HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 99/2/814    most recent 00972.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Hurwitz, I. Articles by Susswein, A. J. PubMed PubMed Citation Articles by Hurwitz, I. Articles by Susswein, A. J.

Currents Contributing to Decision Making in Neurons B31/B32 of Aplysia

¹Leslie and Susan Gonda (Goldschmied) Multidisciplinary Brain Research Center, ²Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat Gan, Israel; and ³Center for Neurobiology and Behavior and ⁴Department of Psychiatry, Columbia University, New York, New York

Submitted 28 August 2007; accepted in final form 18 November 2007

Biophysical properties of neurons contributing to the ability of an animal to decide whether or not to respond were examined. B31/B32, two pairs of bilaterally symmetrical Aplysia neurons, are major participants in deciding to initiate a buccal motor program, the neural correlate of a consummatory feeding response. B31/B32 respond to an adequate stimulus after a delay, during which time additional stimuli influence the decision to respond. B31/B32 then respond with a ramp depolarization followed by a sustained soma depolarization and axon spiking that is the expression of a commitment to respond to food. Four currents contributing to decision making in B31/B32 were characterized, and their functional effects were determined, in current- and voltage-clamp experiments and with simulations. Inward currents arising from slow muscarinic transmission were characterized. These currents contribute to the B31/B32 depolarization. Their slow activation kinetics contribute to the delay preceding B31/B32 activity. After the delay, inward currents affect B31/B32 in the context of two endogenous inactivating outward currents: a delayed rectifier K⁺ current (I_K-V) and an A-type K⁺ current (I_K-A), as well as a high-threshold noninactivating outward current (I_maintained). Hodgkin-Huxley kinetic analyses were performed on the outward currents. Simulations using equations from these analyses showed that I_K-V and I_K-A slow the ramp depolarization preceding the sustained depolarization. The three outward currents contribute to braking the B31/B32 depolarization and keeping the sustained depolarization at a constant voltage. The currents identified are sufficient to explain the properties of B31/B32 that play a role in generating the decision to feed.