Microcircuitry for two types of achromatic ganglion cell in primate fovea

J Neurosci. 2007 Mar 7;27(10):2646-53. doi: 10.1523/JNEUROSCI.4739-06.2007.


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 +/- 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 +/- 5; DB2, 48 +/- 4. A complete parasol cell (30 microm dendritic field diameter) would collect from approximately 50 cones via approximately 120 bipolar and approximately 85 amacrine contacts; a complete garland cell (25 microm dendritic field) would collect from approximately 40 cones via approximately 75 bipolar and approximately 145 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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amacrine Cells / physiology
  • Animals
  • Cell Communication
  • Dendrites / physiology
  • Dendrites / ultrastructure
  • Fovea Centralis / cytology*
  • Fovea Centralis / physiology*
  • Fovea Centralis / ultrastructure
  • Image Processing, Computer-Assisted
  • Macaca fascicularis
  • Male
  • Microscopy, Electron
  • Neural Pathways / physiology
  • Retinal Bipolar Cells / classification
  • Retinal Bipolar Cells / physiology*
  • Retinal Bipolar Cells / ultrastructure
  • Retinal Cone Photoreceptor Cells / physiology
  • Synapses / physiology*