During brain development, billions of neuron nerve cells must find their accurate pathway in the brain in order to form trillions of neuronal circuits enabling cognitive, sensory and emotional wellbeing. To achieve this remarkable precision, migrating neurons use special protein receptors that sense the environment around them and guide the way so these neurons and their long extensions stay on the right path and avoid faulty turns. Rare defects in these neuronal guidance proteins can result in severe neurological conditions such as ataxia and epilepsy.