Neurophysiological Investigation of the Pretectal Nucleus lentiformis mesencephali in <i>Rana pipiens</i>

Abstract

Previous studies have demonstrated that the large-celled, optic pretectal nucleus lentiformis mesencephali (nLM) is essential for horizontal optokinetic nystagmus, yet little is known about its neurophysiology. In the present study, single-unit analysis of nLM utilized a large-field, patterned stimulus presented for 8 directions and 3 velocities of movement. All units localized in nLM were spontaneously active, motion sensitive, with response profiles that ranged from strongly directional and narrowly tuned to asymmetric and broadly tuned. Only about one-third of the units could be classified as directional, and no response bias for horizontal or temporal-to-nasal motion was observed. The majority of directional units showed greatest responsiveness at the lowest stimulus velocity, while the reverse occurred for many broadly tuned units. These low-velocity, highly directional units may be comparable to the ''retinal slip'' neurons recently described in the large-celled pretectal nucleus of mammals. Directional information in the nLM of Rana pipiens thus appears to be represented in the activity of a large population of motion-sensitive units which includes both narrowly and broadly tuned individual response profiles. These results are consistent with the population-coding hypothesis recently advanced to account for directional coding in other sensorimotor systems, including primate motor cortex and superior colliculus.

It's not all black and white: visual scene parameters influence optokinetic reflex performance in Xenopus laevis tadpoles

“…The information for both motion directions, i.e. temporonasal and naso-temporal, is likely processed in separate channels, which begin with motion-sensitive retinal ganglion cells and project as separate signaling pathways to different premotor nuclei in the pretectum (Fite et al, 1989;Masseck and Hoffmann, 2009b).…”

Visual Responses of Neurons in the Pretectal Nucleus lentiformis mesencephali to Moving Patterns Within and Beyond Receptive Fields in Pigeons

“…Traditionally, large-field stimuli such as random-dots or checks [Hoffmann and Distler, 1989;Volchan et al, 1989;Klauer et al, 1990;Fan et al, 1995;Li et al, 1996], stripes [Fite et al, 1989;Fu et al, 1998a, b], or gratings [Ibbotson and Mark, 1996] have been used to study the visual response properties of optokinetic neurons in various species of animals. The present study provides electrophysiological evidence that motion of a random-dot pattern outside the receptive field does not exert any obvious influence on the visual responses of pigeon nLM cells, regardless of the direction, velocity, and onset time of motion over a large region surrounding the receptive field.…”

“…However, large-field stimulation is needed for both repeatedly stimulating a single cell and simultaneously stimulating an assembly of optokinetic cells. Thus, the direction and magnitude of optokinetic nystagmus could be coded by activity patterns of groups of optokinetic cells [Lee et al, 1988;Fite et al, 1989;Fu et al, 1998a].…”

“…In these studies, large-field patterns are usually used to evoke visual responses in neurons within these optokinetic nuclei. These patterns are composed of random dots or checks [Hoffmann and Distler, 1989;Volchan et al, 1989;Klauer et al, 1990;Fan et al, 1995;Li et al, 1996], stripes [Fite et al, 1989;Fu et al, 1998a, b], or sine-wave gratings [Ibbotson and Mark, 1996] that frequently cover the whole screen at which the animal looks. Therefore, we asked whether stimulation in a large region beyond the receptive field could affect the visual responsiveness of optokinetic neurons in the pigeon nLM.…”

Telencephalic projections to the nucleus of the basal optic root and pretectal nucleus lentiformis mesencephali in pigeons

“…of the AOS is homologous to the medial and lateral terminal nucleĩ MTN, LTN! of the mammalian AOS~Simpson, 1984;McKenna & Wallman, 1985a;Fite, 1985;Weber, 1985;Simpson et al, 1988a!. It has been shown in several species that AOS and pretectal neurons have large receptive fields in the contralateral visual field and exhibit direction selectivity to large-field moving visual stimuli~e.g., NOT: Collewijn, 1975a,b;Hoffmann & Schoppmann, 1975Hoffmann et al, 1988;Hoffmann & Distler, 1989;Volchan et al, 1989;Mustari & Fuchs, 1990;Distler & Hoffmann, 1993;Ibbotson et al, 1994;Ilg & Hoffmann, 1996;LM: Katte & Hoffmann, 1980;McKenna & Wallman, 1985b;Winterson & Brauth, 1985;Fite et al, 1989;Fan et al, 1995;Wylie & Frost, 1996;Wylie & Crowder, 2000;MTN0LTN: Grasse & Cynader, 1982, 1984Cooper & Magnin, 1986;Natal & Britto, 1987;Soodak & Simpson, 1988;nBOR: Burns & Wallman 1981;Morgan & Frost 1981;Gioanni et al, 1984;Rosenberg & Ariel, 1990;Wylie & Frost, 1990a!. The nBOR and LM receive primary input from the contralateral retina~Karten et al., 1977;Reiner et al, 1979;Fite et al, 1981;Gamlin & Cohen, 1988a!, and nonretinal afferents include~1! a heavy reciprocal connection between LM and nBOR~Clarke, 1977;...…”