An MEG neuroimaging study on the developmental changes of face processing in pre-school aged children

Abstract

Event Abstract Back to Event An MEG neuroimaging study on the developmental changes of face processing in pre-school aged children Wei He1*, Jon Brock1 and Blake W. Johnson1 1 Macquarie University, Department of Cognitive Science, Australia Introduction: An important research question in developmental neuroscience concerns how the underlying neural mechanisms of face perception develop in early childhood. Magnetoencephalography (MEG) holds great promise for examining this question, because it measures a well-known face sensitive brain response, termed the M170, from young children in an entirely passive manner. The M170 and its electrical equivalent N170 discriminate faces from other non-face objects based on larger amplitudes to face stimuli around 170 ms from stimulus onsets in adults (Rossion & Jacques, 2011). The current study measured the M170 from pre-schoolers using a unique child custom-sized magnetoencephalography (MEG) system (Johnson et al., 2010). Furthermore, we evaluated the effective connectivity of cortical networks underlying the M170 using dynamic causal modelling (DCM); and compared the connectivity patterns in children to those of adults. Methods: Brain responses were measured from 15 young children (aged 4.46 ± 0.93 years) and 15 adults (aged 27.6 ± 6.46 years) during flashing pictures of faces, cars, as well as their phase-scrambled counterparts (Kuefner et al, 2010). There were 64 channels in the child MEG system and 160 channels in the adult MEG system. Surface waveforms were analysed by averaging the strongest response across occipital and temporal sensors separately on each hemisphere based on the time window determined by visual checking on individual data. DCM analyses assumed that the M170 was mediated by sources in the occipital face area (OFA), fusiform face area (FFA), and superior temporal sulcus (STS). Using Bayesian model selection, we evaluated three models of the interconnections between these regions based on previous studies using DCM (Fairhall & Ishai, 2007; Chen, et al., 2009; David et al., 2006). Results: In the surface waveform analysis, the child M170 was slower than the adult M170, but it already showed an adult function pattern (i.e., faster and stronger to faces than cars). Analyses of DCM models showed that the first and simplest model with only forward intra-hemispheric connections from OFA to FFA and STS had the largest model evidence in adults, while in children, the second model with extra inter-hemispheric connections between OFA and contralateral FFA showed the largest model evidence. Conclusions: Early face sensitive brain responses indexed by the M170 are present and functioning in the adult pattern in children as young as 4 years old. However, the functional neural mechanism underlying the M170 undergoes further development and fine-tuning before it reaches adult capacities. Acknowledgements This work was supported by Australian Research Council Linkage Infrastructure Equipment and Facilities Grant LEO668421, Australian Research Council Linkage Project Grant LP0669471, and the Australian Research Council Centre of Excellence for Cognition and its Disorders (CE110001021), http://www.ccd.edu.au. The authors thank Romina Polermo and Douglas Cheyne for helpful comments during the design of the experiment and Bruno Russion for providing the picture stimuli.