The balance of CDK5 activation and its phosphorylation of different substrates is key for the proper performance of the neural network, synapses and for neuronal plasticity; changes that may affect this balance have been associated with pathological conditions such as AD, amyotrophic lateral sclerosis, Parkinson's disease and cerebral ischemia, among other disorders (Ip and Tsai, 2008). The gene discussed is CDK5; the disease is Alzheimer disease.