Term: spiny projection neuron

Definition: A superficial spiny neuron sharing some somatodendritic features with SSNs (see above), is a projection cell also lying in the lateral part of the shell of the nucleus (Figs. 7B and 16, neuron 6). The soma of SPNs is usually pear-shaped, measuring from 22 to 32 micrometers in the longest axis. Three to six primary dendrites originate in the soma and give rise to short secondary or preterminal branches. Tertiary dendrites are longer (100 to 200 micrometers) than those from CSNs. An important, distinctive feature of SPNs is that secondary and successively distal dendrites are laden with dendritic spines.