title: A circuit model for saccadic suppression in the superior colliculus.
abstract: Attenuation of visual activity in the superficial layers (SLs), stratum griseum superficiale and stratum opticum, of the superior colliculus during saccades may contribute to reducing perceptual blur during saccades and also may help prevent subsequent unwanted saccades. GABAergic neurons in the intermediate, premotor, layer (SGI), stratum griseum intermedium, send an inhibitory input to SL. This pathway provided the basis for a model proposing that the SGI premotor cells that project to brainstem gaze centers and discharge before saccades also activate neighboring GABAergic neurons that suppress saccade-induced visual activity in SL. The in vitro method allowed us to test this model. We made whole-cell patch-clamp recordings in collicular slices from either rats or GAD67-GFP knock-in mice, in which GABAergic neurons could be identified by their expression of green fluorescence protein (GFP). Antidromic electrical stimulation of SGI premotor cells was produced by applying pulse currents in which their axons congregate after exiting the superior colliculus. The stimulation evoked monosynaptic EPSCs in SGI GABAergic neurons that project to SL, as would be predicted if these neurons receive excitatory input from the premotor cells. Second, IPSCs were evoked in SL neurons, some of which project to the visual thalamus. These IPSCs were polysynaptically mediated by the GABAergic neurons that were excited by the antidromically activated SGI neurons. These results support the hypothesis that collaterals of premotor neuron axons excite GABAergic neurons that inhibit SL visuosensory cells.
authors.affiliation: National Institute for Physiological Sciences, Okazaki 444-8585, Japan.
authors.forename: Penphimon
authors.initials: P
authors.lastname: Phongphanphanee
authors.forename: Fengxia
authors.initials: F
authors.lastname: Mizuno
authors.forename: Psyche H
authors.initials: PH
authors.lastname: Lee
authors.forename: Yuchio
authors.initials: Y
authors.lastname: Yanagawa
authors.forename: Tadashi
authors.initials: T
authors.lastname: Isa
authors.forename: William C
authors.initials: WC
authors.lastname: Hall
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D030801:Animals, Genetically Modified; D000831:Animals, Newborn; D001703:Biophysics; D004558:Electric Stimulation / Q000379:methods; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D005968:Glutamate Decarboxylase / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics; D066298:In Vitro Techniques; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008959:Models, Neurological; D009415:Nerve Net / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D018408:Patch-Clamp Techniques / Q000379:methods; D011724:Pyridazines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects; D012438:Saccades / Q000502:physiology*; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013477:Superior Colliculi / Q000166:cytology* / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D014633:Valine / Q000031:analogs & derivatives / Q000494:pharmacology; D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D011724:Pyridazines; D026941:Sodium Channel Blockers; D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate; D049452:Green Fluorescent Proteins; D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; C056639:2-amino-5-phosphopentanoic acid; C049853:gabazine; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1; D014633:Valine