Spikes and ribbon synapses in early vision

Trends Neurosci. 2013 Aug;36(8):480-8. doi: 10.1016/j.tins.2013.04.006. Epub 2013 May 22.


Image processing begins in the retina, where neurons respond with graded voltage changes that must be converted into spikes. This conversion from 'analog' to 'digital' coding is a fundamental transformation carried out by the visual system, but the mechanisms are still not well understood. Recent work demonstrates that, in vertebrates, graded-to-spiking conversion of the visual signal begins in the axonal system of bipolar cells (BCs), which transmit visual information through ribbon-type synapses specialized for responding to graded voltage signals. Here, we explore the evidence for and against the idea that ribbon synapses also transmit digital information. We then discuss the potential costs and benefits of digitization at different stages of visual pathways in vertebrates and invertebrates.

Keywords: action potential; analog-to-digital conversion; bipolar cell; retina; ribbon synapse; spike.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Action Potentials / physiology*
  • Animals
  • Models, Neurological
  • Retinal Bipolar Cells / physiology
  • Retinal Bipolar Cells / ultrastructure
  • Synapses / physiology*
  • Synapses / ultrastructure*
  • Visual Pathways / growth & development
  • Visual Pathways / physiology*
  • Visual Pathways / ultrastructure*