CALCIUM-BINDING PROTEINS IMMUNOREACTIVITY IN THE HUMAN SUBCORTICAL AND CORTICAL VISUAL STRUCTURES

The distribution of neurons and fibers immunoreactive (ir) to the thre e calcium-binding proteins parvalbumin (PV), calbindin D-28k (CB), and calretinin (CR) was studied in the human lateral geniculate nucleus ( LGN), lateral inferior pulvinar, and optic radiation, and related to t hat in the visual cortex. In the LGN, PV, CR, and CB immunoreactivity was present in all laminae, slightly stronger in the magnocellular tha n in the parvocellular laminae for CB and CR. PV-ir puncta, representi ng transversally cut axons, and CR-ir fibers were revealed within the laminae and interlaminar zones, and just beyond the outer border of la mina 6 in the geniculate capsule. In the optic radiation both PV- and CR-immunoreactive neurons, puncta, and fibers were present. CB immunor eactivity was revealed in neurons of all laminae of the lateral genicu late nucleus, including S lamina and interlaminar zones. There were ha rdly any CB-ir puncta or fibers in the laminae, interlaminar zones, ge niculate capsule, or optic radiation. In the lateral inferior pulvinar , immunoreactive neurons for the three calcium-binding proteins were p resent in smaller number than in the LGN, as well as PV-ir puncta and CR-ir fibers within the nucleus and in the pulvinar capsule. In the wh ite matter underlying area 17, fibers intermingled with a few scattere d neurons were stained for both PV and CR, but very rarely for CB. The se fibers stopped at the limit between areas 17 and 18. Area 17 showed a dense plexus of PV-ir puncta and neurons in the thalamo-receptive l ayer IV and CR-ir puncta and neurons both in the superficial layers I- II, IIIC, and in layer VA. Cajal-Retzius CR-ir neurons were present in layer I. CB-ir puncta were almost confined to layer I-III and CB-ir n eurons to layer II. Finally the superior colliculus exhibited mostly p opulations of PV and CR pyramidal-like immunoreactive neurons, mainly in the intermediate tier. These data suggest that in the visual thalam us most calcium-binding protein immunoreactive neurons project to the visual cortex, while in the superior colliculus a smaller immunoreacti ve population represent projection neurons.