Dendritic spikes amplify the synaptic signal to enhance detection of motion in a simulation of the direction-selective ganglion cell

Michael J. Schachter, Nicholas Oesch, Robert G. Smith, William Taylor

Research output: Contribution to journalArticle

46 Citations (Scopus)

Abstract

The On-Off direction-selective ganglion cell (DSGC) in mammalian retinas responds most strongly to a stimulus moving in a specific direction. The DSGC initiates spikes in its dendritic tree, which are thought to propagate to the soma with high probability. Both dendritic and somatic spikes in the DSGC display strong directional tuning, whereas somatic PSPs (postsynaptic potentials) are only weakly directional, indicating that spike generation includes marked enhancement of the directional signal. We used a realistic computational model based on anatomical and physiological measurements to determine the source of the enhancement. Our results indicate that the DSGC dendritic tree is partitioned into separate electrotonic regions, each summing its local excitatory and inhibitory synaptic inputs to initiate spikes. Within each local region the local spike threshold nonlinearly amplifies the preferred response over the null response on the basis of PSP amplitude. Using inhibitory conductances previously measured in DSGCs, the simulation results showed that inhibition is only sufficient to prevent spike initiation and cannot affect spike propagation. Therefore, inhibition will only act locally within the dendritic arbor. We identified the role of three mechanisms that generate directional selectivity (DS) in the local dendritic regions. First, a mechanism for DS intrinsic to the dendritic structure of the DSGC enhances DS on the null side of the cell's dendritic tree and weakens it on the preferred side. Second, spatially offset postsynaptic inhibition generates robust DS in the isolated dendritic tips but weak DS near the soma. Third, presynaptic DS is apparently necessary because it is more robust across the dendritic tree. The pre- and postsynaptic mechanisms together can overcome the local intrinsic DS. These local dendritic mechanisms can perform independent nonlinear computations to make a decision, and there could be analogous mechanisms within cortical circuitry.

Original languageEnglish (US)
Article numbere1000899
JournalPLoS Computational Biology
Volume6
Issue number8
DOIs
StatePublished - Aug 2010

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Selectivity
Spike
Ganglia
Motion
Cell
simulation
dendritic cells
Synaptic Potentials
Simulation
Dendritic Cells
Tuning
Carisoprodol
cells
Null
Enhancement
Null Lymphocytes
retina
Retina
Conductance
Direction compound

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience
  • Ecology
  • Molecular Biology
  • Genetics
  • Ecology, Evolution, Behavior and Systematics
  • Modeling and Simulation
  • Computational Theory and Mathematics

Cite this

Dendritic spikes amplify the synaptic signal to enhance detection of motion in a simulation of the direction-selective ganglion cell. / Schachter, Michael J.; Oesch, Nicholas; Smith, Robert G.; Taylor, William.

In: PLoS Computational Biology, Vol. 6, No. 8, e1000899, 08.2010.

Research output: Contribution to journalArticle

Schachter, Michael J. ; Oesch, Nicholas ; Smith, Robert G. ; Taylor, William. / Dendritic spikes amplify the synaptic signal to enhance detection of motion in a simulation of the direction-selective ganglion cell. In: PLoS Computational Biology. 2010 ; Vol. 6, No. 8.
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