The superior colliculus (SC) is a part of midbrain network that plays a crucial role in attention. Inhibitory interneurons in the SC regulate the information streams that involve in sensory processing. Here the authors demonstrate that, the population of inhibitory interneurons in the SC can be immunohistochemically classified into subgroups based on their expression of calcium-binding proteins, such as paNalbumin (PV) and calbindin (Calb)
While PV-immunoreactive neurons distributed all over the layers of the SC, Calb-immunoreactive neurons appeared only in superficial layer. Furthermore, Calb-immunoreactive neurons in the superficial layer distributed in two separate sub layers, grey layer and optic layer, in which, neurons in grey layer were clearly oriented and polarized. The number of Calb-immunoreactive neurons in the superficial layer was higher than that of PV-immunoreactive neurons. Furthermore, the size of Calb-immunoreactive neurons in the optic layer was bigger than those of grey layer and PV-immunoreactive neurons in the superficial layer.