
Using Gyroscope data to confirm the hypothesis
The research team examined the impact of movement on brain signals using a 3-axis gyroscope. As anticipated, the gyroscope readings indicated more movement in the ‘move’, followed by ‘pedal’, and least in ‘still’ condition.
To analyse the relationship between motion and ERPs, they classified each subject’s trials based on movement intensity. The gyroscope data confirmed no significant effect of movement level on the P300 amplitude.
Decrease in alpha power in outdoor EEG also supported the hypothesis
Another interesting finding was a decrease in alpha power during the move condition. The alpha power decrease and P300 reduction both suggest the higher cognitive load and task difficulty. These results confirm that increased cognitive demands come from the outdoor, dynamic environment.
Influence on movement on the single-trial P300 accuracy
The study shows that P300 accuracy detection differs based on movement conditions. Accuracy was highest when participants were still and lowest when moving. Importantly, individuals with larger P300 amplitude had better accuracy, regardless of the condition. The data shows similar results even when the classification was performed on the training data from other two conditions.
Conclusions
This study’s findings support the usage of mobile EEG for outdoor studies. The outdoor EEG can assess the covert cognitive processes in real-time, even in complex environments. This way we may be closer to understand the distinctive neural responses in such environments.
The study provides robust evidence that the brain’s attentional resources lower when cognitive load increase. The findings could have essential implications in various neuroscience fields. For instance, these findings can translate to designing more efficient Brain-computer interfaces (BCI). It can help us understand how physical environments affect cognitive processing. This can finally lead to improving cognitive performance in complex and dynamic situations.
Despite the limitations of this study, this research opens a promising avenue for outdoor EEG in neuroscience. These results brings us one step closer to understanding our brain functions in the real-world and every day life.
The original paper source: https://iopscience.iop.org/article/10.1088/1741-2560/13/4/046017/meta
