One of the most common and best studied type of RNA editing in higher eukaryotes is the hydrolytic deamination of adenosine to inosine within doublestranded RNAs (dsRNAs), by the enzyme family adenosine deaminases acting on RNA (ADAR). As inosine base-pairs with cytidine (C), it is translated and reversetranscribed as a guanosine (G), changing the sequence of an RNA. ADAR1 edits cellular dsRNA to prevent aberrant activation of cytoplasmic antiviral dsRNA sensors and missense mutations, that change ADAR1 residues and reduce RNA editing activity, cause Aicardi-Goutieres Syndrome, a childhood encephalitis and interferonopathy. ADAR2 is most highly expressed in brain and it is primarily required for site-specific editing of glutamate receptor transcripts. Mutations in ADAR2 could contribute to excitability syndromes such as epilepsy, to seizures and to diseases involving neuronal plasticity defects.