The role of ethnicity and environment on the regulation of response to sensory stimuli in children : a neurophysiological study

Abstract

Background: The world is full of sensory stimuli and adaptation to this is necessary for childhood development. Adaptation involves regulation, a response to the demands of the environment through modifications at the neurophysiological level. The activity between parasympathetic and sympathetic branches of the autonomic nervous systems has been suggested to be appropriate measures of neurophysiological regulation. Various factors have been suggested to influence the neurophysiological regulation of response towards sensory stimuli. However, the role of ethnicity and environment has rarely been examined. Ethnicity refers to distinct populations that share biological origins and genetic similarities. On the other hand, the environment is defined as the geographic niche that serves as dwelling place among groups of individuals. Understanding the influence of ethnicity and the environment on the regulations of neurophysiological mechanism in response to external challenges can provide a better understanding of the development of adaptive abilities in children. Aim: This thesis aims to examine the role of ethnicity and environment of the regulation of response towards sensory stimuli among children using neurophysiological methods. It is hypothesised that children from different ethnicities and environments have significantly different regulation of response to sensory stimuli. Methods. There are four main hypotheses tested in this thesis that recruited 156 typically developing children ages 7-12 years old from different ethnic groups or environment: geographic (country of habitat) or physical (urban or rural setting) as follows: [1] 31 Chinese children living in Hong Kong (CHK); [2] 28 Filipino children living in Hong Kong (FHK); [3] 52 Filipino children who are living in urban areas (FU); and [4] 43 Filipino children who are living in rural areas (FR) in the Philippines. Heart rate variability (HRV) and electrodermal activity (EDA) were respectively recorded and measured using a Polar H2 heart rate monitor and the eSense GSR skin response sensor. Children were subjected to a sensory laboratory paradigm with a resting, auditory stimulation and recovery conditions. Neurophysiological measures of regulation of response to sensory stimuli between groupwise (CHK, FHK, FU and FR) and different pairwise (CHK and FHK, FHK and FU, CHK and FU, FU and FR) combinations at different conditions were tested using mixed factorial analysis of variance, multivariate analysis of variance and correlation set a p=0.05. Results: The pattern of neurophysiological regulation of response to sensory stimuli was generally similar across children from different ethnicities and environments. However, pairwise combinations between groups described the influence of ethnicity and environments on differences in the regulation of response to sensory stimuli using neurophysiological measure. The key findings in this thesis are: [1] Between children (CHK and FHK groups) with different ethnicities but lives in the same geographic environments (Hong Kong) and environment landscapes (urban setting), there is no significant difference in the LF n.u., high-frequency bands of HRV (HF n.u.) and skin conductance level/response (SCL/SCR) at resting (Δ= 0.01, F(3,11)= 0.20, p= 0.89, d= 0.21), stimulation (Δ= 0.03, F(3,11)= 0.52, p= 0.67, d= 0.34) and recovery (Δ= 0.00, F(3,11)= 0.05, p= 0.99, d= 0.10) conditions. [2] Between children (FHK and FU groups) with the same ethnicity (Filipino) but lives in different geographic environments (Hong Kong and Philippines) and similar environment landscapes (urban settings), there is significant difference in the LF n.u., HF n.u. and SCL/SCR at resting (Δ= 0.23, F(3,32)= 7.42, p<0.00, d= 1.08), stimulation (Δ= 0.14, F(3,32)= 4.26, p= 0.01, d= 0.82) and recovery (Δ= 0.10, F(3,32)= 2.712, p= 0.05, d= 0.65) conditions. [3] Between children (CHK and FU groups) with different ethnicities living in geographic environments (Hong Kong and Philippines) but similar environment landscapes (urban setting), there is significant difference in the LF n.u., HF n.u. and SCL/SCR) at resting (Δ= 0.17, F(3,38)= 5.60, p<0.00, d= 0.91), stimulation (Δ= 0.15, F(3,38)= 4.66, p= 0.01, d= 0.83) and recovery (Δ= .14, F(3,38)= 4.44, p= 0.001, d= 0.81) conditions. [4] Between children (FU and FR groups) from similar ethnicities (Filipinos) and geographic environments (Philippines) living in different physical environments (urban and rural setting) there is significant difference in the LF n.u., HF n.u. and SCL/SCR at resting (Δ= 0.19, F(3,11)= 7.29, p<0.00, d= 0.97), stimulation (Δ= 0.30, F(3,11)= 13.09, p<0.00, d= 1.31) and recovery (Δ= 0.14, F(3,11)= 5.00, p<0.00, d= 0.81) conditions. Conclusion: In this study, the neurophysiological autonomic activity among four groups of children (CHK, FHK, FU and FR) was examined. This thesis found that in response to sensory stimuli: 1) there are differences in the patterns of change in the SCL among CHK and FHK groups; and there are differences in the levels of autonomic activity between: a) FHK and FU groups; b) CHK and FU groups; and FU and FR group. To conclude, this thesis provides evidence on the influence of ethnicity and environments on the regulation of response to sensory stimuli using a neurophysiological perspective. The notion that autonomic activity as an underlying neurophysiologic mechanism that enables adaptation is further reinforced. The results of this study have implication on clinical, research and policy studies on the influence of the environment on children's response to sensory stimuli, as well as the implicit influence of migration on children's health, behaviour and well-being.