Functional dissection of circuitry in a neural integrator.
In neural integrators, transient inputs are accumulated into persistent firing rates that are a neural correlate of short-term memory. Integrators often contain two opposing cell populations that increase and decrease sustained firing as a stored parameter value rises. A leading hypothesis for the mechanism of persistence is positive feedback through mutual inhibition between these opposing populations. We tested predictions of this hypothesis in the goldfish oculomotor velocity-to-position integrator by measuring the eye position and firing rates of one population, while pharmacologically silencing the opposing one. In complementary experiments, we measured responses in a partially silenced single population. Contrary to predictions, induced drifts in neural firing were limited to half of the oculomotor range. We built network models with synaptic-input thresholds to demonstrate a new hypothesis suggested by these data: mutual inhibition between the populations does not provide positive feedback in support of integration, but rather coordinates persistent activity intrinsic to each population.
Aksay
Emre
E
Department of Physiology and Biophysics, Weill Medical College of Cornell University, 1300 York Avenue, Box 75, New York, New York 10021, USA. ema2004@med.cornell.edu
Olasagasti
Itsaso
I
Mensh
Brett D
BD
Baker
Robert
R
Goldman
Mark S
MS
Tank
David W
DW
D000200:Action Potentials / Q000502:physiology*; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal; D001921:Brain / Q000166:cytology; D003198:Computer Simulation; D023882:Dominance, Ocular; D005133:Eye Movements / Q000502:physiology; D005246:Feedback; D006054:Goldfish; D008012:Lidocaine / Q000494:pharmacology; D008959:Models, Neurological; D009407:Nerve Block / Q000379:methods; D009415:Nerve Net / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000145:classification / Q000502:physiology*; D009799:Ocular Physiological Phenomena
D000779:Anesthetics, Local; D008012:Lidocaine