EP 139. Cortical maturation during the first years of life as assessed by steady state flicker VEP

Abstract

Cognitive and motor development are closely coupled to structural and functional brain maturation during the first years of life. During this developmental period brain maturation is dominated by the differentiation and grow of dendritic arbours, forming of synapses and the axons of the cortical neurons get isolated by the myelin shade. Children with learning disabilities often show a delayed functional and structural maturation of their brain early in life. However most of these children are diagnosed only after the clinical symptoms are apparent. In order to diagnose a delayed maturation early quantitative markers are required. Several studies in the past have shown that evoked potentials can be used to assess brain maturation. Recently it was shown (Dubois et al., 2008), that the myelinisation as measured by T2-MR imaging and the latency parameters of flash visual evoked potentials (VEP) closely correlate during early development. Therefore VEPs could function as surrogate marker for myelinisation. However flash VEPs still show a range of variability that makes a conclusive judgment difficult. Most studies so far analyze VEP in the time domain. However the analysis of the VEP in frequency space delivers stable and reproducible results (Pieh et al., 2009). The aim of the study presented her was to establish a method to use steady state flicker VEP in order to assess brain development. We recorded VEP from children aged between 0 days and 12 years. Classical VEP were calculated using time-locked grand averages and the latency of the P100 components were measured. Second, we analyzed the steady state signal of the cortex to the presented visual stimuli. In order to do so the measured signal was transferred to the frequency space using a fast Fourier transformation. We analyzed the power of the first and second harmonic in relation to different visual stimulation frequencies presented. Using this data we could derived a synchronization parameter. We could show that this parameter closely correlates to the maturation of the classical VEP and therefore -according to (Dubois et al., 2008)- also to the maturation of myelinisation in general. To conclude we have derived a technique which delivers an objective and quantitative marker for brain development in young children using VEP.