Feature Article: Evolution of Isocortical Organization. A Tentative Scenario Including Roles of Reelin, p35/cdk5 and the Subplate Zone

摘要: This paper proposes an evolutionary hypothesis for the origin of (i) inside-out pattern mammalian corticogenesis in which late-generated cells become located more superficially than early-generated cells, and (ii) predominantly radial organization isocortical inputs mammals. It is suggested that outside-in neurogenetic gradient (in are cells), as occurs reptilian cortex, would have positioned late-produced, associative neurons (destined to supragranular layers modern isocortex) below early-produced output neurons. may limited possibilities synaptic contacts between younger afferent terminals were superficial layer I. There was probably adaptive benefit those individuals late-produced capable passing through already migrated thus making with afferents generating corticocortical local circuits processed information before producing output. Reelin, extracellular glycoprotein found I, a cyclin-dependent kinase (cdk5) its neuronal-specific activator (p35) played key roles generation gradient. Additionally, by serving waiting compartment thalamic axons while cortical plate develops, subplate zone participated change from emphasis tangential arrangement characteristic cortex mode termination observed isocortex.