DEMONSTRATION OF THE PRECEDENCE EFFECT IN AN INSECT

Field crickets are interesting models for study of auditory phenomena because they solve many of the same acoustic problems as humans, but with simpler nervous systems. Previous work in this lab and others has investigated sound localization, frequency and temporal pattern discrimination, habituation and dishabituation, and categorical perception. This paper demonstrates the precedence effect in crickets, using a standard two-pulse paradigm with a directional escape response to ultrasound. When two pulses of ultrasound are presented from opposite sides with a delay between, crickets respond only to the first pulse for delays of approximately 4 to 75 ms. For delays of 0 to 2 ms, the direction of response is variable (the first wave front does not have precedence); for delays over approximately 75 ms, crickets respond directionally to each of the two pulses. Some neural correlates of the precedence effect were studied by using this paradigm during recordings from a bilateral pair of ascending second-order auditory interneurons known to initiate ultrasound avoidance. There are no ipsilateral-contralateral differences in their responses that could account for the precedence effect; such interactions in the brain must be involved instead. This seems to be the first test of precedence effect in a nonmammal.