The Journal of Neuroscience, April 1, 1999, 19(7):2765-2779
Network Oscillations Generated by Balancing Graded Asymmetric
Reciprocal Inhibition in Passive Neurons
Yair
Manor1,
Farzan
Nadim1,
Steven
Epstein2, 3,
Jason
Ritt3,
Eve
Marder1, and
Nancy
Kopell3
1 Volen Center, Brandeis University, Waltham,
Massachusetts 02454, 2 Department of Mathematical Sciences,
Rensselaer Polytechnic Institute, Troy, New York 12180, and
3 Department of Mathematics and Center for BioDynamics,
Boston University, Boston, Massachusetts 02215
We describe a novel mechanism by which network oscillations can
arise from reciprocal inhibitory connections between two entirely passive neurons. The model was inspired by the activation of the gastric mill rhythm in the crab stomatogastric ganglion by the modulatory commissural ganglion neuron 1 (MCN1), but it is studied here
in general terms. One model neuron has a linear current-voltage (I-V) curve with a low (L) resting potential, and the
second model neuron has a linear current-voltage curve with a high (H)
resting potential. The inhibitory connections between them are graded. There is an extrinsic modulatory excitatory input to the L neuron, and
the L neuron presynaptically inhibits the modulatory neuron. Activation
of the extrinsic modulatory neuron elicits stable network oscillations
in which the L and H neurons are active in alternation. The
oscillations arise because the graded reciprocal synapses create the
equivalent of a negative-slope conductance region in the
I-V curves for the cells. Geometrical methods are used
to analyze the properties of and the mechanism underlying these network oscillations.
Key words:
neural oscillators; central pattern generators; crustaceans; coupled oscillators; phase plane analysis, mathematical
model
Copyright © 1999 Society for Neuroscience 0270-6474/99/1972765-15$05.00/0