April 1, 2003 (Bethesda, MD) How do we hear when some of us chatter all day? When we sing in the shower, why doesnt the active voice smother the rest of our bodys sensory systems? The answer to these questions may be found in the simple male cricket (Gryllus bimaculatus), which sing for hours at over 100 decibels sound pressure levels (dB SPL) in order to attract females.

Background
The songs of crickets (except the one from Disneys famous character, Jiminy Cricket, are generated by rhythmically rubbing the fore wings together resulting in a form of sound production called stridulation. As crickets ears are located on the forelegs, they are fully exposed to the self-generated sounds. Many animals reduce the responsiveness of their peripheral auditory system during sound production, but crickets do not. Despite this, behavioral experiments have shown that singing crickets can respond to external sounds.

A modulation in the sensitivity to reafferent (self-generated) stimulation by centrally generated neural signals has been identified in a variety of sensory systems, e.g., visual, electroreceptive, proprioceptive (perception at the subconscious level), and mechanoreceptive. A reduction in the responsiveness of auditory neurons in the brain has been recorded in humans and other vertebrates during vocalization, but the nature and source of the inhibition has never been characterized.

Crickets sing so loudly that reafferent sound could be confused with external sound and/or desensitize the crickets own auditory system. One solution to this problem could be to modulate the biophysical sensitivity of the ear during sound production. However, the tympanic membrane of the cricket remains fully responsive during stridulation.

A New Study
Researchers have examined how their central and simple auditory system copes with the intense reafferent stimulation through desensitizing effect of loud sounds on the responsi
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Contact: Donna Krupa
djkrupa1@aol.com
703-527-7357
American Physiological Society
2-Apr-2003

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