Analysis of Parvocellular and Magnocellular Visual Pathways in Human Retina

Abstract

Two main subcortical pathways serving conscious visual perception are the midget-parvocellular (P), and the parasol-magnocellular (M) pathways. It is generally accepted that the P pathway serves red-green color vision, but the relative contribution of P and M pathways to spatial vision is a long-standing and unresolved issue. Here, we mapped the spatial sampling properties of P and M pathways across the human retina. Data were obtained from immunolabeled vertical sections of six postmortem male and female human donor retinas and imaged using high-resolution microscopy. Cone photoreceptors, OFF-midget bipolar cells (P pathway), OFF-diffuse bipolar (DB) types DB3a and DB3b (M pathway), and ganglion cells were counted along the temporal horizontal meridian, taking foveal spatial distortions (postreceptoral displacements) into account. We found that the density of OFF-midget bipolar and OFF-midget ganglion cells can support one-to-one connections to 1.05-mm (3.6°) eccentricity. One-to-one connections of cones to OFF-midget bipolar cells are present to at least 10-mm (35°) eccentricity. The OFF-midget ganglion cell array acuity is well-matched to photopic spatial acuity measures throughout the central 35°, but the OFF-parasol array acuity is well below photopic spatial acuity, supporting the view that the P pathway underlies high-acuity spatial vision. Outside the fovea, array acuity of both OFF-midget and OFF-DB cells exceeds psychophysical measures of photopic spatial acuity. We conclude that parasol and midget pathway bipolar cells deliver high-acuity spatial signals to the inner plexiform layer, but outside the fovea, this spatial resolution is lost at the level of ganglion cells.

Identification of retinal ganglion cell types expressing the transcription factor Satb2 in three primate species

“…The total ganglion cell density as estimated from RBPMS labeling decreased from an average of 10,428 cells/mm 2 at 1–3 mm eccentricity, SD = 4812, n = 7 ROIs) to 2969 cells/mm 2 at 3–6 mm eccentricity (SD = 1348; n = 12 ROIs) and declined further to 724 cells/mm 2 at 6–10.5 mm eccentricity (SD = 480; n = 7 ROIs) in temporal retina (Figure 7(a)). The total ganglion cell density determined here is consistent with previous estimates calculated from flat mount preparations (Curcio & Allen, 1990) and vertical sections (Masri et al, 2020) at equivalent eccentricities. The proportion of Satb2 positive ganglion cells in human retina increases slightly from an average of about 1% at 1.3–6 mm eccentricity to an average of 3.4% at eccentricities above 6 mm (Figure 7(b)).…”

Generative Models for Active Vision

“…Color vision could be incorporated simply by repeating section The Retinocortical Pathway for several different wavelengths of light-specifically, the red, green, and blue wavelengths detected by different cone photoreceptors (Nathans et al, 1986). This would aid in disambiguating the roles of magnocellular and parvocellular streams, involved in dissociable aspects of trichromatic and monochromatic vision (Masri et al, 2020). The magnocellular stream also seems to have a key role in detecting motion (Merigan et al, 1991) -something that is highly relevant in the context of active event recognition (Ognibene and Demiris, 2013).…”

Reduced Visual Magnocellular Event-Related Potentials in Developmental Dyslexia

“…This procedure separately stimulated the right or left parafoveal hemifields, avoiding the central foveal 5° of the visual field. Since there are far fewer magno- than parvocells in the fovea [ 18 ], avoiding stimulating the fovea prevented parvocell responses from dominating these recordings.…”