IRFP: Signal detection in noise in the grasshopper Chorthippus biguttulus

Reichert Michael S, Columbia MO

Investigators

Abstract

The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a twenty-four month research fellowship by Dr. Michael S. Reichert to work with Dr. Michael Greenfield at the Research Institute on Insect Biology in Tours, France. Animal communication often takes place in noisy environments and noise imposes constraints on the important tasks of signal transmission, detection and localization. In addition, communication is often a multi-directional process: signals can be transmitted to multiple receivers and signalers may engage in reciprocal signaling interactions with one another. Despite this, few studies have examined the effects of noise on multi-directional signaling interactions in animals. This study examines the effects of noise on communication in a species that engages in acoustic duets involved in mate recognition and localization, the European grasshopper Chorthippus biguttulus. Both males and females of this species produce and respond to acoustic signals during these processes. By using the tools of signal detection theory and controlled experiments examining the responses to signals in noise of individual males and females, as well as duetting pairs, this study tests the prediction that noise has stronger impacts on multi-directional signaling, and examines the consequences of noise on natural communication interactions. This study involves three specific projects. In the first, the signal detection abilities of males and females are compared by exposing individuals of both sexes to synthetic song models of the opposite sex in various levels of masking noise and measuring individual response thresholds. In the second, signal detection in noise is compared for unidirectional and duetting signal interactions, with the prediction that duetting interactions will suffer from greater levels of signal detection errors. In the third, assays of the response of females to mating signals under varying levels of noise are used to determine how signal attractiveness is affected by masking noise. The benefits of this project include an increased understanding of the effects of noise on acoustic signal detection and recognition. The processing of sound in the brain of the study species is well-described. Therefore, this project generates new insights on how simple nervous systems deal with the challenges of signal perception in complex and noisy environments. This has broad implications that could lead to a better understanding of hearing in noise that applies to other systems, including humans. In addition to these benefits, this research will provide the PI with important opportunities to develop collaborations with major international research groups at the Research Institute on Insect Biology (Prof. Michael Greenfield) and at Humboldt University in Berlin, Germany (Prof. Bernhard Ronacher).