Journal of Neuroscience, Vol 8, 2635-2639, Copyright © 1988 by Society for Neuroscience
Selective attention in an insect auditory neuron
GS Pollack
Department of Biology, McGill University, Montreal, Quebec, Canada.
Previous work (Pollack, 1986) showed that an identified auditory neuron of
crickets, the omega neuron, selectively encodes the temporal structure of
an ipsilateral sound stimulus when a contralateral stimulus is presented
simultaneously, even though the contralateral stimulus is clearly encoded
when it is presented alone. The present paper investigates the
physiological basis for this selective response. The selectivity for the
ipsilateral stimulus is a result of the apparent intensity difference of
ipsi- and contralateral stimuli, which is imposed by auditory
directionality; when simultaneous presentation of stimuli from the 2 sides
is mimicked by presenting low- and high- intensity stimuli simultaneously
from the ipsilateral side, the neuron responds selectively to the
high-intensity stimulus, even though the low-intensity stimulus is
effective when it is presented alone. The selective encoding of the more
intense (= ipsilateral) stimulus is due to intensity-dependent inhibition,
which is superimposed on the cell's excitatory response to sound. Because
of the inhibition, the stimulus with lower intensity (i.e., the
contralateral stimulus) is rendered subthreshold, while the stimulus with
higher intensity (the ipsilateral stimulus) remains above threshold.
Consequently, the temporal structure of the low-intensity stimulus is
filtered out of the neuron's spike train. The source of the inhibition is
not known. It is not a consequence of activation of the omega neuron. Its
characteristics are not consistent with those of known inhibitory inputs to
the omega neuron.