“…The distinction between these two cell types was first established by Burke and Sefton (5446,331) working in the rat LGNd, and the two types have subsequently been identified in the cat LGNd (194,274,279,313). In response to a single shock applied to the optic tract, P-cells are characterized by a single spike followed by a prolonged inhibitory phase, and LGNd illustrating interneuronal connections and connections from visual cortex and reticular formation on a principal cell (P) and an interneuron (I).…”