Microcircuitry for Two Types of Achromatic Ganglion Cell in Primate Fovea

Abstract

Synaptic circuits in primate fovea have been quantified for midget/parvocellular ganglion cells. Here, based on partial reconstructions from serial electron micrographs, we quantify synaptic circuits for two other types of ganglion cell: the familiar parasol/magnocellular cell and a smaller type, termed "garland." The excitatory circuits both derive from two types of OFF diffuse cone bipolar cell, DB3 and DB2, which collected unselectively from at least 6 Ϯ 1 cones, including the S type. Cone contacts to DB3 dendrites were usually located between neighboring triads, whereas half of the cone contacts to DB2 were triad associated. Ribbon outputs were as follows: DB3, 69 Ϯ 5; DB2, 48 Ϯ 4. A complete parasol cell (30 m dendritic field diameter) would collect from ϳ50 cones via ϳ120 bipolar and ϳ85 amacrine contacts; a complete garland cell (25 m dendritic field) would collect from ϳ40 cones via ϳ75 bipolar and ϳ145 amacrine contacts. The bipolar types contributed differently: the parasol cell received most contacts (60%) from DB3, whereas the garland cell received most contacts (67%) from DB2. We hypothesize that DB3 is a transient bipolar cell and that DB2 is sustained. This would be consistent with their relative inputs to the brisk-transient (parasol) ganglion cell. The garland cell, with its high proportion of DB2 inputs plus its high proportion of amacrine synapses (70%) and dense mosaic, might correspond to the local-edge cell in nonprimate retinas, which serves finer acuity at low temporal frequencies. The convergence of S cones onto both types could contribute S-cone input for cortical areas primary visual cortex and the middle temporal area.

Identification of myopia-associated WNT7B polymorphisms provides insights into the mechanism underlying the development of myopia

“…Together with our findings indicating that WNT7B was localized to retinal ganglion cells and that its expression was significantly upregulated in experimental myopic eyes, these data support the hypothesis that WNT7B and GJD2 co-operatively regulate the normal growth of the eye through interactions between the alpha-ganglion cells and AII amacrine cells. Interestingly, alpha-ganglion cells are predominantly observed in the peripheral retina and have large dendritic regions to receive inputs from amacrine cells 47,[53][54][55][56][57] . The hypothesis that alpha- ganglion cells and AII amacrine cells are implicated in emmetropization is consistent with the peripheral defocus theory, a theory of myopia development that has been supported by clinical evidence [58][59][60][61] .…”

Functional architecture of the retina: Development and disease

“…Another ganglion cell type in macaque retina, the parasol ganglion cells, displays much more convergence compared to midget ganglion cells (Jacoby et al, 2000). Serial section electron micrographic reconstructions of the synaptic connectivity of a foveal parasol retinal ganglion cell has revealed that each cell pools input from ~ 50 cones via ~ 120 bipolar cells (Calkins and Sterling, 2007). This enables the parasol cells to encode for luminance.…”

Retinal connectomics: Towards complete, accurate networks

“…Previous TEM montaging efforts produced only arrays of single images for humans to track as stacks of photographs or low resolution digital files. For neuroscience, this meant that legacy ultrastructural anatomy, which (albeit heroic in scope) actually delivered only a broad-brush concepts and only fragments of retinal networks at best (Calkins and Sterling, 1996; 2007; Calkins et al, 1998; Klug et al, 2003; Kolb and Famiglietti, 1974b; Kolb and Nelson, 1993; Stevens et al, 1980; Strettoi et al, 1992). That said, these studies discovered the baseline network for understanding signal flow in the retina.…”