|
| |
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
First published online March 2, 2006
Journal of Experimental Biology 209, 1122-1134 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02080
The role of single spiking spherical neurons in a fast sensory pathway
1 Department of Integrative and Computational Neurosciences, Instituto de
Investigaciones Biológicas Clemente Estable, Associated Unit of the
Facultad de Ciencias, Universidad de la República, Av. Italia 3318,
Montevideo, Uruguay
2 Department of Histology and Embriology, Facultad de Medicina, Universidad
de la República, Gral. Flores 2515, Montevideo, Uruguay
* Author for correspondence (e-mail: angel{at}iibce.edu.uy)
Accepted 5 January 2006
One difficulty in understanding the brain is that of linking the structure of the neurons with their computational roles in neural circuits. In this paper we address this subject in a relative simple system, the fast electrosensory pathway of an electric fish, where sensory images are coded by the relative latency of a volley of single spikes. The main input to this path is a stream of discrete electric images resulting from the modulation of a self-generated carrier by the environment. At the second order cell level, a window of low responsiveness, reducing potential interference from other stimuli, follows activation of the path.
In the present study, we further characterize the input–output relationship at the second order neurons by recording field potentials, and ascertain its cellular basis using in vitro whole cell patch recordings. The field potentials from freely behaving, socially interacting fish were obtained from chronically implanted fish restrained in a mesh pen. In addition, at the end of some experiments the fish was curarized and the fast electrosensory path responses to artificial stimuli were further explored. These in vivo approaches showed that larger stimuli cause larger and longer windows of low responsiveness. The simple spherical geometry of the second order cells allowed us to unveil the membrane mechanisms underlying this phenomenon in vitro. These spherical cells respond with a single spike at the onset of current steps of any amplitude and duration, showing inward and outward rectification, and a long refractory period. We postulate that a low-threshold K+ conductance generates the outward rectification. The most parsimonious interpretation of our data indicates that slow deactivation of this conductance causes the long refractory period. These non-linear properties of the membrane explain the single spiking profile of spherical cells and the low-responsiveness window observed in vivo. Since the electric organ discharges are emitted at intervals slightly longer than the duration of the low-responsiveness window, we propose that the described cellular mechanisms allow fish streaming self-generated images.
Key words: intrinsic properties, electroreception, time coding, low-responsiveness window, onset neuron, electric fish
Related articles in JEB:
This article has been cited by other articles:
|
|
 |
|
  Y. van Bergen BLOCKING THE BUZZ OF INTERFERENCE J. Exp. Biol., March 15, 2006; 209(6): i - ii. [Full Text] [PDF]
|
|
