Spatially reciprocal inhibition of inhibition within a stimulus selection network in the avian midbrain.
Reciprocal inhibition between inhibitory projection neurons has been proposed as the most efficient circuit motif to achieve the flexible selection of one stimulus among competing alternatives. However, whether such a motif exists in networks that mediate selection is unclear. Here, we study the connectivity within the nucleus isthmi pars magnocellularis (Imc), a GABAergic nucleus that mediates competitive selection in the midbrain stimulus selection network. Using laser photostimulation of caged glutamate, we find that feedback inhibitory connectivity is global within the Imc. Unlike typical lateral inhibition in other circuits, intra-Imc inhibition remains functionally powerful over long distances. Anatomically, we observed long-range axonal projections and retrograde somatic labeling from focal injections of bi-directional tracers in the Imc, consistent with spatial reciprocity of intra-Imc inhibition. Together, the data indicate that spatially reciprocal inhibition of inhibition occurs throughout the Imc. Thus, the midbrain selection circuit possesses the most efficient circuit motif possible for fast, reliable, and flexible selection.
Department of Neurobiology, Stanford University, Stanford, California, United States of America.
C Alex
CA
Goddard
Department of Neurobiology, Stanford University, Stanford, California, United States of America.
Shreesh P
SP
Mysore
Department of Neurobiology, Stanford University, Stanford, California, United States of America.
Astra S
AS
Bryant
Department of Neurology, Stanford Medical School, Stanford, California, United States of America.
John R
JR
Huguenard
Department of Neurobiology, Stanford University, Stanford, California, United States of America.
Eric I
EI
Knudsen
D000818:Animals; D001369:Axons / Q000502:physiology / Q000528:radiation effects; D002645:Chickens / Q000502:physiology*; D007266:Inhibition, Psychological; D053444:Inhibitory Postsynaptic Potentials / Q000528:radiation effects; D008027:Light; D008636:Mesencephalon / Q000502:physiology* / Q000528:radiation effects; D009415:Nerve Net / Q000502:physiology* / Q000528:radiation effects*; D009433:Neural Inhibition / Q000502:physiology / Q000528:radiation effects*; D009474:Neurons / Q000502:physiology / Q000528:radiation effects