Mechanisms regulating input-output function and plasticity of neurons in the absence of FMRP

The function of brain circuits relies on high-fidelity information transfer within neurons. Synaptic inputs arrive primarily at dendrites, where they undergo integration and summation throughout the somatodendritic domain, ultimately leading to the generation of precise patterns of action potentials. Emerging evidence suggests that the ability of neurons to transfer synaptic information and modulate their output is impaired in a number of neurodevelopmental disorders including Fragile X Syndrome. In this review we summarise recent findings that have revealed the pathophysiological and plasticity mechanisms that alter the ability of neurons in sensory and limbic circuits to reliably code information in the absence of FMRP. We examine which aspects of this transform may result directly from the loss of FMRP and those that a result from compensatory or homeostatic alterations to neuronal function. Dissection of the mechanisms leading to altered input-output function of neurons in the absence of FMRP and their effects on regulating neuronal plasticity throughout development could have important implications for potential therapies for Fragile X Syndrome, including directing the timing and duration of different treatment options.