EEG Data Collection in Challenging Children: The Role of State in Data Quality and Spectral Power

Background:

Resting-state EEG is commonly recorded during an eyes-closed condition, free of sensory stimuli. In studies of young children or children with limited cognitive ability, this pure “resting state” is challenging to consistently capture. These children may be unable to follow directions to keep their eyes closed, and require some stimulus in order to remain engaged and calm, thus introducing more variability in state. Child state during the EEG recording may influence both the success of data acquisition and EEG variables (Webb et al., 2015). In order for EEG to be related to clinical relevant traits, this distinction between state and trait must be elucidated. This is especially salient when comparing children with ASD to TD children, who may systematically differ in terms of their state during the EEG recording.

Objectives:

We quantified the “state” of participants (ASD and TD) during EEG recording. We examined how state related to: (1) child characteristics (age, IQ, diagnosis), (2) EEG data quality (percent of data retained), and (3) EEG power, particularly focusing on alpha due to its documented relationship with the resting state, attention and emotion regulation.

Methods:

Participants included a heterogeneous group of children with ASD (N=39) ages 5-10, and an age-matched TD group (N=16). Specific strategies were used to acclimate participants to the EEG testing environment, including modeling, incremental practice and positive reinforcement. Resting EEG was recorded while participants watched a video of bouncing soap bubbles. The state of the participant during the EEG recording was rated using a 5-point likert scale (Perceived State Rating; PSR), where higher scores correspond to higher levels of anxiety/agitation.

Results: EEG data was successfully collected 85% of participants with ASD. Participants with ASD were significantly more likely to have PSR above 1 than TD participants (p=0.002). Percent of EEG data retained was not related to chronological age, verbal IQ or non-verbal IQ. In the ASD group, significantly less data was retained in participants with PSR 2-5 compared with PSR 1 (t=3.22, p=0.003). Using linear regression, PSR significantly predicted percent of data retained (t=-2.69, p=.01), while VIQ, NVIQ and chronological age were not significant (p-values .17-.74). Children in the TD group had significantly higher alpha power compared with children in the ASD group (p-values 0.003-0.036). Within the ASD group, participants with high PSR had the lowest frontal alpha (t=2.49, p=0.02).

Conclusions: Given appropriate supportive strategies, EEG data can be successfully collected from children across cognitive and language levels. The child’s state during the EEG recording was significantly related to both the amount of EEG data retained, and alpha spectral power. Alpha suppression has been consistently linked to attention and vigilance (Boiten et al., 1992; Klimesch, 1999), suggesting that reduced alpha power in children with an elevated state rating may reflect that these participants were less “at rest” during the EEG recording. These data highlight the importance of quantifying and addressing state when conducting EEG studies with challenging participants, both to increase data retention rates, and to reduce the influence of state on EEG variables of interest.