The Journal of Neuroscience, May 15, 2000, 20(10):3822-3829
Population Vector Coding by the Giant Interneurons of the
Cockroach
Rafael
Levi and
Jeffrey M.
Camhi
Department of Cell and Animal Biology, Life Sciences Institute,
Hebrew University, Jerusalem, Israel 91904
We tested two alternative models of integration among the cockroach
giant interneurons (GIs) for determining the directions of wind-evoked
escape turns. One model, called steering wheel, pits contralateral GIs
against one another; the other, called population vector model,
involves a vector computation among the GIs. In testing each model
theoretically, the population vector was found to account far better
for the actual behavior. Both models could account for the results of
previous behavioral-physiological experiments in which spikes had been
added to the right GI3 together with wind stimuli from the right side.
The two models revealed a critical behavioral-physiological
experimental test that we then performed; namely, when delivering wind
from the right side, adding spikes experimentally to the right GI2
should increase turn size according to the steering wheel model but
should decrease turn size according to the population vector model. The
latter result was obtained. The population vector, but not the steering wheel, model also could account for previous behavioral-physiological experiments in which spikes were added experimentally to a GI contralateral to the wind stimuli. The results support the population vector model as accounting for direction determination among the cockroach GIs.
Key words:
escape behavior; electrical stimulation; neural control; population coding; population vector; giant interneurons; interneuron; cockroach
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