Conduction velocity distribution of the retinal input to the hamster's superior colliculus and a correlation with receptive field characteristics

Abstract

Cells driven reliably by shocks delivered to the optic nerve or optic chiasm were encountered throughout the depth of the colliculus. The incidence of such cells, however, decreased markedly in the laminae ventral to the stratum opticum. The distribution of conduction velocities for the retinal afferents to the tectum was quite broad (range: 1.7-25.5 m/sec) and clearly biomodal with peaks at about 6 and 12 m/sec. A small number of cells were innervated by rapidly (greater than 15 m/sec) conducting axons. No evidence of an indirect-fast pathway from the retina to the colliculus via the lateral geniculate nucleus and visual cortex was obtained. Afferent conduction velocity was not correlated with retinal eccentricity, collicular depth or speed selectivity. It was, however, clearly related to directional selectivity. Ninety percent of the tectal neurons receiving inputs from axons having conduction velocities of less than 5 m/sec were directionally selective while only 41% of those neurons innervated by more rapidly conducting fibers (greater than 5 m/sec) exhibited selectivity. One hundred and sixteen cells in the anterior portion of the colliculus were tested with shocks delivered to the ipsilateral optic nerve and photic stimulation of the ipsilateral eye. Of these, 11% exhibited some degree of binocularity and only 6% were responsive to optic nerve shocks. These electrophysiological findings were correalted with the limited nature of the retinal input to the ipsilateral superior colliculus.

Effects of neonatal enucleation on the functional organization of the superior colliculus in the golden hamster.

“…This has never been observed in normal hamsters (Tiao & Blakemore, 1976;Chalupa & Rhoades, 1977;Finlay et al 1978;Rhoades & Chalupa, 1979) nor was it seen in the colliculus contralateral to the remaining eye in the experimental animals. Of the fifty-one extravisual and multimodal cells that were isolated in the laminae Fig.…”

“…3 and these data are again in good agreement with those which have been reported for normal animals of this species (Tiao & Blakemore, 1976;Chalupa & Rhoades, 1977;Finlay et at. 1978;Rhoades & Chalupa, 1979 The data for the colliculus ipsilateral to the remaining eye are qualitatively different. Of the 384 units recorded in 119 electrode penetrations on this side (see Table 1 B) only 330/ (n = 127) were exclusively visual.…”

“…0022-3751/80/7650-0993 $07.50 © 1980 The Physiological Society INTRODUCTION Numerous anatomical experiments have demonstrated that the visual and extra, visual inputs to the mammalian superior colliculus are largely segregated. The retinal (Laties & Sprague, 1966;Wilson & Toyne, 1970;Frost, 1975;Graybiel, 1975;Lund & Lund, 1976;Chalupa & Rhoades, 1979) and visual cortical (Lund, 1966;Garey, Jones & Powell, 1968;Wilson & Toyne, 1970;Kawamura, Sprague & Niimi, 1974; afferents terminate for the most part in the superficial tectal laminae and the extravisual inputs innervate neurones in the layers ventral to the stratum opticum (Kuypers & Lawrence, 1967;Garey et al 1968;Paula-Barbosa & SousaPinto, 1973;Antonetty & Webster, 1975;Moore, Karapas & Moore, 1977;Wise & Jones, 1977).…”

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

“…In the rodent, the results of several studies (e.g., Fukuda, 1977, Rhoades andChalupa, 1979;Chalupa and Thompson, 1980;Linden and Perry, 1983) have indicated that all classes of retinal ganglion cells send axons to the SC. There is, however, evidence from both cats and rodents that the finer and more slowly conducting axons terminate most superficially, whereas larger caliber axons innervate the deeper parts of the SGS and SO (e.g., Mcllw'ain and Lufkin, 1976;Mcllwain, 1978;Bowling and Michael, 1980;Behan, 1981;Hofbauer and Drgger, 1981;ltoh et al, 1981;Mize, 1983;Sachs and Schneider, 1984).…”

“…In hamsters, the only significant correlation between the conduction velocity of retinal afferents and SC receptive fields was with respect to direction selectivity. Rhoades and Chalupa (1979) reported that directionally selective neurons had a strong tendency to be driven by slowly conducting retinal axons. Those data fit well with our current finding that stellate and especially marginal cells were directionally selective more often than other morphological types.…”