Transmission of scotopic signals from the rod to rod-bipolar cell in the mammalian retina

W. Rowland Taylor, Robert G. Smith

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


Mammals can see at low scotopic light levels where only 1 rod in several thousand transduces a photon. The single photon signal is transmitted to the brain by the ganglion cell, which collects signals from more than 1000 rods to provide enough amplification. If the system were linear, such convergence would increase the neural noise enough to overwhelm the tiny rod signal. Recent studies provide evidence for a threshold nonlinearity in the rod to rod bipolar synapse, which removes much of the background neural noise. We argue that the height of the threshold should be 0.85 times the amplitude of the single photon signal, consistent with the saturation observed for the single photon signal. At this level, the rate of false positive events due to neural noise would be masked by the higher rate of dark thermal events. The evidence presented suggests that this synapse is optimized to transmit the single photon signal at low scotopic light levels.

Original languageEnglish (US)
Pages (from-to)3269-3276
Number of pages8
JournalVision Research
Issue number28 SPEC.ISS.
StatePublished - Dec 2004
Externally publishedYes


  • Photoreceptor
  • Retina
  • Scotopic vision
  • Single photon
  • Synaptic transmission
  • Visual threshold

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems


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