Fragile X syndrome is a form of syndromic autism whose genetic causes have been relatively well uncovered. It is actually mainly caused by a CGG triplet expansion in the 5’ UTR sequence of FMR1 gene, affecting mostly men. FMR1 encodes a mRNA binding protein which is involved in the regulation of local translation at the synaptic level. The mechanisms leading from such gene mutations to a neurodevelopmental disorder still need to be investigated. While several studies have shown that the neuronal development is driven by cellular activity and connectivity, we aim to further investigate the effect of FMR1 repression on the neuronal activity taking advantage of IPSC-derived neurons from patient’s cells. IPSC-derived neurons will be investigated through calcium imaging to characterized their pattern of spontaneous activities, as well as their capability to respond to neurotransmitter through extra-synaptic receptors. A multielectrode array approach is going to be used to analyse the overall network activities. Those studies should provide further information on the impairment of activity-dependent neuronal development in Fragile X syndrome.