Cell Types of the Neocortex
In principle, we distinguish between projec-tion neurons with long axons (excitatory gluta-matergic pyramidal cells) and interneuronswith short axons (inhibitory GABAergic inter-neurons).
The pyramidal cell (A1) is characterized by one apical dendrite (A2), which ascends to the molecular layer and branches there, and numerous basal dendrites (A3). Its de-scending axon gives off numerous recurrent collaterals (A4). The cell-deficient molecu-lar layer (layer I) contains Cajal – Retzius cells (A5) with tangentially running axons. The different types of granule cells or stellate cells are predominantly interneurons and are found in all layers at various densities. They include Martinotti’s cells (A6), the ver-tically ascending axons of which ramify in various cortical layers and reach as far as the molecular layer. The cellules à doublebouquet dendritique of Cajal, cells with twovertically oriented dendritic trees (A7) (pri-marily in layers II, III, and IV), possess long ascending or descending axons. The axon of some stellate cell types arborizes after a short course (A8), or it bifurcates and termi-nates with basketlike networks (basketcells) (A9) on adjacent pyramidal cells. Axonbifurcations may run horizontally and ter-minate on distant pyramidal cells (A10). Their inhibitory function has been con-firmed by detection of GABA in the synapses of basket cells.