Randolph M. Nesse

Center for Evolution & Medicine, School of Life Sciences

Arizona State University

 

Mechanisms that regulate facultative responses are especially prone to cause problems for several reasons. When information is incomplete, they inevitably sometimes respond when it is not necessary, and they fail to respond when that would be useful. While normal and inevitable such mistakes are nonetheless major medical problems. Responses of such systems are also prone to distortion by novel cues, such as drugs or modern media. The focus of this talk is the special challenge faced by systems that adjust the magnitude or threshold of response as a function of experience. If the system decreases response, it may be deficient when needed in the future. If the system increases response, positive feedback is a high risk. For instance, experiencing danger reliably indicates an environment in which there are benefits from increased threat monitoring and a decreased response threshold. Such systems are intrinsically vulnerable to failure from positive feedback. This presentation considers how selection shapes protections against such feedback, and gives examples of disorders that arise when those protections fail.