CDK5 and Cognitive impairment: Its excessive phosphorylation by Tau regulatory kinases such as glycogen synthase kinase-3β (GSK-3β), mitogen-activated protein kinase (MAP kinase), cyclin-dependent kinase 5 (CDK5), cAMP-dependent protein kinase A (PKA), protein kinase C (PKC), etc. allows MTs depolymerisation leading to destabilization of MTs and the neuronal cytoskeleton and consequently impairs mitochondrial respiration, axonal transport, post-synaptic function as well as compromises cell signalling, resulting in cognitive impairments [27,32,33,34,35,36,37].