In addition, knock down of RSK by RNAi in Aplysia sensory neurons impairs LTF, suggesting that this may be a useful single-cell system to study aspects of defective synaptic plasticity in Coffin-Lowry Syndrome (CLS), a cognitive disorder that is caused by mutations in rsk2 and associated with deficits in learning and memory. This evidence concerns the gene RPS6KA2 and cognitive disorder.