ERP markers are associated with neurodevelopmental outcomes in 1-5 month old infants in rural Africa and the UK

Abstract

Introduction: Infants and children in low- and middle-income countries are frequently exposed to a range of poverty-related risk factors, increasing their likelihood of poor neurodevelopmental outcomes. There is a need for culturally objective markers, which can be used to study infants from birth, thereby enabling early identification and ultimately intervention during a critical time of neurodevelopment.

Method: In this paper, we investigate developmental changes in auditory event related potentials (ERP) associated with habituation and novelty detection in infants between 1 and 5 months living in the United Kingdom and The Gambia, West Africa. Previous research reports that whereas newborns' ERP responses are increased when presented with stimuli of higher intensity, this sensory driven response decreases over the first few months of life, giving rise to a cognitively driven, novelty-based response. Anthropometric measures were obtained concurrently with the ERP measures at 1 and 5 months of age. Neurodevelopmental outcome was measured using the Mullen Scales of Early Learning (MSEL) at 5 months of age.

Results: The described developmental change was observed in the UK cohort, who exhibited an intensity-based response at 1 month and a novelty-based response at 5 months of age. This change was accompanied by greater habituation to stimulus intensity at 5 compared to 1 month. In the Gambian cohort we did not see a change from an intensity-to a novelty-based response, and no change in habituation to stimulus intensity across the two age points. The degree of change from an intensity towards a novelty-based response was further found to be associated with MSEL scores at 5 months of infant age, whereas infants' growth between 1 and 5 months was not.

Discussion: Our study highlights the utility of ERP-based markers to study young infants in rural Africa. By implementing a well-established paradigm in a previously understudied population we have demonstrated its use as a culturally objective tool to better understand early learning in diverse settings world-wide. Results offer insight into the neurodevelopmental processes underpinning early neurocognitive development, which may in the future contribute to early identification of infants at heightened risk of adverse neurodevelopmental outcome.

Keywords: Event related potentials; Global health; Habituation; Infants; Neurodevelopment; Novelty detection.

Fig. 1

Rates of data retention at 1 and 5 month age points in UK cohort.

Fig. 2

Rates of data retention at 1 and 5 month age points in Gambian cohort.

Fig. 3

Schematic of stimulus presentation. Presented were three categories of stimuli: Frequent sounds consisting of 500 Hz pure tones were presented at 80% probability, Infrequent sounds, consisting of white noise segments presented at 10% probability and Trial Unique sounds also presented at 10% probability and consisting of clicks, pure tones of different frequencies or digitized vocalizations. Trial Unique sounds were different at each presentation and each only presented once during a session.

Fig. 4

BRIGHT EEG testing set up. Shown are the electrode montage during data acquisition (left) and the testing set up at the 1-month (middle) and 5-month age point (right).

Fig. 5

ERP waveforms for the UK cohort (top row) and the Gambian cohort (bottom row) at 1 month (left) and 5 month (right) of age. Displayed are micro voltage changes elicited by Frequent (blue), Infrequent (red) and Trial Unique (yellow) sounds. Time windows over which mean amplitudes for each component were assessed are highlighted.

Fig. 6

P3 amplitude change between 1 and 5 months of age for Frequent, Infrequent and Trial Unique sounds in the UK cohort UK and the Gambian cohort. Error bars indicate 95% confidence intervals.

Fig. 7

Differences in P3 mean amplitude between first and second half of recording session, per Condition, Age and Cohort. Higher scores indicate a response decrement between the first and the second half of the session. Scores close to 0 indicate no amplitude change over the course of the session.

Fig. 8

Correlation of ΔP3 and MSEL cognitive composite score at 5 months for the Gambian (blue diamonds) and UK (green circles) cohort. ΔP3 and MSEL scores were significantly correlated in both cohorts with larger ΔP3 scores being associated with higher MSEL composite scores.