Correlations between the structural and functional characteristics of neurons in the superficial laminae and the hamster's superior colliculus.

Intracellular recording, receptive field mapping, and horseradish peroxidase (HRP) injection techniques were used to determine the structural and functional characteristics of neurons in the superficial laminae (stratum griseum superficiale and stratum opticum) of the hamster's superior colliculus (SC). Fifty-nine neurons (from 38 different hamsters) were successfully characterized, injected with HRP, and recovered. Of these, 8 were marginal cells, 14 had stellate morphology, 10 had narrow, vertically oriented dendritic trees, 12 had wide, vertically oriented dendritic arbors, and 8 were horizontal cells. Seven neurons had somatodendritic morphologies which did not fall into any of these groups. Overall, the distribution of receptive field properties for these cells matched that obtained in previous extracellular recordings from the superficial SC laminae in this species (Chalupa, L.M., and R.W. Rhoades (1977) J. Physiol. (Lond.) 270: 595-626; Chalupa, L.M. and R.W. Rhoades (1978) J. Physiol. (Lond.) 274: 571-592). There were significant correlations between receptive field properties and morphology. Sixty-four percent of the stellate cells and 75% of the marginal cells were directionally selective. Only 17% of the other cell types exhibited this response property. In addition, only 36% of the stellate cells and 25% of the marginal neurons were discharged by stationary, flashed spots. Eighty-one percent of the other recovered cells gave reliable responses to such stimuli. Stellate and marginal cells could also be differentiated from the other cell types on the basis of speed selectivity. Only 29% of the stellate and 13% of the marginal cells responded to stimulus speeds in excess of 20 degrees/sec.(ABSTRACT TRUNCATED AT 250 WORDS)