Remember that sodium channels are necessary for action potentials to take place. When a neuron receives a signal from a presynaptic cell, the membrane on the postsynaptic cell depolarized slightly. When this occurs, if the membrane reaches a certain threshold, voltage-gated sodium channels will open, allowing sodium ions to rush into the neuron. If these channels were non-functional, the neuron would be unable to depolarize, therefore inhibiting its ability to produce an action potential. This would keep the neuron from communicating with other cells. I hope this helps you!