title: Parallel mechanisms encode direction in the retina.
abstract: In the retina, presynaptic inhibitory mechanisms that shape directionally selective (DS) responses in output ganglion cells are well established. However, the nature of inhibition-independent forms of directional selectivity remains poorly defined. Here, we describe a genetically specified set of ON-OFF DS ganglion cells (DSGCs) that code anterior motion. This entire population of DSGCs exhibits asymmetric dendritic arborizations that orientate toward the preferred direction. We demonstrate that morphological asymmetries along with nonlinear dendritic conductances generate a centrifugal (soma-to-dendrite) preference that does not critically depend upon, but works in parallel with the GABAergic circuitry. We also show that in symmetrical DSGCs, such dendritic DS mechanisms are aligned with, or are in opposition to, the inhibitory DS circuitry in distinct dendritic subfields where they differentially interact to promote or weaken directional preferences. Thus, pre- and postsynaptic DS mechanisms interact uniquely in distinct ganglion cell populations, enabling efficient DS coding under diverse conditions.
authors.affiliation: Department of Anatomy and Neurobiology, Dalhousie University, 5850 College Street, Halifax, NS B3H 1X5, Canada.
authors.forename: Stuart
authors.initials: S
authors.lastname: Trenholm
authors.forename: Kyle
authors.initials: K
authors.lastname: Johnson
authors.forename: Xiao
authors.initials: X
authors.lastname: Li
authors.forename: Robert G
authors.initials: RG
authors.lastname: Smith
authors.forename: Gautam B
authors.initials: GB
authors.lastname: Awatramani
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D003712:Dendrites / Q000502:physiology / Q000648:ultrastructure; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009039:Motion Perception / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation; D012160:Retina / Q000166:cytology / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000502:physiology* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology*
chemical_list: D049452:Green Fluorescent Proteins