The Effect of Baseline on Toddler Event-Related Mu-Rhythm Modulation

Abstract

Event-related mu-rhythm activity has become a common tool for the investigation of different socio-cognitive processes in pediatric populations. The estimation of the mu-rhythm desynchronization/synchronization (mu-ERD/ERS) in a specific task is usually computed in relation to a baseline condition. In the present study, we investigated the effect that different types of baseline might have on toddler mu-ERD/ERS related to an action observation (AO) and action execution (AE) task. Specifically, we compared mu-ERD/ERS values computed using as a baseline: (1) the observation of a static image (BL1) and (2) a period of stillness (BL2). Our results showed that the majority of the subjects suppressed the mu-rhythm in response to the task and presented a greater mu-ERD for one of the two baselines. In some cases, one of the two baselines was not even able to produce a significant mu-ERD, and the preferred baseline varied among subjects even if most of them were more sensitive to the BL1, thus suggesting that this could be a good baseline to elicit mu-rhythm modulations in toddlers. These results recommended some considerations for the design and analysis of mu-rhythm studies involving pediatric subjects: in particular, the importance of verifying the mu-rhythm activity during baseline, the relevance of single-subject analysis, the possibility of including more than one baseline condition, and caution in the choice of the baseline and in the interpretation of the results of studies investigating mu-rhythm activity in pediatric populations.

Impact of the baseline temporal selection on the ERD/ERS analysis for Motor Imagery-based BCI

“…In previous studies [10], [9], the optimal baseline was found to be subject-dependent, with no common preferred baseline for all subjects. Such a time-specific analysis of the ERD should be performed on our data and could confirm these inter-subject variability findings.…”

“…Since ERD is a ratio, the estimation of ERD is directly related to the selection of the baseline used to compute it [3], [9]. Several studies have already shown that the selection of the nature of the baseline is significant and could affect the visualization of ERD/ERS [10], [9]. In particular, Tangwiriyasakul et al, used five different baseline movies in a motion imagery task and showed that the majority of the subjects had significantly higher mu power for particular baseline conditions, thus resulting in more pronounced mu ERD [9].…”

“…In particular, Tangwiriyasakul et al, used five different baseline movies in a motion imagery task and showed that the majority of the subjects had significantly higher mu power for particular baseline conditions, thus resulting in more pronounced mu ERD [9]. Another study showed that a baseline taken during a static image seems better (i.e., lead to a larger ERD) compared to a baseline taken during a period of stillness [10]. While the selection of the nature of the baseline seems to affect the visualized ERD, the effect of the time at which the baseline is selected is not well-documented.…”