Synaptic mechanisms generating orientation selectivity in the on pathway of the rabbit retina

Sowmya Venkataramani, W. Rowland Taylor

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Neurons that signal the orientation of edges within the visual field have been widely studied in primary visual cortex. Much less is known about the mechanisms of orientation selectivity that arise earlier in the visual stream. Here we examine the synaptic and morphological properties of a subtype of orientation-selective ganglion cell in the rabbit retina. The receptive field has an excitatory ON center, flanked by excitatory OFF regions, a structure similar to simple cell receptive fields in primary visual cortex. Examination of the light-evoked postsynaptic currents in these ON-type orientation-selective ganglion cells (ON-OSGCs) reveals that synaptic input is mediated almost exclusively through the ON pathway. Orientation selectivity is generated by larger excitation for preferred relative to orthogonal stimuli, and conversely larger inhibition for orthogonal relative to preferred stimuli. Excitatory orientation selectivity arises in part from the morphology of the dendritic arbors. Blocking GABAA receptors reduces orientation selectivity of the inhibitory synaptic inputs and the spiking responses. Negative contrast stimuli in the flanking regions produce orientation-selective excitation in part by disinhibition of a tonic NMDA receptor-mediated input arising from ON bipolar cells. Comparison with earlier studies of OFF-type OSGCs indicates that diverse synaptic circuits have evolved in the retina to detect the orientation of edges in the visual input.

Original languageEnglish (US)
Pages (from-to)3336-3349
Number of pages14
JournalJournal of Neuroscience
Volume36
Issue number11
DOIs
StatePublished - Mar 16 2016

Keywords

  • Electrophysiology
  • NMDA receptors
  • Neural circuit
  • Receptive field
  • Retinal ganglion cell
  • Synaptic transmission

ASJC Scopus subject areas

  • Neuroscience(all)

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