Auditory and visual novelty processing in normally-developing Kenyan children

Abstract

Objective: The aim of this study was to describe the normative development of the electrophysiological response to auditory and visual novelty in children living in rural Kenya.

Methods: We examined event-related potentials (ERPs) elicited by novel auditory and visual stimuli in 178 normally-developing children aged 4-12 years (86 boys, mean 6.7 years, SD 1.8 years and 92 girls, mean 6.6 years, SD 1.5 years) who were living in rural Kenya.

Results: The latency of early components (auditory P1 and visual N170) decreased with age and their amplitudes also tended to decrease with age. The changes in longer-latency components (Auditory N2, P3a and visual Nc, P3a) were more modality-specific; the N2 amplitude to novel stimuli decreased with age and the auditory P3a increased in both latency and amplitude with age. The Nc amplitude decreased with age while visual P3a amplitude tended to increase, though not linearly.

Conclusions: The changes in the timing and magnitude of early-latency ERPs likely reflect brain maturational processes. The age-related changes to auditory stimuli generally occurred later than those to visual stimuli suggesting that visual processing matures faster than auditory processing.

Significance: ERPs may be used to assess children's cognitive development in rural areas of Africa.

Fig. 1

Visual representation of the auditory and visual paradigms. In the auditory experiment (left panel), the dark dot represents the frequent stimuli, the light dot, the infrequent stimuli and the pictures represent novel noises. The left panel consists of a frequently presented face (labelled 1), an infrequent face (2) and abstract paintings (3) used in the visual experiment.

Fig. 2

Grand averaged auditory ERP traces for frequent, infrequent and novel stimuli by age-group at midline scalp sites.

Fig. 3

Normal development of auditory novelty processing in school-age children. Each line-graph shows plots of ERP components (latency and amplitude) averaged at midline electrodes (Fz, FCz, Cz, Pz) as a function of age-group.

Fig. 4

Grand average visual ERP traces for frequent, infrequent and novel stimuli by age-group at midline scalp sites. The visual P3a and Nc components. The N170 component is not shown here as it was derived from T5/T6 electrode.

Fig. 5

Normal development of visual novelty processing in school-age children. Line-graphs for N170 show ERP components (latency and amplitude) averaged at T5 and T6, while P3a and Nc are averaged at Midlines (Fz, FCz, Cz, Pz) as a function of age-group. Data for 4–5 year olds not available for the N170.